Plant Diversity In Grasslands Research Articles

Will small-scale ploughing increase the plant diversity of species-poor grasslands?

Will small-scale ploughing increase the plant diversity of species-poor grasslands?

Exotic wild boars and native wild guinea pigs maintain plant diversity in Argentinean coastal grasslands by decreasing plant dominance

Exotic wild boars and native wild guinea pigs maintain plant diversity in Argentinean coastal grasslands by decreasing plant dominance

Seed dispersal limitation causes negative legacy effect on restoration of grassland plant diversity on ski slopes.

Past forest use often has a long-term negative impact on the recovery of the original plant composition of semi-natural grasslands, which is known as a legacy effect. This study investigates the impact of seed dispersal limitations on the restoration of grassland plant diversity on ski slopes with past forest use, highlighting the negative legacy effect on biodiversity recovery. Focusing on ski areas, our research contrasts the vegetation on ski slopes originally created on semi-natural grasslands such as pasture (pasture slopes) and constructed by clearing secondary forests or conifer plantations (forest slopes). We examined species richness and diversity, considering seed dispersal modes, grassland management history, and seed source proximity. We reveal that the proximity to species-rich grassland sources is pivotal for the restoration of native grassland vegetation. Particularly, wind-dispersed species show significant recovery on slopes with sustained management for more than 70 years and those with neighboring species-rich grasslands, suggesting that both the duration of management and the proximity to seed sources are critical for overcoming the legacy effects of past forest use. Meanwhile, gravity-dispersed species failed to recover their richness and diversity regardless of both the duration of management and the proximity to seed source grasslands, which their diversity recovered where seed sources neighbored. Our findings emphasize the importance of considering seed dispersal limitation and management history in the restoration and conservation of grasslands and their biodiversity, particularly in landscapes experiencing past human intervention.

Drivers of plant diversification along an altitudinal gradient in the alpine desert grassland, Northern Tibetan Plateau

Revealing alpine plant diversity patterns can contribute to conserving mountain plant diversity. However, the spatial variation in the ecological niche and diversity patterns of the plant community and the mechanism by which it maintains itself in alpine desert grasslands remain poorly understood. Here, we conducted a field investigation across altitudinal gradients (3093, 3296, 3549, and 3790 m) in the northern Tibetan Plateau and compared species composition, diversity indices, Levins' niche breadth, and Pianka's niche overlap. The results showed that perennial herbs replaced semi-shrubs and xermesophytes and mesophytes replaced xerophytes with increasing altitude. The plant community heights decreased with altitude. The cover of the herb layer increased with altitude, whereas that of the shrub layer was hump-shaped. Species diversity indices (Patrick, Pielou, Shannon-Wiener, and Simpson) increased with increasing altitude. Sympegma regelii (1.05), Leymus chinensis (1.03), and Reaumuria kaschgarica (0.94) had larger niche breadths and were widespread. Species with a high niche overlap occupied a considerable proportion at higher altitudes, indicating strong interactions among species. The redundancy analysis revealed that altitude, soil water content, soil organic matter content, and pH were the main factors driving changes in plant diversity (P = 0.036, F = 3.7). Our study illustrated that environmental filtering and biotic interactions jointly shape plant composition and diversity in alpine desert grasslands along altitudinal gradients.

Abandonment or biomass production? Phytodiversity responses to land-use changes of semi-natural grasslands in northern Europe

