Long-term effects of daily grazing orbits on nutrient availability in Sahelian West Africa: 2. Effects of a phosphorus gradient on spatial patterns of annual grassland production

Abstract. This paper reports on an investigation of the effect of a livestock-generated gradient in phosphorus-availability on spatial patterns of annual rangeland production around pastoral watering points in the Sahelian region of West Africa. The study was conducted along a major transhumance corridor used for at least the past century by herds managed by agropastoralists of the Inland Niger Delta of Mali. Eighteen sites on sandy substrate were established at varying distances from: (1) a more persistent pan from which livestock disperse to graze primarily during the early dry season (D1); and (2) a line of ephemeral pans from which livestock disperse to graze during the rainy season (D2). Data on the species composition, standing herbaceous mass, and annual herbaceous cover were collected at these sites over the 2 years following a significant drought. These vegetative parameters show considerable interannual variation in their spatial pattern. As reported elsewhere (companion paper), chemical analyses of soil and plant samples collected at these sites show a significant negative correlation between phosphorus availability and D2. This is consistent with livestock-mediated nutrient transfer from outlying zones toward rainy-season pans. The effect of this phosphorus gradient on annual rangeland production was analysed using a regression modelling approach. Two vegetative production parameters, vegetated surface fraction (VSF) and herbaceous above-ground standing mass of vegetated surface (VAGM), were regressed in a two-and three-step process on the following factors: (1) background soil and rainfall data; (2) forb fraction of herbaceous production (for VAGM only), followed by: (3) D1 and D2. These analyses find that while the phosphorus-availability gradient had a significant effect on spatial patterns of herbaceous production during the year immediately following the drought, it had little effect in the subsequent year's production. This difference is explained by the increased importance of nitrogen in limiting herbaceous production during the second year, resulting from its different rainfall history.     

Pulses of soil phosphorus availability in a Mexican tropical dry forest: effects of seasonality and level of wetting

Intact cores from the upper soil profile and surface litter were collected at the peak of the dry season and during the rainy period in the tropical deciduous forest of the Chamela region, Jalisco, México, to (1) analyze upper soil phosphorus (P) movement and retention, (2) compare soil P dynamic pools (soluble, bicarbonate, and microbial) in dry and rainy seasons, and (3) determine the response of these P pools to wetting. Unperturbed litter-soil cores were treated in the laboratory with either 10 mm or 30 mm of simulated rain with carrier-free ³²P and compared to a control (no water addition) to determine the fate and retention of added P. ³¹P concentrations and pools in most litter and soil fractions were higher in the dry than in the rainy season. Soluble P was 0.306 g/m² and microbial P was 0.923 g/m² in the dry season (litter plus soil) versus 0.041 (soluble) and 0.526 (microbial) g P/m² in the rainy season. After water addition, rainy-season cores retained 99.9 and 94% of ³²P in the 10- and 30-mm treatments, respectively. Dry-season samples retained 98.9 and 80% of inputs in the same treatments. Retention after wetting occurred mostly in soil (bicarbonate and microbial fractions). Simulated rainfall on rainy-season soils increased P immobilization. On the other hand, simulated rainfall on dry-season soils released P through mineralization. The P release represents between 46 and 99% of the annual litterfall return. Our results suggest that both soluble and microbial P constitute important sources for initiation of plant growth at the onset of the rainy season in tropical dry forest. Received: 23 September 1997 / Accepted: 2 February 1998     

Vegetation and soil responses to livestock grazing in Central Asian grasslands: a review of Chinese literature

