Forests

11 pages, 1771 KiB

Open AccessArticle

Is Phylogeny More Useful than Functional Traits for Assessing Diversity Patterns Under Community Assembly Processes?

by Jinshi Xu, Han Dang, Mao Wang, Yongfu Chai, Yaoxin Guo, Yu Chen, Chenguang Zhang and Ming Yue

Forests 2019, 10(12), 1159; https://doi.org/10.3390/f10121159 - 17 Dec 2019

Cited by 15 | Viewed by 3504

Abstract

Phylogenetic and functional diversities and their relationship are important for understanding community assembly, which relates to forest sustainability. Thus, both diversities have been used in ecological studies evaluating community responses to environmental changes. However, it is unclear whether these diversity measures can uncover [...] Read more.

Phylogenetic and functional diversities and their relationship are important for understanding community assembly, which relates to forest sustainability. Thus, both diversities have been used in ecological studies evaluating community responses to environmental changes. However, it is unclear whether these diversity measures can uncover the actual community assembly processes. Herein, we examined their utility to assess such assembly processes by analyzing similarities in phylogenetic, functional, and taxonomic α- and β-diversities along an elevational gradient. Additionally, we examined the relationships among environment, phylogeny, and functional traits within the community. Based on our results, we evaluated whether phylogenetic or functional diversity could better reveal the actual community assembly processes. We found that taxonomic, phylogenetic, and functional α-diversities were correlated with one another. Although the functional α-diversity showed a linear correlation with the elevational gradient, taxonomic and phylogenetic α-diversities showed unimodal patterns. Both phylogenetic and functional β-diversities correlated with taxonomic β-diversity, but there was no significant relationship between the former. Overall, our results evidenced that phylogenetic diversity and taxonomic diversity showed similar patterns, whereas functional diversity showed a relatively independent pattern, which may be due to limitations in the functional trait dimensions used in the present study. Although it is difficult to unravel whether the environment shapes phylogeny or functional traits within a community, phylogenetic diversity is a good proxy for assessing the assembly processes, whereas functional diversity may improve knowledge on the community by maximizing information about the functional trait dimensions. Full article

(This article belongs to the Special Issue Biodiversity Conservation in Managed Forests)

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25 pages, 2480 KiB

Open AccessReview

Pine Pitch Canker (PPC): Pathways of Pathogen Spread and Preventive Measures

by Cristina Zamora-Ballesteros, Julio J. Diez, Jorge Martín-García, Johanna Witzell, Alejandro Solla, Rodrigo Ahumada, Paolo Capretti, Michelle Cleary, Rein Drenkhan, Miloň Dvořák, Margarita Elvira-Recuenco, Mercedes Fernández-Fernández, Luisa Ghelardini, Paolo Gonthier, Laura Hernández-Escribano, Renaud Ioos, Svetlana Markovskaja, Pablo Martínez-Álvarez, E. Jordán Muñoz-Adalia, Justyna Anna Nowakowska, Tomasz Oszako, Rosa Raposo, Alberto Santini and Jarkko Hantula Show full author list Hide full author list

Forests 2019, 10(12), 1158; https://doi.org/10.3390/f10121158 - 17 Dec 2019

Cited by 20 | Viewed by 7305

Abstract

Fusarium circinatum (Nirenberg and O’ Donnell) is the causal agent of pine pitch canker (PPC) disease, one of the most devastating forest diseases worldwide. Long-distance spread occurs mainly through the movement of infected seeds whereas at regional level, the movement of seedlings, substrates, [...] Read more.

Fusarium circinatum (Nirenberg and O’ Donnell) is the causal agent of pine pitch canker (PPC) disease, one of the most devastating forest diseases worldwide. Long-distance spread occurs mainly through the movement of infected seeds whereas at regional level, the movement of seedlings, substrates, or containers may play an important role in fungal dispersal. Invasion of nurseries takes place via infected seeds and further spread can occur by planting contaminated seedlings, especially due to the possibility of infected plants remaining symptomless. Once established, F. circinatum spreads by rain, wind, and insects. The natural spread of the pathogen is limited due to the short dispersal distances of the spores and the fairly short flight distances of disseminating insects. In this review, we summarize the currently known dispersal pathways of the pathogen, discussing both natural and human-assisted processes. With the purpose of understanding how to best intervene in the disease’s development in nurseries and forests, we outline the epidemiology of the pathogen describing the key factors influencing its spread. Preventive measures to control the spread of F. circinatum locally and globally are described with special emphasis on the challenges in implementing them. Full article

(This article belongs to the Section Forest Ecology and Management)

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13 pages, 2642 KiB

Open AccessArticle

Genome-Wide Identification and Characterization of Heat-Shock Transcription Factors in Rubber Tree

by Yan Li, Wencai Yu, Yueyi Chen, Shuguang Yang, Shaohua Wu, Jinquan Chao, Xinlong Wang and Wei-Min Tian

Forests 2019, 10(12), 1157; https://doi.org/10.3390/f10121157 - 17 Dec 2019

Cited by 9 | Viewed by 2978

Abstract

Heat-shock transcription factors (Hsfs) play a pivotal role in the response of plants to various stresses. The present study aimed to characterize the Hsf genes in the rubber tree, a primary global source of natural rubber. In this study, 30 Hsf genes were [...] Read more.

Heat-shock transcription factors (Hsfs) play a pivotal role in the response of plants to various stresses. The present study aimed to characterize the Hsf genes in the rubber tree, a primary global source of natural rubber. In this study, 30 Hsf genes were identified in the rubber tree using genome-wide analysis. They possessed a structurally conserved DNA-binding domain and an oligomerization domain. On the basis of the length of the insert region between HR-A and HR-B in the oligomerization domain, the 30 members were clustered into three classes, Classes A (18), B (10), and C (2). Members within the same class shared highly conserved gene structures and protein motifs. The background expression levels of 11 genes in cold-tolerant rubber-tree clone 93-14 were significantly higher than those in cold-sensitive rubber-tree clone Reken501, while four genes exhibited inverse expression patterns. Upon cold stress, 20 genes were significantly upregulated in 93-114. Of the upregulated genes, HbHsfA2b, HbHsfA3a, and HbHsfA7a were also significantly upregulated in three other cold-tolerant rubber-tree clones at one or more time intervals upon cold stress. Their nuclear localization was verified, and the protein–protein interaction network was predicted. This study provides a basis for dissecting Hsf function in the enhanced cold tolerance of the rubber tree. Full article

(This article belongs to the Section Forest Ecophysiology and Biology)

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(A) Gene organization of HbHsfs and (B) motifs identified by MEME tool. Ten motifs (1–10) were indicated by different colors. Full article ">Figure 2
Unrooted phylogenetic tree of rubber tree, Arabidopsis, and Populus trichocarpa heat-shock transcription-factor (Hsf) family (A) and multiple sequence alignment of HR-A/B regions (oligomerization domain (OD)) of HbHsf proteins (B). Amino acid sequences of Hsf proteins were analyzed using the neighbor-joining method, with genetic distance calculated by MEGA5.10. Full article ">Figure 3
Evaluation of cold-stress intensity of rubber trees. (A) Phenotype and (B) statistical analysis of cold tolerance of rubber-tree clones Reken501 and 93-114. Full article ">Figure 4
Expression profiles of 30 HbHsf genes in stem bark of Reken501 and 93-114 in response to cold stress. ** and *: very significant difference (p < 0.01) and significant difference (p < 0.05), respectively, in expression levels between corresponding time intervals in Reken501 and 93-114. Full article ">Figure 5
Expression profiles of HbHsfA1b (A), HbHsfA2b (B), HbHsfA3a (C), HbHsfA4a (D), HbHsfA7a (E) and HbHsfB4a (F) genes in three cold-sensitive rubber-tree clones (Haiken1, Reken514, and Reken515), and three cold-tolerant rubber-tree clones (GT1, Zhanshi327-13, and Guiyan73-165) under cold treatment. ** and *: very significant difference (p < 0.01) and significant difference (p < 0.05), respectively. Full article ">Figure 6
(A) Subcellular localization and (B) predicted protein–protein interaction network of HbHsfA2b, HbHsfA3a, and HbHsfA7a. Bars = 20 μm. Full article ">

22 pages, 2261 KiB

Open AccessArticle

Linkages between Phosphorus and Plant Diversity in Central European Forest Ecosystems—Complementarity or Competition?

by Isaak Rieger, Ingo Kowarik, Daniel Ziche, Nicole Wellbrock and Arne Cierjacks

Forests 2019, 10(12), 1156; https://doi.org/10.3390/f10121156 - 17 Dec 2019

Cited by 11 | Viewed by 3730

Abstract

The phosphorus nutrition status of European forests has decreased significantly in recent decades. For a deeper understanding of complementarity and competition in terms of P acquisition in temperate forests, we have analyzed α-diversity, organic layer and mineral soil P, P nutrition status, and [...] Read more.

The phosphorus nutrition status of European forests has decreased significantly in recent decades. For a deeper understanding of complementarity and competition in terms of P acquisition in temperate forests, we have analyzed α-diversity, organic layer and mineral soil P, P nutrition status, and different concepts of P use efficiency (PUE) in Fagus sylvatica L. (European beech) and Picea abies (L.) H. Karst. (Norway spruce). Using a subset of the Second National Soil Survey in Germany, we correlated available data on P in the organic layer and soil with α-diversity indices for beech and spruce forests overall and for individual vegetation layers (tree, shrub, herb, and moss layers). Moreover, we investigated α-diversity feedbacks on P nutrition status and PUE of both tree species. The overall diversity of both forest ecosystems was largely positively related to P content in the organic layer and soil, but there were differences among the vegetation layers. Diversity in the tree layer of both forest ecosystems was negatively related to the organic layer and soil P. By contrast, shrub diversity showed no correlation to P, while herb layer diversity was negatively related to P in the organic layer but positively to P in soil. A higher tree layer diversity was slightly related to increased P recycling efficiency (P_Plant/P_{organic layer}) in European beech and P uptake efficiency (P_Plant/P_soil) in Norway spruce. The diversity in the herb layer was negatively related to P recycling and uptake efficiency in European beech and slightly related to P uptake efficiency in Norway spruce. In spruce forests, overall and herb species richness led to significantly improved tree nutrition status. Our results confirm significant, non-universal relationships between P and diversity in temperate forests with variations among forest ecosystems, vegetation layers, and P in the organic layer or soil. In particular, tree species diversity may enhance complementarity and hence also P nutrition of dominant forest trees through higher PUE, whereas moss and herb layers seemed to show competitive relationships among each other in nutrient cycling. Full article

(This article belongs to the Section Forest Ecology and Management)

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13 pages, 1111 KiB

Open AccessArticle

Well-Aerated Southern Appalachian Forest Soils Demonstrate Significant Potential for Gaseous Nitrogen Loss

by Peter Baas, Jennifer D. Knoepp and Jacqueline E. Mohan

Forests 2019, 10(12), 1155; https://doi.org/10.3390/f10121155 - 17 Dec 2019

Cited by 4 | Viewed by 2484

Abstract

Understanding the dominant soil nitrogen (N) cycling processes in southern Appalachian forests is crucial for predicting ecosystem responses to changing N deposition and climate. The role of anaerobic nitrogen cycling processes in well-aerated soils has long been questioned, and recent N cycling research [...] Read more.

