Light Grazing Intensity Research Articles

Grazing legacy mediates the diverse responses of grassland multidimensional stability to resource enrichment

Long-term grazing and resource enrichment are known to affect grassland ecosystem stability independently. However, the interactive effects of grazing legacy and resource enrichment on ecosystem multidimensional stability (e.g., temporal stability (TS): the degree of constancy of ecosystem components over time and temporal resistance (TR): the ability of ecosystem components to withstand the environmental change) in grassland ecosystems remain underexplored. In this study, we conducted a field manipulation experiment to assess the impact of 4-yr of resource addition (water and nitrogen) on multidimensional stability of multiple ecosystem components and underlying drivers in Inner Mongolia steppe with 7-yr different experimental grazing history. We found that the positive effects of water + nitrogen addition on multifunctional TS increased with increasing grazing intensity and an opposing trend was observed for multifunctional TR response. However, neither grazing legacy nor resource addition had an effect on community compositional stability. Resource addition enhanced the stability of species evenness, CWM (community weighted mean) species biomass and CWM-traits. Furthermore, water + nitrogen additions stimulated soil temperature TS but reduced its TR in heavy grazing intensity, with high grazing intensity bolstering soil moisture stability. Multifunctional stability was primarily governed by species asynchrony, while stability of species evenness fostered compositional stability. In particular, TS of functional diversity enhanced multifunctional TS in light grazing intensity, while TS of CWM-traits promoted multifunctional TS in heavy grazing intensity. Our study underscores the decoupling responses of functional stability and compositional stability to grazing legacy combined with resource enrichment. These findings highlight that the significance of concurrently considering multiple stability dimensions and components for a comprehensive understanding of grassland ecosystem stability under intensifying land use and global change scenarios.

Linkage between soil stoichiometric imbalance and microbial carbon use efficiency in desert steppe under different grazing intensities.

Long-term grazing alters soil resource availability and microbial biomass stoichiometry in grassland ecosystems. Exploring the relationship between soil stoichiometric imbalance and microbial carbon use efficiency (CUE) in grazed desert steppe can help understand soil carbon dynamics from a microbial perspective. Based on a long-term grazing platform in Stipa breviflora desert steppe of Inner Mongolia established in 2004, taking heavy, moderate and light grazing intensities, using no grazing as a control, we measured soil available nutrients, microbial biomass and associated enzyme activities for their acquisition, and calculated soil microbial CUE using ecological stoichiometry. The results showed that grazing inhibited soil microbial CUE by 1.0%-10.3%. Soil C:N imbalance was significantly increased by 20.6% in the moderate grazing treatment, while both C:P imbalance and N:P imba-lance were significantly increased by 20.7% and 25.2% in the heavy grazing treatment, indicating that soil microbial communities were more susceptible to N and P limitation. Soil microbial communities maintained their stoichiometric balance by regulating the threshold of elemental stoichiometry ratios and the production of extracellular enzymes. Structural equation modelling (SEM) results indicated that stoichiometric imbalance indirectly affected microbial CUE by altering the threshold of elemental stoichiometry ratios, microbial biomass stoichiometry, and enzyme stoichiometry.

Vegetation diversity and composition in relation to different grazing intensity levels in an arid environment in Jordan

