Forest canopies are often stratified by species; little is known about the depth distribution of ... more Forest canopies are often stratified by species; little is known about the depth distribution of tree roots in mixed stands because they are not readily identified by species. We used diagnostic characteristics of wood anatomy and gross morphology to distinguish roots by species and applied these methods to test for differences in the rooting depth of sugar maple (Acer saccharum Marsh.), American beech (Fagus grandifolia Ehrh.), and yellow birch (Betula alleghaniensis Britt.) in two northern hardwood forests. We also distinguished hobblebush (Viburnum lantanoides Michx.) and white ash (Fraxinus americana L.) roots. Analysis of plastid DNA fragment lengths confirmed that 90% of the roots were correctly identified. The vertical distribution of fine roots of these species differed by 2–4 cm in the median root depth (P = 0.03). There was a significant difference in the distribution of roots by size class, with fine roots (0–2 mm) being more concentrated near the soil surface than coarser roots (2–5 mm; P = 0.004). The two sites differed by <2 cm in median rooting depths (P = 0.02). The visual identification of roots for the main tree species in the northern hardwood forest allows species specific questions to be posed for belowground processes. Résumé : La stratification des essences est fréquente dans le couvert forestier. La distribution verticale des racines des arbres est peu connue dans les peuplements mélangés parce que l'identification des racines n'est pas facile. Nous avons utilisés les caractéristiques diagnostiques de l'anatomie et de la morphologie grossière du bois pour différencier les racines selon l'espèce et nous avons appliqués ces méthodes pour tester les différences de profondeur d'enracinement de l'e ´rable a ` sucre (Acer saccharum Marsh.), du hêtre d'Amérique (Fagus grandifolia Ehrh.) et du bouleau jaune (Betula alleghaniensis Britt.) dans deux forêts feuillues nordiques. Nous avons aussi distingué les racines de la viorne bois-d'orignal (Viburnum lantanoides Michx.) et du frêne blanc (Fraxinus americana L.). L'analyse de la longueur des fragments d'ADN des plastes a confirmé que 90 % des racines ont e ´té correctement identifiées. La distribution verticale des racines fines e ´taient significativement différente selon l'espèce (P = 0,03) et la différence variait de deux a ` quatre cm en comparant la profon-deur médiane des racines. Il y avait une différence significative dans la distribution des racines selon la classe de dimension : les racines fines (0–2 mm) e ´taient plus concentrées près de la surface du sol que les plus grosses racines (2– 5 mm) (P = 0,004). La profondeur médiane d'enracinement différait de moins de deux cm entre les deux stations (P = 0,02). L'identification visuelle des racines des principales espèces d'arbres dans la forêt feuillue nordique permet de formuler des questions propres a ` chaque espèce au sujet des processus souterrains. [Traduit par la Rédaction]
... Brendan K. Naples Æ Melany C. Fisk ... Mature forest composition is typical of northern hardw... more ... Brendan K. Naples Æ Melany C. Fisk ... Mature forest composition is typical of northern hardwoods, with an overstory dominated by sugar maple (Acer saccharum Marsh), American beech (Fagus grandi-folia Ehrh.), and yellow birch (Betula alleghaniensis Britton). ...
ABSTRACT Limitations to the respiratory activity of heterotrophic soil microorganisms exert impor... more ABSTRACT Limitations to the respiratory activity of heterotrophic soil microorganisms exert important controls of CO2 efflux from soils. In the northeastern US, ecosystem nutrient status varies across the landscape and changes with forest succession following disturbance, likely impacting soil microbial processes regulating the transformation and emission of carbon (C). We tested whether nitrogen (N) or phosphorus (P) limit the mineralization of soil organic C (SOC) or that of added C sources in the Oe horizon of successional and mature northern hardwood forests in three locations in central New Hampshire, USA. Added N reduced mineralization of C from SOC and from added leaf litter and cellulose. Added P did not affect mineralization from SOC; however, it did enhance mineralization of litter- and cellulose- C in organic horizons from all forest locations. Added N increased microbial biomass N and K2SO4-extractable DON pools, but added P had no effect. Microbial biomass C increased with litter addition but did not respond to either nutrient. The direction of responses to added nutrients was consistent among sites and between forest ages. We conclude that in these organic horizons limitation by N promotes mineralization of C from SOC, whereas limitation by P constrains mineralization of C from new organic inputs. We also suggest that N suppresses respiration in these organic horizons either by relieving the N limitation of microbial biomass synthesis, or by slowing turnover of C through the microbial pool; concurrent measures of microbial growth and turnover are needed to resolve this question.