Understanding the dominant soil nitrogen (N) cycling processes in southern Appalachian forests is crucial for predicting ecosystem responses to changing N deposition and climate. The role of anaerobic nitrogen cycling processes in well-aerated soils has long been questioned, and recent N cycling research suggests it needs to be re-evaluated. We assessed gross and potential rates of soil N cycling processes, including mineralization, nitrification, denitrification, nitrifier denitrification, and dissimilatory nitrate reduction to ammonium (DNRA) in sites representing a vegetation and elevation gradient in the U.S. Department of Agriculture (USDA) Forest Service Experimental Forest, Coweeta Hydrologic Laboratory in southwestern North Carolina, USA. N cycling processes varied among sites, with gross mineralization and nitrification being greatest in high-elevation northern hardwood forests. Gaseous N losses via nitrifier denitrification were common in all ecosystems but were greatest in northern hardwood. Ecosystem N retention via DNRA (nitrification-produced NO₃ reduced to NH₄) ranged from 2% to 20% of the total nitrification and was highest in the mixed-oak forest. Our results suggest the potential for gaseous N losses through anaerobic processes (nitrifier denitrification) are prevalent in well-aerated forest soils and may play a key role in ecosystem N cycling. Full article

(This article belongs to the Section Forest Ecology and Management)

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20 pages, 3565 KiB

Open AccessArticle

Lidar-Derived Tree Crown Parameters: Are They New Variables Explaining Local Birch (Betula sp.) Pollen Concentrations?

by Paweł Bogawski, Łukasz Grewling, Katarzyna Dziób, Kacper Sobieraj, Marta Dalc, Barbara Dylawerska, Dominik Pupkowski, Artur Nalej, Małgorzata Nowak, Agata Szymańska, Łukasz Kostecki, Maciej M. Nowak and Bogdan Jackowiak

Forests 2019, 10(12), 1154; https://doi.org/10.3390/f10121154 - 17 Dec 2019

Cited by 14 | Viewed by 3651

Abstract

Birch trees are abundant in central and northern Europe and are dominant trees in broadleaved forests. Birches are pioneer trees that produce large quantities of allergenic pollen efficiently dispersed by wind. The pollen load level depends on the sizes and locations of pollen [...] Read more.

Birch trees are abundant in central and northern Europe and are dominant trees in broadleaved forests. Birches are pioneer trees that produce large quantities of allergenic pollen efficiently dispersed by wind. The pollen load level depends on the sizes and locations of pollen sources, which are important for pollen forecasting models; however, very limited work has been done on this topic in comparison to research on anthropogenic air pollutants. Therefore, we used highly accurate aerial laser scanning (Light Detection and Ranging—LiDAR) data to estimate the size and location of birch pollen sources in 3-dimensional space and to determine their influence on the pollen concentration in Poznań, Poland. LiDAR data were acquired in May 2012. LiDAR point clouds were clipped to birch individuals (mapped in 2012–2014 and in 2019), normalised, filtered, and individual tree crowns higher than 5 m were delineated. Then, the crown surface and volume were calculated and aggregated according to wind direction up to 2 km from the pollen trap. Consistent with LIDAR data, hourly airborne pollen measurements (performed using a Hirst-type, 7-day volumetric trap), wind speed and direction data were obtained in April 2012. We delineated 18,740 birch trees, with an average density of 14.9/0.01 km², in the study area. The total birch crown surface in the 500–1500 m buffer from the pollen trap was significantly correlated with the pollen concentration aggregated by the wind direction (r = 0.728, p = 0.04). The individual tree crown delineation performed well (r² ≥ 0.89), but overestimations were observed at high birch densities (> 30 trees/plot). We showed that trees outside forests substantially contribute to the total pollen pool. We suggest that including the vertical dimension and the trees outside the forest in pollen source maps have the potential to improve the quality of pollen forecasting models. Full article

(This article belongs to the Special Issue Study of Tree Pollen and Pollination)

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Study area. Full article ">Figure 2
Examples of birch tree stands in an open habitat (A) and in a forest (B) in the study area. The normalised point cloud is plotted as small colour points. The 3D shapes reflect individual segmented birch trees. Images on the right were acquired using Google Earth software. Full article ">Figure 3
Hourly birch pollen concentration in the outskirts of Poznań city in 2012 according to the wind direction and speed (A) and significant structures within the data considering different numbers of clusters determined on the basis of partitioning around medoids (B). Full article ">Figure 4
LiDAR derived mean values of crown parameters attributed to different sectors around the pollen monitoring site: A—birch tree density, B—birch tree height, C—birch tree crown surface and D—birch tree crown volume. Full article ">Figure 5
Validation of the tree segmentation based on counting trees in Google Earth and in the field for 52 randomly selected plots (100 plots were drawn, but 48 showed no birch trees). The confidence interval was at the 0.95 level. Full article ">Figure 6
Differences in crown surface between birch trees growing within different land-use types (Analysis of Variance (ANOVA), F = 1524, p < 0.0001). N = 18,740 segmented trees (6805 urban, 5202 agricultural area, 6733 forests). Full article ">Figure 7
Statistically significant relationship (p = 0.0406) between the hourly birch pollen concentration summed by the influx direction and the total birch crown surface within 500 to 1500 m from the pollen sampler. Full article ">

15 pages, 2245 KiB

Open AccessArticle

Accumulation and Translocation of Phosphorus, Calcium, Magnesium, and Aluminum in Pinus massoniana Lamb. Seedlings Inoculated with Laccaria bicolor Growing in an Acidic Yellow Soil

by Xirong Gu, Xiaohe Wang, Jie Li and Xinhua He

Forests 2019, 10(12), 1153; https://doi.org/10.3390/f10121153 - 17 Dec 2019

Cited by 7 | Viewed by 2343

Abstract

Research Highlights: We demonstrate that ectomycorrhizal (ECM) fungi improve plant aluminum (Al)-tolerance in the field and Laccaria bicolor S238A is a promising ECM isolate. Furthermore, we interpret the underlying nutritional mechanism that ECM inoculation facilitates aboveground biomass production as well as nutrients accumulation [...] Read more.

Research Highlights: We demonstrate that ectomycorrhizal (ECM) fungi improve plant aluminum (Al)-tolerance in the field and Laccaria bicolor S238A is a promising ECM isolate. Furthermore, we interpret the underlying nutritional mechanism that ECM inoculation facilitates aboveground biomass production as well as nutrients accumulation and translocation. Background and Objectives: Al toxicity is a primary limiting factor for plants growing in acidic soils. Hydroponic/sand culture studies have shown that some ECM fungi could enhance plant Al-tolerance. However, the underlying mechanisms of ECM fungi in improving plant Al-tolerance in the field are still unknown. To fill this knowledge gap, the present study aimed to examine roles of ECM inoculation in biomass production, accumulation and translocation of nutrients and Al in the host plant grown in the field under Al treatment. Materials and Methods: 4-week-old Pinus massoniana seedlings were inoculated with three Laccaria bicolor isolates (L. bicolor 270, L. bicolor S238A or L. bicolor S238N) and grown in an acidic yellow soil under 1.0 mM Al treatment for 12 weeks in the field. Biomass production, accumulation and translocation of P, Ca, Mg, and Al were investigated in these 16-week-old P. massoniana seedlings. Results: All three of these L. bicolor isolates improved biomass production as well as P, Ca and Mg accumulation in P. massoniana seedlings. Moreover, the three ECM isolates facilitated the translocation of P, Ca, and Mg to aboveground in response to Al treatment, particularly when seedlings were inoculated with L. bicolor S238A. In addition, both L. bicolor 270 and L. bicolor S238A had no apparent effects on Al accumulation, while enhanced Al translocation to aboveground. In contrast, L. bicolor S238N decreased Al accumulation but had no significant effect on Al translocation. Conclusions: ECM fungi in the field improved plant Al-resistance by increasing nutrient uptake, and this was mostly due to translocation of P, Ca, and Mg to aboveground, not by decreasing the uptake and translocation of Al. Full article

(This article belongs to the Section Forest Ecophysiology and Biology)

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Graphical abstract

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Biomass production in 16-week-old Pinus massoniana Lamb. seedlings grown in an acidic yellow soil in response to Al treatment. “−Al” and “+Al” indicated that seedlings were watered once weekly with Hoagland solution (pH 3.8) containing 0.0 mM Al3+ or 1.0 mM Al3+, respectively. Data (means ± SD, n = 3) followed by different uppercase or lowercase letters indicate significant differences between Al treatments or between ectomycorrhizal treatments compared with Fisher’s LSD test at p < 0.05 level. Full article ">Figure 2
Accumulation of P (a), Ca (b), Mg (c), and Al (d) in 16-week-old Pinus massoniana Lamb. seedlings grown in an acidic yellow soil in the absence (−Al) or the presence (+Al) of 1.0 mM Al3+. Data (means ± SD, n = 3) followed by different uppercase or lowercase letters indicate significant differences between Al treatments or between ectomycorrhizal treatments compared with Fisher’s LSD test at p < 0.05 level. Full article ">Figure 3
Shoot/root ratio in 16-week-old Pinus massoniana Lamb. seedlings grown in an acidic yellow soil with (+Al) or without (−Al) added Al. Data (means ± SD, n = 3) followed by different uppercase or lowercase letters indicate significant differences between Al treatments or between ectomycorrhizal treatments compared with Fisher’s LSD test at p < 0.05 level. Full article ">Figure 4
Translocation factors for P (a), Ca (b), Mg (c), and Al (d) in 16-week-old Pinus massoniana Lamb. seedlings grown in an acidic yellow soil with (+Al) or without (−Al) added Al. Data (means ± SD, n = 3) followed by different uppercase or lowercase letters indicate significant differences between Al treatments or between ectomycorrhizal treatments compared with Fisher’s LSD test at p < 0.05 level. Full article ">

9 pages, 2451 KiB

Open AccessArticle

Biological Durability of Sapling-Wood Products Used for Gardening and Outdoor Decoration

by Christian Brischke, Lukas Emmerich, Dirk G.B. Nienaber and Susanne Bollmus

Forests 2019, 10(12), 1152; https://doi.org/10.3390/f10121152 - 17 Dec 2019

Cited by 2 | Viewed by 2596

Abstract

Sapling-wood products from different wood species such as willow (Salix spp. L.) and Common hazel (Corylus avellana L.) are frequently used for gardening and outdoor decoration purposes. Remaining bark is suggested to provide additional biological durability. Even for temporary outdoor use [...] Read more.

Sapling-wood products from different wood species such as willow (Salix spp. L.) and Common hazel (Corylus avellana L.) are frequently used for gardening and outdoor decoration purposes. Remaining bark is suggested to provide additional biological durability. Even for temporary outdoor use it seemed questionable that durability of juvenile sapwood can provide acceptably long service lives of horticultural products. Therefore, sapling-wood from seven European-grown wood species was submitted to laboratory and field durability tests. In field tests, specimens with and without bark were tested in comparison and submitted to differently severe exposure situations, i.e., in-ground contact, and above-ground situations with and without water trapping. All materials under test were classified ‘not durable’ independently from any potential protective effect of remaining bark, which contradicted their suitability for outdoor applications if multi-annual use is desired. Full article

(This article belongs to the Special Issue Wood Protection and Preservation)

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9 pages, 2316 KiB

Open AccessArticle

Visualization and Localization of Submicron-Sized Ammonium Sulfate Particles on Needles of Japanese Larch (Larix kaempferi) and Japanese Cedar (Cryptomeria japonica) and Leaves of Japanese Beech (Fagus crenata) and Japanese Chinquapin (Castanopsis sieboldii) after Artificial Exposure

by Kenichi Yamane, Satoshi Nakaba, Masahiro Yamaguchi, Katsushi Kuroda, Yuzou Sano, I. Wuled Lenggoro, Takeshi Izuta and Ryo Funada

Forests 2019, 10(12), 1151; https://doi.org/10.3390/f10121151 - 17 Dec 2019

Viewed by 2518

Abstract

We applied a method combining field-emission scanning electron microscopy (FE-SEM) with energy dispersive X-ray spectrometry (EDX) to visualize the deposition and localization of the submicron-sized ammonium sulfate (AS) particles. The AS particles emitted from an aerosol generator in the laboratory were spherical in [...] Read more.

