An Ecological Comparison of the Two Arid-Zone Kangaroos of Australia, and Their Anomalous Prosperity Since the Introduction of Ruminant Stock to Their Environment

In biodiversity conservation of agriculture‐driven landscapes, grasslands have an outstanding importance; their conservation became a top priority both in research and practice. In many regions, sheep or cattle grazing are the best options for biodiversity conservation. In our study, we compared the effects of cattle and sheep grazing on short‐grass steppe vegetation under various grazing intensities. We tested the following study hypotheses: (i) sheep grazing maintains a lower taxonomic and functional diversity, lower amount of forbs compared with cattle grazing; and (ii) the effects of grazing are highly intensity dependent: the differences detected between cattle and sheep grazing are more pronounced at low grazing intensities than at high ones, because the selectivity of grazing decreases at higher intensities. We found lower taxonomic and functional diversity, and lower cover of forbs in sheep‐grazed steppes compared with cattle‐grazed ones. Grazing intensity had a significant effect only on species richness, while on Shannon diversity and evenness, only livestock type had a significant effect. While most single trait indices were affected by the type of the grazer, significant effect of intensity was detected only in few cases. These findings indicated that the selection of the livestock type is the most crucial in conservation; however, for proper ecosystem functioning and high trait variability, the suitable grazing intensity should also be carefully adjusted. Copyright © 2016 John Wiley & Sons, Ltd.

Mixed cattle and sheep grazing reduces the root lifespan of the community in a desert steppe

Herbivore grazing has major effects on soil nutrient dynamics in a variety of grassland ecosystems. Previous studies have examined how large herbivores as a group affect nutrient cycling, but little information is available on how assemblages of different herbivore species may influence nutrient cycling, and whether herbivore assemblage effects are influenced by plant community characteristics (e.g. composition, diversity) of the grazed grassland. We conducted a 5‐year, replicated grazing experiment to test the effects of different large herbivore assemblages (cattle grazing, sheep grazing, combined cattle and sheep grazing, no grazing) under moderate grazing intensity on soil nitrogen (N) mineralization rate in two types of grassland communities (high forbs/high diversity and low forbs/low diversity) in meadow steppe habitat of northeast China. Moreover, we examined two distinctly different pathways that herbivores could influence soil N availability: directly through urine and dung deposition and indirectly by shifting grassland species composition (i.e. the grass: forb ratio), thereby the quality of plant litter available to soil decomposers. We found that grazer effects on soil N availability (indexed with anion and cation adsorption strips) depended on herbivore assemblage, and the herbivore assemblage effects varied in the two types of grasslands. In one type of grassland characterized by low diversity, grazing by each of the herbivore assemblages enhanced soil N availability compared to the ungrazed plots, and mixed species (cattle and sheep) grazing had a greater effect than single species grazing. In high diversity grassland, single species herbivore grazing significantly increased soil N availability, but mixed grazing had no effect. Mixed linear modelling revealed that soil N availability was facilitated primarily by excreta additions to the soil and secondarily by the abundance of grasses. Synthesis. Grazers increased soil N availability directly by adding readily accessible N in urine and dung to the soil. Herbivores indirectly influenced soil N availability by altering the plant composition (grass: forb cover). Both mechanisms contributed to the variation in how different herbivore assemblages affected soil N availability in the two grassland types.

Plant functional traits reflect species ecological strategies and determine how plants respond to environmental changes, however, how dominant species in the Inner Mongolia grassland adapt to different grazing systems by changing their functional traits has not been systematically investigated. In this study, we established four 7-year grazing treatments in the Inner Mongolia grassland: cattle grazing, sheep grazing, mixed sheep and cattle grazing, and no grazing. Fourteen functional traits of three dominant species (Stipa grandis, Leymus chinensis, and Cleistogenes squarrosa) were measured under the different grazing treatments. We found convergences of plant functional traits that indicate herbivory avoidance or tolerance. Plants reduced their vegetative height (VH) and stem: leaf ratio (SLR) to avoid grazing; increased their ability to acquire resources by increasing their specific leaf area (SLA), leaf nitrogen concentration (LNC), and leaf phosphorus concentration (LPC); and reduced their leaf dry matter content (LDMC) to tolerate grazing. Moreover, plants may adapt to grazing by increasing the intraspecific variability of their functional traits. Sheep-only grazing adversely affected L. chinensis growth and survival, while cattle-only grazing hindered S. grandis growth and increased the intraspecific variability of its plant functional traits. Our study emphasizes that intraspecific variability is an important indicator of the responses of plant functional traits to grazing. Since single grazing is more detrimental to the functional traits of dominant plants, we suggest that mixed cattle and sheep grazing may be a more environmentally friendly and sustainable practice for the Inner Mongolia grassland than single grazing.