Background/Question/Methods Concern about the role of acidic deposition in the long-term depletio... more Background/Question/Methods Concern about the role of acidic deposition in the long-term depletion of calcium (Ca) in soil and vegetation led to the initiation of watershed, plot and mesocosm-scale Ca addition experiments at the Hubbard Brook Experimental Forest (HBEF) in New Hampshire. An 11.8 ha watershed (W1) was treated with 850 kg Ca/ha of the Ca-silicate mineral (wollastonite) to restore the Ca that was estimated to have leached from the ecosystem by 50 years of acidic deposition. We expected that the Ca addition and associated pH increase would stimulate microbial nitrogen cycling. Surprisingly, we observed declines in soil inorganic nitrogen (N) and potential net N mineralization, and no change in either net or gross nitrification rates in the treated watershed. To explore these responses in more detail, small (5 m x 5 m) field plots and plant-free mesocosms were established in 2006 with four treatments involving fertilization with Ca (850 or 4,250 kg/ha) as wollastonite, ph...
Acid deposition can deplete soil calcium (Ca) and be detrimental to the health of some forests. W... more Acid deposition can deplete soil calcium (Ca) and be detrimental to the health of some forests. We examined effects of soil Ca and phosphorus (P) availability on microbial activity and nitrogen (N) transformations in a plot-scale nutrient addition experiment at the Hubbard Brook Experimental Forest in New Hampshire, USA. We tested the hypotheses that (1) microbial activity and N transformations
The extent to which complex interrelationships between plants and microorganisms influence organi... more The extent to which complex interrelationships between plants and microorganisms influence organic matter dynamics is critical to our understanding of global C cycles in changing environments. We examined the hypothesis that patterns of soil microbial activity and functional composition differ among vegetation types in northern peatland ecosystems. Microbial characteristics were compared among peatlands differing in plant growth form (tree, shrub/moss,
... Brendan K. Naples Æ Melany C. Fisk ... Mature forest composition is typical of northern hardw... more ... Brendan K. Naples Æ Melany C. Fisk ... Mature forest composition is typical of northern hardwoods, with an overstory dominated by sugar maple (Acer saccharum Marsh), American beech (Fagus grandi-folia Ehrh.), and yellow birch (Betula alleghaniensis Britton). ...
Background/Question/Methods Theory suggests that greater effort should be allocated to roots and ... more Background/Question/Methods Theory suggests that greater effort should be allocated to roots and mycorrhizae for nutrient acquisition in settings where nutrient availability is low. Fine root biomass gives one indication of plant allocation to acquisition of belowground resources. Soil respiration is another indicator, since it reflects carbon allocation to the growth and activity of roots and mycorrhizae. We measured root biomass once and soil respiration for two growing seasons in three sites in the White Mountains of New Hampshire, USA: Jeffers Brook is the most fertile, Hubbard Brook is intermediate, and Bartlett is the least fertile. At each site, we had one mature stand (~100 years post-harvest) and one young stand (~30 years post-harvest). We also measured litterfall, to account for soil respiration not coming from allocation to roots and mycorrhizae. We quantified net N mineralization and resin-available P as indicators of fertility. We predicted that fine root biomass and b...
Background/Question/Methods . Although temperate forests have long been thought to be primarily n... more Background/Question/Methods . Although temperate forests have long been thought to be primarily nitrogen limited, resource optimization theory suggests that ecosystem productivity should be co-limited by multiple nutrients. In northeastern North America, air pollution and forest harvesting disturbance elevate N availability and contribute to the likelihood of P limitation. We explored the relative limitation by N and P in northern hardwood forests by simulating productivity with the Multiple Element Limitation Model (MEL) and by testing several indices of nutrient availability and acquisition, in replicate young (26-30 years) and mature (>100 years) forests in the Bartlett Experimental Forest (BEF), NH. Results/Conclusions . The model predicted a greater response of aboveground productivity to N+P than N or P alone. In older stands, MEL predicted a greater response to N than to P addition, but in younger stands, the supply of N from detritus was predicted to be sufficient to crea...
Background/Question/Methods Nonnative species invasions are a major component of global change. I... more Background/Question/Methods Nonnative species invasions are a major component of global change. In the eastern deciduous of forests of North America, nonnative earthworm invasions have been transforming the structure and function of forest floor environments and having complex effects on the plants and animals that depend on those environments. Earthworms are an important prey to many predators including woodland salamanders, and prior research shows earthworm invasions drive spatial and temporal variation in salamander abundance and prey availability. We used double-labeled leaf litter applied to forest 72 replicated plots with and without earthworms to measure how earthworm invasions altered the rates and total amounts of energy and nutrients that move from leaf litter to salamander populations. Results/Conclusions Red-backed salamanders (Plethodon cinereus) occupied 100% of the 72 study plots, and the number of salamanders uniquely marked during pre-monitoring ranged from 2-10 pe...