We applied a method combining field-emission scanning electron microscopy (FE-SEM) with energy dispersive X-ray spectrometry (EDX) to visualize the deposition and localization of the submicron-sized ammonium sulfate (AS) particles. The AS particles emitted from an aerosol generator in the laboratory were spherical in shape and individually deposited without aggregation on the surface of a silicon substrate. We determined the AS particles on the surfaces of the needles of Japanese larch (Larix kaempferi) and Japanese cedar (Cryptomeria japonica), and the leaves of Japanese beech (Fagus crenata) and Japanese chinquapin (Castanopsis sieboldii), using EDX. The particles were deposited on either the adaxial or abaxial side of the leaves and needles. The AS particles deposited on the surfaces of the leaves and needles did not aggregate, and they were deposited on the surfaces of the leaves and needles in the same manner, regardless of leaf structure. These results, using a new method, highlight the early stages of the deposition and localization of submicron-sized AS particles on the surfaces of the leaves and needles of forest trees. Full article

(This article belongs to the Special Issue Responses of Trees to Pollutants)

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Secondary electron images captured by field-emission scanning electron microscope (FE-SEM) and energy dispersive X-ray spectrometry (EDX) spectra of the silicon substrates. (a) Ammonium sulfate (AS) particles (diameter 300–600 nm) were distributed on the silicon substrates and were not aggregated. (b) Higher magnification image of an AS particle. (c) EDX spectrum of Spot 1 in (b) showing a clear peak corresponding to sulfur. (d) EDX spectrum of Spot 2 in (b). No peaks corresponding to sulfur were obtained from the silicon substrate. Black arrows indicate focal points for the EDX analysis. White arrows indicate sulfur peaks. Full article ">Figure 2
Secondary electron images captured by field-emission scanning electron microscope (FE-SEM) and energy dispersive X-ray spectrometry (EDX) spectra of leaves from Japanese cedar (Cryptomeria japonica) seedlings. (a) Secondary electron image of leaves from seedlings after exposure to ammonium sulfate (AS) particles. The leaf surface was covered with waxy structures. (b) Backscattered electron image of the leaves corresponding to (a). AS particles (white specks) contrasted with the waxy structures. (c–f). EDX spectra of spots 1 (c), 2 (d), 3 (e), and 4 (f) in (b). Clear peaks corresponding to sulfur were observed in particles (c–e), but no peak was observed in areas without such particles (f). Black arrows indicate focal points for the EDX analysis. Arrowheads indicate indistinguishable particles from the waxy structures shown in (a). White arrows indicate sulfur peaks. Full article ">Figure 3
Field-emission electron scanning microscopy (FE-SEM) and energy dispersive X-ray spectrometry (EDX) images of ammonium sulfate (AS) particles on leaves from Japanese beech (Fagus crenata) seedlings. (a) Secondary electron image of leaves from Fagus crenata seedlings after exposure to AS particles. Non-aggregated AS particles were distributed on the leaves. (b) Elemental mapping image of the area marked by the rectangle in (a). Particles containing sulfur are shown in red. Arrowheads indicate particles containing sulfur. Small arrowhead indicates a particle without sulfur. Full article ">Figure 4
The secondary electron images of the leaves and needles after exposure to ammonium sulfate (AS) particles: Cryptomeria japonica (a,b), Japanese larch (Larix kaempferi) (c,d), Fagus crenata (e), and Japanese chinquapin (Castanopsis sieboldii) (f). The surfaces of the leaves were either covered with tubules (a,c), smooth layers (e), and plates (f) of waxy structures, or rarely covered with these structures (b,d). AS particles were deposited on both dense (a,c) and sparse (b,d) areas of the waxy tubule structures. Black arrows indicate AS particles. Full article ">

17 pages, 3883 KiB

Open AccessArticle

Carbon Cycles of Forest Ecosystems in a Typical Climate Transition Zone under Future Climate Change: A Case Study of Shaanxi Province, China

by Siqi Liang, Shouzhang Peng and Yunming Chen

Forests 2019, 10(12), 1150; https://doi.org/10.3390/f10121150 - 16 Dec 2019

Cited by 6 | Viewed by 2746

Abstract

As global climate change has a large effect on the carbon cycle of forests, it is very important to understand how forests in climate transition regions respond to climate change. Specifically, the LPJ-GUESS (Lund-Potsdam-Jena General Ecosystem Simulator) model was used to simulate net [...] Read more.

As global climate change has a large effect on the carbon cycle of forests, it is very important to understand how forests in climate transition regions respond to climate change. Specifically, the LPJ-GUESS (Lund-Potsdam-Jena General Ecosystem Simulator) model was used to simulate net ecosystem productivity (NEP) and soil heterotrophic respiration (Rh) dynamics of two forest ecosystems of different origins between 1951 and 2100, to quantitatively analyze the carbon source and sink functions and potential changes in soil carbon dynamics in arid and humid regions under future climate change, simulate the dynamics of forest net primary productivity (NPP) under different climatic factors, and analyze the sensitivity of forests in arid and humid regions to temperature, precipitation, and carbon dioxide (CO₂) concentration. We found that: (1) in both the historical and future periods, the average NEP of both studied forests in the humid region was larger than that in the arid region, the carbon sink function of the humid region being predicted to become stronger and the arid zone possibly becoming a carbon source; (2) between 1951 and 2100, the forest soil Rh in the arid region was lower than that in the humid region and under future climate change, forest in the humid region may have higher soil carbon loss; (3) increasing temperature had a negative effect and CO₂ concentration had a positive effect on the forests in the study area, and forests in arid areas are more sensitive to precipitation change. We believe our research could be applied to help policy makers in planning sustainable forest management under future climate change. Full article

(This article belongs to the Section Forest Ecology and Management)

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12 pages, 2842 KiB

Open AccessArticle

An Ant-Plant Mesocosm Experiment Reveals Dispersal Patterns of Myrmecochorous Plants

by Gerriet Fokuhl, Jürgen Heinze and Peter Poschlod

Forests 2019, 10(12), 1149; https://doi.org/10.3390/f10121149 - 16 Dec 2019

Cited by 1 | Viewed by 2717

Abstract

For Central European herbs, ants are one common dispersal vector acting at relatively small spatial scales. Though extensively studied concerning the different benefits to plants, specific dispersal patterns mediated by ants have been reportedly very sparsely and without any validation. Thus, we studied [...] Read more.

For Central European herbs, ants are one common dispersal vector acting at relatively small spatial scales. Though extensively studied concerning the different benefits to plants, specific dispersal patterns mediated by ants have been reportedly very sparsely and without any validation. Thus, we studied the seed dispersal pattern of a set of myrmecochorous plant species in a novel mesocosm experiment. We examined the seed dispersal distances of four forest herbs (Hollow Root–Corydalis cava (L.) Schweigg. & Körte, Alpine Squill–Scilla bifolia L., and Common Dog-violet–Viola riviniana Rchb. and the annual Ivy-leaved Speedwell–Veronica hederifolia L.) by the red ant Myrmica ruginodis Nylander in 8.25 m^² large plots under natural conditions with and without ants. In the presence of Myrmica ants, the bulb geophytes C. cava and S. bifolia showed a significantly higher fraction of dispersed seedlings and a maximum dispersal distance of 322 cm. Estimated by nearest neighbor analyses, distances between single C. cava seedlings were significantly higher in ant plots than in exclosures without ants. The annual species Veronica hederifolia showed a few dispersed seedlings in ant plots only, while the diplochorous hemicryptophyte Viola riviniana germinated in a widely scattered manner with distances up to 241 cm due to ballochorous dispersal in both ant and exclosure plots, but with a maximum of 324 cm only by means of ants. Our results indicate the escape from the mother plant and dispersal for distance as an important benefit for myrmecochorous species, potentially accompanied by benefits through reduced competition. Full article

(This article belongs to the Special Issue Plant-Animal Interactions in Forest Ecosystems)

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Schematic view of the mesocosm experiment with Myrmica showing one ant plot and one exclosure plot. Full article ">Figure 2
Spatial distribution of seedlings in Myrmica mesocosms. Seven replicates are plotted in one graph each. The open circles show the positions of seedlings. The grey circles represent each center of two to four initial mother plants (Cc–Corydalis cava, Sb–Scilla bifolia, Vh–Veronica hederifolia, Vr–Viola riviniana; + with ant nest, − without ant nest) and the triangles indicate the position of the Myrmica ant nest. The x- and y-axes represent the spatial mesocosm dimensions in cm. Full article ">Figure 3
Dispersal curves of the seeds of the four study species (Corydalis cava, Scilla bifolia, Veronica hederifolia, and Viola riviniana) in ant plots and exclosures. Distances are given in 50 cm intervals beginning with 0–50 cm from the mother plants. The dashed line represents the mean dispersal curve of seedlings averaged over seven replicates and the dots represent the number of seedlings in single plots. Full article ">Figure 4
Corrected neighborhood density function (NDF) of Corydalis cava, Scilla bifolia, and Viola riviniana in ant plots and in exclosures. The black line represents the corrected NDF dependent on distance and the grey lines represent the 99% confidence interval for random distribution. Full article ">

18 pages, 3505 KiB

Open AccessArticle

Impact of Climate, Stand Growth Parameters, and Management on Isotopic Composition of Tree Rings in Chestnut Coppices

by Francesco Marini, Giovanna Battipaglia, Maria Chiara Manetti, Piermaria Corona and Manuela Romagnoli

Forests 2019, 10(12), 1148; https://doi.org/10.3390/f10121148 - 16 Dec 2019

Cited by 12 | Viewed by 2523

Abstract

Research Highlights: Chestnut trees’ (Castanea sativa Mill.) growth and their responses to climate are influenced by stand-characteristics and managements. This study highlighted that chestnut tree-ring growth is not particularly influenced by climate, while minimum temperature showed a positive relation with both intrinsic [...] Read more.