European semi-natural grasslands are hotspots for biodiversity and important for the provisioning of multiple ecosystem services, but their extent has declined considerably during the past century. Increasing demands for agricultural and forest biomass risk causing further loss of grasslands, raising concern about a goal conflict between climate mitigation and biodiversity conservation. This study focused on the loss of semi-natural grasslands in a mixed farm-forest landscape in southern Sweden by comparing plant diversity in grasslands with continuous grazing regimes to recently abandoned grasslands, improved grasslands (sown leys), and afforested grasslands. Compared to actively grazed grasslands, grasslands where grazing had been abandoned showed a lower plant species richness and fewer plant species of conservation concern, but similar species composition. In contrast, both improved and afforested grasslands showed >50 % lower species richness than abandoned and grazed grasslands, with profoundly different species composition. The dissimilarity in plant diversity between sites was primarily driven by the replacement of species (turnover), and trait-based analyses indicated that environmental filtering of light, management, and nutrient requirements of plants shaped the community differences. Furthermore, an increased cover of semi-natural grassland around the sites positively related to plant species richness and diversity, while an increased cropland coverage around the sites showed a negative relationship. Our results emphasize the importance of integrated land-use strategies that prioritize biodiversity conservation in mixed farm-forest landscapes, such as restoration of semi-natural grasslands and strategic planning of biomass production to avoid serious biodiversity losses.

Effects of experimental drought and plant diversity on multifunctionality of a model system for crop rotation

In low-diversity productive grasslands, modest changes to plant diversity (richness, composition and relative abundance) may affect multiple ecosystem functions (multifunctionality), including yield. Despite the economic importance of productive grasslands, effects of plant diversity and environmental disturbance on multifunctionality are very rarely quantified. We systematically varied species richness, composition, and relative abundance of grassland ley communities and manipulated water supply (rainfed and drought) to quantify effects of diversity and environmental disturbance on multifunctionality. We then replaced the grassland leys with a monoculture crop to investigate ‘follow-on’ effects. We measured six agronomy-related ecosystem functions across one or both phases: yield, yield consistency, digestibility and weed suppression (grassland ley phase), legacy effect (effect on follow-on crop yield), and nitrogen fertiliser efficiency (full rotation). Drought reduced most ecosystem functions, although effects were species- and function-specific. Increased plant diversity affected mean performance, and reduced variation, across the six functions (contributing to multifunctional stability). Multifunctionality index values across a wide range of mixture diversity were higher than the best monoculture under both rainfed and drought conditions (transgressive over-performance). Higher-diversity, lower-nitrogen (150N) mixtures had higher multifunctionality than a low-diversity, higher-nitrogen (300N) grass monoculture. Plant diversity in productive grasslands is a practical farm-scale management action to mitigate drought impacts and enhance multifunctionality of grassland-crop rotation systems.

Impact of exotic plantation on native Grassland Biodiversity: A 30-Year analysis in Tanzania’s southern highlands

Exotic trees have been introduced in various parts of the world for commercial and environmental reasons such as restoring degraded land and regulating the climate. Despite their economic benefits, they have been found to cause habitat loss and fragmentation, affect soil nutrient cycling, and deplete water quality and quantity. This study examined the extent of land use and land cover changes over the past 30 years, as well as the influence of exotic plant species on native grassland plant composition and diversity in Tanzania’s southern highlands. Drivers and the extent of changes were studied using Landsat imagery in 1990, 2000, 2010 and 2020. The study examined understory native plant species in 12 study sites, including grasslands as control sites near exotic plantations. The study used transects and rectangular plots to compare native plant species with those in exotic tree plantations. Trees with a stem diameter at breast height (DBH) of 10 cm or more were documented in 25 x 20 m plots, while shrubs with a DBH of 5 cm or more but less than 10 cm were recorded in 5 x 2 m sub-plots and grass as well as herbs were recorded in sub-sub plots of 2 x 0.5 m. The native plant composition and diversity were compared among exotic plantations (pine, eucalyptus and black wattle) and neighbouring grasslands. The generalised linear model (GLM) calculated the species abundance, while the native plant diversity in exotic plantations and grasslands was compared using a one-way analysis of variance (ANOVA). The study found that native species diversity is negatively impacted by exotic tree plantations, which displace natural grasslands (p < 0.05). Thus, wild medicinal plants, edible foods and habitats for flora and fauna, including pollinators, have decreased. The study recommends that afforestation and reforestation should emphasise native tree species for nature conservation.

