Effects Of Grazing Exclusion Research Articles

Effects of grazing exclusion on soil properties, fungal community structure, and diversity in different grassland types.

Soil fungi are involved in the decomposition of organic matter, and they alter soil structure and physicochemical properties and drive the material cycle and energy flow in terrestrial ecosystems. Fungal community assembly processes were dissimilar in different soil layers and significantly affected soil microbial community function and plant growth. Grazing exclusion is one of the most common measures used to restore degraded grasslands worldwide. However, changes in soil fungal community characteristics during grazing exclusion in different types of grasslands are unknown. Here, we investigated the effects of a 9-year grazing exclusion on soil properties, fungal community composition, and diversity in three grassland types (temperate desert, temperate steppe, and mountain meadow). The results showed that (1) in the 0-5 cm soil layer, grazing exclusion significantly increased the differences in SWC, SOC, KN, and N:P among the three grassland types, while the final pH, BD, TP, C:N, and C:P values were consistent with the results before exclusion. In the 5-10 cm soil layer, grazing exclusion significantly increased total phosphorus (TP) in temperate deserts by 34.1%, while significantly decreasing bulk density (BD) by 9.8% and the nitrogen: phosphorus ratio (N:P) by 47.1%. (2) The soil fungal community composition differed among the grassland types, For example, significant differences were found among the three grassland types for the Glomeromycota and Mucoromycota. (3) Under the influence of both grazing exclusion and grassland type, there was no significant change in soil fungal alpha diversity, but there were significant differences in fungal beta diversity. (4) Grassland type was the most important factor influencing changes in fungal community diversity, and vegetation cover and soil kjeldahl nitrogen were the main factors influencing fungal diversity. Our research provides a long-term perspective for better understanding and managing different grasslands, as well as a better scientific basis for future research on grass-soil-microbe interactions.

Different effects of long-term grazing exclusion and growth stages on soil fungi and bacteria in an alpine steppe on the Qinghai-Tibetan Plateau

Changes in soil microorganisms caused by enclosure have long been an important topic in grassland ecology. However, few studies have described the responses of the soil microbial community composition, functional groups, and co-occurrence networks at different growth stages to long-term grazing exclusion or compared the indicative abilities of diversity and network parameters on soil ecosystem functions after grazing exclusion. In this study, we conducted a field experiment to evaluate the response of soil microbes to long-term grazing exclusion in an alpine steppe on the Qinghai-Tibetan Plateau. Our results showed that both soil fungal and bacterial community compositions at different growth stages showed significant differences. However, the enclosure only altered the fungal community composition. Differences in soil microbial functional groups between fungi and bacteria were also detected. The leading group in soil fungi was governed by grazing exclusion, and most bacterial functional groups showed significant differences between the growth stages. The co-occurrence network patterns of the fungi and bacteria differed significantly. Unexpectedly, the enclosure did not significantly alter the fungal or bacterial co-occurrence networks. Network parameters had a stronger ability to indicate soil ecosystem functions than the diversity index, displaying better relationships between network parameters and soil organic carbon and nitrate. These findings suggest that elucidating the responses of soil microbes at different growth stages is necessary to comprehensively understand soil ecosystems after long-term grazing exclusion in the alpine steppe.

Effects of Grazing Exclusion on Microbial Community Diversity and Soil Metabolism in Desert Grasslands

In this study, the effect of 14 years of GE exclusion in a desert grassland on soil microbial community diversity and metabolites was examined. GE changed the bacterial community structure, the alpha diversity of the bacterial community, and the total phosphorus (TP) and total potassium (TK) content in the soil. More specifically, the relative abundance of Actinobacteria, Proteobacteria, and Chloroflexi increased with GE. In contrast, the relative abundance of Acidobacteria was higher during grazing (G), so it is believed that soil bacteria adapt to environmental changes. Both amino acid and carbohydrate metabolism were enhanced, while lipid metabolism was decreased under GE. It was concluded that GE could trigger changes in both bacterial diversity and soil metabolites, increase the energy supply, and regulate ecosystem function. Consequently, GE would have positive effects on the restoration of desert grasslands by altering the soil microbial community. This work provides new insights into the response of soil microbes to GE.