Research Highlights: Chestnut trees’ (Castanea sativa Mill.) growth and their responses to climate are influenced by stand-characteristics and managements. This study highlighted that chestnut tree-ring growth is not particularly influenced by climate, while minimum temperature showed a positive relation with both intrinsic water-use efficiency (WUEi) and δ¹⁸O. Background and Objectives: The aim is to check the responses of chestnut trees to climate conditions and the role of stand structure and management. Materials and Methods: Stands with 12–14-year-old shoots were studied using dendrochronological and isotopic (δ¹⁸O and δ¹³C) approaches. Correlations with climate parameters were investigated and principal component analysis was performed using site-characteristics and tree growth parameters as variables. Results: Correlations between tree-ring width (TRW), tree-ring δ¹⁸O, and δ¹³C-derived intrinsic water-use efficiency (WUEi) revealed stand-dependent effects. The highest Correlations were found between climate and tree-rings’ isotopic composition. Chestnut was sensitive to high-minimum temperature in March and April, with a negative relationship with TRW and a positive relationship with WUEi. δ¹⁸O signals were not significantly different among stands. Stand thinning had a positive effect on WUEi after 1–2 years. Stand competition (indicated by shoots/stump and stumps/ha) positively influenced both WUEi and δ¹⁸O. Full article

(This article belongs to the Special Issue Mechanisms of Adaptation of Trees and Shrubs to Dry and Hot Environments)

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Study site in central Italy and Bagnouls–Gaussen climatic diagram of Piancastagnaio (SI) meteo station related to the period 2004–2016. Full article ">Figure 2
Climatic diagram of the mean annual temperature and total amount of precipitation for the Piancastagnaio meteo station. Full article ">Figure 3
Principal component analysis (PCA) of dendrometric variables. Full article ">Figure 4
(a) Raw tree-ring width (TRW) series of the five stands of chestnut coppices at Monte Amiata, (b) Residual values of TRW by the ARMA model. Full article ">Figure 5
Correlation function of TRW with (a) mean minimum temperature and (b) precipitation for each stand. Full article ">Figure 6
(a) δ18O time series and (b) intrinsic water-use efficiency (WUEi) time series for each stand. Full article ">Figure 7
Correlation among climate parameters and stable isotopes. Full article ">

10 pages, 2060 KiB

Open AccessCommunication

Comparisons of Estimated Circuity Factor of Forest Roads with Different Vertical Heights in Mountainous Areas, Republic of Korea

by Hyeongkeun Kweon

Forests 2019, 10(12), 1147; https://doi.org/10.3390/f10121147 - 16 Dec 2019

Cited by 7 | Viewed by 3652

Abstract

Distance is one of the important factors in determining transportation cost and travel time, and it can be easily estimated by measuring the circuity of road networks. This study calculated the circuity factors to estimate the network distance for 27 forest roads (about [...] Read more.

Distance is one of the important factors in determining transportation cost and travel time, and it can be easily estimated by measuring the circuity of road networks. This study calculated the circuity factors to estimate the network distance for 27 forest roads (about 105 km) in South Korea. For this purpose, ridge, mid-slope, and valley roads were classified according to the construction location of the mountain slope, and the weighted and unweighted circuity factor (each 500-m section) were calculated. The average value of weighted circuity was 1.55: mid-slope roads (2.09), ridge roads (1.36), and valley roads (1.09). The average unweighted circuity factors were 1.61 for mid-slope roads, 1.21 for ridge roads, and 1.07 for valley roads. This study found that the circuity of the forest road network was most affected by the mountain terrain. In addition, the circuity factor increased with increasing network distance in the mid-slope roads but was not affected by the network distance in ridges and valleys. To improve the efficiency of transportation in the forest road network, it is important to locate the ladings and properly connect with the public road network. Full article

(This article belongs to the Special Issue Planning, Design, and Maintenance of Forest Road Networks)

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12 pages, 3472 KiB

Open AccessArticle

Control of Fungal Diseases and Increase in Yields of a Cultivated Jujube Fruit (Zizyphus jujuba Miller var. inermis Rehder) Orchard by Employing Lysobacter antibioticus HS124

by Jun-Hyeok Kwon, Sang-Jae Won, Jae-Hyun Moon, Chul-Woo Kim and Young-Sang Ahn

Forests 2019, 10(12), 1146; https://doi.org/10.3390/f10121146 - 15 Dec 2019

Cited by 13 | Viewed by 4677

Abstract

The objective of this study is to investigate the inhibitory effects of Lysobacter antibioticus HS124 on fungal phytopathogens causing gray mold rot, stem rot, and anthracnose. Another objective of this study is to promote the yield of fruit in jujube farms. L. antibioticus [...] Read more.

The objective of this study is to investigate the inhibitory effects of Lysobacter antibioticus HS124 on fungal phytopathogens causing gray mold rot, stem rot, and anthracnose. Another objective of this study is to promote the yield of fruit in jujube farms. L. antibioticus HS124 produces chitinase, a lytic enzyme with the potential to reduce mycelial growth of fungal phytopathogens involving hyphal alterations with swelling and bulbous structures, by 20.6 to 27.3%. Inoculation with L. antibioticus HS124 decreased the appearance of fungal diseases in jujube farms and increased the fruit yield by decreasing fruit wilting and dropping. In addition, L. antibioticus HS124 produced the phytohormone auxin to promote vegetative growth, thereby increasing the fruit size. The yield of jujube fruits after L. antibioticus HS124 inoculation was increased by 6284.67 g/branch, which was 2.9-fold higher than that of the control. Auxin also stimulated fine root development and nutrient uptake in jujube trees. The concentrations of minerals, such as K, Ca, Mg, and P in jujube fruits after L. antibioticus HS124 inoculation were significantly increased (1.4- to 2.0-fold greater than the concentrations in the control). These results revealed that L. antibioticus HS124 could not only control fungal diseases but also promote fruit yield in jujube farms. Full article

(This article belongs to the Special Issue Forest, Foods and Nutrition)

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Graphical abstract

Graphical abstract
Full article ">Figure 1
Locations of the study sites (a). Cultivated jujube orchard at the experimental site (b), gray mold rot by B. cinerea (left), stem rot by B. dothidea (center), and anthracnose by C. gloeosporioides (right) (c). Full article ">Figure 2
Cell growth curve of L. antibioticus HS124 in CY medium at 30 °C for 10 days. Error bars represent the standard deviation of three replications. CFU: colony forming unit. Full article ">Figure 3
Chitinase activity of L. antibioticus HS124 cultured in CPD broth at 30 °C for 10 days. Quantitative measurement of chitinase enzymes produced by strain HS124 was done using a UV-spectrophotometer at 420 nm. Full article ">Figure 4
Inhibitory effect of L. antibioticus HS124 on mycelial growth of B. cinerea, B. dothidea, and C. gloeosporioides (a), and antagonistic activity of L. antibioticus HS124 against fungal pathogens (b) by the dual culture method. Full article ">Figure 5
Deformed hyphal morphologies of B. cinerea (d); B. dothidea (e); and C. gloeosporioides (f) affected by L. antibioticus HS124 compared to B. cinerea control (a); B. dothidea control (b); and C. gloeosporioides control (c) under a light microscope. Arrows indicate hyphal alterations with swelling and bulbous structures caused by L. antibioticus HS124. Full article ">Figure 6
IAA (indole-3-acetic acid) production by L. antibioticus HS124. Full article ">

22 pages, 3139 KiB

Open AccessArticle

Temperature and Rainfall Are Separate Agents of Selection Shaping Population Differentiation in a Forest Tree

by João Costa e Silva, Brad Potts, Peter A. Harrison and Tanya Bailey

Forests 2019, 10(12), 1145; https://doi.org/10.3390/f10121145 - 14 Dec 2019

Cited by 18 | Viewed by 3203

Abstract

Research highlights: We present evidence indicating that covariation of functional traits among populations of a forest tree is not due to genetic constraints, but rather selective covariance arising from local adaptation to different facets of the climate, namely rainfall and temperature. Background [...] Read more.

Research highlights: We present evidence indicating that covariation of functional traits among populations of a forest tree is not due to genetic constraints, but rather selective covariance arising from local adaptation to different facets of the climate, namely rainfall and temperature. Background and Aims: Traits frequently covary among natural populations. Such covariation can be caused by pleiotropy and/or linkage disequilibrium, but also may arise when the traits are genetically independent as a direct consequence of natural selection, drift, mutation and/or gene flow. Of particular interest are cases of selective covariance, where natural selection directly generates among-population covariance in a set of genetically independent traits. We here studied the causes of population-level covariation in two key traits in the Australian tree Eucalyptus pauciflora. Materials and Methods: We studied covariation in seedling lignotuber size and vegetative juvenility using 37 populations sampled from throughout the geographic and ecological ranges of E. pauciflora on the island of Tasmania. We integrated evidence from multiple sources: (i) comparison of patterns of trait covariation within and among populations; (ii) climate-trait modelling using machine-learning algorithms; and (iii) selection analysis linking trait variation to field growth in an arid environment. Results: We showed strong covariation among populations compared with the weak genetic correlation within populations for the focal traits. Population differentiation in these genetically independent traits was correlated with different home-site climate variables (lignotuber size with temperature; vegetative juvenility with rainfall), which spatially covaried. The role of selection in shaping the population differentiation in lignotuber size was supported by its relationship with fitness measured in the field. Conclusions: Our study highlights the multi-trait nature of adaptation likely to occur as tree species respond to spatial and temporal changes in climate. Full article

(This article belongs to the Section Forest Ecophysiology and Biology)

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Geographic variation in: (a) lignotuber diameter at the cotyledonary node (LIGD); and (b) the percentage of nodes expanded at six months of age which had petiolate leaves (PET), measured on seedlings from 37 Eucalyptus pauciflora provenances distributed within the island of Tasmania (re-analysed data from Gauli et al. (2015). The provenance estimates of marginal means (EMMeans) for LIGD are plotted such that the larger the brown circle the greater the LIGD mean is above the grand mean, and the larger the green triangle the more the mean is below the grand mean. For PET, the plotting is reversed such that the smaller values of the EMMeans for PET (thus plants are more juvenile) are depicted with larger brown circles. Seedlings from provenances in the central region of the distribution tend to have larger lignotubers and to retain juvenility longer (i.e., low proportion of nodes with petiolate leaves). Full article ">Figure 2
Importance of the climate principal components and Moran’s eigenvector map variables in the final extended forests models fitted for: (a) lignotuber diameter at the cotyledonary node (LIGD); and (b) percentage of nodes expanded at six months of age which had petiolate leaves (PET). The independent variables used in the extended forests model were the four climate principal components (PC1–PC4) presented in <a href="#app1-forests-10-01145" class="html-app">Table S1</a>, which accounted for 95% of the climate variation among provenances. Moran’s eigenvector map (MEMs) variables (MEM 1–8) were additionally fitted to account for spatial processes and unmeasured environmental variation and were derived using an inverse-weighted Euclidean distance matrix among provenance home-sites. MEM1 reflected a significant positive latitudinal cline in similarity among provenances (r = 0.78, p < 0.001); however, MEM2 to MEM8 were independent of the provenance home-site geographic co-ordinates and climate after Bonferroni adjustment for multiple testing (data not shown), and any importance is likely to reflect unmeasured environmental or historic facets of the variation. The importance of the independent variables was assessed through the percentage increase in mean-squared error (IncMSE) of the extended forests model, using the conditional permutation method of Strobl et al. (2008). Independent variables causing a decrease in IncMSE were sequentially dropped during model development. The lower and upper 95% confidence intervals (red bar) associated with each independent variable were derived from iterative bootstrapping (1000 bootstraps) of the extended forests model. Full article ">Figure 3
Partial dependency plots from the final extended forests models fitted as a function of climate principal components and Moran’s eigenvector map variables. The plots show the marginal effect of the climate principal component 1 (PC1; see <a href="#app1-forests-10-01145" class="html-app">Table S1</a>) on the provenance estimates of marginal means for: (a) lignotuber diameter at the cotyledonary node (LIGD); and (b) percentage of nodes expanded at six months of age which had petiolate leaves (PET; lower values of PET pertain to seedling leaves that are more juvenile). The red tick marks show the deciles of the data. The grey shading indicates the 95% confidence intervals derived by iterative bootstrapping (1000 bootstraps). Increasing scores on PC1 corresponds to increasing home-site aridity (i.e., high summer temperatures and low summer rainfall; see <a href="#app1-forests-10-01145" class="html-app">Table S1</a>). The images show the development of the basal lignotuber in the top panel (yellow arrow), and the ontogenetic change from opposite, sessile (bottom) to alternate, petiolate (top) leaves in the lower panel. The yellow arrow at the bottom panel corresponds to the node of the first petiolate leaf (node 4, left; node 6, right). Full article ">Figure 4
Importance of specific climate variables and Moran’s eigenvector map variables in the final extended forest models fitted for: (a) lignotuber diameter at the cotyledonary node (LIGD); and (b) percentage of nodes expanded at six months of age which had petiolate leaves (PET). The importance of each independent variable was assessed through the percentage increase in mean-squared error (IncMSE) of the extended forests model, following the conditional permutation method of Strobl et al. (2008) (see the Materials and Methods Section and <a href="#forests-10-01145-f002" class="html-fig">Figure 2</a> caption for further details). The original climate variables initially fitted in preliminary models are detailed in <a href="#app1-forests-10-01145" class="html-app">Table S1</a>. Independent variables causing a decrease in IncMSE were sequentially dropped during model development. The most important independent variables in the models for LIGD and PET were the provenance home-site maximum temperature of the warmest week (TMXWW) and the precipitation of the driest quarter (RDRYQ), respectively. The MEMs are as detailed in the <a href="#forests-10-01145-f002" class="html-fig">Figure 2</a> caption. Full article ">Figure 5
Partial dependency plots from the final extended forests models fitted as a function of specific climate variables and Moran’s eigenvector map variables. The plots show the marginal effects of maximum temperature of the warmest week (TMXWW) and precipitation of the driest quarter (RDRYQ) for each of the extended forests models applied for: (a,b) lignotuber diameter at the cotyledonary node (LIGD); and (c,d) percentage of nodes expanded at six months of age which had petiolate leaves (PET). The importance of the climate variables in the different models is given in <a href="#forests-10-01145-f004" class="html-fig">Figure 4</a>. Full article ">Figure 6
The provenance home-site maximum temperature of the warmest week (TMXWW) plotted against the precipitation of the driest quarter (RDRYQ). Increasing circle size pertains to increasing provenance home-site altitude (meters above sea level). The colour of each circle reflects the provenance score along the climate principal component 1 (PC1; see <a href="#app1-forests-10-01145" class="html-app">Table S1</a>), such that mesic provenances are dark blue (more negative values on PC1) and arid provenances are dark red (more positive values on PC1). The TMXWW and RDRYQ values for the contemporary (LTA: 1976–2005, centred on 1990) and growing (GP: 2014–2018) climate periods at the trial site are indicated. All provenances are from home-sites with a contemporary climate cooler than the growing period TMXWW, but seven provenances originate from home-sites with a contemporary climate drier than the growing period RDRYQ. Full article ">

