Grazed Plots Research Articles

Interactive influence of rainfall manipulation and livestock grazing on species diversity of the herbaceous layer community in a humid savannah in Kenya

Changes in rainfall regime and grazing pressure affect vegetation composition and diversity with ecological implications for savannahs. The savannah in East Africa has experienced increased livestock grazing and rainfall variability but the impacts associated with those changes on the herbaceous layer have rarely been documented. We investigated the effect of livestock grazing, rainfall manipulation and their interaction on the composition and diversity of the herbaceous community in the savannah for two years in Lambwe, Kenya. Rainfall manipulation plots were set up for vegetation sampling; these plots received either 50% more or 50% less rainfall than control plots. Simpson's diversity and Berger–Parker indices were used to determine diversity changes and dominance respectively. The frequency of species was used to compute their abundance and their life forms as determined from the literature. Grazing significantly increased species diversity through suppression of dominant species. Rainfall manipulation had no significant impact on plant diversity in fenced plots, but rainfall reduction significantly reduced diversity in grazed plots. In contrast, rainfall manipulation had no impact on dominance in either fenced or grazed plots. The interaction of grazing and rainfall manipulation is complex and will require additional survey campaigns to create a complete picture of the implications for savannah structure and composition.

Winter grazing does not affect soybean yield despite lower soil water content in a subtropical crop-livestock system

Commercial-scale integrated crop-livestock systems intensify land use by combining complementary agricultural enterprises and leveraging synergistic ecosystem services to achieve both productive and environmental outcomes. Although widely implemented in southern Brazil as an annual beef/soybean rotation, tradeoffs such as competing soil water use between pasture and crop phases may result from seasonal grazing in this system. We compared soil water and plant physiological variables in the crop phase of an integrated annual beef-soybean system managed with no-till and best grazing practices with those of an ungrazed cover crop control as part of a long-term experiment in southern Brazil. A mixed black oat (Avena strigosa Schreb.) and Italian ryegrass (Lolium multiflorum Lam.) pasture was either grazed by beef cattle to 20-cm sward height or left as an ungrazed cover crop in the winter, and direct-planted to soybean (Glycine max [L.] Merr.) in the summer. Although soybean yields did not differ between grazed and ungrazed treatments, soil matric potential was on average 25% lower across depths and growth stages in plots that had been grazed during winter. Soybeans in grazed plots also exhibited up to 34% lower light-use efficiency and a 2-week slower time to physiological maturation than soybeans in plots that had not been previously grazed. These results describe for the first time the differential crop growing conditions and crop physiological responses created after 16 years of integration with grazing animals. As integrated crop-livestock systems grow in importance in commercial production settings, this research can inform adaptive management practices to ensure the sustainability of these systems into the future and under a variety of environmental conditions.

Effects of grazing on plant composition, conservation status and ecosystem services of Natura 2000 shrub-grassland habitat types

The Natura 2000 network is crucial to conserve biodiversity in the European Union and provides hotspots for certain ecosystem services. Grazing, a common land use in different Natura 2000 habitat types, may contribute to the maintenance of protected plant communities and reduce fuel loads and wildfire hazard. Our study aims to assess the effects of grazing on plant composition and conservation status of calcareous shrub-grassland Natura 2000 habitat types, as well as its effects on fire hazard reduction and aboveground carbon storage. We surveyed plant communities grazed by goats in fenced (ungrazed) and open (grazed) plots in a mosaic of calcareous shrub-grassland habitat types and assessed plant species composition and habitat conservation status. We also assessed aboveground plant biomass in grazed and ungrazed plots and modelled potential fire behaviour in those plots for each habitat. With the exception of cryptogams, grazing did not affect plant cover, but positively affected species richness (mean ± SD: 26.80 ± 11.65 vs. 29.37 ± 8.59, P = 0.01; fenced vs. unfenced) and Shannon diversity (2.11 ± 0.81 vs. 2.33 ± 0.55, P < 0.01) in the habitat mosaic. Furthermore, grazing did not affect the conservation status of two out of three of the studied habitat types. Additionally, grazing decreased the fire hazard in grass and dwarf shrub communities without reducing aboveground carbon stocks significantly. Our results show that moderate grazing is a management practice that effectively contribute to the conservation of Natura 2000 shrub-grassland habitat types through reduction of wildfire hazard and maintenance of habitat conservation status.

