Influence Of Grazing Intensity Research Articles

Influence of grazing intensity on richness, phylogenetic and functional dimensions of highly diverse mountainous grasslands from Mazandaran, Iran

Influence of grazing intensity on richness, phylogenetic and functional dimensions of highly diverse mountainous grasslands from Mazandaran, Iran

The influence of grazing intensity on soil organic carbon storage in grassland of China: A meta-analysis

Grazing can potentially affect grassland soil carbon storage through selective feeding, trampling and fecal excretion of livestock. The numerous case studies and a few meta-analyses have focused on grazing-induced changes in soil organic carbon (SOC) storage, but the effects of grazing on SOC in major grassland types of China are not clear. In this study, we performed a comprehensive meta-analysis to identify the impact of grazing on soil carbon in China. We found that the key factors affecting the SOC content of grazing grasslands is grazing intensity. Heavy grazing (HG) significantly decreased the SOC content by 7.5 % in major grassland types of China (95 % confidence interval (CI), −11.43 % to −3.57 %, P < 0.001). The SOC content in temperate desert steppes (7.22 %), temperate meadow-steppes (10.89 %) under heavy grazing (HG) showed significantly (P < 0.05) decreased. HG resulted in significant (P < 0.01) decreases in SOC content (6.91 %) of Kastanoze. Our study highlighted that formulating rational grazing strategies according to grassland and soil types was the key to increasing SOC storage and sequestration under climate change and increased human pressure.

Response characteristics of grassland ecosystem biomass to grazing intensity in China

AbstractGrassland ecosystem functions are affected to a large extent by grazing activities. However, owing to the associated spatial heterogeneity, the influence of grazing intensity on grassland ecosystem biomass and the underlying mechanisms remains unclear. In this study, we analyzed data from 335 field data to clarify the response of grassland ecosystem biomass to grazing activities in China. We established that the size of the priming effect of grazing activities on total biomass, aboveground biomass and belowground biomass is −0.25 ± 0.09 (95% confidence interval [CI]: −0.42 to −0.07), −0.47 ± 0.05 (−0.57 to −0.37) and −0.18 ± 0.04 (−0.29 to −0.10), respectively. Grazing was found to significantly reduce both the biomass of grassland ecosystems (p &lt; 0.01) and the average effect value of temperate, meadow and desert steppes with respect to vegetation type (p &lt; 0.05). The descending order of the effects of grazing intensity on biomass was heavy, light and moderate, with light and heavy grazing significantly reducing grassland biomass (p &lt; 0.01), whereas moderate grazing made a comparatively smaller contribution. Furthermore, explained heterogeneity analysis revealed that soil water content was positively associated with the effect size, and path analysis indicated that soil bulk density, precipitation and average annual temperature have a significant direct influence on the effect value (p &lt; 0.05). Given the minimal impact of moderate grazing on biomass, we suggest that stocking at moderate densities could represent an effective approach for restoring degraded grasslands. Moreover, increasing soil water content could contribute to effectively reducing grazing‐related damage to the biomass of grassland ecosystems.

Short-term yak-grazing alters plant-soil stoichiometric relations in an alpine meadow on the eastern Tibetan Plateau

Over-grazing have significantly altered above- and belowground functions in terrestrial ecosystem. However, the influence of grazing intensity on plant-soil stoichiometric relations in alpine ecosystems remains unclear. We investigated the responses of plant-soil nutrient stoichiometric relationships to four grazing intensities (un-grazing (UG), light grazing (LG), moderate grazing (MG) and heavy grazing (HG)) in an alpine meadow on the eastern Tibetan Plateau. We measured carbon (C), nitrogen (N), phosphorus (P) and potassium (K) concentrations and their ratios in plants and soils in the peak growing season after three years of yak-grazing. Compared to UG and LG plots, heavier grazing intensity at community levels and taxonomic groups decreased plant C and K concentrations by 7.6–10.5% and 17.6–21.3%, respectively, while grazing did not significantly influence plant N and P concentrations. Grazing intensity altered plant C:N and C:P ratios but not C:K and N:P ratios. By contrast, grazing intensity had no significant effects on soil nutrients and stoichiometry. Thus, the differential responses of plant and soil nutrients to grazing intensity caused that plants were more sensitive to grazing than soils. Our results confirm that grazing intensity has differential effects on plant and soil nutrients, implying that plant nutrients do not covary with soil nutrients under changing grazing intensity and challenging the past positive relations between plant and soil nutrients. Further long-term grazing experiments are required to understand the drivers of grazing effect on plant-soil nutrient interactions.