Grasslands in northern China and the Qinghai-Tibetan plateau are particularly important to both ecosystem functioning and pastoral livelihoods. Although there are numerous degradation studies on the effect of livestock grazing across the region, they are largely only published in Chinese, and most focus on single sites. Based on case studies from 100 sites, covering a mean annual precipitation gradient of 95–744 mm, we present a comprehensive, internationally accessible review on the impact of livestock grazing on vegetation and soils. We compared ungrazed or slightly grazed sites with moderately and heavily grazed sites by evaluating changes in two indicator groups: vegetation (plant species richness, vegetation cover, aboveground biomass, belowground biomass and root/shoot ratio) and soil (pH, bulk density, organic C, total N, total P and available P). Most indicators declined with intensified grazing, while soil pH, bulk density and belowground biomass increased. Available P showed no clear response. Variables within indicator groups were mostly linearly correlated at a given grazing intensity. Relative grazing effects on different indicators varied along specific abiotic gradients. Grazing responses of plant species richness, aboveground biomass, soil bulk density, total N and available P interacted with precipitation patterns, while grazing effects on belowground biomass were influenced by temperature. Elevation had impact on grazing responses of aboveground biomass and soil organic carbon. Complex grazing effects reflect both methodological inconsistency and ecological complexity. Further assessments should consider specific characteristics of different indicators in the context of the local environment.     

Responses of vegetation and soils to three grazing management regimes in a semi‐arid highland mixed crop‐livestock system

Three grazing regimes [Cut‐and‐carry (CC), seasonal grazing (SG) and continuous grazing (CG)] currently applied in Tigrai region of northern Ethiopia were compared to identify the best grazing management in key native vegetation and soil attributes. More than 50% of the desirable species such as Andropogon, Cynodon and Phalaris spp were located in the CC and SG regimes. During the rainy season, the CC regime produced 1.7 and 2.7 more biomass than the SG and CG regimes, respectively. Herbaceous basal cover was 6.8 times more in the CC than in the CG regime. During the rainy season, herbaceous species diversity and richness were the least in the CG regime but similar in the CC and SG regimes. This similarity, however, changed during the dry season when the SG regime is grazed by livestock that led to a reduction in diversity. These results suggest that CC is superior to the traditional CG, but not always necessarily superior to the SG. The SG regime improved soil P status while the CG regime affected soil bulk density and total N negatively. The predominantly native vegetation grazing systems in Tigrai region can be improved cost effectively through cut‐and‐carry and seasonal grazing.     

Effects of long-term management practices on grassland plant assemblages in Mediterranean cork oak silvo-pastoral systems

The assessment of the effects of long-term management practices is relevant in understanding the current patterns of plant assemblages in semi-natural ecosystems. We hypothesized that the variety of management practices across different farming systems under the same ecological conditions directly and indirectly shapes these patterns via the long-term changes induced in soil features. The aims of this paper were to evaluate the influence of two sets of variables describing long-term management practices and soil features on plant assemblages and their importance in the context of Mediterranean silvo-pastoral systems. The analysis of variance revealed that richness and grazing value were not affected at all by grazing livestock species and soil tillage frequency and that they both showed relatively high absolute values for the specific context under study. Trifolium subterraneum was a key species in contributing to grassland grazing value and habitat biodiversity. The Canonical Correspondence Analysis highlighted the influence of management practices and soil features on plant assemblage composition, which was significantly affected by grazing livestock species and stocking rate and by soil pH and K content. The Redundancy Analysis showed that soil pH and related features were in turn affected by stocking rate, supporting our hypothesis that management practices influenced plant assemblage composition directly and indirectly via their long-term effects on soil features. The results also highlighted that a systemic analytical perspective applied at a grazing system scale can be effective in addressing sustainable grassland management issues in Mediterranean silvo-pastoral systems.     