A link between the numbers of Loghtan Sheep Ovis aries var. and breeding pairs of Red-Billed Choughs Pyrrhocorax pyrrhocorax has been described for the Calf of Man, Isle of Man, UK, through the analysis of data from 1969 to 1982. Recent research has included further data on populations of Choughs and Sheep grazing, as well as data on brood sizes, Rabbit Oryctolagus cuniculus populations and summer rainfall. Data from 1969 to 1994 show a significant relationship between Sheep and Chough numbers, although data for the period 1983 to 1994 in isolation show no significant association. The mean (± se) brood size ringed in the nest in the period 1959–94 was 2.91 ± 0.011. Between 1972 and 1994, as Sheep numbers peaked, mean brood size decreased, only to rise again as Sheep numbers declined. High Rabbit populations correspond statistically with large Chough broods and increased fledging success. Declines in the Chough breeding population appear to be most closely linked to declines in Rabbit numbers due to outbreaks of myxomatosis, even during periods when Sheep numbers were maintained. The recovery of the Chough population after 1970 corresponds with a change in the effects of myxomatosis outbreaks. Rabbit grazing appears to be equally as important as Sheep grazing in the maintenance of the sward characteristics favoured by breeding Choughs. Combined data on Sheep and Rabbit grazing describe the fluctuations observed in Chough breeding success more fully than data for either grazer alone.

CASE STUDY: Effect of cattle and sheep grazing on stocking rate and botanical composition of subirrigated pasture

The performance of sheep and cattle grazing together was compared with that of sheep grazing only with sheep and of cattle grazing only with cattle. Comparisons were made at five stocking rates over three years at the Ginninderra Experiment Station, near Canberra, A.C.T. The cattle, Aberdeen Angus steers, gained less weight in autumn and winter if grazing with sheep (Merino ewes) than did cattle grazing only with cattle. During spring, however, they grew faster and, by late spring, differences between the groups were small and not significant. Sheep grazing with cattle grew more wool, and produced more lambs with higher weaner weights, than sheep grazing only with sheep. The effect of stocking rate on animal performance varied greatly through the year. In spring and summer, gains of young cattle were not greatly affected by stocking rate, and were sometimes highest at highest stocking rates. In autumn, winter, and early spring an additional one-eighth steers per acre decreased daily gains by 0.2 kg, or even more. Older steers at highest stocking rates gained much more in spring than did those on lowest stocking rates. Stocking rate affected all attributes of sheep when grazing alone, but had little effect on sheep grazing with cattle. This study indicates that there could be substantial advantages from running cattle with sheep. The performance of sheep would be improved, and that of cattle reduced only slightly, compared with systems running the species separately. Compensatory gains in spring offer considerable benefits to cattle management, but may limit the value of practices such as supplementary feeding of cattle in winter. Similar results are likely wherever cool temperate, improved pastures are grazed at high stocking rates. Different results are likely from native pastures, and semi-arid environments.

Grazing exerts a profound influence on both the plant diversity and productivity of grasslands, while simultaneously exerting a significant impact on regulating grassland soil carbon sequestration. Moreover, besides altering the taxonomic diversity of plant communities, grazing can also affect their diversity of functional traits. However, we still poorly understand how grazing modifies the relationship between plant functional diversity (FD) and soil carbon sequestration in grassland ecosystems. Here, we conducted a grazing manipulation experiment to investigate the effects of different grazing regimes (no grazing, sheep grazing (SG) and cattle grazing (CG)) on the relationships between plant FD and soil carbon sequestration in meadow and desert steppe. Our findings showed that different livestock species changed the relationships between plant FD and soil organic carbon (SOC) in the meadow steppe. SG decoupled the originally positive relationship between FD and SOC, whereas CG changed the relationship from positive to negative. In the desert steppe, both SG and CG strengthened the positive relationship between FD and SOC. Our study illuminates the considerable impact of livestock species on the intricate mechanisms of soil carbon sequestration, primarily mediated through the modulation of various measures of functional trait diversity. In ungrazed meadows and grazed deserts, maintaining high plant FD is conducive to soil carbon sequestration, whereas in grazed meadows and ungrazed deserts, this relationship may disappear or even reverse. By measuring the traits and controlling the grazing activities, we can accurately predict the carbon sequestration potential in grassland ecosystems.