Grazing Affects the Ecological Stoichiometry of the Plant–Soil–Microbe System on the Hulunber Steppe, China

Grazing affects nutrient cycling processes in grasslands, but little is known by researchers about effects on the nutrient stoichiometry of plant–soil–microbe systems. In this study, the influence of grazing intensity (0, 0.23, 0.34, 0.46, 0.69, and 0.92 AU ha−1) on carbon (C), nitrogen (N) and phosphorus (P) and their stoichiometric ratios in plants, soil, and microbes was investigated in a Hulunber meadow steppe, Northeastern China. The C:N and C:P ratios of shoots decreased with grazing increased. Leaf N:P ratios &lt;10 suggested that the plant communities under grazing were N-limited. Heavy grazing intensities increased the C:N and C:P ratios of microbial biomass, but grazing intensity had no significant effects on the stoichiometry of soil nutrients. The coupling relationship of C:N ratio in plant–soil–microbial systems was tightly significant compared to C:P ratio and N:P ratio according to the correlation results. The finding suggested grazing exacerbated the competition between plants and microorganisms for N and P nutrition by the stoichiometric changes (%) in each grazing level relative to the no grazing treatment. Therefore, for the sustainability of grasslands in Inner Mongolia, N inputs need to be increased and high grazing intensities reduced in meadow steppe ecosystems, and the grazing load should be controlled within G0.46.

Effects of grazing on crop crown temperature: implications for phenology

In many regions, livestock are allowed to graze grain crops during their vegetative development, before grain is harvested at crop maturity. Little is known of the effects of grazing on crop microclimate, particularly the effects of defoliation on crown temperatures. Knowledge of such effects is important because temperature is the main factor underpinning crop ontogeny, and ontogeny drives dry matter allocation, leaf appearance rates and the timing of anthesis, which are key determinants of grain yield. The primary aim of this study was to examine the influence of grazing intensity and duration on the crown temperatures of winter wheat crops grown at Canberra, Australia. A secondary aim was to examine the association between crown temperature and phenology. In 2007, wheat cv. Mackellar was grazed at intensity–duration combinations of low–short (LS, 33 sheep/ha for 31 days), heavy–short (HS, 67 sheep/ha for 31 days) or low–long (LL, 33 sheep/ha for 62 days). In 2008, cvv. Mackellar and Naparoo were grazed at the HS intensity-duration. Cubic smoothing splines were fitted to crown temperature data measured between the end of grazing and anthesis to facilitate identification of long-term trends and statistical differences caused by the effects of defoliation on crown temperature. Grazing treatments with greater intensity or longer duration significantly elevated maximum daily crown temperature; differences of 6–7°C were common in the month following grazing. Cubic-spline analysis showed that long-term trends in maximum crown temperature of the HS and LL treatments were significantly greater than corresponding temperatures of controls for the entire post-grazing duration. By contrast, effects of grazing on minimum diurnal crown temperature were small. Increasing biomass removal significantly delayed stem elongation and anthesis. We demonstrate that although initial phenological delays caused by defoliation are large, greater diurnal crown temperature fluctuation in grazed crops leads to greater growing degree-day accumulation between the end of grazing and anthesis. This increases the rate of thermal time accumulation during the post-grazing–anthesis period and is likely prominent in driving greater development rates of grazed crops. We further demonstrate that delays in phenology associated with grazing can be largely accounted for by a thermal time constant, with the LS, HS and LL treatments delaying stem elongation by ~52, 141 and 214 degree-days, respectively, above a base temperature of 0°C. Results from these experiments and interpretations herein will be of use in designing crop-grazing regimes, and in studies examining implications of defoliation on vegetative microclimate and on physiological feedback effects caused by elevated temperature.

The Influence of Grazing Intensity on Exchanging Fluxes of Nitrous Oxide, Methane and Carbon Dioxide from Grassland

Grassland ecosystem is the main part of terrestrial ecosystem. The variations of greenhouse gas (N2O, CH4 and CO2) exchanging fluxes from grassland can influence global greenhouse gases payments balance. And the main land use pattern of grassland is grazing. The grazing impacts on the exchanging fluxes of N2O, CH4 and CO2 from soil of grassland by influencing soil physical properties (such as soil moisture, temperature and porosity) of grassland. This paper analyzed the results of previous studies by the way of comparison, and we summarised that the grazing reduced CH4 uptake and N2O emissions of grassland, but which does not change the sources and sinks pattern of atmospheric greenhouse gases. However, the grazing significantly increased the emissions of CO2 from grassland.