The effects of grazing and burning on soil and plant nutrient concentrations in Colombian páramo grasslands

The impact of extensive livestock farming on the physical and chemical characteristics of the volcanic soils and on the nutrient status of green plant tissues of neotropical alpine grasslands (páramo) is studied. Soil and plant samples were taken over a one-year period at five sites with different agricultural (grazing and burning) management. In the undisturbed páramo ecosystem, soil moisture (50–250%) and organic matter content are high (7–27%) and decomposition (11–35% yr^-1) and element concentrations are low. Low temperatures (max < 10°C) and phosphorus fixation by the soil (5 mg P g^-1 soil) determine the low mineralization and turn-over rates.Multivariate analysis of laboratory results indicates that the season of sampling and the agricultural practice are the most important explanatory factors for variation of soil characteristics. After long-term heavy grazing, soils have a higher bulk density and a lower moisture content. The outcome of a litterbag experiment confirms the hypothesis of higher decomposition rates at grazed sites. In the intermediate (wet-dry) season, conditions were somewhat better for plant growth but the system remained nutrient limited.Surprisingly, no relation between soil density, moisture or carbon content and concentrations of available nutrients in the soil is found. This is supported by the rather uniform nutrient concentrations in green plant tissue among the sites. It is concluded therefore that the effect of burning and grazing on páramo soils is principally restricted to physical characteristics, and that differences in chemical characteristics of the soil do not cause differences in vegetation structure between grazed, burned and undisturbed sites.The Netherlands Centre for Geo-ecological Research, ICG.     

放牧强度对高寒嵩草草甸土壤养分特性的影响

植物-土壤系统是草地生态和生产服务价值实现的基础,放牧是草地植物群落演替的重要因素。植物、土壤亚系统对放牧的敏感性是评价草地稳定性和提高草地恢复力的重要依据。以不同放牧强度下的高寒嵩草(Kobresia)草甸为研究对象,探讨土壤养分特征对放牧强度的响应及作用位点,结果表明:改变放牧强度可以明显改变植物群落数量特征,但没有明显改变土壤层次分类特征,说明土壤养分特征对一定范围内放牧强度具有自我稳定维持功能;但放牧干扰强度不同时,土壤剖面过渡层养分含量存在差异,说明长期放牧强度的差异会对土壤剖面养分性质产生影响,且这种影响起源于土壤剖面过渡层。在放牧高寒嵩草草甸植物-土壤系统中土壤剖面养分特征较植物群落数量特征更稳定;土壤剖面过渡层养分特征是土壤亚系统中对放牧的敏感因素;而放牧引起土壤剖面养分特征的改变主要表现在各过渡层上,并构成土壤发生层迁移的风险,因此推测,更为持久和更高强度的放牧干扰将最终改变土壤剖面特征及养分性质。     

Effects of experimental season of prescribed fire and nutrient addition on structure and function of previously grazed grassland

Aims Understanding the drivers of grassland structure and function following livestock removal will inform grassland restoration and management. Here, we investigated the effects of fire and nutrient addition on structure and function in a subtropical semi-native grassland recently released from grazing in south-central Florida. We examined responses of soil nutrients, plant tissue nutrients, biomass of live, standing dead and litter, and plant species composition to experimental annual prescribed fire applied during different seasons (wet season vs. dry season), and nutrient additions (N, P and N + P) over 9 years.Methods Experimental plots were set up in a randomized block split-plot design, with season of prescribed fire as the main treatment and nutrient addition as the subplot treatment. Species cover data were collected annually from 2002 to 2011 and plant tissue and plant biomass data were collected in 2002–2006 and 2011. Soil nutrients were analyzed in 2004, 2006 and 2011.Important findings Soil total phosphorus (P) levels increased substantially with P addition but were not influenced by prescribed fire. Addition of P and N led to increased P and N concentrations in live plant tissues, but prescribed fire reduced N in live tissue. Levels of tissue N were higher in all plots at the beginning of the experiment, an effect that was likely due to grazing activity prior to removal of livestock. Plant tissue N steadily declined over time in all plots, with annually burned plots declining faster than unburned plots. Prescribed fire was an important driver of standing dead and litter biomass and was important for maintaining grass biomass and percent cover. Nutrient addition was also important: the addition of both N and P was associated with greater live biomass and woody forbs. Removal of grazing, lack of prescribed fire, and addition of N + P led to a reduction of grass biomass and a large increase in biomass of a woody forb. Annual prescribed fire promoted N loss from the system by reducing standing dead and litter, but maintained desirable biomass of grasses.     