Grazing practices fundamentally shape plant community composition and biodiversity worldwide, more importantly in water-limited environments. This study aimed to investigate plant community composition, species distribution of occurrence and diversity indices in an arid rangeland under different grazing intensities. The quadrat method was used to select 90 × 1 m2 quadrats in heavy-grazing, light-grazing and ungrazed sites. Plant species frequency, relative frequency, abundance, relative abundance and density, as well as species richness, evenness, Shannon diversity index and Simpson’s diversity index were calculated. A total of 46 plant species belonging to 17 families were recorded. The Asteraceæ family was represented with the highest frequency (28%). Overall in the study area, around 95%, 70% and 40% of recorded plant families existed in light-grazing, ungrazed and heavy-grazing sites, respectively. The species richness of identified plants in light-grazing and ungrazed sites was 300% and 200% greater, respectively, than in the heavy-grazing sites. Around 85% of existing plants in heavy-grazing sites were therophyte plants. The species frequency, abundance, density and diversity indices were higher in light-grazing sites compared to those under heavy grazing, which indicates a more diverse, heterogenous and balanced plant community in the light-grazing site. Plant communities in light-grazing and ungrazed sites were similar, except for higher species frequency, density and evenness in light-grazing sites. This suggests that light-grazing intensities in the arid rangelands of Jordan enhance plant diversity more than grazing exclusion, which encourages decision-makers and environmentalists to implement regulations prohibiting intensive grazing in the arid rangelands of Jordan.

Integrated crop and livestock systems increase both climate change adaptation and mitigation capacities

Integrated crop-livestock systems (ICLS) are proposed as key solutions to the various challenges posed to present-day agriculture which must guarantee high and stable yields while minimizing its impacts on the environment. Yet the complex relationships between crops, grasslands and animals on which they rely demand careful and precise management. In this study, from a 18-year ICLS field experiment in Brazil, that consists in annual no-till soybean-pastures grazed by beef cattle, we investigated the impacts of contrasted pastures grazing intensities (defined by sward heights of 10, 20, 30 and 40 cm, plus an ungrazed treatment) on the agroecosystem productivity and soil organic carbon (SOC) under both historical and future (2040–2070, RCP8.5) climatic conditions. We used an innovative methodology to model the ICLS with the STICS soil-crop model, which was validated with field observations. Results showed that the total system production increased along with grazing intensity because of higher stocking rates and subsequent live weight gains. Moderate and light grazing intensities (30 and 40 cm sward heights) resulted in the largest increase in SOC over the 18-year period, with all ICLS treatments leading to greater SOC contents than the ungrazed treatment. When facing climate change under future conditions, all treatments increased in productivity due to the CO2 fertilization effect and the increases in organic amendments that result from the larger stocking rate allowed by the increased pasture carrying capacity. Moderate grazing resulted in the most significant enhancements in productivity and SOC levels. These improvements were accompanied by increased resistance to both moderate and extreme climatic events, benefiting herbage production and live weight gain. Globally, our results show that adding a trophic level (i.e. herbivores) into cropping systems, provided that their carrying capacities are respected, proved to increase their ability to withstand climate change and to contribute to its mitigation.

How does grazing pressure affect feed intake and behavior of livestock in a meadow steppe in northern China and their coupling relationship

Livestock feeding behavior and intake play a crucial role in influencing grassland health and productivity. A comprehensive investigation into livestock feeding behavior and intake can effectively elucidate the interactions and impacts of livestock and grasslands, providing scientific evidence and technical support for the formulation and implementation of sustainable grassland development strategies. Based on a long-term controlled grazing experiment platform conducted over 13 years, the feeding behavior and forage intake of cattle under different grazing intensities were observed and analyzed. Additionally, we used GPS sensors to study cattle grazing behavior trends. Using Mantel's test, we analyzed the relationship between cattle movement distance, forage intake, and environmental factors. The results demonstrated that cattle forage intake decreased with increasing grazing intensity. Forage intake peaked at the end of July and beginning of August, with the highest efficiency observed in August. Moreover, under light grazing intensity, cattle exhibited greater fluctuations in forage intake than those under moderate and heavy grazing intensity. Cattle movement levels increased with higher grazing intensity, and during the period of lush grass growth, cattle displayed significantly higher movement levels than during grass senescence. The accuracy of the behavior determination model based on cattle velocity ranged from 60 to 80 %. Using this model, we found that under heavy grazing conditions, cattle spent significantly more time roaming than under light and moderate grazing. Conversely, under light grazing conditions, cattle spent significantly more time feeding. A negative correlation was identified between cattle forage intake and movement distance. Cattle's forage intake was significantly positively correlated with grass height and grass biomass and significantly negatively correlated with stocking rate and movement distance. Thorough research on livestock feeding behavior and intake offers scientific evidence and technical support for formulating and implementing sustainable grassland development strategies.