Effects of Grazing Exclusion on Vegetation and Soil Properties of a Leymus chinensis Steppe in China

Effects of Grazing Exclusion on Vegetation and Soil Properties of a Leymus chinensis Steppe in China

Transient shifts in composition of degraded temperate native grassland following grazing exclusion

AbstractQuestionsGlobally, grassy ecosystems are threatened and are still declining in extent in many areas. Improving the management of degraded native temperate grasslands that are grazed by livestock is important to the conservation of this critically endangered ecosystem. Questions remain about the role of grazing in the management of such grasslands, particularly in the face of climate change and given the sensitivity of these systems to inter‐annual rainfall variability. Here, we investigate the effect of livestock exclusion on grassland composition.LocationTemperate grassland, Victoria, Australia.MethodsOver 9 years (2009–2017), we monitored plant functional groups in plots open‐to‐grazing or ungrazed exclusion plots within five fields of degraded native temperate grassland on private land.ResultsIn the years after grazing had been excluded, we found significant differences in cover between grazed and ungrazed plots for some functional groups (e.g. native perennial graminoids) in some years, but we did not observe long‐term divergence in cover or composition of the treatments. At the final monitoring point there were no significant differences in native or exotic species richness between the grazed and ungrazed plots. We show that the years in which differences were observed correspond with the 2010–2011 La Niña high‐rainfall event, suggesting that grazing exclusion effects are mediated by rainfall, and are likely to be evident only under certain conditions.ConclusionIn grassy ecosystems already degraded by long‐term grazing, excluding grazing has limited potential to shift plant species composition in favour of native dominance. Such grasslands may persist in the medium term in a stable but degraded state with or without continued light to moderate livestock grazing pressure. Hence, managed livestock grazing need not be incompatible with the conservation of degraded temperate grasslands particularly where biomass management is important for the maintenance of faunal habitat. However, improving the function and diversity of these degraded grasslands will seemingly require additional management, including seed addition and experimentation with alternative disturbance regimes.

Optimized soil bacterial structure following grazing exclusion promotes soil nutrient cycling and plant growth

Grazing exclusion is a common grassland restoration strategy, and the effectiveness on optimizing plant species community, increasing vegetation diversity and biomass, and improving soil fertility, has been widely documented in literatures. Soil bacterial community, as one of important ecological components, closely relates to plants and soil features. However, there is no definite conclusion of grazing exclusion effects on various ecological components, especially on soil bacterial community. To clarify this question, we compared the soil bacterial community characteristics and their corresponding vegetation characteristics and soil properties on one 40 years-grazing exclusion (GE) and three free grazing (FG) areas within a Leymus chinensis steppe of Inner Mongolia, China. Our results showed that grazing exclusion could significantly increase the soil bacterial abundance, and optimize the soil bacterial structure, with the synergistic increase of the soil bacterial diversity. The abundance of Euryarchaeota, Verrucomicrobia, Nitrospirae, Proteobacteria, Elusimicrobia, Latescibacteria, and Microgenomates phyla, some taxa of which involved in the N and P cycles, increased significantly following grazing exclusion, while the abundance of Chloroflexi, Firmicutes, Thaumarchaeota, and Pacearchaeota phyla which are often considered to contain many pathogens, decreased significantly. The bacterial phyla increased by grazing exclusion have a significant positive correlation with vegetation biomass and diversity, and soil alkali-hydrolyzable nitrogen content, total nitrogen content, total phosphorus content, organic matter content and water content. The reducing of pathogenic abundance after grazing exclusion provides a healthier environment for plant growth. This work indicates that grazing exclusion optimizes the soil bacterial structure to promote the growth of plants in more sufficient soil nutrients and healthier soil environments, making the enclosed grassland soil ecology form a virtuous circle.