Wind erosion changes induced by different grazing intensities in the desert steppe, Northern China

Desert steppes are fragile ecosystems, which generally suffer severe wind erosion hazards, especially when they experiencing external disturbances such as grazing. Therefore, the effects of grazing on the wind erosion process are very important for improving our understanding of the effects of the stocking rate on grassland degradation and enacting reasonable grazing strategies in grasslands. However, few studies have discussed the wind erosion changes induced by different grazing intensities thus far. Herein, a series of grazing experiments was carried out in a desert steppe in Urad Back Banner, Inner Mongolia. These experiments included 2 types of grasslands that are shrub dominated grassland (SDG) and grass dominated grassland (GDG). Each grassland type had 3 grazing rate treatments: no grazing as the control (CK), moderate grazing (MG), and heavy grazing (HZ). After the grazing experiments lasting for 4 years, sand traps were set in the grazing plots to detect the horizontal sand flux at different grazing intensities. In addition to the wind erosion observed, the vegetation and soil particles were also surveyed and sampled. Our results showed that the vegetation cover (VC) and aboveground biomass (AGB) in the MG and HG plots all had obvious differences compared to the CK plot, regardless of whether it was SDG or GDG. The soil particle analysis showed that the fractions of erodible particles (60–200 μm) in the MG and HG plots decreased significantly. In the GDG, the soil particles exhibited a coarsening trend from CK to HG plots for the sorting action of the wind. Suffering a grazing disturbance, the wind erosion in a desert steppe exhibited significant changes. For instance, in the SDG, the horizontal sand flux in the MG and HG plots were 1.78 and 2.06 times the sand flux in the CK plots, respectively, and, in the GDG, they were 17.86 and 56.53 times the flux in the CK plots, respectively. Except in the MG and HG plots of the GDG, the saltation height of sand was generally lower than 20 cm. In the SDG, the particle size of the entrained sand mainly ranged from 80 to 200 μm, and, in the GDG, it ranged from 80 to 300 μm. This finding also indicated the validity of Shao’s sand entrainment equation. We also found that particle size of saltating sand increased with their saltation height for the tough surface of the MG and HG plots in the GDG. Based on the different fractions of horizontal flux in different directions, we also discussed the threshold wind velocity for sand entrainment, and we confirmed that the threshold wind velocities for no grazing in SDG and GDG were approximately 16.5 m·s−1 and 15 m·s−1, respectively. Using our previous wind erosion model, we estimated the dust emission in the total desert steppe of China and found that different grazing scenarios would change the magnitude and distribution of dust emissions.

Impacts of feral horses and deer on an endangered woodland of Kosciuszko National Park

SummaryIn recent years, the impacts of rapidly increasing populations of feral horses and deer on the vegetation and stability of soils have become highly visible and widespread in Kosciuszko National Park. We investigated these impacts in the White Cypress Pine (Callitris glaucophylla Joy Thomps. &amp; L.A.S. Johnson) – White Box (Eucalyptus albens Benth) woodlands of the lower Snowy River valley. This woodland is a component of the White Box‐Yellow Box‐Blakely's Red Gum Grassy Woodland and Derived Native Grasslands complex that is nationally listed as a critically endangered ecological community. To investigate the severity of the impacts of feral horse (Equus caballus) and deer (Dama dama and Rusa unicolor) in the valley in 2013 and 2017/18, we surveyed fenced exclosures and paired grazed plots that were first established and surveyed in 1984 and re‐surveyed in 1987. Using LFA and VAST methodologies (not used in 1987), we compared the relative response of environmental variables in plots inside and outside the exclosures in an attempt to ascertain recent herbivore impacts. While there was no evidence of horses or deer from dung surveys in 1987, in 2018, 84% of the dung was from horses, 13% from deer, 1% from rabbits and 2% from macropods. Total herbivore dung density increased fourfold since the 1987 survey. On the understanding that all plots had the same starting condition in 1984 with respect to prior herbivory, we deduce that horses and deer are having significant ecological impacts. There was a far greater cover of understorey plants and the midstorey was denser and taller inside the exclosures. Outside the exclosures, the vegetation cover was far more sparse and soil erosion was active and extensive. The total number of invertebrates captured in small pitfall traps was nearly twice as many within the exclosures compared to the grazed plots. The dense even‐aged regrowth overstorey stands of White Cypress Pine, inside and outside the exclosures, have changed little in 34 years.