17 pages, 1393 KiB

Open AccessReview

Assessing the Impact of Ozone on Forest Trees in An Integrative Perspective: Are Foliar Visible Symptoms Suitable Predictors for Growth Reduction? A Critical Review

by Riccardo Marzuoli, Giacomo Gerosa, Filippo Bussotti and Martina Pollastrini

Forests 2019, 10(12), 1144; https://doi.org/10.3390/f10121144 - 14 Dec 2019

Cited by 17 | Viewed by 4129

Abstract

Plant growth reduction (GR) is the most widely accepted damage parameter to assess the sensitivity of trees to tropospheric ozone (O₃) pollution since it integrates different physiological processes leading to loss of photosynthetic activity and distraction of metabolic resources from growth [...] Read more.

Plant growth reduction (GR) is the most widely accepted damage parameter to assess the sensitivity of trees to tropospheric ozone (O₃) pollution since it integrates different physiological processes leading to loss of photosynthetic activity and distraction of metabolic resources from growth to defense, repair, and recovery pathways. Because of the intrinsic difficulty to assess the actual O₃ risk assessment for forests in field conditions, foliar visible symptoms (FVS) induced by O₃ have been proposed as a proxy to estimate possible GR in forest trees. The rationale for this assumption is that the onset of FVS implies a reduction of the photosynthetic capacity of plants. In this review, we show that GR and FVS can be the consequences of independent physiological pathways involving different response mechanisms that can cause both FVS without GR and GR without FVS. The onset of FVS may not lead necessarily to significant GR at plant level for several reasons, including the rise of compensatory photosynthesis, the time lag between growth processes and the accumulation of critical O₃ dose, and the negligible effect of a modest amount of injured leaves. Plant GR, on the other hand, may be induced by different physiological mechanisms not necessarily related to FVS, such as stomatal closure (i.e., carbon starvation) to avoid or reduce O₃ uptake, and the increase of respiratory processes for the production of metabolic defense compounds. Growth reduction and FVS can be interpreted as different strategies for the acclimation of plants to a stressful environment, and do not mean necessarily damage. Growth reduction (without FVS) seems to prevail in species adapted to limiting environmental conditions, that avoid loss and replacement of injured leaves because of the high metabolic cost of their production; conversely, FVS manifestation (without GR) and the replacement of injured leaves is more common in species adapted to environments with low-stress levels, since they can benefit from a rapid foliar turnover to compensate for the decreased rate of photosynthesis of the whole plant. Full article

(This article belongs to the Special Issue Impacts of Ozone on Forest Plants and Ecosystems)

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16 pages, 2497 KiB

Open AccessArticle

Drought-Induced Reductions and Limited Recovery in the Radial Growth, Transpiration, and Canopy Stomatal Conductance of Mongolian Scots Pine (Pinus sylvestris var. mongolica Litv): A Five-Year Observation

by Hongzhong Dang, Ping Lu, Wenbin Yang, Hui Han and Jun Zhang

Forests 2019, 10(12), 1143; https://doi.org/10.3390/f10121143 - 13 Dec 2019

Cited by 18 | Viewed by 2855

Abstract

Determining plant–water relationships in response to drought events can provide important information about the adaptation of trees to climate change. The Mongolian Scots pine (Pinus sylvestris var. mongolica Litv), as one of the major tree species to control soil loss and desertification [...] Read more.

Determining plant–water relationships in response to drought events can provide important information about the adaptation of trees to climate change. The Mongolian Scots pine (Pinus sylvestris var. mongolica Litv), as one of the major tree species to control soil loss and desertification in northern China, has experienced severe degradation in recent decades. Here, we aimed to examine the impacts of a two-year consecutive drought and another year of drought on the radial growth, transpiration, and canopy stomatal conductance of Mongolian Scots pine over a five-year period, especially in terms of its recovery after drought. The study period during 2013–2017 consisted of a ‘normal’ year, a ‘dry year’, a ‘very dry’ year, a ‘wet’ year, and a ‘dry’ year, according to annual precipitation and soil moisture conditions. Based on measurements of the sap flow and diameters at breast height of 11 sample trees as well as the concurrent environmental factors, we quantified the reductions in tree radial growth, transpiration, and canopy stomatal conductance during the drought development as well as their recovery after the drought. The results showed that the tree radial growth, transpiration, and canopy stomatal conductance of Mongolian Scots pines decreased by 33.8%, 51.9%, and 51.5%, respectively, due to the two consecutive years of drought. Moreover, these reductions did not fully recover after the two-year drought was relieved. The minimum difference of these parameters between before and after the two-year consecutive drought period was 8.5% in tree radial growth, 45.1% in transpiration levels, and 42.4% in canopy stomatal conductance. We concluded that the two consecutive years of drought resulted in not only large reductions in tree radial growth and water use, but also their lagged and limited recoveries after drought. The study also highlighted the limited resilience of Mongolian Scots pine trees to prolonged drought in semi-arid sandy environmental conditions. Full article

(This article belongs to the Section Forest Ecophysiology and Biology)

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Environmental factors: (a) anomalies in monthly precipitation from the long-term averages, (b) monthly mean volumetric soil moisture content (<math display="inline"><semantics> <mrow> <mover accent="true"> <mi>θ</mi> <mo stretchy="true">¯</mo> </mover> </mrow> </semantics></math>) in the 0–1 m soil layer, (c) monthly mean vapor pressure deficit (VPD). The error bars represent standard error (S.E.). <math display="inline"><semantics> <mrow> <mover accent="true"> <mi>P</mi> <mo stretchy="true">¯</mo> </mover> </mrow> </semantics></math> is the multiple-year annual precipitation, based on measurements over the 30 years period during 1983–2012. The horizontal line in (b) indicates the lower limit of relative extractable soil water, i.e., 0.4 [<a href="#B56-forests-10-01143" class="html-bibr">56</a>], corresponding to a value of <math display="inline"><semantics> <mrow> <mover accent="true"> <mi>θ</mi> <mo stretchy="true">¯</mo> </mover> </mrow> </semantics></math> 0.086 cm3·cm−3 in this study. The five years in the study period during 2013–2017 are marked as a ‘normal’ year, a ‘dry’ year, a ‘very dry’ year, a ‘wet’ year, and a ‘dry’ year, respectively, according to annual precipitation and soil moisture conditions. Full article ">Figure 2
Diameter at breast height (DBH, cm) measured at the end of the season (a), and annual radial increment in DBH (cm·yr−1) of sample trees (b), from 2013 to 2017 in Zhanggutai, Liaoning Province, China. The value is the average of the 11 sample trees. Different lowercase letters indicate a significant difference (p = 0.05). Full article ">Figure 3
Total transpiration per year (tons·tree−1) during 2013–2017. Values presented are the statistical values of 11 sample trees. Different lowercase letters indicate significant difference between the means (p < 0.05). Full article ">Figure 4
Seasonal dynamics of daily transpiration per tree (Qt, kg·tree−1·d−1) during the growing season in each year during 2013–2017 were plotted in (a–e), respectively. The circles represent the daily averages, and the whisker lines indicate the standard error (±S.E.) for the 11 sample trees. The dashed lines represent the averages of daily transpiration. Full article ">Figure 5
Seasonal dynamics of daily mean canopy stomatal conductance (Gs, cm·s−1) in the daytime of the growing season during 2013–2017 were plotted in (a–e), respectively. The circles represent daytime averages. The whisker lines indicate the standard error (±S.E.) from 11 sample trees. The dashed line is the average for the year. Full article ">Figure 6
Diurnal courses of transpiration (Qt) on sunny days in the early, mid-, and late parts of the growing season in 2013 (the ‘normal’ year), 2015 (the ‘very dry’ year), and 2016 (the ‘wet’ year) were plotted in (a–c), respectively. Canopy stomata conductance (Gs) from the same periods were plotted in (d–f), respectively. The maxima of daily VPD values on sunny days were 2.5 kPa in the early and mid-part of the growing season, with 1.5 kPa in the late part of the growing season, over the entire study period. Three sunny days were selected from the early, mid-, and late parts of the growing season, which were DOY 155, DOY 222, and DOY 285 in 2013; DOY 160, DOY 216, and DOY 278 in 2015; and DOY 149, DOY 233, and DOY 272 in 2016. The bars indicate standard errors from 11 sample trees. The value of Gs was calculated only when hourly VPD > 0.6 kPa. DOY: Day of the year. Full article ">

14 pages, 2254 KiB

Open AccessArticle

Residents’ Attention and Awareness of Urban Edible Landscapes: A Case Study of Wuhan, China

by Qijiao Xie, Yang Yue and Daohua Hu

Forests 2019, 10(12), 1142; https://doi.org/10.3390/f10121142 - 13 Dec 2019

Cited by 8 | Viewed by 4035

Abstract

More and more urban residents in China have suffered from food insecurity and failed to meet the national recommendation of daily fruit and vegetable consumption due to rapid urbanization in recent years. Introducing edible landscapes to urban greening systems represents an opportunity for [...] Read more.