Light grazing intensity enhances ecosystem services in semi-arid grasslands through plant trait associations

Grasslands provide multiple ecosystem services (ESs) including provisioning, regulating, supporting, and cultural services that are largely affected by livestock grazing. Linking plant functional traits (PFTs) to ecosystem processes and functions has attracted extensive ecological research to explore the responses and inter-relations of ecosystem services to environmental and management changes. However, little information is available on the links between PFTs and ESs in most ecosystems. We conducted a grazing experiment to investigate the response of PFTs at different levels, including in plant organs (leaves and stems), individual plants, and the overall community in a typical steppe region of Inner Mongolia. Additionally, we examined the effect of animal grazing at four intensities (nil, light, moderate, and heavy) and explored the dynamic interconnections between PFTs and ecosystem services in grasslands. Our analysis revealed that the highest total ecosystem service and provisioning service were achieved under light- and moderate-grazing treatments, respectively. Heavy grazing also increased provisioning service but with a large decline in regulating and total ecosystem services. These changes in ESs were closely associated with grazing-induced variations in PFTs. Compared to no grazing, light grazing increased plant size-related functional traits, such as height, leaf length, leaf area, stem length, and the ratio of stem length to diameter. In contrast, heavy grazing decreased these PFTs. Provisioning and regulating services were determined by plant above-ground community function and structural properties, while supporting service was jointly affected by the below-ground community and soil properties. Our results indicate that light grazing should be recommended for the best total ESs, although moderate grazing may lead to high short-term economic benefits. Moreover, PFTs are powerful indicators for provisioning and regulating services. These findings provide a valuable reference for developing effective management practices to achieve targeted ESs using PFTs as indicators.

The interactive effect of grazing and fertilizer application on soil properties and bacterial community structures in a typical grassland in the central Inner Mongolia Plateau

Appropriate grazing pressure and fertilizer application of nitrogen (N) and phosphorus (P) are effective measures to increase grassland productivity. In this study, we report on the interactive effects of grazing intensity and fertilizer application on soil properties, enzyme characteristics, and soil bacterial community compositions. The experiment was set up in a typical grassland in Xilingol, Inner Mongolia, and had 12 treatments (CC, CN, CP, CNP, LC, LN, LP, LNP, HC, HN, HP, and HNP). These consisted of three grazing intensity levels crossed with four fertilizer application treatments: no fertilizer, N fertilizer, P fertilizer addition alone, and both N and P fertilizers addition, subjected to field sampling and laboratory analysis. The results showed that soil alkaline hydrolysis nitrogen was increased by 15 and 13.6% in LN over LC in the 0–10 and 10–20 cm soil depth layers, respectively. Soil available P was 135.6% higher in LP than in LC at 0–10 cm but similar between LP and LC at 10–20 cm. Soil urease activity rose by 46.8 and 39.3% in 0–10 cm soil and was augmented by 63.1 and 60.3% in 10–20 cm soil of LN and LP relative to LC, respectively. Soil catalase (CAT) activity was decreased in response to LNP by 29.4, 23.5, and 26.5% vis-à-vis LC, LN, and LP in the 0–10 cm layer. Soil CAT activity also decreased in 0–20 cm layer for HN and HNP in comparison with HP. The relative abundance of Actinobacteria increased by 38.1 and 45.0% in HC over that in CC and LC, respectively, in 0–10 cm soil; compared with LC, it increased by 35.8 and 21.7% in LN and LNP, respectively. The relative abundance of Proteobacteria was increased in LNP versus LC in 0–10 cm soil. Overall, fertilizer application coupled with a light grazing intensity promoted key soil properties and the relative abundance of a dominant bacterial phylum.