重度放牧对欧亚温带草原东缘生态样带土壤氮矿化及其温度敏感性的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 重度放牧对欧亚温带草原东缘生态样带土壤氮矿化及其温度敏感性的影响 DOI: 10.5846/stxb201810082172 作者: 作者单位: 中国农业科学院草原研究所,中国农业科学院草原研究所,中国农业科学院草原研究所,中国农业科学院草原研究所,中国农业科学院草原研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点基础研究发展计划（973计划）项目（2014CB138806）；国家重点研发计划政府间国际科技创新合作重点专项（2016YFE0116400）；中央级公益性科研院所基本科研业务费专项（1610332016013） Effects of heavy grazing on soil nitrogen mineralization and temperature sensitivity along the Eastern Eurasia Steppe Transect Author: Affiliation: Grassland Research Institute，Chinese Academy of Agricultural Sciences,Grassland Research Institute，Chinese Academy of Agricultural Sciences,,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:以欧亚温带草原东缘生态样带为平台，以样带上未放牧和重度放牧配对样地为研究对象，开展重度放牧对欧亚温带典型草原土壤氮矿化及其温度敏感性的影响研究。结果表明：（1）在室内培养条件下，土壤氮积累量和土壤净氮矿化速率呈现出干燥度指数较大的样点显著大于干燥度指数最低的样点（P < 0.05）。在相对湿润的样点，土壤氮素矿化周转速率较快；（2）重度放牧对不同样点土壤氮积累量和土壤氮矿化速率的影响是不同的。在干燥度指数较高样点，重度放牧样地土壤铵态氮减少量和速率较未放牧样地低（P < 0.05），重度放牧显著降低了土壤硝态氮积累量、无机氮积累量、硝化速率、净氮矿化速率（P < 0.05）；在干燥度指数较低样点，重度放牧样地土壤铵态氮减少量和速率较未放牧样地高（P < 0.05），重度放牧对土壤硝态氮积累量、无机氮积累量、硝化速率、净氮矿化速率影响不大（P > 0.05）；（3）土壤氮矿化作用温度敏感性（Q10）变化范围在1.61-2.06，重度放牧对Q10无显著影响。随着纬度的升高，Q10呈升高趋势。Q10与基质质量指数以及表观活化能与基质质量指数均呈显著的负相关关系（P < 0.05）；（4）土壤硝态氮积累量、无机氮积累量、硝化速率、净氮矿化速率对重度放牧的响应比与干燥度指数呈极显著负相关（P < 0.01），重度放牧对欧亚温带典型草原土壤氮矿化的影响受气候条件（温度和降水）的调控。 Abstract:Effects of heavy grazing on soil nitrogen mineralization and temperature sensitivity in the Eastern Eurasian Steppe were studied using laboratory incubation methods by comparing non-grazing plots with heavy grazing plots at different sites. The results showed that accumulations of soil nitrogen and soil nitrogen mineralization rates were significantly higher in sites with a higher aridity index (AI) than sites with a lower AI (P < 0.05), which indicated that soil nitrogen turnover rates were high in relatively humid sites. In sites with a higher AI, the amount and rate of soil ammonium nitrogen reduction in heavy grazing plots were lower than that of non-grazing plots (P < 0.05), and heavy grazing significantly decreased accumulations of soil nitrate nitrogen (Anit), accumulations of soil inorganic nitrogen (Amin), soil nitrification rate (Rnit), and net nitrogen mineralization rate (Rmin) (P < 0.05). In sites with lower AI, the amount and rate of soil ammonium nitrogen reduction in heavy grazing plots were higher than that of non-grazing plots (P < 0.05), and heavy grazing had little effect on Anit, Amin, Rnit, and Rmin (P>0.05). The temperature sensitivity of net nitrogen mineralization (Q10) ranged from 1.61 to 2.06 and heavy grazing had little effect on Q10. Q10increased with increasing latitude and showed a significant negative correlation with the substrate quality index (P < 0.05). There was a significant negative correlation between substrate quality index and apparent activation energy (P < 0.05). Furthermore, the response ratios of Anit, Amin, Rnit, and Rmin to heavy grazing were significantly negatively correlated with AI (P < 0.01). Our results emphasized that the effects of heavy grazing on soil nitrogen mineralization in the Eastern Eurasian Steppe was regulated by climate (temperature and precipitation). 参考文献 相似文献 引证文献

Research on Dynamic Rotational Grazing Assignment Model based on Grass Resource Leveling

Rotational grazing is an effective way to improve grassland resources utilization and develop animal husbandry. Rational grazing scheme can avoid eco-environment damage caused by overgrazing, and it can ensure the livestock normal feeding. The rationality of rotational grazing management is affected by many complex and dynamic factors. This paper establishes a model of rotational grazing assignment based on grass resource leveling. Firstly, each rotational grazing plot’s forage yield in each rotational grazing assignment stage is predicted by seasonal prediction method. Then, constrained by the rotational grazing plots’ forage yield and livestock’s forage demand, a dynamic rotational grazing assignment model is established, which combines the assignment model and carrying capacity constraint. Thus, the maximum edible forage in a rotational grazing cycle is contained and the distribution of the corresponding rotational grazing plots is determined. In each rotational grazing cycle, each rotational grazing plot can only be assigned once, which embodies the principle of ecological protection. And livestock have as much forage as possible in a rotational grazing cycle. Finally, through a case analysis, a feasible solution in a rotational grazing cycle is obtained. Through taking carrying capacity in each rotational grazing assignment stage as a standard to scheme the grazing order in each plot, the uncertainty of eco-environment is better reflected. A reasonable decision scheme of dynamic rotational grazing can make resources used efficiently in time and space.

