Lawrence Oates

This dataset contains single-day N2O flux measurements at the plot level and concurrent ancillary measurements of soil properties. These data were used to generate Tables 1-2 and Figures 2-4. Details of flux estimation are given in the paper

Do pastures under management-intensive rotational grazing (MIRG) differ from grasslands under other management in terms of forage quality and quantity, carbon sequestration and biological soil activity? Researchers at the University of Wisconsin-Madison set out to answer these questions and discover some of the reasons behind differences in pasture productivity. They compared MIRG to continuous grazing, mechanically harvested forages, and unmanaged grassland similar to land enrolled in the Conservation Reserve Program (CRP). Their findings indicate that MIRG may provide a higher quality and quantity of forage, and more potential for carbon sequestration, compared to the other management systems.

A growing awareness of the negative consequences induced by post-WWII conventional agriculture has led to renewed interest for grazing-based livestock farming systems. A major characteristic of grassland based farming systems is the high unpredictability of forage resource in grassland ecosystems due to weather uncertainty. Two main management strategies can be followed by farmers to cope with this uncertainty: rely on ecosystem resistance — the ability of the system to remain viable for a wide range of environmental conditions or work with ecosystem flexibility by monitoring and adapting management strategies in response to perturbations. With a strategy based on resistance the farmer defines a priori the grazing sequence and does not modify it with time, while a strategy based on flexibility (also called adaptive management) requires defining grazing sequences that can be modified (adapted) in response to the environmental conditions observed. In this study we developed a simple model of a grassland agroecosystem dynamics under the mathematical framework of viability theory so as to quantify the resistance and flexibility of a set of grazing sequences. Our results show (1) for a given grazing sequence, applying a flexibility strategy leads to higher levels of production than a resistance strategy (+100LUdaysha−1 on average), (2) the number of adaptations needed to maintain system viability increases with the level of production and decreases with the resistance of the system, and (3) grazing sequences requiring the most adaptations to stay viable are also the ones with the lowest potential of adaptation (flexibility). We conclude that grazing sequences are located along a gradient ranging from low production with high resistance and high flexibility, to high production with low resistance and low flexibility and requiring constant adaptations to remain viable. Adaptive management makes it possible to benefit from environmental variability and increase the level of production, while management strategies based on resistance are coherent when managers do not target maximal production and can maintain a margin to cope with unexpected events.

Microbial communities are important drivers and regulators of ecosystem processes. To understand how management of ecosystems may affect microbial communities, a relatively precise but effort-intensive technique to assay microbial community composition is phospholipid fatty acid (PLFA) analysis. PLFA was developed to analyze phospholipid biomarkers, which can be used as indicators of microbial biomass and the composition of broad functional groups of fungi and bacteria. It has commonly been used to compare soils under alternative plant communities, ecology, and management regimes. The PLFA method has been shown to be sensitive to detecting shifts in microbial community composition. An alternative method, fatty acid methyl ester extraction and analysis (MIDI-FA) was developed for rapid extraction of total lipids, without separation of the phospholipid fraction, from pure cultures as a microbial identification technique. This method is rapid but is less suited for soil samples because...

Nitrogen (N) fertilization can greatly improve plant productivity but needs to be carefully managed to avoid harmful environmental impacts. Nutrient management guidelines aimed at reducing harmful forms of N loss such as nitrous oxide (N2O) emissions and nitrate (NO3-) leaching have been tailored for many cropping systems. The developing bioenergy industry is likely to make use of novel cropping systems, such as polycultures of perennial species, for which we have limited nutrient management experience. We studied how a switchgrass (Panicum virgatum) monoculture, a 5-species native grass mixture and an 18-species restored prairie responded to annual fertilizer applications of 56 kg N ha-1 in a field-scale agronomic trial in south-central Wisconsin over a 2-year period. We observed greater fertilizer-induced N2O emissions and sub-rooting zone NO3- concentrations in the switchgrass monoculture than in either polyculture. Fertilization increased aboveground net primary productivity in ...