Effects of long-term grazing exclusion on vegetation structure, soil water holding capacity, carbon and nitrogen sequestration capacity in an alpine meadow on the Tibetan Plateau

Effects of long-term grazing exclusion on vegetation structure, soil water holding capacity, carbon and nitrogen sequestration capacity in an alpine meadow on the Tibetan Plateau

Effects of a decade of grazing exclusion on three Wyoming big sagebrush community types

Livestock grazing is the most extensive land use in Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis [Beetle & A. Young] S.L. Welsh) steppe and its effects on plant community characteristics have been greatly debated. However, most of the studies used to support grazing removal evaluated the impacts of excluding historic grazing, rather than the impacts of excluding moderate contemporary grazing (40–50% utilization, altering season of use) which has vastly different effects on plant communities. Thus, to understand the effects of removing contemporary grazing, we compared contemporary grazed areas to long-term (+10 yrs.) grazing exclusion areas in three common Wyoming big sagebrush community types: intact, degraded, and exotic annual grass-dominated types. Plant community characteristics (cover, density, diversity, richness, dissimilarity) were measured in 2020 and 2021 in five grazed and grazing excluded areas within each community type. Most plant community characteristics were not influenced by grazing exclusion, suggesting that the removal of contemporary grazing has little effect on Wyoming big sagebrush plant communities. The effect of grazing exclusion on Sandberg bluegrass (Poa secunda J. Presl) abundance and litter cover varied among community types, suggesting that grazing exclusion effects slightly varied among community types. In contrast, most plant community characteristics varied among community types and between years, suggesting that grazing management plans need to account for the spatial and temporal variability among Wyoming big sagebrush communities. Furthermore, our results suggest that contemporary grazing exclusion has negligible effects compared to contemporary grazing on plant communities, and that exclusion of contemporary grazing (passive restoration) does not promote the recovery of degraded and annual grass invaded plant communities.

Effects of long-term enclosing on distributions of carbon and nitrogen in semia-arid grassland of Inner Mongolia

The effects of long-term grazing exclusion on Carbon (C) and Nitrogen (N) partitioning in the green-plant–litter–root–soil system of grassland are unknown. As such, in this study, we evaluated the C and N contents, stocks, and ecological stoichiometry in Inner Mongolian grasslands by enclosing them for 18 and 39 years inside a fence (F18 and F39, respectively), in comparison with those outside the fence (F0), an area that was under long-term grazing. In F18 and F39, C and N stocks were higher in green plants and litter (undecomposed, incompletely decomposed, and completely decomposed litter), but C and N stocks were lower in the roots and soil (P < 0.05). The N stocks in F39 in incompletely and completely decomposed litter were lower (P < 0.05) compared with those in F18. The C contents in green plants and soil were 5% higher in F39 than in F18, whereas the N contents of litter and soil were 17.13%–37.92% lower. The C/N ratio in green plants and litter substantially increased after long-term enclosure, but decreased in roots and soil. The C/N ratio in litter and soil in F39 was 6.5%–36% higher than at F18, but 1.2%–8.2% lower in green plants and roots. Finally, following long-term enclosure, C and N were primarily transported from the soil and roots to green plants and litter. After 39 years of enclosing, C primarily moved from the litter to soil, while N primarily transferred from the soil to roots, compared with 18 years of enclosing. Our results indicated that the duration of enclosure has different effects on C and N distribution in the green-plant–litter–root–soil system. In conclusion, long-term grazing exclusion is not beneficial for soil C and N sequestration in the grasslands of Inner Mongolia.

Effect of Grazing Exclusion and Rotational Grazing on Soil Aggregate Stability in Typical Grasslands in Inner Mongolia, China

Soil aggregate is extremely important for soil health and sustainable land management. Overgrazing has caused serious degeneration of grassland in the past decades and how to restore the degraded soil through grazing management is urgently needed. In this research, we investigated effects of long-term grazing exclusion and short-term rotational grazing with different grazing intensities on aggregate stability in the upper 10 cm of soil at two grazing sites in Xilinhot, Inner Mongolia. Treatments included long-term (34 years) exclusion, moderate-term (21 years) exclusion, and continuous grazing at adjacent reference plots. In addition, effects of rotational grazing under different grazing intensity [i.e., no grazing (0 days/month), light grazing (3 days/month), moderate grazing (6 days/month) and high grazing (12 days/month)] were investigated after 5 years. Stability of aggregate fractions were determined using wet sieving. Our results showed that the stable aggregates fraction were significantly increased under grazing exclusion for both fine (0.25–1 mm) and coarse (1–2 mm) size fractions. At the rotational grazing site, stability of fine aggregates was significantly enhanced under grazing compared with no grazing, while there was little influence on stability of coarse aggregates. Our results showed that grazing exclusion significantly increased soil aggregate stability and the peak appeared in moderate-term exclusion, meanwhile, rotational grazing had little influence on aggregate stability. We suggest that rotational grazing rather than long-term grazing exclusion is a better way for soil aggregate stability and soil health, and current grazing prohibition policies may need to be adjusted.

