High Grazing Intensity Research Articles

Grazing intensity as a management strategy in tropical grasses for beef cattle production: a meta-analysis

Correct pasture management associated with the adjustment of grazing intensity determines pasture persistence and the level of production per animal and per land area. The objective of this review was to examine the effect of grazing intensity in tropical pastures on the performance and productivity of beef cattle by a meta-analytical approach. The review followed a protocol developed and tested based on the PICOS strategy to formulate the guiding question: population (beef cattle), intervention (high grazing intensities), comparison (low grazing intensities), outcome (animal performance and productivity), and study design (experimental). Data were collected from papers published in the electronic databases of SCOPUS (Elsevier), Web of Science (Main collection), SpringerLink, Wiley Online Library, and Science Direct (Elsevier) by a single cross-reference search. The selected studies were considered relevant when they: (1) were primary research published in the format of a research article; (2) included grazing intensities as a management strategy; and (3) evaluated average daily gain (ADG, kg/animal per day), stocking rates (SR, animal unit (AU)/ha; AU = 450 kg), and weight gain per area (WGH, kg/ha). Thirteen manuscripts were selected due to their methodological strength for data extraction. The means under continuous stocking were 0.67 kg/animal per day for ADG, 518.12 kg/ha for WGH, and 4.19 AU/ha for SR. Under intermittent stocking, the means were 0.62 kg/animal per day for ADG, 980.18 kg/ha for WGH, and 5.10 AU/ha for SR. In tropical forages, the heights of 20 to 40 cm for pastures under continuous stocking and the defoliation intensities of 40 to 50% for those under intermittent stocking result in greater individual performance and animal productivity per land area.

Impact of European Bison Grazing (Bison bonasus (L.)) on Species and Functional Traits of Carabid Beetle Assemblages in Selected Habitats in Poland.

Simple SummaryCurrently, we are observing a drastic decline in insect biodiversity. The aim of this study was to determine whether grazing by European bison (Bison bonasus (L.)) has potential for the implementation of conservation measures. Therefore, a study on a free-ranging European bison population and captive herds in enclosures was carried out in order to determine whether this animal’s grazing activity impacts species composition and the ecological characteristics of carabid beetle assemblages. No notable influence on the numbers of individuals of carabid beetles could be detected, but there was an indication that high-intensity grazing may cause an increase in the number of species. Increased grazing activity had a stronger influence on the ecological characteristics of the species assemblages than on the species composition. This result indicates that using European bison grazing as a method for nature conservation may have more potential in regulating properties and functions of the ecosystem than in the conservation of specific species or species assemblages of carabid beetles.Currently we are observing a drastic decline in insect fauna on a large scale. Grazing is regularly used as an ecological method of protecting or restoring special biotopes that are important for species conservation. The European bison (Bison bonasus (L.)) is the largest living wild terrestrial animal in Europe; therefore, a large impact on flora and fauna as a result of its grazing activity can be assumed. There might be potential for implementing conservation measures that employ active grazing. Therefore, a study on a free-ranging European bison population and captive herds in enclosures was carried out in order to determine whether European bison grazing has an impact on carabid beetle assemblages and whether the degree of this impact (if any) depends on the intensity of grazing. No notable influence on numbers of individuals of carabid beetles could be detected, but there was an indication that high-intensity grazing may cause an increase in the number of species. Increased intensity of grazing seems to have only a weak impact on the species assemblage structure, but it has a stronger impact on the composition of functional traits in the assemblage, as demonstrated in particular by the significant impact of captive herds. The stronger relation between grazing intensity and the functional traits of the carabid beetle assemblages than between grazing intensity and assemblage structure indicates that using European bison grazing as a method of ecological engineering in the context of nature conservation may have more potential in regulating properties and functions of the ecosystem than in the conservation of specific species or species assemblages of carabid beetles.