Background/Question/Methods Although temperate forests have long been thought to be primarily nit... more Background/Question/Methods Although temperate forests have long been thought to be primarily nitrogen limited, resource optimization theory suggests that ecosystem productivity should be co-limited by multiple nutrients. Mechanisms for maintaining stochiometric balance in ecosystems include nutrient resorption in senescing tissues, uptake by plants or microbes, and feedbacks on soil nutrient mineralization. In the northeastern USA, air pollution and forest harvesting disturbance elevate nitrogen availability and contribute to the likelihood of phosphorus limitation. We examined foliar resorption of N and P in 6 northern hardwood stands with differing native soil fertility and tested whether resorption of one nutrient depended on the availability of the other. We also began a long-term nutrient manipulation experiment, fertilizing 13 stands with 30 kg/ha N, 10 kg/ha P, or N and P together. We examined nitrogen and phosphorus availability (assayed with buried ion-exchange resin strip...
Background/Question/Methods The weathering of parent material is the primary source of Ca, Mg, K,... more Background/Question/Methods The weathering of parent material is the primary source of Ca, Mg, K, and P in soils and ecosystems. The influence of parent material on N cycling is less often investigated. The objective of this study was to examine foliar nutrients and soil mineralization in relation to parent material in 20 sites in the White Mountains of New Hampshire, USA. We measured concentrations of total Ca, Mg, K, and P in C horizon material collected in 1-3 soil pits per site. Nitrogen mineralization was measured in laboratory incubations of Oe horizon material. Leaf litter was collected and analyzed for N, P, Ca, Mg, and K by species: sugar maple (Acer saccharum Marsh.), American beech (Fagus grandifolia Ehrh.), yellow birch (Betula alleghaniensis Britt.), white birch (Betula papyrifera Marsh.), red maple (Acer rubrum L.), and pin cherry (Prunus pensylvanica). Hierarchical cluster analysis was applied to nutrients in the C horizon. A two-way ANOVA was used to investigate the ...
Forest canopies are often stratified by species; little is known about the depth distribution of ... more Forest canopies are often stratified by species; little is known about the depth distribution of tree roots in mixed stands because they are not readily identified by species. We used diagnostic characteristics of wood anatomy and gross morphology to distinguish roots by species and applied these methods to test for differences in the rooting depth of sugar maple (Acer saccharum Marsh.), American beech (Fagus grandifolia Ehrh.), and yellow birch (Betula alleghaniensis Britt.) in two northern hardwood forests. We also distinguished hobblebush (Viburnum lantanoides Michx.) and white ash (Fraxinus americana L.) roots. Analysis of plastid DNA fragment lengths confirmed that 90% of the roots were correctly identified. The vertical distribution of fine roots of these species differed by 2–4 cm in the median root depth (P = 0.03). There was a significant difference in the distribution of roots by size class, with fine roots (0–2 mm) being more concentrated near the soil surface than coarser roots (2–5 mm; P = 0.004). The two sites differed by <2 cm in median rooting depths (P = 0.02). The visual identification of roots for the main tree species in the northern hardwood forest allows species specific questions to be posed for belowground processes. Résumé : La stratification des essences est fréquente dans le couvert forestier. La distribution verticale des racines des arbres est peu connue dans les peuplements mélangés parce que l'identification des racines n'est pas facile. Nous avons utilisés les caractéristiques diagnostiques de l'anatomie et de la morphologie grossière du bois pour différencier les racines selon l'espèce et nous avons appliqués ces méthodes pour tester les différences de profondeur d'enracinement de l'e ´rable a ` sucre (Acer saccharum Marsh.), du hêtre d'Amérique (Fagus grandifolia Ehrh.) et du bouleau jaune (Betula alleghaniensis Britt.) dans deux forêts feuillues nordiques. Nous avons aussi distingué les racines de la viorne bois-d'orignal (Viburnum lantanoides Michx.) et du frêne blanc (Fraxinus americana L.). L'analyse de la longueur des fragments d'ADN des plastes a confirmé que 90 % des racines ont e ´té correctement identifiées. La distribution verticale des racines fines e ´taient significativement différente selon l'espèce (P = 0,03) et la différence variait de deux a ` quatre cm en comparant la profon-deur médiane des racines. Il y avait une différence significative dans la distribution des racines selon la classe de dimension : les racines fines (0–2 mm) e ´taient plus concentrées près de la surface du sol que les plus grosses racines (2– 5 mm) (P = 0,004). La profondeur médiane d'enracinement différait de moins de deux cm entre les deux stations (P = 0,02). L'identification visuelle des racines des principales espèces d'arbres dans la forêt feuillue nordique permet de formuler des questions propres a ` chaque espèce au sujet des processus souterrains. [Traduit par la Rédaction]
... Brendan K. Naples Æ Melany C. Fisk ... Mature forest composition is typical of northern hardw... more ... Brendan K. Naples Æ Melany C. Fisk ... Mature forest composition is typical of northern hardwoods, with an overstory dominated by sugar maple (Acer saccharum Marsh), American beech (Fagus grandi-folia Ehrh.), and yellow birch (Betula alleghaniensis Britton). ...