More and more urban residents in China have suffered from food insecurity and failed to meet the national recommendation of daily fruit and vegetable consumption due to rapid urbanization in recent years. Introducing edible landscapes to urban greening systems represents an opportunity for improving urban food supply and security. However, residents’ opinion on urban edible landscapes has rarely been discussed. In this study, questionnaire surveys were performed in eight sample communities in Wuhan, China, to collect the information on residents’ attention and awareness of urban edible landscapes. Results indicated that nearly one-third of the respondents were unaware of edible landscapes before the interview. Most residents thought that an edible landscape could promote efficient land use (57.26%) and express special ornamental effects (54.64%), but quite a few didn’t believe that growing edible plants in urban public spaces could increase food output (37.10%) and improve food quality (40.12%). Overall, 45.65% and 32.73% of the growers performed their cultivation behavior in private and semiprivate spaces, respectively. Lack of public areas for agriculture use was regarded as the main barrier restricting the development of urban horticulture by 55.86% of growers and 59.51% of non-growers. The residents were also worried about their property manager’s opposition, possible conflicts, and complex relationships with their neighbors. Food policies and infrastructure support from local governments and official institutions were needed to ensure the successful implementation of edible landscapes in urban areas. Full article

(This article belongs to the Special Issue Forest, Foods and Nutrition)

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17 pages, 8147 KiB

Open AccessArticle

Discovery and Profiling of microRNAs at the Critical Period of Sex Differentiation in Xanthoceras sorbifolium Bunge

by Xu Wang, Yaqi Zheng, Shuchai Su and Yan Ao

Forests 2019, 10(12), 1141; https://doi.org/10.3390/f10121141 - 13 Dec 2019

Cited by 15 | Viewed by 2947

Abstract

Research Highlights: The critical period of sex differentiation in Xanthoceras sorbifolium was investigated. Multiple microRNAs (miRNAs) were identified to influence female and male flower development, with some complementary functions. Background and Objectives: Xanthoceras sorbifolium Bunge is widely cultivated owing to its multipurpose usefulness. [...] Read more.

Research Highlights: The critical period of sex differentiation in Xanthoceras sorbifolium was investigated. Multiple microRNAs (miRNAs) were identified to influence female and male flower development, with some complementary functions. Background and Objectives: Xanthoceras sorbifolium Bunge is widely cultivated owing to its multipurpose usefulness. However, as a monoecious plant, the low female–male flowers ratio and consequent low seed yield are the main bottlenecks for industrial-scale development of seed utilization. MiRNAs play crucial regulatory roles in flower development and sex differentiation; therefore, we evaluated the roles of miRNAs in the critical period of sex differentiation in X. sorbifolium. Materials and Methods: Four small RNA libraries for female and male flower buds of the critical period of sex differentiation were constructed from paraffin-embedded sections. The miRNAs were characterized by high-throughput sequencing, and differentially expressed miRNAs were validated by reverse transcription-quantitative polymerase chain reaction. Results: There were obvious differences in male and female pistil and stamen flower buds, with elongated inflorescence and clear separation of flower buds marking the critical period of sex differentiation. A total of 1619 conserved miRNAs (belonging to 34 families) and 219 novel miRNAs were identified. Among these, 162 conserved and 14 novel miRNAs exhibited significant differential expression in the four libraries, and 1677 putative target genes of 112 differentially expressed miRNAs were predicted. These target genes were involved in diverse developmental and metabolic processes, including 17 miRNAs directly associated with flower and gametophyte development, mainly associated with carbohydrate metabolism and glycan biosynthesis and metabolism pathways. Some miRNA functions were confirmed, and others were found to be complemented. Conclusions: Multiple miRNAs closely related to sex differentiation in X. sorbifolium were identified. The theoretical framework presented herein might guide sex ratio regulation to enhance seed yield. Full article

(This article belongs to the Section Forest Ecophysiology and Biology)

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12 pages, 5541 KiB

Open AccessArticle

Experimental and Numerical Determination of the Mechanical Properties of Spruce Wood

by Gorazd Fajdiga, Denis Rajh, Branko Nečemer, Srečko Glodež and Matjaž Šraml

Forests 2019, 10(12), 1140; https://doi.org/10.3390/f10121140 - 13 Dec 2019

Cited by 13 | Viewed by 3524

Abstract

The objective of this paper is the computational and experimental study of the fracture behavior of spruce wood under quasi-static loading conditions during a three-point bending test. The experimental tests were performed on the electronic testing machine Zwick Z100 (Zwick-Roell GmbH & Co. [...] Read more.

The objective of this paper is the computational and experimental study of the fracture behavior of spruce wood under quasi-static loading conditions during a three-point bending test. The experimental tests were performed on the electronic testing machine Zwick Z100 (Zwick-Roell GmbH & Co. KG, Ulm, Germany) with displacement control, according to the standard International Standard Organisation (ISO) 13061-4: 2014. The specimens were made of Norway spruce (Picea abies) wood, with dimensions of 25 mm × 25 mm in cross-section and 549 mm in length. Six tests were performed for each orientation (radial and tangential) of the wood fibres. Based on the experimental results, the computational model was created and validated by considering the mechanical responses in two different directions due to the orientation of the wood fibres. An orthotropic material model with damage evolution was selected as the computational model. The computational model was validated using the inverse procedure for the determination of the constitutive material parameters, including the damage parameters of three-point bending test specimens. A finite element method (FEM) in the framework of program package ABAQUS was used for the computational simulation, while the open code Optimax was used for the optimization procedure. Comparison between the experimental and computational force vs. the displacement response showed a very good correlation in the results for the spruce wood specimens under three-point bending tests, with Pearson′s correlation coefficient of r = 0.994 for the tangential and r = 0.988 for the radial orientation. Therefore, validation of the proposed computational model was confirmed, and can be used further in numerical simulations of the fatigue behavior of wood specimens. Full article

(This article belongs to the Section Forest Ecology and Management)

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14 pages, 2230 KiB

Open AccessArticle

Patterns of Effective Pollen Dispersal in Larch: Linking Levels of Background Pollination with Pollen Dispersal Kernels

by Jarosław Burczyk, Elżbieta Sandurska and Andrzej Lewandowski

Forests 2019, 10(12), 1139; https://doi.org/10.3390/f10121139 - 12 Dec 2019

Cited by 7 | Viewed by 2386

Abstract

Monitoring patterns of mating and pollen dispersal in forest tree populations subjected to nature conservation is essential to understanding the dynamics of their reproductive processes and might be helpful in making management decisions aimed at conserving genetic diversity and integrity over the long [...] Read more.

Monitoring patterns of mating and pollen dispersal in forest tree populations subjected to nature conservation is essential to understanding the dynamics of their reproductive processes and might be helpful in making management decisions aimed at conserving genetic diversity and integrity over the long term. However, little is known about effective pollen dispersal in natural populations of conifers, particularly in subdominant species such as larch. We investigated patterns of pollen dispersal in the Polish larch population of Świętokrzyski National Park. The studied population was located on Chełmowa Mountain in a forest complex 160 ha in size, which is relatively isolated from other forest stands. We assessed if local pollen dispersal inferred from pollen dispersal kernels could provide indications of the level of background pollination from sources located outside of the forest complex. The analysis focused on two plots, each encompassing 126 adult trees, and seed samples (n = 600) collected from 20 trees. Using 11 nuclear microsatellites and spatially explicit mating models, we identified details of mating patterns. The rate of self-fertilization was low (0.0268). Background pollination was moderate (0.4058), and the mean pollen dispersal was found to be 167 m and 111 m, based on exponential-power and Weibull dispersal kernels, respectively. Specific simulations performed based on the estimated pollen dispersal kernels provided background pollination levels comparable to those observed for real data, suggesting that the pollen contributing to background pollination likely originated from the studied forest complex and not from other surrounding populations. These results confirm the high potential for maintaining the genetic integrity of the larch population and support efforts aimed at promoting regeneration of the stands, either natural or through the artificial planting of seedlings derived from trees growing in the core larch population of the protected area. Full article

(This article belongs to the Section Forest Ecology and Management)

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Figure 1
Location of the studied forest complex, including the two sample plots (plot A and plot B) and the distribution of sampled adult individuals. Full article ">Figure 2
The probability density distribution of pollen dispersal estimated based on exponential- power and Weibull kernels; (a) linear scale of probability, (b) logarithmic scale of probability. Full article ">Figure 3
The relationship between individual male mating success and tree diameter at breast height (DBH). The DBH scale is adjusted to standardized DBH values with DBH = 72.3 (the sample mean) corresponding to z = 0, DBH = 16.5 to z =−3S, and DBH = 128.1 to z = +3S, where S is the standard deviation of the sample. Full article ">Figure 4
Relationships between the neighborhood size and the probability of local outcross mating (1−s−m) within the neighborhood vs. pollen immigration (m) from outside of the neighborhood, simulated based on the parameters of exponential-power and Weibull dispersal kernels estimated from real data. The simulations are made for the population distributed over the circular area with a radius of 715 m, equivalent to the area of 160 ha, corresponding to the studied forest complex. Full article ">

12 pages, 1977 KiB

Open AccessArticle

“Diminishing Returns” in the Scaling between Leaf Area and Twig Size in Three Forest Communities Along an Elevation Gradient of Wuyi Mountain, China

by Guojie Zhu, Karl Joseph Niklas, Man Li, Jun Sun, Min Lyu, Xiaoping Chen, Mantang Wang, Quanlin Zhong and Dongliang Cheng

Forests 2019, 10(12), 1138; https://doi.org/10.3390/f10121138 - 12 Dec 2019

Cited by 18 | Viewed by 2413

Abstract

Background and aims: The “diminishing returns” hypothesis postulates that the scaling exponent governing the lamina area versus lamina mass scaling relationships has, on average, a numerical value less than one. Theoretically, a similar scaling relationship may exist at the twig level. However, this [...] Read more.

Background and aims: The “diminishing returns” hypothesis postulates that the scaling exponent governing the lamina area versus lamina mass scaling relationships has, on average, a numerical value less than one. Theoretically, a similar scaling relationship may exist at the twig level. However, this possibility has not been explored empirically. Methods: We tested both hypotheses by measuring the lamina area and mass, petiole mass of individual leaves, and the total foliage area and stem mass of individual current-year shoots (twigs) of 64 woody species growing in three characteristic forest community types: (1) Evergreen broad-leaved, (2) mixed coniferous and broad-leaved, and (3) deciduous. Key results: The results demonstrate that lamina area vs. mass and lamina area vs. petiole mass differ significantly among the three forest types at both the individual leaf and twig levels. Nevertheless, the scaling exponents of lamina area vs. mass were <1.0 in each of the three community types, as were the corresponding exponents for lamina area vs. petiole mass, both within and across the three community types. Similar trends were observed at the individual twig level. The numerical values of the scaling exponent for lamina area vs. petiole mass and total foliage area vs. stem mass per twig decreased with increased elevation. Conclusions: These data support the “diminishing returns” hypothesis at both the individual leaf level and at the individual twig level, phenomena that can inform future inquiries into the mechanistic basis of biomass allocation patterns to physiological (leaf) and mechanical (stem) plant organs. Full article

(This article belongs to the Section Forest Ecophysiology and Biology)

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6 pages, 676 KiB

Open AccessEditorial

Protection Strategy against Spruce Budworm

by David A. MacLean

Forests 2019, 10(12), 1137; https://doi.org/10.3390/f10121137 - 12 Dec 2019

Cited by 7 | Viewed by 2915

Abstract

Spruce budworm is one of the most significant forest insects worldwide, in terms of outbreak extent, severity, and economic impacts. As a defoliator, spruce budworm larvae are susceptible to insecticide protection, and improvements in efficacy and reductions in non-target environmental effects have made [...] Read more.