Resilience of vegetation to drought: Studying the effect of grazing in a Mediterranean rangeland using satellite time series

Understanding how resilient rangelands are to climatic disturbances such as drought is of major importance to land managers. The resilience of ecosystems can be reduced by livestock grazing and by environmental conditions. Most studies quantifying resilience are based on model simulations. However, natural time series from satellite data offer the possibility to infer aspects of resilience from real systems. The objective of this study was to investigate two aspects of ecological resilience, namely resistance to climate variability and recovery from drought, by applying a change detection method (Breaks For Additive Seasonal and Trend; BFAST) spatially on a 28-year Landsat NDVI time series in a dry rangeland in southern Cyprus. First, we used the number of breakpoints fitted by the BFAST model as an inverted proxy for long-term vegetation resistance to climate variability (the ability to withstand change during a disturbance reduces the likelihood to trigger a breakpoint in the time series). Second, we used the linear slope of the BFAST model after a known drought as a proxy of the recovery rate of the vegetation. This information was then used to analyse the spatial distribution of the total number of breakpoints and of the NDVI recovery trend in relation to grazing and environmental properties. Our results show that high NDVI and a northern orientation (i.e. favourable environmental conditions) were associated with a highly resilient system, due to high resistance to climate variability and fast recovery after drought. Intermediate conditions were associated with low resistance. Unfavourable conditions and high grazing intensities were associated with an unresponsive ecosystem state characterised by high resistance and slow recovery after a drought event. Low grazing intensities positively affected the NDVI recovery trend, but did not improve resistance. On northern slopes, terrain slope had a positive effect on the NDVI recovery trend, while on southern slopes it had a negative effect. Our satellite-driven approach has a strong potential for resilience monitoring, because it can be applied on broad spatial and temporal scales in areas with low availability of field data. Moreover, it allows to jointly extract two important components of resilience: resistance and recovery rate.

Effect of Transhumant Livestock Grazing on Pseudo-Alpine Grassland Bird Communities

Transhumance is a traditional animal husbandry system, but its effects on grassland avian communities have not been dealt with in depth. In this study, we quantified the influence of transhumance on the grassland avifauna, in representative pseudo-alpine grasslands with no (NGG), low (LGG), and high (HGG) grazing intensity in the Pindos Mountains, Central Greece. Two point count surveys were conducted within 20 sites in each grassland during the bird breeding season of 2016. We assessed bird diversity indices and accounted for whether the recorded habitat and topographic variables were involved in their variation. A total of 25 bird species were recorded, with the grazed grasslands supporting the most species of high conservation value, while the NGG showed the highest bird diversity. Bird species richness and diversity increased with the decrease of vegetation height, vegetation height heterogeneity, and the increase of rock cover. Bird communities exhibited different patterns among the three grazing regimes and specific bird species of high conservation value appeared to prefer different grasslands. Six species preferred HGG, one preferred LGG, while two preferred NGG. Our study highlights the necessity of heterogeneous pseudo-alpine grasslands with short and tall grass areas in order to maintain highly diverse bird communities.

Spatial Utilization and Microhabitat Selection of the Snow Leopard (Panthera uncia) under Different Livestock Grazing Intensities

AbstractThere is increasing conflict between snow leopards and humans in many protected areas, the main driver of which is the overlap in spatial utilization between snow leopards and livestock. Understanding the spatial utilization and microhabitat selection of snow leopards in areas featuring different levels of livestock grazing is important to better understand and resolve this conflict, but such studies are rare. Here, we conducted line transect and plot surveys in low- and high-grazing-disturbance areas (LGDAs and HGDAs) in Wolong National Reserve, southwestern China. We compared snow leopard spatial utilization and microhabitat characteristics between LGDAs and HGDAs. Results showed that snow leopards had aggregated distribution in both LGDAs and HGDAs, but the distribution of snow leopards in HGDAs was more centralized than in LGDAs. Herb cover and height in LGDAs were greater than in HGDAs. We fit a resource selection function (RSF) that showed that snow leopards preferentially selected higher elevation, smaller basal diameter of shrubs, and lower height of herbs in LGDAs. In contrast, there were no significant microhabitat factors in our snow leopard RSF in HGDAs. Our results indicate that high-intensity grazing tends to reduce the habitat types available to and preferential selectivity of habitat by snow leopards. We recommend that livestock grazing should be controlled to restore the diversity of the alpine ecosystems in Wolong Nature Reserve. Our findings also highlight the need for evaluating the impact of livestock grazing on rare animals in alpine environments (e.g., snow leopard) in other areas facing similar issues.