ABSTRACT Limitations to the respiratory activity of heterotrophic soil microorganisms exert impor... more ABSTRACT Limitations to the respiratory activity of heterotrophic soil microorganisms exert important controls of CO2 efflux from soils. In the northeastern US, ecosystem nutrient status varies across the landscape and changes with forest succession following disturbance, likely impacting soil microbial processes regulating the transformation and emission of carbon (C). We tested whether nitrogen (N) or phosphorus (P) limit the mineralization of soil organic C (SOC) or that of added C sources in the Oe horizon of successional and mature northern hardwood forests in three locations in central New Hampshire, USA. Added N reduced mineralization of C from SOC and from added leaf litter and cellulose. Added P did not affect mineralization from SOC; however, it did enhance mineralization of litter- and cellulose- C in organic horizons from all forest locations. Added N increased microbial biomass N and K2SO4-extractable DON pools, but added P had no effect. Microbial biomass C increased with litter addition but did not respond to either nutrient. The direction of responses to added nutrients was consistent among sites and between forest ages. We conclude that in these organic horizons limitation by N promotes mineralization of C from SOC, whereas limitation by P constrains mineralization of C from new organic inputs. We also suggest that N suppresses respiration in these organic horizons either by relieving the N limitation of microbial biomass synthesis, or by slowing turnover of C through the microbial pool; concurrent measures of microbial growth and turnover are needed to resolve this question.
Background/Question/Methods Concern about the role of acidic deposition in the long-term depletio... more Background/Question/Methods Concern about the role of acidic deposition in the long-term depletion of calcium (Ca) in soil and vegetation led to the initiation of watershed, plot and mesocosm-scale Ca addition experiments at the Hubbard Brook Experimental Forest (HBEF) in New Hampshire. An 11.8 ha watershed (W1) was treated with 850 kg Ca/ha of the Ca-silicate mineral (wollastonite) to restore the Ca that was estimated to have leached from the ecosystem by 50 years of acidic deposition. We expected that the Ca addition and associated pH increase would stimulate microbial nitrogen cycling. Surprisingly, we observed declines in soil inorganic nitrogen (N) and potential net N mineralization, and no change in either net or gross nitrification rates in the treated watershed. To explore these responses in more detail, small (5 m x 5 m) field plots and plant-free mesocosms were established in 2006 with four treatments involving fertilization with Ca (850 or 4,250 kg/ha) as wollastonite, ph...
Acid deposition can deplete soil calcium (Ca) and be detrimental to the health of some forests. W... more Acid deposition can deplete soil calcium (Ca) and be detrimental to the health of some forests. We examined effects of soil Ca and phosphorus (P) availability on microbial activity and nitrogen (N) transformations in a plot-scale nutrient addition experiment at the Hubbard Brook Experimental Forest in New Hampshire, USA. We tested the hypotheses that (1) microbial activity and N transformations
The extent to which complex interrelationships between plants and microorganisms influence organi... more The extent to which complex interrelationships between plants and microorganisms influence organic matter dynamics is critical to our understanding of global C cycles in changing environments. We examined the hypothesis that patterns of soil microbial activity and functional composition differ among vegetation types in northern peatland ecosystems. Microbial characteristics were compared among peatlands differing in plant growth form (tree, shrub/moss,
... Brendan K. Naples Æ Melany C. Fisk ... Mature forest composition is typical of northern hardw... more ... Brendan K. Naples Æ Melany C. Fisk ... Mature forest composition is typical of northern hardwoods, with an overstory dominated by sugar maple (Acer saccharum Marsh), American beech (Fagus grandi-folia Ehrh.), and yellow birch (Betula alleghaniensis Britton). ...