The impact of rabbits and cattle on an arid calcareous shrubby grassland in central Australia

Multivariate methods of classification and ordination were used to examine changes in plant composition over a three year period on a calcareous shrubby grassland grazed by rabbits and cattle in central Australia. In a site-time ordination of the data for all years, the season and amount of rainfall was the most important influence, followed by several soil factors and rabbit density. In a site ordination of each year, rabbit density was a minor influence for the pretreatment data but increased in importance over the three years until it was highly correlated with vector one in the final year. This was a result of the exclosure treatments diverging from the controls with extremely high rabbit populations at two of the eighteen plots. When site-time trajectories were plotted through species space, most sites tended to move with season over the three year period towards a common domain. The two heavily grazed sites exhibited a different trajectory; this was due to the behaviour of seven plant species under grazing. In multiple regression analysis, rabbit density, cattle presence and yearly rainfall explained 66% of the variation in total standing biomass. In general, total cover was not affected by grazing treatment, although short term utilisation effects were usually visible in the late dry season. Given its present degraded state, this arid vegetation type is seen as reasonably resilient, requiring extremely heavy rabbit grazing to prevent the plant community responding to the dominating influence of season.Nomenclature follows J. Jessop (ed.), 1981. Flora of Central Australia. The Australian Systematic Botany Society. Reed Press, Sydney.I thank G. Pearce and K. Jones for their diligent data collection, preparation and analysis.     

Disturbance is more important than seeding or grazing in determining soil microbial communities in a semiarid grassland

A primary goal of ecological restoration is often to return processes and functions to degraded ecosystems. Soil, while often ignored in restoration, supports diverse communities of organisms and is a fundamental actor in providing ecosystem processes and services. We investigated the impact of seeding and livestock grazing on plant communities, soil microorganisms, and soil fertility 3 years after the restoration of a disturbed pipeline corridor in southeastern Arizona. The initial soil disturbance and topsoil treatment, regardless of seeding or grazing, was the most influential factor in determining differences in both plant and microbial communities. Compared with the control, the disturbed and restored sites had greater plant species richness, greater total herbaceous plant cover, greater soil organic matter, higher pH, and differed in soil nutrients. Bacteria and fungi appeared to generally correlate with micro‐environment and soil physiochemical properties rather than specific plant species. The undisturbed control had a smaller proportion of bacterial functional groups associated with the breakdown of plant biomass (polysaccharide decomposition) and a smaller proportion of arbuscular mycorrhizal fungi (AMF) compared with disturbed and restored sites. The ability of the unseeded disturbed site to recover robust vegetation may be due in part to the high presence of AMF. These differences show selection for soil microorganisms that thrive in disturbed and restored sites and may contribute to increased plant productivity. Restoration of specific plant species or ecological processes and services would both benefit from better understanding of the impacts of disturbance on soil microorganisms and soil fertility.     

Spring-water Nitrate Increased with Removal of Livestock Grazing in a California Oak Savanna

We characterized spatial and temporal changes in nitrate concentrations of the leachate from annual grasslands and subsequently emergent spring-waters and tested the effect of livestock grazing removal on them. Nitrate patterns indicated that annual grassland soils are a likely N source to spring-fed wetlands, which appear to intercept and transform N along its hydrologic path from upland soils to spring-fed, headwater streams. Aboveground biomass and soil N extractions suggested that removal of livestock grazing from these wetlands impaired this function by allowing dead plant material to accumulate inhibiting plant production (hence, plant N demand), resulting in elevated stream-water nitrate (NO₃⁻) concentrations. Nitrous oxide (N₂O) fluxes indicated that grazing removal may increase the relative importance of this N-loss pathway. Microbial biomass varied with season but was not affected by grazing treatments suggesting that N₂O losses were related to differences in NO₃⁻ availability rather than grazing effects on microbial community composition or their activity. Spring-fed wetlands provide important ecosystem services such as plant uptake and denitrification at transition zones between terrestrial and aquatic ecosystems. These N-retention and transformation functions may be enhanced through biomass harvesting by livestock.     