Estimation of the inter-annual marginal value of additional feed and its replacement cost for beef cattle systems in the Flooding Pampas of Argentina

The effects of climate variability are projected to increase in the future threatening the expected outcomes of grazing-based animal production, feed use efficiency, and development of sustainable farming livelihoods. The identification of profitable farm management strategies to overcome critical inter-annual feed supply deficits is a worldwide management problem for grazing-based livestock systems and such information is essential for designing resilient feed-bases against climate variability. Increasingly, beef breeding herd (cow-calf) farmers in the Flooding Pampas region of Argentina have added backgrounding enterprises to deal with inter-annual system risks, but the impact of adopting such livestock managements under different forage growth patterns has not been widely investigated in the region. The aims of our study were to explore the marginal value of feed (MVF; it quantifies the economic value of an extra kg DM or MJ of metabolizable energy) in a representative beef cattle farm from the Flooding Pampas region. By combining this variable with the replacement cost method, different feed alternatives available for farmers to increase feed-on-offer were compared, under climate and price variability. The feed scenarios were baseline [unchanged herbage mass accumulation (HMA)] or with an extra 10% of the annual HMA in different seasons (summer, autumn, winter, spring or all year around), within a full range of beef cattle systems (stocking rates and steer/cow rates with different target market liveweights for steers and heifers). These scenarios were tested by integrating forage, livestock and economic models in series. Drier years reached higher MVF, and cumulative curves showed greater absolute values and probabilities of obtaining a higher MVF in winter or spring, and lowest in summer. The backgrounding management alternatives provide opportunities to increase the MVF (by up to 20% >0.09 US$ per extra kg DM added in winter at 0.55 cows ha−1 with a 0.4 steer/cow rate), enabling the purchase of high-quality forages (>0.07 US$ kg−1 DM). However, high stocking rate and grazing intensity (>0.6) may reduce the inter-annual farm performance (LW sales ha−1 and profitability). The framework developed in this study has provided new insights for diversifying into the use of complementary forage sources in the farm feed-base to improve farm resilience against climate and price variability in the Flooding Pampas of Argentina.

Defoliation Dynamics on Grazing Horizons in Pastures Intercropped by Panicum maximum, Brachiaria brizantha, and Brachiaria decumbens

The aim of this study was to quantify and verify the defoliation dynamics process of the Panicum maximum, Brachiaria brizantha, and Brachiaria decumbens intercropping during the formation of four grazing horizons in lenient grazing intensities and high grazing intensity. Pastures were managed in a pregrazing height of 70 cm, and as post-grazing height, the criteria of 40% and 60% were used in relation to the pre-grazing height. The experimental design used was a completely randomized design with a 3x4 factorial arrangement. The first factor was the cultivars of intercropped grasses consisted of 3 cultivars, i.e., BRS Zuri, Xaraés, and Basilisk. The second factor was grazing horizons consisted of 4 levels, i.e., I: one; II: two; III: three; IV: four. In the intercropping managed with 40% of the forage canopy height removal, oscillations were observed in the severity of defoliation of the extended tiller among the intercropped species, in which the tiller reduction of the ‘Basilisk’ was 32% lower in relation to ‘BRS Zuri’. In the intercropping managed with 60% of the forage canopy height removal intensity, disproportionality was observed among the grasses, because the ‘Basilisk’ suffered a higher severity and frequency of pseudostem defoliation. In intercropped pastures managed under grazing intensities of 40%, as the animal explores the grazing horizons, the vertical distribution of the pseudostem could modify the shape and positioning of the depth of the bite, leading the animal to perform less selective grazing among the species. Due to the higher supply of pseudostem mass at the intensity of 60%, it was possible to infer that there was a reduction in forage intake.