Negative effects of vertebrate on invertebrate herbivores mediated by enhanced plant nitrogen content

Abstract Classic theory holds that the main interaction within the herbivore guild is competition, based on research focused on co‐occurring, similarly sized species that reduce the quantity of shared plant resources. However, plant quality may also be crucial in mediating herbivore interspecific interactions. This is especially true when competition occurs between distantly related herbivore species, given that small terrestrial herbivores (e.g., insect herbivores) appear to be more sensitive to alterations of plant quality than plant quantity. In this study, we first tested in the field whether large vertebrate herbivores (cattle Bos taurus) exerted a negative effect on smaller insect herbivores (grasshopper Euchorthippus unicolor) through their overlapping foraging preferences for a dominant grass Leymus chinensis. We measured changes in grass quantity, grass quality, and microclimatic conditions in response to vertebrate grazing and conducted additional manipulative studies in the field and the laboratory to identify potential mechanisms underlying the interaction. Our results showed that grazing by large herbivores caused a significant decline in grasshopper population density and individual performance (survival, size, and weight of both female and male E. unicolor), despite a 38% increase in grass nitrogen (N) content in grazed plots. Experiments manipulating N levels of L. chinensis in the field and the laboratory confirmed that enriching plant N had a negative effect on grasshopper individual performance and population size. Therefore, enhanced quality (N content) of plant resources appears to be an important driver in mediating the negative effect of vertebrate grazing on grasshoppers. Synthesis. We document that phylogenetic relatedness and trait similarity can be poor predictors of interaction strength in some cases, since distantly related herbivores of disparate size can interact indirectly via changes in plant quality. Counter‐intuitively, the observed negative effect of cattle on grasshoppers was mediated, at least in part, by an increase in plant quality in cattle grazed areas. The implication is that light to moderate grazing, a common management strategy, may contribute to suppression of grasshoppers in the Eurasian steppe grassland system by altering plant nutrient supplies.

Influence of exclosure on CT-measured soil macropores and root architecture in a shrub-encroached grassland in northern China

Grassland exclosures with fencing are commonly used to prevent shrub encroachment. However, few studies have been conducted on the effect of exclosures on soil macropores and root architecture during shrub encroachment. This study aimed to quantify the effects of exclosures on soil macropore and root characteristics beneath the encroached shrub C. microphylla L. in the Inner Mongolia grassland. Two exclosure treatments, 9EX (shrubland enclosed for 9 years) and 2EX (shrubland enclosed for 2 years), were designed, with free grazing plots serving as controls. A total of twelve soil cores (0–50 cm deep) were excavated, which included three replicates of each treatment and control. Soil and root architecture of the soil cores were explored using X-ray computed tomography method. Results indicated that macroporosity was 1.03–1.66 times greater in the soil under the enclosed C. microphylla L. than in the soil under the grazed C. microphylla L., and the soil macroporosity increased with exclosure age. Macropores were abundant over the 0–400 mm soil layers under the enclosed shrubland but were mainly present at 0–250 mm soil depth under freely grazed shrubland. Exclosure led to significant proliferation of shrub roots compared with grazing. Root density was 1.04–1.86 times greater in the soil under the enclosed C. microphylla L. than in the soil under the grazed C. microphylla L. Roots were concentrated in the 0–250 mm soil layer in the grazed shrubland, whereas roots were abundant over 0–400 mm in the enclosed shrubland. The high number of macropores under the enclosed shrubland was closely associated with a high root density. These results suggest that exclosure enhances shrub root proliferation and therefore increases soil macroporosity and soil pore connectivity, which would be favourable for shrub encroachment.

High Grazing Pressure of Geese Threatens Conservation and Restoration of Reed Belts.