Influence of Grazing Intensity on Soil Properties and Shaping Herbaceous Plant Communities in Semi-Arid Dambo Wetlands of Zimbabwe

Key issues of concern regarding the environmental impacts of livestock on grazing land are their effects on soil, water quality, and biodiversity. This study was carried out to determine how grazing intensity influences soil physical and chemical properties and occurrence of herbaceous plant species in dambo wetlands. Three categories of grazing intensity were selected from communal, small scale commercial and large scale commercial land. Dambos from the large scale commercial land functioned as the control. Data analysis included ANOVA and multivariate tests from CANOCO. There were significantly negative changes to soil nutrient status in communal dambos though with a higher number of rare taxa. Sodium, phosphorous, pH and infiltration rate were significant determinants of plant species occurrence. Overgrazing is threatening the productivity, stability, and ecological functioning of dambo soils in communal Zimbabwe. These dambos also require special conservation and management priorities as they contain a large number of rare plant species.

The effect of grazing intensity on the transformation of arid-steppe ecosystems in the Manych Valley

The influence of grazing intensity on the state of soils, vegetation, composition of arachnids, and land-nesting birds in arid-steppe ecosystems of the Manych Valley is discussed. It is shown that, with an increase in grazing intensity, the height of plants, projective cover, land phytomass, humus content, and soil humidity decrease, whereas the soil density increases in the surface layer, which entails a change in the structure of arachnid and bird communities.

The influence of grazing intensity and landscape composition on the diversity and abundance of flower‐visiting insects

Summary The loss of semi‐natural grasslands in agro‐ecosystems has increased the importance of adequate management of remaining grasslands. Recommendations for intensive grazing have been debated because the effects of different management practices may differ between taxa and species. The increased fragmentation of grasslands suggests that the influence of management practices should be studied in a landscape context. We studied four groups of flower visitors, many of which are pollinators, bees (Apoidea), butterflies (Lepidoptera), hoverflies (Syrphidae) and beetles (Coleoptera), in semi‐natural grasslands managed at three intensity levels in eight areas in central Sweden. Local characteristics of the grasslands were recorded and landscape diversity was quantified. Vegetation height was correlated with grazing intensity: intensive grazing with the shortest vegetation and abandoned grassland with the tallest. The insect groups responded differently to grazing intensity. Species richness and abundance differed between management regimes for beetles and hoverflies but not for bees and butterflies. The effects of local habitat and landscape composition on species richness, abundance and composition differed between groups. Bee diversity responded to both local and landscape factors. Butterflies were mainly affected by local vegetation height and linear elements in the landscape. More species of hoverflies were recorded in tall vegetation and in landscapes with high forest cover. Beetles responded only to local environment characteristics. Synthesis and applications. We demonstrate the importance of studying different insect groups simultaneously when evaluating habitat and landscape qualities for diversity. The results suggest that planning for conservation of biodiversity at landscape scales may be better than implementing grazing guidelines for individual grasslands. Grazing intensity should vary within or between landscapes to preserve pollinator diversity. Conservation management to encourage flower visitors cannot be generalized to include all groups simultaneously.

Grassland versus non-grassland bird abundance and diversity in managed grasslands: local, landscape and regional scale effects

Declines of West European farmland birds have been associated with intensive agricultural practices, while in Central and Eastern European countries grasslands still harbour a diverse and unique bird community. However, in these countries comparative studies on the effects of agricultural intensity on biodiversity are virtually missing. We compared bird communities of paired extensively and intensively grazed cattle pastures in three different regions of the Hungarian Great Plain. The influence of grazing intensity, landscape and regional effects were tested on the abundance and species richness of two ecological groups of bird species (grassland and non-grassland birds), as well as on the abundance of the three commonest grassland bird species (Skylark, Yellow wagtail, Corn bunting) in linear mixed models. We found significant effects of grazing intensity on the abundance of grassland birds, which were more abundant on the extensive sites, whereas no effects were found on non-grassland birds. This could be explained by a closer dependence of grassland birds on grasslands for nesting and foraging, whereas non-grassland birds only used grasslands opportunistically for foraging. Landscape effect was shown on grassland bird abundance, but not on non-grassland birds. The regions did affect only the species richness of grassland birds. At species level, the effect of management was significant for the three commonest grassland species, which were more abundant on the extensive fields in all regions. Additionally, on Skylark abundance landscape and regional effects were also shown. These findings suggest that conservation of biodiversity in agricultural systems requires the consideration of landscape perspective to apply the most adequate management.