Background/Question/Methods Theory suggests that greater effort should be allocated to roots and ... more Background/Question/Methods Theory suggests that greater effort should be allocated to roots and mycorrhizae for nutrient acquisition in settings where nutrient availability is low. Fine root biomass gives one indication of plant allocation to acquisition of belowground resources. Soil respiration is another indicator, since it reflects carbon allocation to the growth and activity of roots and mycorrhizae. We measured root biomass once and soil respiration for two growing seasons in three sites in the White Mountains of New Hampshire, USA: Jeffers Brook is the most fertile, Hubbard Brook is intermediate, and Bartlett is the least fertile. At each site, we had one mature stand (~100 years post-harvest) and one young stand (~30 years post-harvest). We also measured litterfall, to account for soil respiration not coming from allocation to roots and mycorrhizae. We quantified net N mineralization and resin-available P as indicators of fertility. We predicted that fine root biomass and b...
Background/Question/Methods . Although temperate forests have long been thought to be primarily n... more Background/Question/Methods . Although temperate forests have long been thought to be primarily nitrogen limited, resource optimization theory suggests that ecosystem productivity should be co-limited by multiple nutrients. In northeastern North America, air pollution and forest harvesting disturbance elevate N availability and contribute to the likelihood of P limitation. We explored the relative limitation by N and P in northern hardwood forests by simulating productivity with the Multiple Element Limitation Model (MEL) and by testing several indices of nutrient availability and acquisition, in replicate young (26-30 years) and mature (>100 years) forests in the Bartlett Experimental Forest (BEF), NH. Results/Conclusions . The model predicted a greater response of aboveground productivity to N+P than N or P alone. In older stands, MEL predicted a greater response to N than to P addition, but in younger stands, the supply of N from detritus was predicted to be sufficient to crea...
Background/Question/Methods Nonnative species invasions are a major component of global change. I... more Background/Question/Methods Nonnative species invasions are a major component of global change. In the eastern deciduous of forests of North America, nonnative earthworm invasions have been transforming the structure and function of forest floor environments and having complex effects on the plants and animals that depend on those environments. Earthworms are an important prey to many predators including woodland salamanders, and prior research shows earthworm invasions drive spatial and temporal variation in salamander abundance and prey availability. We used double-labeled leaf litter applied to forest 72 replicated plots with and without earthworms to measure how earthworm invasions altered the rates and total amounts of energy and nutrients that move from leaf litter to salamander populations. Results/Conclusions Red-backed salamanders (Plethodon cinereus) occupied 100% of the 72 study plots, and the number of salamanders uniquely marked during pre-monitoring ranged from 2-10 pe...
Background/Question/Methods Although temperate forests have long been thought to be primarily nit... more Background/Question/Methods Although temperate forests have long been thought to be primarily nitrogen limited, resource optimization theory suggests that ecosystem productivity should be co-limited by multiple nutrients. Mechanisms for maintaining stochiometric balance in ecosystems include nutrient resorption in senescing tissues, uptake by plants or microbes, and feedbacks on soil nutrient mineralization. In the northeastern USA, air pollution and forest harvesting disturbance elevate nitrogen availability and contribute to the likelihood of phosphorus limitation. We examined foliar resorption of N and P in 6 northern hardwood stands with differing native soil fertility and tested whether resorption of one nutrient depended on the availability of the other. We also began a long-term nutrient manipulation experiment, fertilizing 13 stands with 30 kg/ha N, 10 kg/ha P, or N and P together. We examined nitrogen and phosphorus availability (assayed with buried ion-exchange resin strip...
Background/Question/Methods The weathering of parent material is the primary source of Ca, Mg, K,... more Background/Question/Methods The weathering of parent material is the primary source of Ca, Mg, K, and P in soils and ecosystems. The influence of parent material on N cycling is less often investigated. The objective of this study was to examine foliar nutrients and soil mineralization in relation to parent material in 20 sites in the White Mountains of New Hampshire, USA. We measured concentrations of total Ca, Mg, K, and P in C horizon material collected in 1-3 soil pits per site. Nitrogen mineralization was measured in laboratory incubations of Oe horizon material. Leaf litter was collected and analyzed for N, P, Ca, Mg, and K by species: sugar maple (Acer saccharum Marsh.), American beech (Fagus grandifolia Ehrh.), yellow birch (Betula alleghaniensis Britt.), white birch (Betula papyrifera Marsh.), red maple (Acer rubrum L.), and pin cherry (Prunus pensylvanica). Hierarchical cluster analysis was applied to nutrients in the C horizon. A two-way ANOVA was used to investigate the ...
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