Reed (Phragmites australis (Cav.) Trin. ex Steud.) beds are important habitat for marsh birds, but are declining throughout Europe. Increasing numbers of the native marsh bird, the Greylag goose (Anser anser L.), are hypothesized to cause reed bed decline and inhibit restoration of reed beds, but data are largely lacking. In this study, we experimentally tested the effect of grazing by Greylag geese on the growth and expansion of reed growing in belts along lake shorelines. After 5 years of protecting reed from grazing with exclosures, reed stems were over 4-fold denser and taller than in the grazed plots. Grazing pressure was intense with 50–100% of the stems being grazed among years in the control plots open to grazing. After 5 years of protection we opened half of the exclosures and the geese immediately grazed almost 100% of the reed stems. Whereas this did not affect the reed stem density, the stem height was strongly reduced and similar to permanently grazed reed. The next year geese were actively chased away by management from mid-March to mid-June, which changed the maximum amount of geese from over 2300 to less than 50. As a result, reed stem density and height increased and the reed belt had recovered over the full 6 m length of the experimental plots. Lastly, we introduced reed plants in an adjacent lake where no reed was growing and geese did visit this area. After two years, the density of the planted reed was six to nine-fold higher and significantly taller in exclosures compared to control plots where geese had access to the reed plants. We conclude that there is a conservation dilemma regarding how to preserve and restore reed belts in the presence of high densities of Greylag geese as conservation of both reed belts and high goose numbers seems infeasible. We suggest that there are three possible solutions for this dilemma: (1) effects of the geese can be mediated by goose population management, (2) the robustness of the reed marshes can be increased, and (3) at the landscape level, spatial planning can be used to configure landscapes with large reed bed reserves surrounded by unmown, unfertilized meadows.

Intraspecific variation in litter palatability to macroarthropods in response to grazing and soil fertility

Abstract Clarifying the functional consequences of intraspecific trait variability in response to interacting trophic levels would provide a significant improvement in our understanding of above‐ground–below‐ground linkages. In particular, the effects of grazing on plant traits may translate into altered litter quality, with potentially important consequences for litter‐feeding decomposers. Plant and litter variability in response to grazing is expected to depend on soil fertility levels, with tolerance and defensive strategies more commonly expressed on fertile and poorer soils, respectively. However, how grazing and fertility interactively alter litter quality and palatability to detritivores has not been explored yet. We conducted a cafeteria experiment with three common millipede (Diplopoda) species feeding on leaf litter from two plant species, the grass Bromopsis erecta and the forb Potentilla verna. Each millipede was offered a binary choice between litter types produced by the same plant species, but sampled in plots with distinct herbivory and fertilization status: litter originating from grazed areas or from 1‐year sheep exclosures, both in native areas and in adjacent paddocks that received chemical N and P fertilization, as well as litter from a 25‐year sheep exclosures in the native area. We found that fertilization and herbivore exclusion interactively affected Bromopsis litter quality and palatability, whereas Potentilla was much less affected. Bromopsis litter palatability was not affected by grazing when litter was collected in native plots, except for the long‐term exclosure which led to low palatability. In contrast, and in line with our expectations, herbivory was associated with much higher palatability in fertilized plots. The changes in palatability were associated with important alterations of litter quality. Overall, our study demonstrates that intraspecific variation in litter can have profound consequences for soil functioning. It emphasizes the role of grazing as a key, but plant species‐specific factor controlling litter intraspecific variability, and its complex interaction with soil fertility level. Moreover, our results advocate for a better understanding of the response of the different organisms involved in the decomposition process, in particular litter‐feeding macro‐detritivores. We encourage future studies aiming at disentangling the various and complex relationships between above‐ground processes such as herbivory and soil functioning.

Behavioral and Ecological Implications of Bunched, Rotational Cattle Grazing in East African Savanna Ecosystem

Rangelands and the wildlife and livestock they support are critical to human livelihoods, but rangeland ecosystems increasingly suffer from overgrazing and degradation. Planned grazing, a strategy that commonly involves time-controlled rotations of high-density (bunched) groups of cattle across a pasture, is marketed as a method to enhance rangeland health and lessen livestock impacts. However, the behavioral mechanisms underlying any potential rangeland improvements resulting from rotational, high-density planned grazing have rarely been examined. To investigate these mechanisms, we compared planned grazing with conventional continuous grazing management in a savanna ecosystem in Kenya. We surveyed cattle grazing behavior, measured changes in vegetation characteristics through surveys conducted before and after cattle grazing, and measured native ungulate abundance following grazing using camera traps. Stocking rates were held constant across treatments, resulting in a commensurate decline in total foliar hits per pin (a proxy for vegetative biomass) across treatments. Planned grazing management altered cattle behavior and reduced grazing selectivity by restricting movements, causing cattle to walk more slowly while grazing and to take more bites per step. Vegetation survey results supported this finding: cattle in the planned grazing treatment ate significantly more Pennisetum grasses (typically avoided because of their unpalatability), creating the opportunity for regrowth of more palatable species after seasonal rains. We also documented significantly higher zebra presence in planned grazing plots after cattle grazing, likely due to increased relative abundance of more palatable grass species. This investigation of grazing behavior, and specifically decreased grazing selectivity as a mechanism underpinning the benefits of planned grazing, shows that when conducted at appropriate stocking densities, planned grazing has the potential to help mitigate rangeland degradation and improve rangeland sustainability for both livestock and wildlife in pastoral African savanna ecosystems.