Effects of long-term grazing exclusion on plant and soil properties vary with position in dune systems in the Horqin Sandy Land

Grazing exclusion is an important policy currently being employed by the Chinese government to recover degraded grasslands. Despite many field experiments, controversy still exists concerning the effects of grazing exclusion on the restoration of sand dune ecosystems. In order to examine the response of plant and soil parameters to grazing exclusion, a 32-year field experiment was conducted in active dune systems in the Horqin Sandy Land. The results showed that the dominant species changed significantly at the windward and leeward sides of dunes, and at interdune lowlands after long-term grazing exclusion. Plant density, cover, species richness, and soil organic carbon and total nitrogen (N) significantly increased across all topographic locations in areas with grazing exclusion. The effects of grazing exclusion on plant and soil parameters varied as a function of position in the dune system. In general, the recovery of plant and soil parameters occurred more rapidly at the windward side than at the leeward side when grazers were excluded. Soil organic carbon and total N were positively correlated with plant community density, cover, and species richness in active and stabilized sand dune systems. In addition, grazing exclusion strengthened the relationship between soil and plant parameters. The results showed that the effects of grazing exclusion on plant and soil properties were strongly dependent on dune position. These findings should prompt those responsible to assess the recovery of sand dune systems by synthesizing the effects of multiple positions within a dune system.

Effects of Climate Change vs. Grazing Exclusion on Species Diversity Over 18 Years Along an Elevation Gradient in the European Alps

Climate change was already shown to increase species numbers in high elevations. In contrast, grazing might interfere with climate change effects. To disentangle both the effects remains a major challenge of alpine ecology. The present study investigated both the effects on species diversity along an elevation gradient in the Austrian Central Alps. We aimed to answer the following questions: How do species diversity and frequency of subalpine–alpine–subnival plant communities change in grazed sites with time? Do competitive plant species increase in the communities? How does grazing exclusion affect species diversity, functional groups, and strategy types? Are environmental changes (temperature, sunshine duration, precipitation) responsible for diversity changes or does grazing override climate effects? The study was carried out for 18 years along an elevation gradient from 1,958 to 2,778 m a.s.l. at Obergurgl (Tyrol, Austria), including six different plant communities. A total of 11 grazing exclusions were established. At each community, the frequency of the species was counted in 1 m2 plots yearly or at least every 3–4 years. Environmental data were obtained from the weather station Obergurgl. Changes of the community parameters and the species composition were analyzed by partial redundancy analyses and mixed-effect models. Species diversity increased with time at all grazed sites, but this increase was suppressed under grazing exclusion. Grazing exclusion effects became pronounced after 5 years. The most consistent result was the increase of bryophytes throughout. At the subalpine grassland, tall-growing species expanded in the exclosures; at the upper alpine Carex curvula grassland, snow bed species decreased with grazing exclusion. Among the environmental factors, sunshine duration of the previous year’s autumn quartal was found to be the essential variable for the changes. We concluded that diversity increases in grazed communities of the Austrian Central Alps can be attributed to climate change. An indication of slightly reduced and altered weather effects under grazing exclusion was found.

Cattle Grazing Exclusion Increases Basal, Crown and Mulch Cover in the Sierra de Órganos National Park, Sombrerete, Zacatecas, Mexico

Objective: To estimate the effects of cattle grazing exclusion on soil and vegetation conditions in grasslands of Sierra de Órganos National Park (SONP), Sombrerete, Zacatecas, Mexico. Design/Methodology/Approach: Four transects with cattle grazing exclusion were strategically established in SONP grasslands. In each transect the basal, crown and organic mulch cover, soil cover, bare soil, and the form of the autumn plant were measured from 2008, 2010, 2012 and 2014. Results: Cattle grazing exclusion caused an increase in basal, crown and organic mulch cover, soil cover, as well as over- rested plants and deteriorated plants; bare soil cover and the percentage of normal plants decreased. Study Limitations/Implications: Increase of organic mulch cover implies the accumulation of combustible material that represents a potential risk of fire occurring in the SONP. Findings/Conclusions: Increase of organic mulch, over-rested plants and deteriorated plants shows that SONP grasslandsare transiting to a less stable ecological state.