Grazing alters vegetation phenology by regulating regional environmental factors on the Tibetan Plateau

Grazing can alter vegetation material and energy flow, influencing ecosystem structure and function. However, the direction and magnitude of the phenological response to grazing intensity remain relatively unexplored. Using grazing datasets encompassing 114 counties on the Tibetan Plateau (TP) combined with satellite retrievals of solar-induced chlorophyll fluorescence, we investigated the impact of grazing intensity on vegetation photosynthetic phenology from 2000 to 2015. Results showed earlier trends for the start of the growing season (SOS) and the end of the growing season (EOS) across an increased grazing intensity gradient. We found that the sensitivity of the SOS and the EOS to grazing intensity decreased with increasing grazing intensity level. Importantly, structural equation modeling (SEM) indicated that grazing indirectly contributed to the shift of SOS and EOS by regulating environmental factors. Specifically, decreasing grazing intensity increased soil moisture, which contributed to the earlier SOS under light grazing intensity level in spring. In contrast, higher near-surface maximum temperatures and decreased soil moisture induced by grazing promoted the earlier EOS in autumn under moderate and heavy grazing intensity levels. These findings improve our understanding of the response of vegetation phenology to grazing intensity and present new insights for assessing the effects of grazing on vegetation phenology changes.

Integrated response of carbon sequestration along co-varying gradients of climate and grazing intensity in a desert steppe ecosystem

The interactive effects of grazing and climate on carbon (C) storage are important for the global C budget and regional C management. In a regional-scale field experiment based on multiple grazing gradients, we examined how changes in grazing intensity and climate affected the C sequestration rate and C storage at five desert steppe sites. The mean total ecosystem C storage at each site ranged from 1502 to 3728 g C m−2 and averaged 2341 g C m−2. The peak value of the C sequestration rate (290 g C m−2 yr−1) occurred in the light grazing intensity. The light grazing and fencing management were more beneficial to C sequestration. The rising temperature would decrease C storage in desert steppe, while rising precipitation would promote C sequestration. Soil nitrogen content plays an important role in the driving mechanism of C sequestration in desert steppe. The soil C pool, which dominated the C dynamics in desert steppe, was influenced by the changes of precipitation and grazing intensity. Grazing affects soil nitrogen content by changing the aboveground C pool. Precipitation changes may change soil C storage by influencing the aboveground C pool to change soil nitrogen content and microbial biomass. Such information improves understanding of the dynamics of C storage and sequestration in desert steppe, and is critical for improving the sustainability of grassland ecosystem services and C management.

Effects of grazing on soil aggregate composition and stability in Stipa breviflora desert steppe

Grazing, one of the main grassland utilization modes, has notable impacts on grassland ecosystem structure and functions. However, the effects of long-term grazing on soil aggregate composition and stability are poorly understood. Based on a long-term grazing experiment platform in Inner Mongolia Stipa breviflora desert steppe established in 2004, with treatements of no grazing (control), light, moderate, and heavy grazing intensities, we studied the changes of soil aggregate composition and stability under different grazing intensities. With the measurement of relevant soil physical and chemical characteristics, we explored the main factors that affecting the stability of soil aggregates. The results showed that grazing significantly altered soil aggregate composition. Compared with control, the content of large aggregates (0.25-2 mm) was unchanged in light grazing but significantly decreased in treatments with moderate and heavy grazing intensities. Heavy grazing significantly decreased the content of small aggregates (0.053-0.25 mm), while light and moderate grazing significantly increased that of microaggregates (<0.053 mm). Soil aggregate stability was maintained at a high level under light grazing, but significantly decreased under moderate and heavy grazing treatments. Soil aggregate stability was positively correlated with macroaggregate content but negatively correlated with microaggregate content. Soil pH, bulk density, organic carbon and other physicochemical indices jointly contributed to the changes of soil aggregate composition and hence affect soil aggregate stability. In conclusion, our results showed that appropriate grazing could maintain high level of soil aggregate stability in desert steppe.