Nutrients cause grassland biomass to outpace herbivory

Human activities are transforming grassland biomass via changing climate, elemental nutrients, and herbivory. Theory predicts that food-limited herbivores will consume any additional biomass stimulated by nutrient inputs (‘consumer-controlled’). Alternatively, nutrient supply is predicted to increase biomass where herbivores alter community composition or are limited by factors other than food (‘resource-controlled’). Using an experiment replicated in 58 grasslands spanning six continents, we show that nutrient addition and vertebrate herbivore exclusion each caused sustained increases in aboveground live biomass over a decade, but consumer control was weak. However, at sites with high vertebrate grazing intensity or domestic livestock, herbivores consumed the additional fertilization-induced biomass, supporting the consumer-controlled prediction. Herbivores most effectively reduced the additional live biomass at sites with low precipitation or high ambient soil nitrogen. Overall, these experimental results suggest that grassland biomass will outstrip wild herbivore control as human activities increase elemental nutrient supply, with widespread consequences for grazing and fire risk.

Nutrient concentrations in two savannah grass species and their implications for grazers

The diversity of grazers on savannahs exerts pressure on the grass to provide nutrition. In this study the concentrations of major and trace animal nutrients in above ground grass tissue as influenced by grazing were examined. Two palatable grass species grazed by both livestock and wild grazers were sampled: Brachiaria nigropedata and Eragrostis lehmanniana. Samples of grass tissue were collected from widely spread sampling sites in both livestock and wildlife grazing sites, at the end of the growing season. Although B. nigropedata had higher nutrient concentrations, there was general covariance in nutrient levels in the two grasses. The covariance indicated that the respective sites generally had location context-dependent low or high nutrient concentrations in all grasses. The adequacy of the nutrient concentrations for grazer nutrition was assessed using literature-sourced minimum and maximum tolerable limit requirements of cattle and the high population gazelle-like species as illustration. The results showed that, in these nitrogen-limited savannahs, the grass generally met grazer requirements in terms of crude protein, potassium, molybdenum, nickel and zinc but that it had deficiencies in phosphorous, sodium, and boron, as well as grazing intensity-related localised toxic levels of potassium, phosphorous, magnesium, iron and manganese. The deficiencies and toxicities were inferred to result in abnormalities in grazer physical condition and reproduction. Given the importance of livestock in semiarid savannahs, these effects on livestock grazers were inferred as threatening human food security. The study shows that high grazing intensity can raise the concentrations of some animal nutrients in above ground grass tissue to levels above grazer tolerable limits. Grazing rotation to reduce grazing intensity is recommended as a proactive grazing management strategy to limit the effects.

Grassland greening on the Mongolian Plateau despite higher grazing intensity

AbstractChanges in land management and climate alter vegetation dynamics, but the determinants of vegetation changes often remain elusive, especially in global drylands. Here we assess the determinants of grassland greenness on the Mongolian Plateau, one of the world's largest grassland biomes, which covers Mongolia and the province of Inner Mongolia in China. We use spatial panel regressions to quantify the impact of precipitation, temperature, radiation, and the intensity of livestock grazing on the normalized difference vegetation indices (NDVI) during the growing seasons from 1982 to 2015 at the county level. The results suggest that the Mongolian Plateau experienced vegetation greening from 1982 to 2015. Precipitation and animal density were the most influential factors contributing to higher NDVI on the grasslands of Inner Mongolia and Mongolia. Our results highlight the dominant effect of climate variability, and especially of the precipitation variability, on the grassland greenness in Mongolian drylands. The findings challenge the common belief that higher grazing pressure is the key driver for land degradation. The analysis exemplifies how representative wall‐to‐wall results for large areas can be attained from exploring space–time data and adds empirical insights to the puzzling relationship between grazing intensity and vegetation growth in dryland areas.