Interactive influence of livestock grazing and manipulated rainfall on soil properties in a humid tropical savanna

The effect of uncontrolled grazing and unpredictable rainfall pattern on future changes in soil properties and processes of savanna ecosystems is poorly understood. This study investigated how rainfall amount at a gradient of 50%, 100%, and 150% would influence soil bulk density (ρ), volumetric water content (θv), carbon (C), and nitrogen (N) contents in grazed (G) and ungrazed (U) areas. Rainfall was manipulated by 50% reduction (simulating drought—50%) and 50% increase (simulating abundance—150%) from the ambient (100%) in both G and U areas. Plots were named by combining the first letter of the area followed by rainfall amount, i.e., G150%. Samples for soil ρ, C, and N analysis were extracted using soil corer (8 cm diameter and 10 cm height). Real-time θv was measured using 5TE soil probes (20 cm depth). The EA2400CHNS/O and EA2410 analyzers were used to estimate soil C and N contents respectively. The interaction between grazing and rainfall manipulation increased θv and C but decreased N with no effect on ρ and C:N ratio. Rainfall reduction (50%) strongly affected most soil properties compared to an increase (150%). The highest (1.241 ± 0.10 g cm−3) and lowest (1.099 ± 0.05 g cm−3) ρ were in the G50% and U150% plots respectively. Soil θv decreased by 34.0% (grazed) and 25.8% (ungrazed) due to drought after rainfall cessation. Soil ρ increased with grazing due to trampling effect, therefore reducing infiltration of rainwater and soil moisture availability. Consequently, soil C content (11.45%) and C:N ratio (24.68%) decreased, whereas N increased (7.8%) in the grazed plots due to reduced C input and decomposition rate. The combined effect of grazing and rainfall variability will likely increase soil θv, thereby enhancing C and N input. Grazing during drought will induce water stress that will destabilize soil C and N contents therefore affecting other soil properties. Such changes are important in predicting the response of soil properties to extreme rainfall pattern and uncontrolled livestock grazing that currently characterize most savanna ecosystems.

Grazing modulates soil temperature and moisture in a Eurasian steppe

Few studies have addressed the potential grazing effects on microclimate, such as surface temperature and moisture, and their feedback effects on grassland function. A continuous, approximately three-year long study was conducted in experimental plots of various grazing intensities, and in situ soil temperature and moisture were measured. The results indicated that grazing significantly altered soil temperature and moisture. Soil temperature increased exponentially with increasing grazing intensity in the warm season due to the removal of aboveground biomass (AGB) and decreased linearly with increasing grazing intensity in the cold season due to decreases in both AGB and wind-blown snow accumulation. Heavy grazing increased soil temperature (10 cm depth) by an average of 2.6 °C from April to October (the largest hourly temperature increase was 8.8 °C), representing a soil warming effect 3.7 times that of global warming. Our findings showed that, compared with ungrazed plots, grazed plots had decreased soil water storage due to less winter snow accumulation, especially in the early growing season (EGS) because of the smaller amount of winter snow accumulation than in ungrazed plots. In the EGS, the average water storage in the 0–100 cm layer of the ungrazed plots was 23.3%, which was 1.3–1.8 times that of the grazed plots. Our results showed that grazing also produced warming and drying effects on grassland soil. The long-term feedback effects of grazing-induced soil warming and drying on the ecosystem might be an important mechanism accelerating the degradation and desertification of these grasslands.

Performance of growing pigs reared indoors or outdoors in sweet-potato fields

The study aimed to evaluate the effect of the genetic type (Large White [LW] vs Creole [CR]) and feeding management (indoors with concentrate [CSC], outdoors on sweet potato plots [OSP], indoors with the same ration as outdoors [CSP]) on 54 growing pigs. OSP animals had a growth rate of 240 grams per day, compared to 360 and 580 g/d for CSP and CSC pigs, respectively (p &lt; 0.001). Outdoors, LWs were more physically active than CRs (15% of the time in exploratory activities vs 10%, respectively; p &lt; 0.01). The distances covered over 24 hours were 90 meters for CRs and 150 meters for LWs (p &lt; 0.01). Blood profiles suggested a faster adaptive hematological response of CRs to system change (from indoors to outdoors). The study of soil macrofauna after passage of animals showed an increase on the grazed plots in macroinvertebrates (notably Oligochaeta, Dermaptera) that decompose organic matter. This study suggests that alternative livestock systems, although less efficient, may meet farmers’ needs for economic gain in animal production, using agricultural residues or minimizing human intervention.