Differential Responses of Dominant Plants to Grazing in Typical Temperate Grassland in Inner Mongolia

Leymus chinensis, Stipa grandis, Artemisia frigida, and Cleistogenes squarrosa are the dominant plant species in typical temperate grasslands in Xilingol. Intensive studies related to overgrazing, which resulted in a dominant plant shift, have been carried out in recent years, but the ways in which these four species respond to different grazing intensities remain elusive. In this study, the contents of primary metabolites, secondary metabolites, and phytohormones in the leaves of these species under five grazing intensities were assayed and compared. The results showed that A. frigida contained higher amounts of lignin, while C. squarrosa contained higher amounts of total flavonoids than the other species. Leymus chinensis showed a different accumulation of cellulose and tannin in response to grazing, compared with the other three species. Stipa grandis and A. frigida increased in soluble protein contents in response to different grazing treatments. In particular, the contents of phytohormones, such as abscisic acid, salicylic acid, and gibberellins, were markedly changed under grazing. Leymus chinensis exhibited different abscisic acid and gibberellins accumulation patterns compared with the other species, under the different grazing intensities. Patterns of salicylic acid accumulation were similar (except under light and moderate grazing intensities in A. frigida) among the four species. The results indicated that the four species differed in adaptive strategies to cope with the different grazing intensities, and phytohormones played important roles in coordinating the regulation of their growth and grazing tolerance. This study provides a foundation for elucidating the mechanisms of overgrazing-induced degradation of the Xilingol grassland.

Transcriptional Memory in Taraxacum mongolicum in Response to Long-Term Different Grazing Intensities.

Grazing, as an important land use method in grassland, has a significant impact on the morphological and physiological traits of plants. However, little is known about how the molecular mechanism of plant responds to different grazing intensities. Here, we investigated the response of Taraxacum mongolicum to light grazing and heavy grazing intensities in comparison with a non-grazing control. Using de novo transcriptome assembly, T. mongolicum leaves were compared for the expression of the different genes under different grazing intensities in natural grassland. In total, 194,253 transcripts were de novo assembled and comprised in nine leaf tissues. Among them, 11,134 and 9058 genes were differentially expressed in light grazing and heavy grazing grassland separately, with 5867 genes that were identified as co-expression genes in two grazing treatments. The Nr, SwissProt, String, GO, KEGG, and COG analyses by BLASTx searches were performed to determine and further understand the biological functions of those differentially expressed genes (DEGs). Analysis of the expression patterns of 10 DEGs by quantitative real-time RT-PCR (qRT-PCR) confirmed the accuracy of the RNA-Seq results. Based on a comparative transcriptome analysis, the most significant transcriptomic changes that were observed under grazing intensity were related to plant hormone and signal transduction pathways, carbohydrate and secondary metabolism, and photosynthesis. In addition, heavy grazing resulted in a stronger transcriptomic response compared with light grazing through increasing the of the secondary metabolism- and photosynthesis-related genes. These changes in key pathways and related genes suggest that they may synergistically respond to grazing to increase the resilience and stress tolerance of T. mongolicum. Our findings provide important clues for improving grassland use and protection and understanding the molecular mechanisms of plant response to grazing.

Remotely Sensed Spatiotemporal Variation in Crude Protein of Shortgrass Steppe Forage