Soil microbial communities respond to an environmental gradient of grazing intensity in south Patagonia Argentina

Soil microorganisms communities regulate key functions in terrestrial ecosystems and contributes to the formation of stable organic matter and hence climate change mitigation. The structure, diversity and activity of soil microbial communities are influenced by the quantity and quality of organic compounds entering soils through the contribution of their root exudates and plant litter, which the microorganisms use as a substrate for biosynthesis and energy source. However, grazing effect on the soil microorganisms showed variable results dependent on the ecosystem under study. One of the main challenges of this millennium is the sustainability of agricultural production, especially in fragile soils such as those present in Patagonia. Therefore, our objective was to evaluate the responses of microbial biomass carbon (MBC), soil basal respiration (SBR), the derived coefficients and the abundance of fungi and bacteria under contrasting long-term grazing intensities in an environmental gradient. The study was established in three ecological areas Mata Negra Thicket (MNT), Dry Magellanic Steppe (DMS) and Humid Magellanic Steppe (HMS) with two grazing intensities. Soil samples were taken over two years in different seasons (autumn, winter, spring and summer). Results showed that biotic and abiotic factors (temperature and precipitation), plant communities and soil characteristics modulated the microbial structure and function in ecological area. On the other hand, high grazing intensity decreased the MBC and microbial coefficient (qM). There was a seasonal and interannual dynamic in the MBC and the bacteria and fungal communities, attributed mainly to temperature and precipitation. The results indicated that the effect of grazing intensity in soil microbial communities depends largely on intrinsic characteristics of each ecological area defined by the environmental gradient.

Effects of livestock grazing on plant species diversity vary along a climatic gradient in northeastern Iran

AbstractQuestions(a) Do patterns of species diversity and composition differ between plots exposed to high vs. low grazing intensity? (b) Do these differences vary among three regions with different climates, representing a gradient from arid to sub‐humid conditions?LocationNortheastern Iran.MethodsWe compared plots intensively grazed by sheep and goat (HG) to plots with low grazing intensity (LG), across three climatic regions: arid, semi‐arid and sub‐humid. Species diversity (expressed as Shannon H) was compared using linear mixed‐effect models. Dissimilarity analysis was used to estimate the compositional heterogeneity of different types of plots, reflecting the differences in species composition. Indicator Species Analysis was used to identify individual species associated with particular types of plots.ResultsThe HG plots had lower values of Shannon H than LG plots, across all climatic regions. Further, the effect of grazing on species diversity varied between the climatic regions, with the most pronounced differences between the HG and LG plots in the sub‐humid region. Although no differences in species diversity were detected between the three climatic regions, compositional heterogeneity was the highest in the sub‐humid region and the lowest in the semi‐arid region, with the most pronounced differences between the HG and LG plots in the sub‐humid region. Indicator Species Analysis showed significant main effects of both climate and grazing on species composition, revealing species that respond to grazing in each of the three climatic regions.ConclusionsOvergrazing was detected to reduce the diversity of species in all three climatic regions, even though its effect was most pronounced in the sub‐humid region. Therefore, the control of overgrazing or reduction of its intensity appears an effective management tool for protecting species diversity, applicable in areas with different climates.

Grazing and aridity have contrasting effects on the functional and taxonomic diversity of ants