Interacting effects of fertilization,mowing and grazing on plant species diversity of 1500 grasslands in Germany differ between regions

The relationship of different types of grassland use with plant species richness and composition (functional groups of herbs, legumes, and grasses) has so far been studied at small regional scales or comprising only few components of land use. We comprehensively studied the relationship between abandonment, fertilization, mowing intensity, and grazing by different livestock types on plant diversity and composition of 1514 grassland sites in three regions in North-East, Central and South-West Germany. We further considered environmental site conditions including soil type and topographical situation. Fertilized grasslands showed clearly reduced plant species diversity (?15% plant species richness, ?0.1 Shannon diversity on fertilized grasslands plots of 16 m²) and changed composition (?3% proportion of herb species), grazing had the second largest effects and mowing the smallest ones. Among the grazed sites, the ones grazed by sheep had higher than average species richness (+27%), and the cattle grazed ones lower (?42%). Further, these general results were strongly modulated by interactions between the different components of land use and by regional context: land-use effects differed largely in size and sometimes even in direction between regions. This highlights the importance of comparing different regions and to involve a large number of plots when studying relationships between land use and plant diversity. Overall, our results show that great caution is necessary when extrapolating results and management recommendations to other regions.     

不同强度牦牛放牧对青藏高原高寒草地土壤和植物生物量的影响

放牧作为家畜饲养方式之一,是草地最简单、有效的利用方式,放牧中的家畜对草地生态系统的影响是全球畜牧生态学研究的焦点。过度放牧导致草地退化严重,虽然在青藏高原地区已有较多放牧对草地影响的研究,但探究连续4年放牧对高寒草地生态系统影响的定位实验却鲜见报道。本研究在青藏高原东缘选取典型高寒草地,使用高原特有且分布最广的牦牛作为大型草食放牧家畜,设置了4个牦牛放牧强度（禁牧：无放牧、轻牧：1头/hm²、中牧：2头/hm²和重牧：3头/hm²）以研究其对高寒草地土壤和植物功能的影响。开展4年试验后的结果表明：放牧条件下土壤含水率显著增加;而土壤容重、全磷和有机质含量对放牧强度均无显著性响应;土壤全氮和pH的响应主要在表层0-20 cm,其中全氮为轻牧和重牧处理分别显著高于中牧,中牧处理下的土壤pH为显著高于轻牧;土壤全钾含量在禁牧处理中显著高于放牧处理;而土壤有效氮和速效钾均为中牧处理显著高于禁牧;放牧可以显著降低植物地上生物量。牦牛放牧强度显著影响土壤含水率、有效养分和植物地上生物量,而对其它土壤理化性质影响较弱。本研究结果揭示放牧对高寒草地土壤理化性质和植物地上生物量的影响,为青藏高原高寒草甸生态系统保护、可持续管理和合理放牧率提供理论依据。     

Effects of Soil Carbon Amendment on Nitrogen Availability and Plant Growth in an Experimental Tallgrass Prairie Restoration