A global meta-analysis on the effects of organic and inorganic fertilization on grasslands and croplands.

A central role for nature-based solution is to identify optimal management practices to address environmental challenges, including carbon sequestration and biodiversity conservation. Inorganic fertilization increases plant aboveground biomass but often causes a tradeoff with plant diversity loss. It remains unclear, however, whether organic fertilization, as a potential nature-based solution, could alter this tradeoff by increasing aboveground biomass without plant diversity loss. Here we compile data from 537 experiments on organic and inorganic fertilization across grasslands and croplands worldwide to evaluate the responses of aboveground biomass, plant diversity, and soil organic carbon (SOC). Both organic and inorganic fertilization increase aboveground biomass by 56% and 42% relative to ambient, respectively. However, only inorganic fertilization decreases plant diversity, while organic fertilization increases plant diversity in grasslands with greater soil water content. Moreover, organic fertilization increases SOC in grasslands by 19% and 15% relative to ambient and inorganic fertilization, respectively. The positive effect of organic fertilization on SOC increases with increasing mean annual temperature in grasslands, a pattern not observed in croplands. Collectively, our findings highlight organic fertilization as a potential nature-based solution that can increase two ecosystem services of grasslands, forage production, and soil carbon storage, without a tradeoff in plant diversity loss.

The effect of livestock grazing on plant diversity and productivity of mountainous grasslands in South America - A meta-analysis.

Mountainous grasslands in South America, characterized by their high diversity, provide a wide range of contributions to people, including water regulation, soil erosion prevention, livestock feed provision, and preservation of cultural heritage. Prior research has highlighted the significant role of grazing in shaping the diversity and productivity of grassland ecosystems, especially in highly productive, eutrophic systems. In such environments, grazing has been demonstrated to restore grassland plant diversity by reducing primary productivity. However, it remains unclear whether these findings are applicable to South American mountainous grasslands, where plants are adapted to different environmental conditions. To address this uncertainty, we conducted a meta-analysis of experiments excluding livestock grazing to assess its impact on plant diversity and productivity across mountainous grasslands in South America. In alignment with studies in temperate grasslands, our findings indicated that herbivore exclusion resulted in increased aboveground biomass but reduced species richness and Shannon diversity. The effects of grazing exclusion became more pronounced with longer durations of exclusion; nevertheless, they remained resilient to various climatic conditions, including mean annual precipitation and mean annual temperature, as well as the evolutionary history of grazing. In contrast to results observed in temperate grasslands, the reduction in species richness due to herbivore exclusion was not associated with increased aboveground biomass. This suggests that the processes governing (sub)tropical grassland plant diversity may differ from those in temperate grasslands. Consequently, further research is necessary to better understand the specific factors influencing plant diversity and productivity in South American montane grasslands and to elucidate the ecological implications of herbivore exclusion in these unique ecosystems.

Effects of grazing on the relationship between plant functional diversity and soil carbon sequestration are regulated by livestock species

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

Interactive effects of grassland utilization and climatic factors govern the plant diversity-soil C relationship in steppe of North China

The relationship between plant diversity and the ecosystem carbon pool is important for understanding the role of biodiversity in regulating ecosystem functions. However, it is not clear how the relationship between plant diversity and soil carbon content changes under different grassland use patterns. In a 3-year study from 2013 to 2015, we investigated plant diversity and soil total carbon (TC) content of grasslands in northern China under different grassland utilization methods (grazing, mowing, and enclosure) and climatic conditions. Shannon-Wiener and Species richness index of grassland were significantly decreased by grazing and mowing. Plant diversity was positively correlated with annual precipitation (AP) and negatively correlated with annual mean temperature (AMT). AP was the primary regulator of plant diversity. Grazing and mowing decreased TC levels in grasslands compared with enclosures, especially in topsoil (0–20 cm). The average TC content was decreased by 58 % and 36 % in the 0–10 cm soil layer, while it was decreased by 68 % and 39 % in 10–20 cm soil layer. TC was positively correlated with AP and negatively correlated with AMT. Principal component analysis (PCA) showed that plant diversity was positively correlated with soil TC, and the correlation decreased with an increase in the soil depth. Overall, this study provides a theoretical basis for predicting soil carbon storage in grasslands under human disturbances and climate change impacts.