Ants are one of the most abundant and ubiquitous organisms on Earth and play critical roles in multiple ecosystem services such as seed dispersal and nutrient cycling. Despite this, the effects of climatic and land use stressors on particular species or groups of ants are poorly known. We conducted a regional field survey across 108 locations in south-eastern Australia, using correlation network analysis and structural equation modelling to identify how ants respond to environmental stressors. We found contrasting relationships amongst ants, and aridity, and vertebrate grazing intensity and history. Increasing aridity was associated with reduced ant richness, whereas increasing grazing intensity was associated with greater ant richness directly, and indirectly, via reductions in litter depth and perennial grass density. However, these taxonomically diverse groups of ant species still shared contrasting responses to increasing aridity and grazing intensity. We found strong associations between grazing, aridity and the abundance of Seed Harvesters, weak indirect relationships with Generalist Foragers, but no relationships for Predators or Sugar Feeders. Taken together, our work identifies contrasting relationships amongst grazing, aridity and ants (ant ‘winners’ or ‘losers’) across contrasting ecological contexts. Given that increasing aridity is generally associated with lower grazing intensity, our results suggest that locations with more arid sites will have lower ant richness with fewer Seed Harvesters, whereas more mesic sites with high grazing intensity might increase ant richness, and the abundance of specific ant species. Such knowledge is important if we are to maintain critical ant-mediated functions as Earth becomes drier and grazing intensity increases.

System diversification and grazing management as resilience-enhancing agricultural practices: The case of crop-livestock integration

Managing for resilience in agriculture will be required to overcome future challenges such as growing food demand, climatic uncertainty, scarce raw materials and economic instability. Identifying resilience-enhancing practices is therefore fundamental for developing sustainable agroecosystems. We aimed to assess the resilience of two agricultural systems with different levels of diversification in southern Brazil: a specialized soybean (Glycine max) system and an integrated soybean-beef cattle system. We assessed the robustness and the adaptive capacity of these systems when facing climate hazards and price volatility. The study was based on a long-term trial that has been carried out since 2001, composed of an annual rotation of no-till soybean production during the summer and grazing of mixed black oat (Avena strigosa) and Italian ryegrass (Lolium multiflorum) pasture in the winter. Treatments consisted of four grazing intensities in the integrated crop-livestock system (ICLS), defined by sward heights: 10, 20, 30 and 40 cm plus an ungrazed control representing the specialized cropping system (CS). The experiment was carried out using a randomized complete block design with three replicates. We analysed system results over five years using two methods: i) a downside risk analysis to estimate the expected losses of yield and gross value added; and ii) the Ecological Network Analysis, which was applied to each treatment and year, for the assessment of the resilience of nitrogen (N-Ɍflow) and phosphorus (P-Ɍflow) flows. Both methods showed that co-located crop-livestock production in an ICLS was more resilient than the specialized soybean system and had improved nutrient cycling and resource-use efficiency. The effects of grazing management on system resilience depended on the output: beef yields were more stable under lower grazing intensities, but the risk of falling below a target economic threshold was inversely proportional to grazing intensity and null when the highest grazing intensity was adopted. The ecological network analysis did not reveal differences in resilience of nutrient flows among grazing management treatments. Our study suggests that Ɍflow (N or P) is a useful proxy for assessing the robustness and adaptability of agroecosystems. Our comprehensive resilience analysis of nutrient and economic flows provides evidence that system diversification through the integration of grazing animals into specialized cropping systems is a good strategy towards the sustainable intensification of agriculture. It would be relevant, however, to consider further studies comparing more complex system configurations and levels of diversification.

HANPP trajectories for Ethiopia reveal recent agricultural efficiency gains but high grazing intensity

This study presents long-term trajectories of biomass flows and dynamics of land use change of Ethiopia between 1961 and 2013. The data from FAO sources are analysed using the Human Appropriation Net Primary Production (HANPP) methodology. By 2015, the population of Ethiopia reached the 100 million mark, with about 80 million Ethiopians subsisting on agricultural production. The average farm size was less than 1 ha. Cereal production yields have remained comparatively low. Productivity of the country’s livestock population continues to be low and about half of the cattle is held for traction. 90% of the total energy demand of Ethiopia is covered from biomass. Study findings show that the total share of potential Net Primary Productivity appropriated for human activities (or HANPP) stands at 63% by 2013. Per hectare biomass extraction from cropland triples in the study timeframe and cropland production increases hint at strong efficiency gains in the last two decades. On grazing land, total HANPP increases from 37 to 68%, mainly due to degradation modelling. Grazing amounts to one-fifth of the total biomass extracted. Ethiopia’s grazing intensity is among the highest observed globally. Forest and woodland HANPP stands at 53% in 2013. By 2005, Ethiopian HANPP levels are more than three times the average for Africa. The demonstrated levels of biomass appropriation from cropland, grazing land and forests may increase negative impacts, such soil degradation and erosion. Promoting sustainable farming practices, improving livestock productivity while reducing herd size, as well as increasing energy efficiency will be vital to reduce impacts on natural resources.