In the Great Plains of central North America, sustainable livestock production is dependent on matching the timing of forage availability and quality with animal intake demands. Advances in remote sensing technology provide accurate information for forage quantity. However, similar efforts for forage quality are lacking. Crude protein (CP) content is one of the most relevant forage quality determinants of individual animal intake, especially below an 8% threshold for growing animals. In a set of shortgrass steppe paddocks with contrasting botanical composition, we (1) modeled the spatiotemporal variation in field estimates of CP content against seven spectral MODIS bands, and (2) used the model to assess the risk of reaching the 8% CP content threshold during the grazing season for paddocks with light, moderate, or heavy grazing intensities for the last 22 years (2000–2021). Our calibrated model explained up to 69% of the spatiotemporal variation in CP content. Different from previous investigations, our model was partially independent of NDVI, as it included the green and red portions of the spectrum as direct predictors of CP content. From 2000 to 2021, the model predicted that CP content was a limiting factor for growth of yearling cattle in 80% of the years for about 60% of the mid-May to October grazing season. The risk of forage quality being below the CP content threshold increases as the grazing season progresses, suggesting that ranchers across this rangeland region could benefit from remotely sensed CP content to proactively remove yearling cattle earlier than the traditional October date or to strategically provide supplemental protein sources to grazing cattle.

Comparison of root traits of Stipa krylovii and Allium polyrhizum under grazing in typical steppe.

Plant ecological adaptation is associated with root traits. To clarify the differences of root traits between two dominant species, Stipa krylovii and Allium polyrhizum, under different grazing intensities (light, moderate, and heavy grazing intensities), we measured root traits, including root length, root surface area, root diameter, root volume, root tips, root bifurcations, specific root length, and specific surface area. We analyzed the root morphological patterns of tip proportion, length proportion, surface proportion and volume proportion of both species, and examined their ecological adaptation strategies under grazing. The results showed that grazing inhibited aboveground and belowground growth of S. krylovii, but promoted belowground growth of A. polyrhizum. In addition, the effects of grazing on belowground part of S. krylovii was greater than aboveground part. These results indicated that the growth of S. krylovii was maintained by the aboveground part and that of A. polyrhizum was maintained by the belowground part under grazing. Root length, root bifurcations, root surface area and root tips were the main factors affecting root traits of S. krylovii, while root length, root surface area and root volume were the main factors affecting root traits of A. polyrhizum. S. krylovii could adapt to grazing stress by increasing length proportion, surface proportion and volume proportion of diameter class of 0-0.7 mm, while A. polyrhizum by increasing the length proportion, surface proportion and volume proportion of diameter class of 1.4-1.8 mm. The study on the differences of root traits between S. krylovii and A. polyrhizum could help provide a scientific basis for controlling grassland degradation.

Short-term effects of grazing intensity on soil stoichiometric characteristics of typical grassland in the agro-pastoral ecotone of northern China.

Grazing is the dominant land use way for natural grasslands. Different grazing intensities could affect soil stoichiometry in grasslands by influencing the selective feeding by livestock, litter input, and microbial community structure. In this study, a grazing experiment was carried out in a grassland of agro-pastoral ecotone in Northern China for three years (2017-2019). The concentrations of total carbon (TC), total nitrogen (TN), dissolved organic carbon (DOC), dissolved nitrogen (DN), microbial biomass carbon (MBC), and microbial biomass nitrogen (MBN) in soils were measured. We analyzed the stoichiometric characteristics of those parameters. The results showed that different grazing intensities (1, 2, 4 sheep·0.2 hm-2) had no significant effect on soil TC after three years. The moderate grazing intensity significantly reduced soil TN in 10-20 cm layer in 2019. The light, moderate, and heavy grazing intensities significantly increased soil C/N at 10-20 cm layer, while grazing intensities did not affect soil DOC, DN and DOC/DN. The soil DOC and DN content showed a decreasing trend with the increase of grazing intensity in 2019. It indicated that continuous high intensity grazing might reduce soil dissolved nutrients. The light grazing inten-sity increased soil MBC, while heavy grazing intensity reduced soil MBC significantly, with the increase of grazing year. Different grazing intensities did not affect soil MBN and MBC/MBN.