Four white clover (Trifolium repens L.) cultivars, 4 pre-release cultivars and 24 breeding lines were evaluated in small plots in mixed species swards under rotational cattle and sheep grazing for 2 years. There was no significant stock class x line interaction for proportion of clover in the sward. There was no evidence that medium- and smallleaved types yielded better under sheep grazing while larger-leaved types yielded better under cattle grazing. Lines with the highest clover content tended to be large leaved and upright irrespective of stock class. They also had moderate to high stolon growing point densities. Breeding programmes have developed lines with high stolon growing point densities, ensuring vegetative persistence, while still maintaining a high proportion of clover in the sward. These pre-release cultivars and breeding lines gave significantly better clover contents than existing cultivars. Keywords cultivars, selections, plant habit, cyanogenesis, stolon growing point density, clover content, cattle grazing, sheep grazing

Cattle grazing mitigates the negative impacts of nitrogen addition on soil nematode communities

In the recent decades, cattle numbers strongly increased whereas sheep numbers decreased in south Portugal. This paper aims to predict the potential agronomical and ecological effects of these trends and clarify about the versatility of cattle and sheep systems in adapting to climate changes in the Mediterranean basin. We monitored livestock management in the dry grasslands of Évora (2012 to 2016) and investigated for the effect of livestock type (TLivest) on (a) sward's characteristics, (b) vegetation taxonomic diversity, and (c) in conforming vegetation communities and promoting species of agronomical interests (SAIs). Generalized linear mixed models were used to link management descriptors and vegetation parameters with TLivest. Redundancy analysis was used to analyse the changes due to TLivest on floristic composition and SAIs. Sheep fields presented (a) higher number of days under grazing and lower instantaneous stocking rates than cattle or mixed fields and (b) lower vegetation height in April in wet years and higher green vegetation cover in May; α‐ and γ‐diversity were poorly related with TLivest, but β‐diversity was lower under mixed grazing than under sheep or cattle grazing. The highest richness of legume species was found in permanent grasslands grazed by sheep. Redundancy analysis provided a good discrimination of TLivest but a poor segregation of vegetation communities. As a conclusion, sheep grazing can be seen as a more powerful tool to increase sward heterogeneity, and thus, a loss of grassland heterogeneity can be expected under cattle grazing. The lower versatility of cattle systems suggests narrower opportunities in adapting to climate change.

Comparative Typology in Six European Low‐Intensity Systems of Grassland Management

Sheep grazing is known to influence soil organic carbon (SOC) storage and dynamics in rangelands. However, very little is known of grazing impacts on measurable SOC pools associated with primary particles, particulate organic matter (POM) and carbohydrates in the heavily grazed rangelands of Zagros Mountains, Iran. Bulk SOC, total nitrogen (N), POM and hot-water extractable carbohydrates (HWC) as well as different SOC and N fractions in particle-size separates were studied in natural mountainous rangelands of arid (Boroujen with 255 mm annual rainfall) and semi-arid (Sabzkouh with 860 mm annual rainfall) sites, Central Zagros. Two sheep grazing regimes including grazed and ungrazed (for 20–25 years) rangelands with four replicates were identified as the grazing treatments at each site. Soil samples (0–15 cm) were taken and analyzed for bulk SOC, total N, POM, HWC, and SOC and N associated with physical fractions. Bulk SOC contents were similar for both ungrazed and grazed regimes, while total N contents significantly decreased under grazed conditions. Bulk soil POM and HWC contents decreased considerably and clearly by sheep grazing, indicating that these fractions of total soil organic matter (SOM) pool may be suitable indicators for detecting the grazing effects on bulk SOC changes and storage in these arid and semi-arid ecosystems. Semi-arid rangeland sites contained more bulk SOC, total N and POM contents than arid rangeland sites. These differences were primarily due to the large differences in vegetation composition, annual rainfall and soil conditions between the two rangelands. After 20–25 years of grazing over 10–33 % of SOC and total N losses occurred in the sand- and clay-size fractions with 10 % increases in the silt fraction. This means sheep grazing increases the contribution of the silt fraction to bulk soil N. We found evidence that sheep grazing decreases soil POM and HWC pools, and the sand fraction C, suggesting a lower recent annual input of decomposable organic C in heavily grazed rangelands. Sheep grazing had no influence on the potential C mineralization of the bulk soil at the semi-arid site (Sabzkouh), but reduced C mineralization at the arid-site (Boroujen), indicating that sheep grazing may affect SOC dynamics by changes in substrate quality at the former, but by substrate quantity at the later. In brief, long-term sheep grazing can potentially lead to losses of both labile and no-labile SOM in these arid and semi-arid rangelands.

The effects of cattle and sheep grazing on pasture productivity, under intensive farmlct management, were measured by a rate-of-growth mowing technique over 4 years (1968–1972). Sheep pastures produced 28% more dry matter than cattle pastures over this period. With sheep grazing, a mixed grass-clover pasture remained ryegrass dominant, but with cattle grazing, the pasture changed to one with ryegrass and cocksfoot as co-dominants. At the end of the experiment the top 7.6 cm of soil was more compacted under cattle grazing than under sheep grazing. The aspect of the gently rolling terrain modified the pasture production results. Sunny aspects produced less dry matter than flat sites and this was a reflection largely of the reduction in minor grass species production on the sunny aspect.

Lower forest–grassland ecotones and 20th Century livestock herbivory effects in northern Mongolia