Effects of grazing on grassland biomass and biodiversity: A global synthesis

ContextLivestock grazing, a common method of grassland utilization, has profound effects on the plant biomass and biodiversity of grassland ecosystems. However, the overall directions and magnitudes of such effects, especially involving multiple livestock types and grazing seasons, remain poorly understood on a global scale. ObjectivesWe conducted a meta-analysis to evaluate the size and direction of the overall effects of grazing on grassland plant biomass and plant diversity; and to estimate the variation of these responses with area types, livestock types, grazing seasons, and grazing intensities. MethodsWe performed a comprehensive search of the Web of Science® and the China National Knowledge Infrastructure (CNKI) (1950–2019) using certain search terms, and considered the studies cited by several recent related syntheses. We compiled data from 175 field manipulative studies at 200 sites by selecting studies that satisfied five criteria. ResultsGrazing significantly decreased aboveground (−38.5%), belowground (−14.7%), and total biomass (−20.6%), but did not significantly change root–shoot ratio, species richness, or evenness. The effects of grazing on plant biomass and diversity depended on climate types and grazing patterns. Specifically, grazing significantly decreased plant total biomass and belowground biomass in dry areas only, but increased rootshoot ratio in wet areas only. Growing season and year-long grazing decreased total biomass, whereas non-growing season grazing had not changed total biomass. Among livestock types (bulk feeder, concentrate selectors, intermediate feeder or mixed), only intermediate feeder grazing significantly decreased belowground biomass (−16.5%) and total biomass (−25.3%). Heavy grazing significantly decreased belowground biomass (−19.2%), total biomass (−24.3%) and plant evenness (−21.2%), but not light and moderate grazing. ConclusionsAboveground biomass was more sensitive to grazing than belowground biomass, and only over grazing decreased grassland biodiversity. Under the same grazing intensities, mixed livestock or bulk feeder grazing in the non-growing season probably is one of the ways to maintain plant diversity and sustainable development of grassland agriculture. ImplicationsOur results highlight the key role of grazing patterns and climate types in mediating plant biomass and biodiversity in response to grazing disturbance, and should be considered in devising the sustainable grazing management of grasslands.

Mid-term changes of dry grasslands with conservation management in the Hainburger Berge Mountains

Our study focused on evaluating plant diversity and vegetation changes in the dry grasslands of the Hainburger Berge Mountains protected within the NATURA 2000 reserve Hundsheimer Berge. Traditionally, these grasslands have been managed through intensive grazing but have experienced significant land-use changes since the 1950′s, including a prolonged period of abandonment. We investigated rocky and xeric grasslands of Festuco-Brometea, and mesic grasslands of Molinio-Arrhenatheretea using six nested plot series of various spatial scales. We also resampled relevés that were initially recorded in 2007 and analyzed them alongside older relevés (1930–2001) from the Austrian Vegetation Database. The compositional data variation was primarily influenced by moisture and nutrient gradients along the first DCA axis, and soil reaction and light availability along the second DCA axis. Grazing intensity had a significant effect on species richness at small spatial scales, while at larger scales, habitat conditions played a more crucial role. A continuous successional development could be detected in grassland composition, leading to a denser vegetation canopy and increased moisture and nutrient availability. However, plot resampling since 2007 revealed only minor changes, primarily due to interannual dynamics rather than a clear directional trend. We conclude that the current conservation management of rocky and xeric grasslands is proving successful in maintaining grassland biodiversity as well as high number and proportion of endangered plant species. Controlling grazing intensity, involving more farmers, and implementing flexible rules for grazing, mowing, and subsidy eligibility, could be instrumental in achieving conservation targets in the future.