Assessing the success of hydrological restoration in two conservation easements within Central Florida ranchland.

In the USA, the United States Department of Agriculture (USDA) Natural Resource Conservation Service (NRCS) has restored millions of acres of wetlands through its Wetland Reserve Easement (WRE) programs. However, few quantitative studies have explored whether WREs have enhanced wetland hydrology and wetland plant communities. Additionally, USDA Compatible Use Permits for cattle grazing and other management practices are sometimes issued for WREs, but little is known about potential benefits/detriments of such practice on the success of wetland restoration. In this study, we tested if hydrological restoration of previously drained species poor pastures increased water depth and hydroperiod. Restoration involved plugging key ditches, adding water control structures and a berm. We also tested if hydrological restoration increased plant diversity (alpha and beta), floristic quality (using coefficient of conservatism) and increased the cover of wetland species (using species wetland status). Finally, we tested if cattle grazing had an effect on the success of restoration by comparing grazed plots to fenced plots. We studied two conservation easements (a total of 748 acres) located on semi-native pastures in central Florida, USA. We monitored vegetation using permanent transects stratified by vegetation type before (2004–2005) and after (2012) the restoration (2008). We assessed wetland hydroperiod using groundwater wells set up in 2003 and located within and outside the boundaries of these two easements. We used linear mixed models and multivariate analyses to compare vegetation and hydroperiods pre- and post-restoration. Number of flooded days increased following restoration in one of the easements, but we did not detect significant changes in hydrology in the other easement. Floristic quality, beta diversity and cover of obligate wetland species increased in both conservation easements and in most vegetation types. These vegetation changes were likely due to restoration activities since annual rainfall was not significantly different pre- and post-restoration. Cattle grazing did not have a negative or positive effect on the success of restoration, nor did we detect any positive effect of grazing on the success of restoration. Overall, our study shows that hydrological restoration can enhance wetland hydroperiod, water depth and wetland vegetation, but more resources should be allocated to short- and long-term monitoring of the restoration success.

Grazing by wild giant pandas does not affect the regeneration of Arundinaria spanostachya

Arundinaria spanostachya is the main bamboo species on which giant pandas forage. Information on its regeneration capacity to meet the foraging demands of pandas is important to ensure the long-term survival of pandas. In 2014, 2 plot types (grazed versus control) were selected in the winter habitat used by one wild giant panda. Various morphological and regeneration characteristics of the bamboo were assessed in the respective plots during 2014 and 2015. The panda avoided feeding on bamboo with a basal diameter of < 6 mm, preferentially feeding on intermediate-sized bamboo. The density of new shoots and the recruitment rate of shoots were significantly higher in the grazed plots compared to the control plots. The annual recruitment rate of shoots was markedly higher than the annual mortality rate in the same plot type. After grazing, the basal diameter and height of new bamboo were similar between the 2 plots. In the grazed plots, the basal diameter of new bamboo was similar to that of the stumps. Innutrition and foraging by insects were the main factors influencing the survival of new shoots. Our results showed that grazing by giant pandas helped the clonal regeneration of A. spanostachya populations, with the basal diameter of new bamboo shoots meeting the foraging demand of pandas. However, information on the carrying capacity of A. spanostachya is necessary to ensure sufficient forage matter is available for reintroduced giant pandas. Furthermore, fertilization and insect control measures should be implemented during the shooting period to optimize A. spanostachya resources.

Altitudinal pattern of grazing exclusion effects on vegetation characteristics and soil properties in alpine grasslands on the central Tibetan Plateau