Soil seed bank in a subtropical grassland under different grazing intensities

ABSTRACT Grazing is an important determinant for the composition and structure of grasslands; however, soil seed bank (SSB) response to grazing intensity is poorly investigated. We analyzed SSB richness and density in a subtropical grassland in southern Brazil with different forage offers (low, intermediate, high and very high), that is, contrasting grazing intensities. The SSB was evaluated by the seedling emergence method. We collected ten SSB samples at two layers (0-5 and 5-10 cm) in spring and autumn in each of grazing intensity treatments. We surveyed the established vegetation to assess its similarity with the SSB. Treatment effects were analyzed by Poisson regression while compositional differences were visualized by ordination. We found 103 species in the SSB, of which 71 were also found in established vegetation. We found a positive correlation between SSB density and grazing intensity. High grazing intensity influences patterns of composition and dominance in the SSB, while no strong differences were found among the other treatments. The SSB was characterized by low participation of dominant grasses in the vegetation and the dominance of ruderal species, indicating that recovery from the SSB after total removal of vegetation (severe disturbance) may be limited in grasslands in the region.

Response of Vegetation and Soil Characteristics to Grazing Disturbance in Mountain Meadows and Temperate Typical Steppe in the Arid Regions of Central Asian, Xinjiang.

Grazing is one of the most common causes of grassland degradation, therefore, an assessment of soil physicochemical properties and plant nutrients under grazing is important for understanding its influences on ecosystem nutrient cycling and for formulating appropriate management strategies. However, the effects of grazing on grassland soil physicochemical properties and plant nutrients in mountain meadow and temperate typical steppe in the arid regions are still unclear. Therefore, we investigated the vegetation nutrient concentrations of nitrogen, phosphorus and potassium (N, P, and K) as well as soil physicochemical properties in the topmost 40 cm depth soil, to evaluate how these factors respond to grazing disturbance in a mountain meadow and temperate typical steppe within a mountain basin system in arid regions. Our results revealed that the soil bulk density values at depth of 0–40 cm increased after grazing in the mountain meadow and temperate typical steppe, whereas the soil water content decreased in the mountain meadow and increased in the temperate typical steppe after grazing. In the mountain meadow, soil total N and available P in addition to vegetation N and P concentrations increased in response to high-intensity grazing, while soil available N, available K and vegetation K decreased after grazing; in addition, soil pH, soil total P and K showed no significant changes. In the temperate typical steppe, the soil total P, soil available N, P, and K, and vegetation N, P, and K increased under relatively low-intensity grazing, whereas soil pH and soil total K showed no significant changes except for the deceasing soil total N. Our findings showed the different responses of different grassland ecosystems to grazing. Moreover, we propose that further related studies are necessary to better understand the effects of grazing on grassland ecosystems, and thereby provide a theoretical basis for the sustainable use of animal husbandry and ecological restoration of grasslands.