ABSTRACT Temperate grasslands are generally considered carbon (C) sinks, but climate and management likely affect whether they accumulate or lose C on an annual time step. The North Central Region of the United States contains highly productive improved pasture that is used exclusively for livestock grazing and mechanical harvest. The objective of this study was to use a net ecosystem carbon balance (NECB) approach to estimate C accumulation or loss in subhumid pastures under four typical livestock management practices: management-intensive rotational grazing (MIRG), continuous grazing (CONT), haymaking (HARV), and land set aside with no harvests (NONE). MIRG lost significantly less C in 2006 than all other treatments, and in 2007 MIRG was the only treatment that had a positive NECB. For 2006, our model resulted in an average change of À236 6 15 (CONT), À100 6 24 (MIRG), À391 6 11 (HARV), and À276 6 28 (NONE) g C Á m À2 Á y À1 . For 2007, the change was À234 6 56 (CONT), 106 6 69 (MIRG), À200 6 25 (HARV), and À171 6 38 (NONE) g C Á m À2 Á y À1 . Increased C fixed as net primary production (NPP) and C imported as hay and grain resulted in the MIRG treatment having the most favorable C balance. Even with imported hay and grain, reduced NPP in the CONT treatment led to a less favorable C balance. In the HARV treatment, high biomass removal drove the negative C balance, while the relationship between reduced NPP and heterotrophic respiration alone drove the negative C balance in the NONE treatment. Climate change mitigation services provided from ecosystem C accumulation relative to cultivation may be warranted for pastures, but when all cross-boundary transfers of C are not considered, significant misconceptions can occur regarding how different management strategies affect the NECB of subhumid pasture.

Spring-fed wetlands perform many important functions within oak-woodland landscapes, and livestock grazing modifies these functions. We used 10-year (long-term) and 3-year (paired-plot) experiments to better understand grazing management ef-fects. We studied spring ecosystem responses in plant composition, di-versity and cover; channel morphol-ogy; water quality; aquatic insects; and greenhouse gases. Lightly and moderately grazed wetlands exhib-ited lower insect family richness than ungrazed springs. Plant cover was

Greenhouse gas (GHG) emissions from soils are a key sustainability metric of cropping systems. During crop establishment, disruptive land-use change is known to be a critical, but under reported period, for determining GHG emissions. We measured soil N2O emissions and potential environmental drivers of these fluxes from a three-year establishment-phase bioenergy cropping systems experiment replicated in southcentral Wisconsin (ARL) and southwestern Michigan (KBS). Cropping systems treatments were annual monocultures (continuous corn, corn–soybean–canola rotation), perennial monocultures (switchgrass, miscanthus, and poplar), and perennial polycultures (native grass mixture, early successional community, and restored prairie) all grown using best management practices specific to the system. Cumulative three-year N2O emissions from annuals were 142% higher than from perennials, with fertilized perennials 190% higher than unfertilized perennials. Emissions ranged from 3.1 to 19.1 kg N2...

Background: Interannual variability in precipitation, particularly drought, can affect lignocellulosic crop biomass yields and composition, and is expected to increase biofuel yield variability. However, the effect of precipitation on downstream fermentation processes has never been directly characterized. In order to investigate the impact of interannual climate variability on biofuel production, corn stover and switchgrass were collected during three years with significantly different precipitation profiles, representing a major drought year (2012) and two years with average precipitation for the entire season (2010 and 2013). All feedstocks were AFEX (ammonia fiber expansion)-pretreated, enzymatically hydrolyzed, and the hydrolysates separately fermented using xylose-utilizing strains of Saccharomyces cerevisiae and Zymomonas mobilis. A chemical genomics approach was also used to evaluate the growth of yeast mutants in the hydrolysates. Results: While most corn stover and switchg...

Negative consequences of the post-WWII conventional model of agriculture has led to renewed interest for grazing-based livestock farming systems (Hassanein and Kloppenburg 1995). However, in such systems farmers have to face high unpredictibility of resource availability and weather uncertainty (Lyon et al. 2011). Two contrasting strategies can be followed to cope with this uncertainty: resistance or flexibility (sensu Ten Napel et al. 2011). Resistance is the ability of a grazing sequence to remain viable for a wide range of environmental conditions. A farmer using a strategy based on resistance will choose a grazing sequence that makes it possible to feed livestock irrespective of those environmental conditions. Flexibility is the ability of a grazing sequence to be modified (adapted) in response to the environmental conditions encountered. A farmer using a flexible strategy will choose a grazing sequence that can be adapted throughout the year as information on environmental cond...