Grazing Exclusion Effects on the Relationship between Species Richness and Vegetation Cover in Mongolian Grasslands

Understanding the role of plant diversity in maintaining vegetation cover is a central focus of assessing the vegetation dynamics of grasslands. The present study assessed the relationship between species richness and vegetation cover, as well as underlying biological mechanisms in three Mongolian grasslands, namely meadow, dry steppe and mountain steppe.Each of three grasslands was set by two treatments: grazing exclusion by fence and freely grazing. I measured plant species richness, vegetation cover, height and phenology. I examined three biological mechanisms, namely plant interactions, the role of dominant species and vegetation growth periods.The results showed that higher species richness generally increased vegetation cover independent of fencing treatment and grassland type. Plant interactions were the strongest in fenced plots of the mountain steppe. Dominant plant species invested more in vegetation cover rather than the height in grazed plots than fenced ones in Mongolian grasslands. Taking vegetation growth periods into account did not alter the strength and the direction of the relationship between species richness and vegetation cover. I thus infer that examining changes in species diversity will allow for a better understanding of vegetation cover dynamics in grasslands. This will help to assess how ecosystem functioning might be impacted by grazing disturbances in Mongolia.

Grazing exclusion alters ecological stoichiometry of plant and soil in degraded alpine grassland

Grazing exclusion is one of the most effective practices to recover the degraded alpine grasslands in Tibetan Plateau. In addition, ecological stoichiometry serves as a key regulator of ecosystem function and is also closely related to nutrient process. However, knowledge about the plant-soil interactions of stoichiometry throughout the growing season is still poorly understood. In this study, we examined how grazing exclusion affected the change of C-N-P stoichiometry of plant-soil by carrying out monthly sampling in three sites. The sites were: 9 years grazing exclusion, GE9; 5 years grazing exclusion, GE5; and free grazing, FG in degraded alpine meadow. Plant and soil samples were collected five times during the growing season (May-September) to analyze plant biomass and ecological stoichiometry. Across plots, profound fencing changed plant biomass and ecological stoichiometry. Specifically, increases in green, litter and root biomass were observed under grazing exclusion. Fencing increased plant C content, C:N, C:P, N:P ratios but declined N and P contents. In contrast to the plant, there was an increasing concentrations of soil C, N and P. Our study highlighted, under grazing exclusion, grasslands advanced soil C not only by greater biomass input but also higher plant C content. Greater soil N was mainly fixed by plant production, while enhancement of soil P was mainly due to plant production recovery to stop water erosion. With a continuous improvement of nutrient pools under short-term (< 9 years) grazing exclusion, our results showed that a long-term fencing practice effect ought to be monitored to recovery degraded alpine grassland. These findings also indicated that ecological stoichiometry provides a new insight for better understanding of the mechanisms of grazing exclusion effects on nutrient process.

Effect of grazing exclusion on nitrous oxide emissions during freeze-thaw cycles in a typical steppe of Inner Mongolia

Grazing exclusion of grasslands has traditionally been considered to reduce nitrogen inputs and decrease nitrous oxide (N2O) emissions. However, recent studies have shown that grazing exclusion may increase N2O emissions because of freeze-thaw cycles. In this study, year-round N2O fluxes (including high-frequency measurements during the freeze-thaw cycles) were measured in three sites that included long-term grazing exclusion (ungrazed since 1979, UG79), short-term grazing exclusion (ungrazed since 1999, UG99), and continuously grazed (CG), in Inner Mongolia grassland. The results showed that: 1) across the entire period of observations, mean annual N2O fluxes were the highest at UG99 (12.2 μg m−2 h-1), followed by CG (8.6 μg m−2 h-1) and UG79 (7.5 μg m−2 h-1); 2) during spring freeze-thaw cycles, cumulative N2O emissions were significantly higher at UG99 than UG79 and CG (P < 0.05); 3) freeze-thaw cycles had significant effects on N2O emissions with strong pulse emissions exhibited at the beginning of the spring thaw period; and 4) structural equation model analysis indicated that soil water content was a predominant environmental factor that caused increased N2O emissions, while other factors tended to affect N2O emissions indirectly. The results confirmed that short-term grazing exclusion could increase N2O emissions owing to the high N2O concentration during freeze-thaw cycles, associated with high quantities of snowmelt water. However, the effects of long-term grazing exclusion on N2O emissions showed no differences compared with grazing management. This suggests that grazing exclusion does not always result in an increase in N2O emissions during freeze-thaw cycles as it is more controlled by soil liquid water content. Thus the new finding of the event emissions of N2O should come up with more reliable estimates of soil‐atmosphere trace fluxes.