Field-scale management and environmental drivers of N2O emissions from pasture-based dairy systems

Emissions of N2O from two dairy farms with different grazing intensity responded non-linearly to increasing soil nitrate availability and total rainfall. Higher N2O emissions were observed immediately after grazing, due to the possible increased incidence of N deposition from animal excreta, increased soil compaction and low plant N uptake. The spatial distribution of N2O fluxes and soil nitrate contents reflected the effect of animal treading and excreta N deposition with N2O fluxes in the proximity of field gateways 11 times higher than the field average. Three years average annual N2O emissions were 6 times higher (9.3 ± 2.6 kg N2O-N ha−1 y−1) in the high grazing intensity farm than in the low grazing intensity farm (1.6 ± 0.2 kg N2O-N ha−1 y−1). This corresponded to 2% and 0.9% of the fertiliser N inputs lost as N2O for the high and low intensity farm, respectively. The GHG intensity (N2O emitted per kg of fat and protein corrected milk FPCM) for the intensive system was only almost two times higher than the non-intensive system (0.12 vs 0.08 kg CO2-eq per kg FPCM y−1 for the high and low intensity system, respectively). The high occurrence of N load hotspots near animal gateways in this study underlines the necessity to account for the spatial N variation in dairy grazing systems. Integrating the spatial management of N loads into improved farming practice has therefore significant scope to reduce N2O emissions and N losses from dairy grazing systems.

Depth and grazing intensity are the main drivers of subtidal hardground benthic community structure on tropical south Atlantic reefs

AbstractMarine hardground bottom (subtidal) benthic (sessile) communities (HBBC) are subjected to various biotic, abiotic, and anthropogenic factors that can vary over space and time and interact with one another. To evaluate the main drivers of the structure of HBBC in a large tropical bay in the southwest Atlantic (Ilha Grande Bay, Brazil), a total of 98 HBBC were sampled using visually estimated quadrats. Ten variables (depth, grazing intensity, irradiance, temperature, salinity, dissolved oxygen, nutrients (nitrite, nitrate, and phosphate), and chlorophyll a concentrations) were also measured. A total of 74 main space‐occupying taxon/functional groups were recorded which fell into six major HBBC groups. These were organized by depth/irradiance and grazing intensities which explained part of the HBBC variation: (a) Communities dominated by zoantharians occurred in the shallow, highest irradiance sites; (b) foliose and erect algae were inversely related to depth and grazing intensity; (c) crustose coralline algae dominated at greater depths and/or under higher grazing intensity; (d) zooxanthellate corals were associated with shallower and heterotrophic invertebrates with deeper stations; (e) photosynthetically efficient algae were associated with deeper stations, with more encrusting forms under higher grazing intensities; and (f) multi‐species turf‐forming algae were ubiquitous (did not present association with any of the measured variables). As communities’ components and main structuring factors were similar to those found in coral reefs, these communities represent compatible receptor habitats for poleward escape, migration, and range extension under the present global warming scenario.

Drought Exacerbates Negative Consequences of High‐Intensity Cattle Grazing in a Semiarid Grassland

Grasslands managed for grazing are the largest land-use category globally, with a significant proportion of these grasslands occurring in semiarid and arid regions. In such dryland systems, the effect of grazing on native plant diversity has been equivocal, some studies suggesting that grazing reduces native plant diversity, others that grazing increases or has little impact on diversity. One impediment toward generalizing grazing effects on diversity in this region is that high levels of interannual variation in precipitation may obfuscate vegetative response patterns. By analyzing a long-term data set collected over a 20-yr period in a semiarid grassland, we explicitly evaluated the role of climate in regulating the effect of cattle grazing on plant communities, finding that climate interacted with grazing intensity to shape grassland communities. Community composition of plots that were intensively grazed varied considerably in response to climatic variation and native species richness was low relative to ungrazed and moderately grazed plots. Following a severe drought in 2002, exotic species richness rapidly increased in the high-intensity grazing plots. While this pattern was mirrored in the other treatments, exotic species richness increased to a greater extent and was slower to return to pre-drought levels in the high-intensity grazing plots. Overall, moderate grazing, even compared to grazing cessation, stabilized grassland communities through time, increased resilience to drought, and maintained the highest levels of native plant diversity and lowest levels of exotic diversity. These findings suggest that grazing, at moderate levels, may support grassland resilience to climate change in semiarid regions. However, grazing that exceeds tolerances, particularly in combination with extreme climatic events, like drought, can alter plant composition over relatively long timescales and possibly increase invasibility by nonnative species.