Restoration of tallgrass prairie on former agricultural land is often impeded by failure to establish a diverse native species assemblage and by difficulties with nonprairie, exotic species. High levels of available soil nitrogen (N) on such sites may favor fast‐growing exotics at the expense of more slowly growing prairie species characteristic of low‐N soils. We tested whether reducing N availability through soil carbon (C) amendments could be a useful tool in facilitating successful tallgrass prairie restoration. We added 6 kg/m² hardwood sawdust to experimental plots on an abandoned agricultural field in the Sandusky Plains of central Ohio, United States, increasing soil C by 67% in the upper 15 cm. This C amendment caused a 94% reduction in annual net N mineralization and a 27% increase in soil moisture but had no effect on total N or pH. Overall, plant mass after one growing season was reduced by 64% on amended compared with unamended soil, but this effect was less for prairie forbs (?34%) than for prairie grasses (?67%) or exotics (?62%). After the second growing season, only exotics responded significantly to the soil C amendment, with a 40% reduction in mass. The N concentration of green‐leaf tissue and of senescent leaf litter was also reduced by the soil C treatment in most cases. We conclude that soil C amendment imparts several immediate benefits for tallgrass prairie restoration––notably reduced N availability, slower plant growth, and lower competition from exotic species.     

Effect of sulfuric acid discharge on river water chemistry in peat swamp forests in central Kalimantan,Indonesia

To estimate the range of area that is affected by sulfuric acid pollution after pyrite oxidation, the surface water chemistry of two rivers in peat swamp forests in central Kalimantan, Indonesia, was surveyed at 1.0- to 3.0-km intervals in September 2003 and 2004 (dry season) and March 2004 and 2005 (rainy season). Water discharged from canals into the main stream of the Sebangau River and the Kahayan River showed lower pH compared to the mainstream water of the rivers, implying sulfuric acid loading from the canal to the main stream of the rivers. The ratio of concentrations of sulfate ion/chloride ion, which was used as a parameter for estimating the contribution of pyritic sulfate to river water chemistry, showed that sulfuric acid loading from pyrite oxidation occurred from the river mouth up to 150 km upstream in both rivers. Water of the main stream of the rivers as well as water discharged from artificial canals into the main stream in the rainy season showed much higher acidity and a higher ratio of sulfate ion/chloride ion than that in the dry season. This result implies that the discharge of pyritic sulfate from peat swamp forests to the limnological system is much higher in the rainy (high water table) season than the dry (low water table) season. Water in the canal in the rainy season was found to be highly acidic (pH = 2.0–3.0). Pyrite oxidation after peatland development causes not only acidification of soil but also acidification of the limnological ecosystem.     

Removal of livestock alters native plant and invasive mammal communities in a dry grassland–shrubland ecosystem

The impacts of domesticated herbivores on ecosystems that did not evolve with mammalian grazing can profoundly influence community composition and trophic interactions. Also, such impacts can occur over long time frames by altering successional vegetation trajectories. Removal of domesticated herbivores to protect native biota can therefore lead to unexpected consequences at multiple trophic levels for native and non-native species. In the eastern South Island of New Zealand large areas of seral grassland–shrubland have had livestock (sheep and cattle) removed following changes in land tenure. The long-term (>10 years) outcomes for these communities are complex and difficult to predict: land may return to a native-dominated woody plant community or be invaded by exotic plants and mammals. We quantified direct and indirect effects of livestock removal on this ecosystem by comparing plant and invasive mammal communities at sites where grazing by livestock ceased c.10–35 years ago (conservation sites) with paired sites where pastoralism has continued to the present (pastoral sites). There was higher total native plant richness and reduced richness of exotic plants on conservation sites compared with pastoral sites. Further, there were differences in the use of conservation and pastoral sites by invasive mammals: rabbits and hedgehogs favoured sites grazed by livestock whereas house mice, brushtail possums and hares favoured conservation sites. Changes in the relative abundance of invasive mammal species after removal of domesticated livestock may compromise positive outcomes for conservation in successional plant communities with no evolutionary history of mammalian grazing.     