Influence of grazing intensity on performance of perennial grass mixtures in the alpine region of the Tibetan Plateau

Effects of grazing intensity on leaf photosynthetic rate (Pn), specific leaf area (SLA), individual tiller density, sward leaf area index (LAI), harvested herbage DM, and species composition in grass mixtures (Clinelymus nutans + Bromus inermis, Elymus nutans + Bromus inermis + Agropyron cristatum and Elymus nutans + Clinelymus nutans + Bromus inermis + Agropyron cristatum) were studied in the alpine region of the Tibetan Plateau. Four grazing intensities (GI), expressed as feed utilisation rates (UR) by Tibetan lambs were imposed as follows: (1) no grazing; (2) 30% UR as light grazing; (3) 50% UR as medium grazing; and (4) 70% UR as high grazing. Leaf Pn rate and tiller density of grasses increased (P < 0.05), while sward LAI and harvested herbage DM declined (P < 0.05) with the increments of GI, although no effect of GI on SLA was observed. With increasing GI, Elymus nutans and Clinelymus nutans increased but Bromus inermis and Agropyron cristatum decreased in swards, LAI and DM contribution. Whether being grazed or not, Elymus nutans + Clinelymus nutans + Bromus inermis + Agropyron cristatum was the most productive sward among the grass mixtures. Thus, two well‐performed grass species (Elymus nutans and Clinelymus nutans) and the most productive mixture of four species should be investigated further as the new feed resources in the alpine grazing system of the Tibetan Plateau. Light grazing intensity of 30% UR was recommended for these grass mixtures when swards, LAI, herbage DM harvested, and species compatibility were taken into account.

Effect of grazing intensity and cultivar on morphology, phenology, and nutritive value of subterranean clover II. Nutritive value during the growing season

With the decline in pasture quality in southern Australia, the development of management strategies to improve nutrient supply for grazing animals is essential and requires a clear understanding of the interaction between animals and plants. The impact of grazing intensity on the morphology of subterranean clover was previously examined. This paper reports the effect of grazing intensity on the nutritive value of subterranean clover, and the variation in quality of cultivars during the growing season. Grazing intensity influenced nutritive value and interacted with cultivar maturity. Heavy grazing depressed dry matter digestibility (DMD) by 5 percentage units in October for early maturity cultivars but increased DMD by 3 percentage units in September for mid maturity cultivars. The influence of grazing intensity on nitrogen content was small. Heavy grazing did not affect acid detergent fibre for the early maturity group, but depressed it for the mid maturity group throughout the season. Acid detergent lignin remained comparable for all cultivars during the season. Mineral content of subterranean clover showed variable response to grazing treatments. Nutritive value varied among cultivars within each maturity group. DMD ranged over 53–64%, 44–62%, and 45–53% for early, mid, and late maturity groups, respectively, at the end of the growing season. The cultivar rank in all nutritional parameters changed with the progress of the season. The large ranges in the decline rate of DMD within each maturity group during the last 8 weeks of growth gave an indication of the potential quality of the cultivars during late spring and early summer. Despite the variation in mineral content there were no cultivars in which the concentration of minerals was below the minimum requirements of sheep. These results indicate that there is a potential for the selection of high quality cultivars within a breeding program, and that indicative targets of grazing intensity need to be further developed with a focus on pasture quality.

Factors affecting the productivity of irrigated annual pastures. 2. Defoliation by dairy cows

The influence of grazing intensity on the productivity of an irrigated annual pasture was studied for 3 years in northern Victoria. Lax-, medium- and hard-grazing intensities were described by post-grazing pasture heights of 7.2, 5.2 and 3.0 cm, respectively. Also, one instance of variable grazing frequency occurred, in winter of year 1. Hard-grazed plots produced 1 3 and 17% less herbage in years 1 and 2, respectively, than did lax- and medium-grazed plots, which produced similar amounts of herbage. When the interval between grazings was extended, the variation in productivity was reversed; lax grazing resulted in 9% less total production than heavier grazing. In years 1 and 2, there was little effect of grazing treatment on botanical composition until spring, at which time there was a marked reduction in the amount of subterranean clover (Trifolium subterraneum) in the hard-grazed plots, with a concomitant increase in grass content. There were no significant effects of grazing intensity on the amounts of weeds in either year. However, in year 3, weeds were important contributors to pasture production early in the season. This, together with reduced clover seed reserves and increased incidence of disease in subterranean clover with hard grazing, suggests that the long-term regenerating ability of an annual pasture may be impaired if severely grazed at regular intervals.