Intense winter grazing impairs subsequent Italian ryegrass re‐establishment in soybean‐pasture rotations

AbstractWe evaluated Italian ryegrass (Lolium multiflorum Lam.) establishment in a factorial of grazing intensity (intense, moderate, moderate‐light, light, and no grazing, with target average sward heights of 10, 20, 30, and 40 cm in the grazed plots) and additional seeding (self‐seeding with or without additional seeding) in an integrated soybean‐beef cattle system in southern Brazil. Grazing treatments were imposed in winter (June–July) and followed by a direct‐seeded soybean crop (November). The establishment was quantified prior to the stocking periods in 2017 and 2018, corresponding to self‐seeding from 2016 and 2017. Intense grazing impaired ryegrass re‐establishment, resulting in larger individual plants (0.54 vs. 0.15 g dry matter plant−1) but lower population density (57 vs. 1,355 plants m−2) than in the other treatments. Additional broadcast ryegrass seeding did not fully compensate for the reduced natural reseeding in this treatment. The addition of seeds under intense grazing increased plant population density to values comparable to moderate grazing intensities but reduced individual plant mass, limiting herbage mass attained by the end of the pasture establishment phase. Contrastingly, the various combinations of individual plant mass and population density were sufficient to maintain herbage masses in moderate to light grazing intensities that were comparable to that in the ungrazed treatment, regardless of seed addition (63 vs. 180 g DM m−2 for intense grazing vs. the average of other treatments over the whole establishment phase). Moderate grazing, e.g., target sward heights of 20 cm or greater, is necessary to achieve a system that can sustain itself without seed addition.

Potential of grazing management to improve beef cattle production and mitigate methane emissions in native grasslands of the Pampa biome.

We tested the hypothesis that improving sward structure through adjustments in forage allowance results in greater forage intake and live weight (LW) gains by beef cattle and lower CH4 emissions per unit LW gain and unit area in a native grassland ecosystem of the Pampa biome. The experiment was carried out during 2012 and 2013 in southern Brazil. The experimental design was a randomized complete block with two replicates. Treatments consisted of five contrasting forage allowances of a native grassland managed under continuous stocking: 4, 8, 8-12, 12, and 16kg of dry matter (DM) 100kg LW-1day-1 (or % LW). The 8-12% LW treatment had a variable forage allowance of 8% LW in spring and 12% LW in summer, autumn, and winter. Forage allowance was controlled by changes in stocking rate (kg LW ha-1). Average daily gain (kg LW day-1) was high for forage allowances of 12 and 16% LW but decreased at 8%, reaching the lowest value at 4% LW treatment (p<0.001). Live weight gain ha-1year-1 was the greatest at forage allowance of 8-12% LW (p<0.001). Forage DM intake peaked at a forage allowance of 12% LW (p=0.005). Individual CH4 emissions remained constant around 150gday-1 for the two highest forage allowances and decreased to 118 and 107gday-1 under forage allowances of 8 and 4% LW, respectively (p=0.002). Emissions per unit LW gain and unit area were driven by animal productivity changes and decreased with increasing forage allowance (p=0.001 and p=0.040, respectively). We propose that the combination of 8% LW forage allowance during spring and 12% LW during the rest of the year should be targeted to best balance animal production and environmental impact in the Pampa biome.

Immobilization and stabilization of volcanic ash in soil aggregates in semiarid meadows of Northern Patagonia