Potential long-term impacts of livestock introduction on carbon and nitrogen cycling in grasslands of Southern South America

Empirical evidence based on grazing exclusion at the scale of years to decades shows that grazing modifies carbon (C) and nitrogen (N) cycling. However, long‐term effects at the scale of centuries are less known, yet highly relevant to understand local and global impacts of grazing. Additionally, most studies have focused on the isolated response of C and N, with little understanding of their interactions. Using CENTURY, a process‐based biogeochemical model, we analyzed the impacts of 370 years of livestock grazing (i.e. long term, from early European colonization to present) in 11 sites across the Río de la Plata grasslands and compared them with those resulting from two decades of grazing (i.e. mid‐term, typical exclosure experiment). In the long term, livestock grazing primarily altered the N cycle through faster N returns to the soil via urine and dung, which were offset by uninterrupted N outputs by volatilization and leaching. As a result, soil organic N decreased by ?880 kg ha^?1 or ?19%. Higher N outputs (mainly as NH₃) opened the N cycle, potentially decreasing N₂O and NO_x emissions and increasing N depositions over the region. These greater outputs of N constrained C accumulation in soils, reducing soil organic C by ?21 200 kg ha^?1 (?22%, a reduction of ?1.5 Pg of C for the whole region) and net primary production by ?2192 kg ha^?1 yr^?1 (?24%). Mid‐term simulations showed that the effects of livestock introduction in a decadal time scale were substantially different both in magnitude and direction from long‐term responses. Long‐term results were not substantially affected when atmospheric CO₂ content, species composition and fire regime were changed within plausible ranges, but highlighted fire‐grazing interactions as a major constraint of long‐term C and N dynamics in these grasslands.     

Recovery of Tawa-dominated forest fragments in the Rotorua Basin, New Zealand, after cessation of livestock grazing

Summary   Tawa ( Beilschmiedia tawa )-dominated forest fragments on farms within the Rotorua Basin were surveyed to quantify the likely recovery processes following exclusion of domestic livestock grazing, using a space-for-time substitution approach. Vegetation structure, plant diversity and soil fertility were measured at 24 sites within 15 forest fragments on six farms, covering a range in time since exclusion from grazing of 1–53 years. The forest fragments were compared with a large area of ungrazed forest in the nearby Lake Okataina Scenic Reserve. As time since exclusion from grazing increased, indigenous plant species diversity increased (up to 30–35 years); ground fern and epiphyte abundance increased (up to 30–35 years); tree seedling and sapling numbers, and litter cover also increased (up to 10–15 years); and overall tree numbers increased, while average tree diameter at breast height and overall tree basal area did not differ significantly. The soil fertility status was highly variable, obscuring clear patterns, although Olsen P status decreased with time since grazing exclusion. Once grazing of forest fragments ceases, significant changes in their diversity, structure and soil characteristics can be expected, which indicate recovery of these plant communities towards the conditions observed in ungrazed forest.     

Using a trait‐based approach for assessing the vulnerability and resilience of hillslope seep wetland vegetation cover to disturbances in the Tsitsa River catchment,Eastern Cape,South Africa

Hill slope seep wetlands are ecologically and economically important ecosystems as they supply a variety of ecosystem services to society. In South Africa, livestock grazing is recognized as one of the most important disturbance factors changing the structure and function of hill slope seep wetlands. This study sought to investigate the potential effect of livestock grazing on the resilience and vulnerability of hillslope seep wetland vegetation cover using a trait‐based approach (TBA). Changes in vegetation cover were used as a surrogate for indicating grazing intensity. The degree of human disturbances was assessed using the Anthropogenic Activity Index. A TBA was developed using seven plant traits, resolved into 27 trait attributes. Based on the developed approach, plant species were grouped into vulnerable and resilient groups in relation to grazing pressure. It was then predicted that species belonging to the vulnerable group would be less dominant at the highly disturbed sites, as well as in the winter season when grazing pressure is at its peak. The approach developed enabled accurate predictions of the responses of hillslope plant species to grazing pressure seasonally, but spatially, only for the summer season. The predicted responses during the winter season across sites did not match the observed results, which could be attributed to the difficulty in species identification and accurate estimation of vegetation cover during winter. Overall, the approach developed here provides a general framework for applying the TBA and can thus be tested and applied elsewhere.