Microbial communities are important drivers and regulators of ecosystem processes. To understand how management of ecosystems may affect microbial communities, a relatively precise but effort-intensive technique to assay microbial community composition is phospholipid fatty acid (PLFA) analysis. PLFA was developed to analyze phospholipid biomarkers, which can be used as indicators of microbial biomass and the composition of broad functional groups of fungi and bacteria. It has commonly been used to compare soils under alternative plant communities, ecology, and management regimes. The PLFA method has been shown to be sensitive to detecting shifts in microbial community composition. An alternative method, fatty acid methyl ester extraction and analysis (MIDI-FA) was developed for rapid extraction of total lipids, without separation of the phospholipid fraction, from pure cultures as a microbial identification technique. This method is rapid but is less suited for soil samples because it lacks an initial step separating soil particles and begins instead with a saponification reaction that likely produces artifacts from the background organic matter in the soil. This article describes a method that increases throughput while balancing effort and accuracy for extraction of lipids from the cell membranes of microorganisms for use in characterizing both total lipids and the relative abundance of indicator lipids to determine soil microbial community structure in studies with many samples. The method combines the accuracy achieved through PLFA profiling by extracting and concentrating soil lipids as a first step, and a reduction in effort by saponifying the organic material extracted and processing with the MIDI-FA method as a second step. Video Link The video component of this article can be found at https://www.jove.com/video/55310/

The choice of crops and their management can strongly influence soil microbial communities and their processes. We used lipid biomarker profiling to characterize how soil microbial composition of five potential bioenergy cropping systems diverged from a common baseline five years after they were established. The cropping systems we studied included an annual system (continuous no-till corn) and four perennial crops (switchgrass, miscanthus, hybrid poplar, and restored prairie). Partial-and no-stover removal were compared for the corn system, while N-additions were compared to unfertilized plots for the perennial cropping systems. Arbuscular mycorrhizal fungi (AMF) and Gram-negative biomass was higher in unfertilized perennial grass systems, especially in switchgrass and prairie. Gram-positive bacterial biomass decreased in all systems relative to baseline values in surface soils (0–10 cm), but not subsurface soils (10–25 cm). Overall microbial composition was similar between the two soil depths. Our findings demonstrate the capacity of unfertilized perennial cropping systems to recreate microbial composition found in undisturbed soil environments and indicate how strongly agroecosystem management decisions such as N addition and plant community composition can influence soil microbial assemblages.

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Greenhouse gas (GHG) emissions from soils are a key sustainability metric of cropping systems. During crop establishment, disruptive land-use change is known to be a critical, but under reported period, for determining GHG emissions. We measured soil N 2 O emissions and potential environmental drivers of these fluxes from a three-year establishment-phase bioenergy cropping systems experiment replicated in southcentral Wisconsin (ARL) and southwestern Michigan (KBS). Cropping systems treatments were annual monocultures (continuous corn, corn–soybean–canola rotation), perennial monocultures (switchgrass, miscanthus, and poplar), and perennial polycultures (native grass mixture, early successional community, and restored prairie) all grown using best management practices specific to the system. Cumulative three-year N 2 O emissions from annuals were 142% higher than from perennials, with fertilized perennials 190% higher than unfertilized perennials. Emissions ranged from 3.1 to 19.1 kg N 2 ON ha À1 yr À1 for the annuals with continuous corn > corn–soybean–canola rotation and 1.1 to 6.3 kg N 2 ON ha À1 yr À1 for perennials. Nitrous oxide peak fluxes typically were associated with precipitation events that closely followed fertilization. Bayesian modeling of N 2 O fluxes based on measured environmental factors explained 33% of variability across all systems. Models trained on single systems performed well in most monocultures (e.g., R 2 = 0.52 for poplar) but notably worse in polycultures (e.g., R 2 = 0.17 for early successional, R 2 = 0.06 for restored prairie), indicating that simulation models that include N 2 O emissions should be parameterized specific to particular plant communities. Our results indicate that perennial bioenergy crops in their establishment phase emit less N 2 O than annual crops, especially when not fertilized. These findings should be considered further alongside yield and other metrics contributing to important ecosystem services.

Do pastures under management-intensive rotational grazing (MIRG) differ from
grasslands under other management in terms of forage quality and quantity,
carbon sequestration and biological soil activity? Researchers at the University
of Wisconsin-Madison set out to answer these questions and discover some of
the reasons behind differences in pasture productivity. They compared MIRG to
continuous grazing, mechanically harvested forages, and unmanaged grassland
similar to land enrolled in the Conservation Reserve Program (CRP). Their findings
indicate that MIRG may provide a higher quality and quantity of forage, and more
potential for carbon sequestration, compared to the other management systems.