Are N, P, and N:P stoichiometry limiting grazing exclusion effects on vegetation biomass and biodiversity in alpine grassland?

Nitrogen (N), phosphorus (P), and N:P stoichiometry have been proposed as an index to assess plant nutrient limitation in grassland. The alpine grasslands in Tibet were investigated to evaluate the relationships between N, P, N:P ratio and vegetation biomass and species biodiversity by comparing free grazing (FG) and grazing exclusion (GE) grasslands. Grazing exclusion had no significant effect on N, P concentrations and N:P ratio of both plant shoot and root, but significantly reduced soil N, P concentrations by 15.5% and 12.6%, respectively. In general, both biomass and biodiversity indicators positively correlated with shoot P, negatively correlated with shoot N:P ratio. Nevertheless, they had different correlation patterns with soil stoichiometry, the biomass indicators positively correlated with soil N and N:P ratios, but the biodiversity indicators negatively correlated with them. Furthermore, the effect sizes of above-ground biomass were significantly correlated with the ratio of soil N:P between GE and FG plots and the effect sizes of biodiversity indicators were significantly correlated with the ratio of soil P between GE and FG plots. Therefore, how extent of grazing exclusion effects on biomass allocation depends on how difference of soil N:P ratio between inside and outside of fencing, while how extent of grazing exclusion effects on biodiversity depends on how difference of soil P ratio between them.

Effects of Grazing Exclusion on Biomass Growth and Species Diversity among Various Grassland Types of the Tibetan Plateau

Livestock grazing is an important determinant of species diversity and plant growth. Overgrazing is identified as one of the most important disturbances resulting in grassland degradation. Although many restoration practices have been implemented, grazing exclusion is one of the most effective methods to restore degraded grasslands. We explored the impact of five years of grazing exclusion on plant growth and species diversity in four types of grasslands: temperate steppe (TS), swamp meadow (SM), alpine steppe (AS), and alpine meadow (AM). Our results showed that grazing exclusion increased plant height, coverage, biomass, and species diversity in all four grasslands. The aboveground biomass in AM (180.8%), TS (117.3%), and SW (105.9%) increased significantly more than AS (10.1%). Grazing exclusion in AM had the greatest effect on proportion of palatable species, and the increase in palatable species in AM was higher than that of the other grassland types significantly. Species diversity increased significantly within the enclosure in SM (23.9%) and AM (20.8%). Our results indicate that grazing exclusion is an effective management strategy to restore degraded grasslands and it works best in alpine meadow. This study contributes to the growing theoretical basis for grassland management strategies and has a significant effect on sustainable development for grassland resources and pastoral areas.

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.

Effects of short-term grazing exclusion on vegetation and soil in early succession of a Subhumid Mediterranean reclaimed coal mine

To assess the short-term effect of herbivory exclusion on vegetation and soil and to relate differences in floristic composition to changes in soil properties in a reclaimed coal mine in northern Spain. Two adjacent main plots of 50 × 50 m, one fenced to prevent ungulates grazing and the other not, were established in a north-facing slope to analyze differences in the soil and plant community in the short time. A clear influence of grazing exclusion on soil properties and plant community composition and structure was found but no influence on species diversity. However, only three soil parameters (organic matter, K, and Mg, with higher values in the ungrazed community) were related to the differences in floristic composition. Species responses to the soil gradient from ungrazed to grazed areas were also related to their particular life-history traits. No trend in the dispersal-mode replacement was found. Herbivores could be a key factor preventing revegetation at early stages of succession in the study area, although they could play a key role as efficient seed dispersers, particularly of endozoochorous legume species, and controlling the expansion of dominant introduced species.