Spruce budworm is one of the most significant forest insects worldwide, in terms of outbreak extent, severity, and economic impacts. As a defoliator, spruce budworm larvae are susceptible to insecticide protection, and improvements in efficacy and reductions in non-target environmental effects have made such protection attractive. In this Special Issue, 12 papers describe the advances in spruce budworm protection, most notably an ‘early intervention strategy’ approach that after six years of trials in New Brunswick, Canada, shows considerable success to date in reducing budworm outbreak occurrence and severity. Full article

(This article belongs to the Special Issue Protection Strategy against Spruce Budworm)

13 pages, 2716 KiB

Open AccessArticle

Conversion of Pinus nigra Plantations with Natural Regeneration in the Slovenian Karst: The Importance of Intermediate, Gradually Formed Canopy Gaps

by Jurij Diaci, Tomaž Adamič, Andrej Rozman, Gal Fidej and Dušan Roženbergar

Forests 2019, 10(12), 1136; https://doi.org/10.3390/f10121136 - 12 Dec 2019

Cited by 7 | Viewed by 2800

Abstract

Since the mid-19th century, Pinus nigra plantations have played a key role in the restoration of degraded European landscapes. Nowadays, these plantations are aging and prone to natural disturbances, insect infestations, and diseases. For their successful gradual conversion, knowledge of optimal gap spatiotemporal [...] Read more.

Since the mid-19th century, Pinus nigra plantations have played a key role in the restoration of degraded European landscapes. Nowadays, these plantations are aging and prone to natural disturbances, insect infestations, and diseases. For their successful gradual conversion, knowledge of optimal gap spatiotemporal dynamics is crucial. We studied herb and natural regeneration patterns along with site factors on 477 subplots within 44 plots distributed over four stand types: closed stand (14% diffuse light), open stand (21%), gap edge (23%), and gap (57%). Despite the abundant Quercus petraea, Q. cerris, and Q. pubescens mast year, no one-year seedlings were recorded, which is likely due to the summer drought. Short seedlings (h < 20 cm) of Quercus sp., Fraxinus ornus and Ostrya carpinifolia were more successful within closed stands. Short Quercus seedlings were positively associated with soil depth and negatively associated with soil nutrients, distance to seed trees, and Sesleria autumnalis coverage. Taller Quercus seedlings required more light than both of its strongest competitors and were positively related to humid soils and less rocky sites. Ungulate overbrowsing significantly impeded natural regeneration. The results indicate a satisfactory Quercus density for conversion and the importance of advanced regeneration, which should be gradually, but persistently, released by progressively widening gaps. Full article

(This article belongs to the Special Issue Role of Gap Factors in Forest Tree Regeneration and Plant Communities)

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Location of eight study areas where 44 research plots were installed. Full article ">Figure 2
Sketch of plot with arrangement of herb subplots (H1–H6) in white and Quercus subplots (Q1–Q12) in grey. Full article ">Figure 3
Box and whisker plots of relative diffuse light, topsoil moisture in 2012 and herb and shrub coverage according to stand type. The numbers above the whiskers denote significance levels between stand types. K–W stands for the Kruskal–Wallis test. Full article ">Figure 4
(a) Seedling species composition according to height class in the herb subplots. (b) Percentage of seedlings with terminal shoot browsed according to tree species and height class. Full article ">Figure 5
Ordination biplot of a principal coordinate analysis (PCoA) for vascular plant cover in the herb layer (Bray–Curtis distance measure) in 2012. Grey circles represent the location of plots on the first and second axes of the PCoA analysis. The arrows show the direction of the gradient, and the length of the arrows is proportional to the correlation between the variable and the ordination. Only factors with a p-value < 0.05 are plotted, with the exception of rockiness (p = 0.1). Smaller angles between the arrow and axis represent a higher correlation between the two values. Green arrows represent regeneration density per species and developmental stage, e.g., F.orn.20 for F. ornus short seedlings. Dark blue arrows represent measured ecological factors, e.g., CWD coverage, LFH thickness, and minimum and average distance to Quercus seed trees. Light blue arrows are for Landolt phytoindication values for light, continentality, temperature, reaction, nutrients, and soil moisture. Full article ">Figure 6
Mean seedling density per m2 (error bars represent the standard error) according to the main tree species, height class, stand type, and subplot type. Full article ">

19 pages, 6651 KiB

Open AccessArticle

Measuring the Strength of Root-Reinforced Soil on Steep Natural Slopes Using the Corkscrew Extraction Method

by Gerrit Meijer, Glyn Bengough, Jonathan Knappett, Kenneth Loades and Bruce Nicoll

Forests 2019, 10(12), 1135; https://doi.org/10.3390/f10121135 - 12 Dec 2019

Cited by 7 | Viewed by 3043

Abstract

Roots can help to stabilise slopes against landslides and anchor trees against wind loading, but their mechanical contribution to the strength of soil is difficult to rapidly quantify under field conditions. A new field measurement method, quantifying the shear strength of rooted soil [...] Read more.

Roots can help to stabilise slopes against landslides and anchor trees against wind loading, but their mechanical contribution to the strength of soil is difficult to rapidly quantify under field conditions. A new field measurement method, quantifying the shear strength of rooted soil by measuring the resistance against extraction of soil cores using a large corkscrew device, was tested across three heterogeneous slopes (unforested, forested and clearfelled) in Scotland. The presence of roots significantly increased the measured shear strength in the surface layer of the Sitka spruce forested slope. Differences in strength between the three areas were however not significant. This could be attributed to the large variation in the soil component of the combined root–soil shear strength, which was strongly affected by variations in both soil density and gravel content. Measured strength on these natural slopes were much more variable compared to previously investigated sites. These results highlight the importance of investigating the variation in soil strength during root-reinforcement measurements, and furthermore demonstrate the need for a sufficiently large number of tests to address this variation. The corkscrew provides rapid estimation of root-reinforced soil shear strength on sites with difficult accessibility. Compared to the more conventional shear vane method, which yielded comparable soil strength results, the corkscrew proved more suitable in stony soil layers and has the additional benefit of simultaneously extracting small (rooted) soil samples that could be used for further root and soil analysis. It therefore proved a useful and effective field tool for use when a rapid estimation of root-reinforced soil shear strength is required. Full article

(This article belongs to the Section Forest Ecology and Management)

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14 pages, 1833 KiB

Open AccessArticle

Changes in Plant Functional Groups during Secondary Succession in a Tropical Montane Rain Forest

by Kexin Fan, Jing Tao, Lipeng Zang, Jie Yao, Jihong Huang, Xinghui Lu, Yi Ding, Yue Xu and Runguo Zang

Forests 2019, 10(12), 1134; https://doi.org/10.3390/f10121134 - 12 Dec 2019

Cited by 4 | Viewed by 2940

Abstract

Aggregating diverse plant species into a few functional groups based on functional traits provides new insights for promoting landscape planning and conserving biodiversity in species-diverse regions. Ecophysiological traits are the basis of the functioning of an ecosystem. However, studies related to the identification [...] Read more.

Aggregating diverse plant species into a few functional groups based on functional traits provides new insights for promoting landscape planning and conserving biodiversity in species-diverse regions. Ecophysiological traits are the basis of the functioning of an ecosystem. However, studies related to the identification of functional groups based on plant ecophysiological traits in tropical forests are still scarce because of the inherent difficulties in measuring them. In this study, we measured five ecophysiological traits: net photosynthetic capacity (A_max), maximum stomatal conductance (g_max), water use efficiency (WUE), transpiration rate (Trmmol), and specific leaf areas (SLA) for 87 plant species dominant in a chronosequence of secondary succession, using four time periods (5 year-primary, 15 year-early, and 40 year-middle successional stages after clear cutting and old growth) in the tropical montane rainforest on Hainan Island, China. These species were grouped using hierarchical cluster analysis and non-metric multidimensional scaling. Finally, the changes in the composition of functional groups and species richness along the chronosequence were analyzed. Results showed that the plant species in the tropical montane rainforest could be classified into eight distinct functional groups. The richness of functional groups was low during the initial early stage and increased as the early and middle stages progressed, and then declined in the late successional stage. The dominant functional groups in the primary stages had the highest A_max, g_max, Trmmol, and SLA, as well as the lowest WUE, while those in the early and middle successional stages had functional traits at a moderate level, and at the late stage they had the lowest A_max, g_max, Trmmol, and SLA, and highest WUE. Our study showed that the diverse plant species in the tropical montane rainforest could be grouped into a few functional groups according to major ecophysiological traits, and the composition and relative abundance of different groups changed with the successional dynamics of the forest ecosystem. Full article

(This article belongs to the Section Forest Ecology and Management)

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15 pages, 3804 KiB

Open AccessArticle

Divergent Growth Responses to Warming between Stand-Grown and Open-Grown Trees in a Dryland Montane Forest in Northwestern China

by Lei Zhang, Hao Shi, Pengtao Yu, Yanhui Wang, Shufen Pan, Bin Wang and Hanqin Tian

Forests 2019, 10(12), 1133; https://doi.org/10.3390/f10121133 - 11 Dec 2019

Cited by 8 | Viewed by 2380

Abstract

Dryland montane forests conserve water for people living in the fluvial plains. The fate of these forests under climate warming is strongly affected by local environmental factors. The question remains of how internal factors contribute to climate change impacts on forest growth in [...] Read more.

Dryland montane forests conserve water for people living in the fluvial plains. The fate of these forests under climate warming is strongly affected by local environmental factors. The question remains of how internal factors contribute to climate change impacts on forest growth in these regions. Here, we investigated tree ring records for similar-aged stand-grown trees and their neighboring open-grown trees at elevation in a dryland montane forest (Picea crassifolia Kom.) in northwestern China. The growth rate of open-grown trees is much higher than their neighboring stand-grown trees across the entire elevation gradient, and the lower the altitude, the greater the difference. Open-grown trees at different elevations showed similar growth patterns, as tree growth at all sites was accelerated over time. In contrast, growth patterns of stand-grown trees were divergent at different altitudes, as growth at high elevations (3100–3300 m a.s.l.) was accelerated, whereas growth at low elevations (2700–2900 m a.s.l.) became stable after the year 1990. Analysis of growth–climate relationships indicated that warming promoted open-grown tree growth across the entire altitude gradient, and also stand-grown tree growth at high elevations, but negatively affected the growth of stand-grown trees at low elevations. Water scarcity can be exacerbated by competition within forests, inhibiting the warming-induced benefits on tree growth. Moving window correlation analysis suggested the negative effect of warming on tree growth at low elevations was diminished after the late 1990s, as the drought stress was alleviated. Our research shows the divergent growth responses to warming of stand-grown and open-grown trees along elevation. It reveals effects of internal factors in determining tree growth response to warming and holds the potential to aid forest management and ecosystem models in responding to climate change. Full article

(This article belongs to the Section Forest Ecology and Management)