Beef production from grass and silage with autumn-born calves. 1. The influence of grazing intensity on efficiency of herbage utilization and live-weight gain of cattle

SUMMARY1. Two experiments are described in which groups of 12 autumn-born calves were strip-grazed at different intensities. In Experiment 1 (1966), ‘standard’ and ‘high’ grazing intensities were compared. In Experiment 2 (1967), ‘standard’ and ‘low’ intensities were compared. In both experiments the same meadow fescue—ryegrass ley provided 0·24 ha per head for grazing and conservation; herbage surplus to grazing requirements was conserved as silage.2. The grazing season was divided into three parts according to the type of grazing, and estimates were made of daily herbage allowances, herbage quality, efficiency of herbage utilization and the live-weight gain of the cattle.3. Grazing intensity was regulated by controlling daily herbage allowances by strip-grazing. Within grazing seasons, differences in grazing intensity had little effect on the digestibility of the herbage dry matter on offer. Dead herbage accumulation was low (10%) in the early and late parts of the season, but rose to 25% in mid-season.4. The efficiency of herbage utilization was estimated in three ways: from sample cuts of herbage on offer and refused; from measurements of herbage intake; and from feeding standards for maintenance and gain. Efficiency was highest for the ‘high’ group of Experiment 1 and lowest for the ‘low’ group of Experiment 2. The validity of efficiency estimates is discussed in relation to measurements of pasture yield, herbage intake and the assessment of the nutrient requirements of growing cattle.5. Live-weight gain over the whole season was 0·59 and 0·89 kg/head per day for the ‘high’ and ‘standard’ groups of Experiment 1, respectively. In Experiment 2, the ‘low’ and ‘standard’ groups gained weight at 0·95 and 0·84 kg/head per day, respectively.

Influence of Grazing Intensity on Cesium-137 Levels in Milk

The influence of grazing intensity on radiocesium concentrations in cows’ milk was studied by the accepted rotational grazing system of the Department of Dairy Industry, Utah State University. Three comparable groups of Holstein cows were chosen. The first group was included in the main herd, the second group followed the main herd in the same rotation but always a plot behind, and the third group had no access to pasture. A difference (P<0.1) based on per cent deviation was found in cesium-137 levels in the milk of the first and second groups. For further statistical analysis, the data for the first and second groups were classified into two periods, based on whether precipitation occurred during sample collection. No significant difference (P>0.1) was evident during the rainy period, but a significant difference (P<0.001) was observed for the dry interval. The correlation coefficient for the same periods was significant (P<0.0001) and positive. For both groups a significant positive correlation (P<0.0001) was also obtained for strontium-90 versus cesium-137 concentration in milk. The third group, consuming only hay and grain, excreted 9 to 10% of its total intake of cesium-137 into the milk.

Influence of Grazing on the Composition of Themeda Triandra Grassland, East Africa

As modern man settled in the grasslands, cultivated them, replaced the wild animals with domestic animals, and altered the frequency and intensity of burning, changes in the grassland vegetation and soil must have occurred. Grazing pressure on the many forage species probably changed because of differences in food preferences and in grazing intensity. Greater human populations in recent years suggest that frequency of burning may have increased but overgrazing has reduced fuel and fire intensity. Although these are recently changed conditions which are known in a general way, knowledge of their long-term effects on the vegetation and soil is more speculative. Numbers and kinds of wild animals were described by early travellers whereas the grassland composition was barely mentioned. Replacement of wild animals by domestic livestock on East African grasslands came before the advent of detailed ecological investigations; therefore original interrelationships between animals and their grassland habitat are subject to considerable conjecture. This study was conceived in the belief that East Africa contained areas where the relative influence of wild animals and domestic livestock on their grassland home could be determined. Ideally, adjacent areas were required where wild grazing animals were abundant and where domestic animals had seldom grazed, such as occur at the edges of tsetse fly infestations and in certain national game parks. Four such locations were selected for detailed study of botanical species composition and soil conditions to determine the effects of grazing by different animal species and to evaluate the influence of grazing intensity. Several difficulties were encountered during the study. First, animal numbers, hence grazing pressure, had to be evaluated by indirect means as movements of nomadic livestock and migrating game animals were poorly known. Second, sampling was possible only at one time near the end of the growing season so that early growth and early growing species were not sampled nor were the vegetational differences in years of more or less rainfall than 1958-59. Third, climatic parameters for the areas are subject to question because the available records were of short duration and some distance away. These unknowns prevent unequivocal interpretations but, on the other hand, the grasslands are composed of perennial plants which tend to ameliorate short-term variations due to climate and grazing. Vegetational changes in response to climatic variation need further study.