Although volcanism may be perceived by the society as a phenomenon with mostly negative consequences, this is not always the case especially for natural systems. There is a limited knowledge on how the deposited pristine ash becomes immobilized and stabilized in the soil after the volcanic event. Here, we studied processes of soil aggregates formation in the buried ash layer in an early stage of the succession as well as the influence of the biological legacy (previous land management history) on these processes after the 2011 volcanic event of the Puyehue–Cordón Caulle Volcanic Complex. 5.5 years after the eruption we collected soil cores to a 10 cm depth in wet and mesic meadows with good and poor grassland conditions induced by light and heavy grazing intensity, respectively, in the East semiarid region of North Patagonia, Argentina. The ash layer was observed down to 5 cm from the soil surface, clearly differentiating a newly developed soil layer formed after the volcanic event. Accordingly, the top 5 cm were examined for the distribution of different size fractions of water-stable soil aggregates and their associated organic carbon (C) and total nitrogen (N) contents. We detected signs of physical and physicochemical changes in respect to the pristine ash collected at these sites in 2011. Soil neoformation processes were detected through the presence of large (4%) and small (21%) macroaggregates, although microaggregates (~45%) and silt + clay fractions (~29%) dominated the soil mass (ash-soil matrix: 0–5 cm depth). C and N contents decreased in a sequence: large macroaggregates ≥ small macroaggregates > microaggregates ≥ silt + clay, highlighting the importance of soil organic matter in the formation of larger-size aggregates and their quality (C and N contents). Biological legacy influenced soil aggregate formation and their quality, as reflected by a higher mass of small macroaggregates and a lower mass of microaggregates (only in mesic meadows) and by higher C and N contents under good grassland conditions. The seasonal hydrological conditions of meadow soils (i.e., soil water content, wetting and drying cycles) via effects on biological and physical processes likely resulted in a reduced aggregation in wet meadows. We noticed an incipient but present soil aggregation processes in these semiarid wetlands translated in the immobilization and stabilization of the buried ashes in the soil. The total C content in the new 0–5 cm soil layer increased at a rate of 1.0 Mg C ha−1 yr−1, on average. This indicates a functional recovery of the ecosystem along with a substantial CO2 mitigation potential in the ashes stabilized with soil organic matter, which might partially counterbalance CO2 emitted during the eruption.

Livestock integration into soybean systems improves long-term system stability and profits without compromising crop yields

Climate models project greater weather variability over the coming decades. High yielding systems that can maintain stable crop yields under variable environmental scenarios are critical to enhance food security. However, the effect of adding a trophic level (i.e. herbivores) on the long-term stability of agricultural systems is not well understood. We used a 16-year dataset from an integrated soybean-beef cattle experiment to measure the impacts of grazing on the stability of key crop, pasture, animal and whole-system outcomes. Treatments consisted of four grazing intensities (10, 20, 30 and 40 cm sward height) on mixed black oat (Avena strigosa) and Italian ryegrass (Lolium multiflorum) pastures and an ungrazed control. Stability of both human-digestible protein production and profitability increased at moderate to light grazing intensities, while over-intensification or absence of grazing decreased system stability. Grazing did not affect subsequent soybean yields but reduced the chance of crop failure and financial loss in unfavorable years. At both lighter and heavier grazing intensities, tradeoffs occurred between the stability of herbage production and animal live weight gains. We show that ecological intensification of specialized soybean systems using livestock integration can increase system stability and profitability, but the probability of win–win outcomes depends on management.

Effect of pasture management on enteric methane emissions from goats.

The effect of pasture management on CH4 emissions was investigated from goats in a tropical climate. Two experiments were conducted in a "Tanzania Guinea grass" (Panicum maximum Jacq.) pasture to assess enteric CH4 production in a completely randomized design. Emissions from light, moderate, and heavy grazing intensities were analyzed in the first experiment, and variations between grazing days were explored in the second experiment. Grazing intensity was defined as 2.4, 1.6, and 0.8 post-grazing leaf area index. Pasture management employed intermittent grazing with variable stocking rate using Anglo Nubian female adult goats. SF6 tracer gas technique was used to measure CH4 production. Grazing intensity was not found to affect CH4 emissions per animal, dry matter forage intake (DMI), and gross energy (GE) intake. However, the second experiment showed that CH4 production was influenced by the grazing day. CH4 emissions were 18.1gday-1, and the variables were 0.88gkg-1 of metabolic weight, 17.45gkg-1 of DMI, and 5.5% of GE. CH4 production increased linearly with the grazing day, possibly reflecting a reduction in forage quality. These findings suggest that the day of occupation in intermittent grazing has a greater effect on CH4 emissions than that by grazing intensity and that a single day grazing of Tanzania Guinea grass could mitigate CH4 emissions.