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Figure 1
Locations of the sampling area and its nearby meteorological station. The inset in the upper right of the figure is an abridged general view of sampling sites. Full article ">Figure 2
Trends of the annual (a) mean temperature, (b) total precipitation, and (c) standardized precipitation evapotranspiration index (SPEI) in the study area during the period 1960–2013. Dashed lines represent the linear regression, while ① and ② indicate the regression line of SPEI for the periods 1960–2013 and 1997–2013, respectively. Full article ">Figure 3
BAI chronologies of (a) stand-grown and (b) open-grown trees along the elevation gradient. Gray lines indicate the yearly measurements and black dashed lines indicate the 15-year moving average. Full article ">Figure 4
Percentage growth change (%GC) of (a) stand-grown and (b) open-grown trees. Major (100%) and minor (50%) growth releases are indicated by the black and gray lines, respectively. Full article ">Figure 5
Ratios of annual BAI values between open-grown trees and their neighboring stand-grown trees at each elevation over the common period 1964–2013. Full article ">Figure 6
Correlation coefficients of BAI chronologies for (a,b) temperature, (c,b) precipitation, and (e,f) standardized precipitation evapotranspiration index (SPEI) for (a,c,e) stand-grown and (b,d,f) open-grown trees at different elevations during the period 1964–2013. Dashed lines indicate a significance level of 0.05. The p indicates the climate variables of the previous year, c indicates the climate variables of the current year, and c5−9 indicates the current growing season (May to September). Full article ">Figure 7
Moving correlations (25-year window) between BAI chronologies and growing season (May to September) mean temperatures for (a) stand-grown and (b) open-grown trees from 1964 to 2013. Dashed lines indicate a significant level of 0.05. Full article ">

17 pages, 2057 KiB

Open AccessArticle

Carbon Limitation and Drought Sensitivity at Contrasting Elevation and Competition of Abies pinsapo Forests. Does Experimental Thinning Enhance Water Supply and Carbohydrates?

by Victor Lechuga, Vinicio Carraro, Benjamín Viñegla, José Antonio Carreira and Juan Carlos Linares

Forests 2019, 10(12), 1132; https://doi.org/10.3390/f10121132 - 11 Dec 2019

Cited by 11 | Viewed by 3208

Abstract

Stand-level competition and local climate influence tree responses to increased drought at the regional scale. To evaluate stand density and elevation effects on tree carbon and water balances, we monitored seasonal changes in sap-flow density (SFD), gas exchange, xylem water potential, secondary growth, [...] Read more.

Stand-level competition and local climate influence tree responses to increased drought at the regional scale. To evaluate stand density and elevation effects on tree carbon and water balances, we monitored seasonal changes in sap-flow density (SFD), gas exchange, xylem water potential, secondary growth, and non-structural carbohydrates (NSCs) in Abies pinsapo. Trees were subjected to experimental thinning within a low-elevation stand (1200 m), and carbon and water balances were compared to control plots at low and high elevation (1700 m). The hydraulic conductivity and the resistance to cavitation were also characterized, showing relatively high values and no significant differences among treatments. Trees growing at higher elevations presented the highest SFD, photosynthetic rates, and secondary growth, mainly because their growing season was extended until summer. Trees growing at low elevation reduced SFD during late spring and summer while SFD and secondary growth were significantly higher in the thinned stands. Declining NSC concentrations in needles, branches, and sapwood suggest drought-induced control of the carbon supply status. Our results might indicate potential altitudinal shifts, as better performance occurs at higher elevations, while thinning may be suitable as adaptive management to mitigate drought effects in endangered Mediterranean trees. Full article

(This article belongs to the Section Forest Ecophysiology and Biology)

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Seasonal dynamics of air temperature (a), air vapor pressure deficit (b), and volumetric soil water content (c) recorded in control plots at low elevation (CL), thinned plots at low elevation (TL), and control plots at high elevation (CH). Vertical lines indicate the sampling days for gas exchange, xylem water potential, and non-structural carbohydrates. Error bars indicate the standard error between plot replicates. Full article ">Figure 2
Mean monthly sap flow density (SFD) in control low elevation (CL), thinning low elevation (TL), and control high elevation (CH) stands. Means ± standard errors of the daily data are shown. Different letters indicate significant differences by repeated measures ANOVA between treatments at a given month. Full article ">Figure 3
Relationship observed between mean monthly sap flux density (SFD) and (a) soil water content (SWC), and (b) air vapor pressure deficit (VPD) using polynomial quadratic relationships. SWC: CL, R2 = 0.50; p = 0.0014; TL, R2 = 0.75; p < 0.0001; CH, R2 = 0.51; p = 0.0012. VPD: CH, R2 = 0.80; p < 0.0001. Dashed lines indicate non-significant relationships. Full article ">Figure 4
Xylem cavitation vulnerability estimated as the percentage loss of conductivity (PLC). Experimental loss in hydraulic conductivity (a) was obtained by injection pressure. Theoretical dynamics (b) were estimated from the adjusted parameters using Equation (2) [<a href="#B29-forests-10-01132" class="html-bibr">29</a>]. CL, n = 7; TL, n = 7; CH, n = 4. Error bars show the standard error. Dashed lines show the 12% (PLC12), 50% (PLC50), and 88% (PLC88) loss of conductivity, respectively. Full article ">Figure 5
Accumulated radial growth (a), photosynthesis rate, AN (b), stomatal conductance, gS (c), and xylem water potential, Ψ (d), in control low elevation (CL), thinning low elevation (TL), and control high elevation (CH). Means ± standard errors are shown. Within each date, different letters indicate significant differences (ANOVA) between treatments at a given sampling. Full article ">Figure 6
Temporal dynamics of non-structural carbohydrates (NSCs) in needles (a–c), branches (d–f), and stem sapwood (g–i). Upper panels show the soluble sugars (a,d,g). Middle panels show the starch (b,e,h). Bottom panels show the total NSCs (c,f,i). CL, n = 5; TL), n = 5; CH, n = 6. Error bars show the standard error. Different letters indicate significant differences (ANOVA) between treatments at a given sampling. Full article ">

14 pages, 11752 KiB

Open AccessArticle

Effects of Salt on Root Aeration, Nitrification, and Nitrogen Uptake in Mangroves

by Yan Zhao, Xun Wang, Youshao Wang, Zhaoyu Jiang, Xiaoyu Ma, Aniefiok Ini Inyang and Hao Cheng

Forests 2019, 10(12), 1131; https://doi.org/10.3390/f10121131 - 11 Dec 2019

Cited by 20 | Viewed by 4059

Abstract

The potential effects of salt on the growth, root anatomy, radial oxygen loss (ROL), and nitrogen (N) dynamics in mangroves were investigated using the seedlings of Avicennia marina (Forsk.) Vierh. The results showed that a moderate salinity (200 mM NaCl) appeared to have [...] Read more.

The potential effects of salt on the growth, root anatomy, radial oxygen loss (ROL), and nitrogen (N) dynamics in mangroves were investigated using the seedlings of Avicennia marina (Forsk.) Vierh. The results showed that a moderate salinity (200 mM NaCl) appeared to have little negative effect on the growth of A. marina. However, higher salt stresses (400 and 600 mM NaCl) significantly inhibited the biomass yield. Concentrations of N in the roots and leaves decreased sharply with increasing salinity. Nevertheless, the presence of salt directly altered root anatomy (e.g., reduced root porosity and promoted suberization within the exodermis and endodermis), leading to a significant reduction in ROL. The results further showed that reduced ROL induced by salt could restrain soil nitrification, resulting in less ammonia-oxidizing archaea and bacteria (AOA and AOB) gene copies and lower concentrations of NO₃⁻ in the soils. While increased root suberization induced by salt inhibited NH₄⁺ and NO₃⁻ uptake and influx into the roots. In summary, this study indicated that inhibited root aeration may be a defense response to salt, however these root symptoms were not advantageous for rhizosphere nitrification and N uptake by A. marina. Full article

(This article belongs to the Special Issue Climate Change Impacts on the Ecosystem Functions and Services of Mangrove Forests)

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Concentrations of Na+ (a) and total N (b) in tissues of A. marina after 2-month exposure to control, 200, 400, and 600 mM NaCl. The different letters indicate significant differences at p < 0.05. Full article ">Figure 2
Radial oxygen loss (ROL) from different root regions in A. marina after a 2-month exposure to salt. The different letters in the same root position indicate significant differences of ROL rates among salt treatments at p < 0.05. Full article ">Figure 3
Root suberization in A. marina subjected to salt. Root sections (0.5, 2, and 4 cm from root the tip, bar = 50 µm) made from control and salt treated (600 mM NaCl for 1 week) roots. (a) Suberization within the exodermis, green-yellow fluorescence indicated suberization, and the formation of biseriate and suberized exodermis (BSEX) is highlighted with the arrows. (b) Characteristics of outer cell layers and the formation of the second additional exodermis. (d) Suberization within endodermis is shown in figure, and the arrows indicate the deposition of suberin within endodermal cell walls. The statistical analysis of suberization within the exodermis (c) and the endodermis (e), n = 8, the different letters indicate significant differences between treatments at p < 0.05. The abbreviations in the figures are the following: BEX: biseriate exodermis; BSEX: biseriate and suberized exodermis; UEX: uniseriate exodermis; ep: epidermis. Full article ">Figure 4
The effects of salt on N dynamics and microenvironment in soils planted with A. marina. (a) NH4+ concentrations. (b) NO3− contents. (c) Soil redox potentials. (d) Nitrification activity. The abundances of AOA (e) and AOB (f). The different letters indicate significant differences among salt treatments at p < 0.05. Full article ">Figure 5
Fluxes of NH4+ (a) and NO3− (b) at the root surface in A. marina as affected by salt. The different letters indicate significant differences among salt treatments at p < 0.05. Full article ">

15 pages, 3263 KiB

Open AccessArticle

Anatomy of the Windmill Palm (Trachycarpus fortunei) and Its Application Potential

by Jiawei Zhu, Jing Li, Chuangui Wang and Hankun Wang

Forests 2019, 10(12), 1130; https://doi.org/10.3390/f10121130 - 10 Dec 2019

Cited by 13 | Viewed by 3149

Abstract

The windmill palm (Trachycarpus fortunei (Hook.) H. Wendl.) is widely distributed and is an important potential source of lignocellulosic materials. The lack of knowledge on the anatomy of the windmill palm has led to its inefficient use. In this paper, the diversity [...] Read more.

The windmill palm (Trachycarpus fortunei (Hook.) H. Wendl.) is widely distributed and is an important potential source of lignocellulosic materials. The lack of knowledge on the anatomy of the windmill palm has led to its inefficient use. In this paper, the diversity in vascular bundle types, shape, surface, and tissue proportions in the leaf sheaths and stems were studied with digital microscopy and scanning electron microscope (SEM). Simultaneously, fiber dimensions, fiber surfaces, cell wall ultrastructure, and micromechanics were studied with atomic force microscopy (AFM) and a nanoindenter. There is diversity among vascular bundles in stems and leaf sheaths. All vascular bundles in the stems are type B (circular vascular tissue (VT) at the edge of the fibrous sheath (FS)) while the leaf sheath vascular bundles mostly belong to type C (aliform (VT) at the center of the (FS), with the wings of the (VT) extending to the edge of the vascular bundles). In addition, variation among the vascular bundle area and tissue proportion in the radial direction of the stems and different layers of the leaf sheaths is also significant. Microscopically, the fibers in the stem are much wider and longer than that in the leaf sheath. The secondary walls of stem fibers are triple layered while those in the leaf sheath are double layered. The indentation modulus and hardness of the cell wall of leaf sheath fibers are higher than that of the stem. An independent sample t-test also showed a significant difference between stems and leaf sheaths. All this indicates that windmill palm stems and leaf sheaths are two different materials and have different application prospects. Full article

(This article belongs to the Special Issue Wood Productions and Renewable Materials)

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