Grazing exclusion by fencing has been widely used for restoring degraded alpine grasslands, but rarely studies have considered the altitudinal difference of grazing exclusion effects on vegetation characteristics and soil properties. In this study, we focused our attention mainly on how alpine grasslands at different altitudes will response to long-term grazing exclusion. A 10-year altitudinal grazing exclusion experiment was conducted along a large altitudinal gradient (six altitudes, from 4400 to 5100 m) in alpine meadows on the central Tibetan Plateau. The vegetation characteristics and soil properties across grazing exclusion plots and free grazing plots were observed at each of six altitudes. Above-ground biomass (AGB), below-ground biomass (BGB), soil organic carbon (SOC), soil total nitrogen (STN), soil microbial biomass carbon (MBC), and soil microbial biomass nitrogen (MBN) showed a unimodal pattern along the altitudinal gradient from 4400 to 5100 m. A similar altitudinal pattern was found in sedges biomass but not in that of grasses, legumes, and herbs. Grazing exclusion practice increased vegetation cover, plant height, AGB, BGB, STN, SOC but has no significant effect on community diversity. Grazing did not alter the altitudinal patterns of AGB, BGB, SOC, and STN, but the stimulation impacts of grazing exclusion on these factors decreased with increasing altitude. The relative changes of MBC and MBN after grazing exclusion were significant related with that of BGB. Our study indicates that grazing exclusion by fencing is effective to restore vegetation and improve soil carbon and nitrogen properties in overgrazed alpine grasslands. However, the stimulation effects of grazing exclusion on alpine grasslands decreased with increasing altitudes. We suggest that in the high-altitude grassland ecosystems, especially where environment is harsh and stocking rate is relative low, grazing exclusion might not be efficient enough for restoring degraded grasslands.

Cattle Grazing Affects Peanut Root Characteristics in a Bahiagrass-Based Crop Rotation System

ABSTRACT The critical aspect of production agriculture in the southeastern US with increasing associated costs is to improve economic and agronomic sustainability. A four yr sod-based rotation system consisting of two yr of bahiagrass (Paspalum notatum Flueggé) (grazed or non-grazed) followed by a yr of peanut (Arachis hypogaea L.) and a yr of cotton (Gossypium hirsutum L.), each with winter cover crop (grazed or non-grazed) was established in Marianna, FL. The effect of grazing on root parameters (length, volume, surface area, and diameter) of peanut was observed using a mini-rhizotron. There were differences in several root parameters between grazed and non-grazed plots including: peanut root length (307 mm in grazed vs 167 mm in non-grazed), volume (50 mm3 in grazed vs. 23 mm3 in non-grazed), surface area (399 mm2 in grazed vs. 197 mm2 in non-grazed), and diameter (2.4 mm in grazed vs. 1.7 mm in non-grazed). Roots at the 45-60 cm and 60-75 cm depths had significantly greater length in the grazed than the non-grazed plots. Likewise, surface area was significantly greater in the grazed plots at the 30-45 cm, 45-60 cm and 60-75 cm depths. Grazed plots at the 40-65 cm depths showed significant increase in root diameter. No significant difference in peanut yield was observed for the grazed or non-grazed treatments. A more developed root system associated with cattle grazing in the sod-based rotation system may enable peanuts to be more resilient in adverse environmental conditions such as drought stress, enhance nutrient cycling without affecting yield, thereby improving long-term sustainability.

Effects of grazing disturbance on plant diversity, community structure and direction of succession in an alpine meadow on Tibet Plateau, China

To elucidate the effects of grazing intensity and grazing time on plant diversity and community structure, as well as the successional differentiation in an alpine meadow, a controlled grazing trial, with six grazing intensities on an alpine meadow was conducted in the eastern Qilian Mountain region for four years. Using species accumulation curves, RDA ordination and variance decomposition, we analyzed the changes in proportion of dominant species, richness, abundance, as well as the life forms of plant communities under grazing disturbance. Both the grazing intensity and grazing time had a significant effect on these dominant species, richness, abundance, as well as the life forms in the plant community (P<0.01). More detailed results showed that: (1) The richness and abundance of plant species were highest in the light grazing plot, and these increased as time passed. In the heavy grazing plot, the abundance of plant species decreased as time passed, but the richness of these species did not change significantly. (2) The abundance of Gramineae and Umbelliferae were negatively and significantly correlated with the duration of grazing treatments, whereas Plantaginaceae and Geraniaceae were positively and significantly correlated with the grazing intensity. Over time, the abundance of bunch-type plants decreased and other life forms of plants have increased. With the increase in grazing intensity, the plants' abundance with the rosette type did not change, but other life forms of plants decreased. The results of variance decomposition indicated that grazing disturbance has had greater effects on life forms and plant populations, followed by the changes in the dominant species and their abundance, with lesser effects on the richness of the species. Grazing intensity had a greater effect than the duration of the grazing treatment had. The results of PCA showed that the climax community in both the lowest and the highest grazing intensity plots had changed over time. In the sample plots with light grazing intensity, the plant community changed to an Elymus nutans+Poa crymophila community, but later changed to a Melilotoides ruthenicus+Kobresia humilis community under heavy grazing.