Additive effects of two agri-environmental schemes on plant diversity but not on productivity indicators in permanent grasslands in Switzerland

Different agri-environmental schemes (AES), such as ecological focus areas and organic farming, have been suggested to reduce the impact of intensive agriculture on the environment and to conserve or even restore farmland biodiversity. However, the effectiveness of such schemes, their ability to actually support biodiversity and associated trade-offs with agricultural production are still debated. We analysed a large dataset from the biodiversity monitoring in the Swiss agricultural landscape to assess the effects of two different grassland AES, i.e., extensively managed ecological focus areas (EFAs versus non-EFAs) and organic farming (versus conventional), on plant diversity, plant community composition and productivity indicators, i.e., weed abundance, forage value and nutrient availability. We also considered environmental factors, i.e., topography and soil conditions, which potentially modulate AES effects on biodiversity. We used in total 1170 plots in permanent grasslands, managed as meadows or pastures.Both AES had significant positive effects on plant diversity. However, EFAs increased plant richness considerably stronger (+6.6 species) than organic farming (+1.8 species). Effects of the two schemes were additive with organic EFA grasslands exhibiting highest plant diversity. Differences in topography partly explained AES effects on diversity as both AES were associated with differences in elevation and slope. Thus, future assessments of the effectiveness of AES need to consider the non-random placement of AES across heterogeneous landscapes. EFA grasslands revealed a considerably reduced agricultural productivity as shown by low forage values and low nutrient availability. Yet, the abundance of agricultural weeds, i.e., agriculturally undesired plant species, was lower in EFA compared to non-EFA grasslands. Productivity indicators were only weakly affected by organic farming and other than for plant diversity, productivity did not differ between organic and conventional EFA grasslands.The positive additive diversity effects of EFAs and organic grassland farming underline the potential of both AES to contribute to biodiversity conservation in agricultural landscapes, though to a different extent. Comparing the effects of the two AES revealed that the lower the reduction in agricultural productivity associated with an AES, the smaller the gains in plant diversity, highlighting the inevitable trade-off between productivity and plant diversity in semi-natural grasslands.

Defoliation enhances the positive effects of soil microbial diversity on plant productivity

Abstract Defoliation, often induced by herbivores, and soil microbiomes are recognized as key drivers of plant diversity and productivity in grasslands. However, lack of experiments simultaneously manipulating defoliation and soil microbial diversity has constrained our understanding of how these two factors interactively influence both above‐ground and below‐ground net primary productivity (ANPP and BNPP). We employed a soil filtering approach to create the gradient of soil microbial diversity and removal of above‐ground biomass by clipping to simulate defoliation effect from herbivores. Our goal was to investigate how soil microbial diversity affected both ANPP and BNPP under the stress of defoliation. We found that defoliation and soil microbial diversity loss decreased the ANPP and BNPP of the plant community, and Medicago falcata (legume) was more responsive to these treatments than Leymus chinensis (grass) and Artemisia frigida (forb). ANPP was positively correlated with soil microbial richness only when plants suffered defoliation. By contrast, BNPP showed a closer relationship with soil fungal richness than bacteria, and defoliation enhanced this relationship. The structural equation model (SEM) showed that defoliation indirectly regulated ANPP by affecting plant P content, while soil bacterial diversity loss decreased the ANPP through altering plant P and fungal diversity loss directly decreased BNPP. The LEfSe and linear regression analysis revealed that the biomarkers of bacteria (e.g. Actinobacteria, Xanthobacteraceae) and fungi (e.g. Ascomycota, Glomerales) significantly contributed to the variation of ANPP and BNPP under defoliation treatment respectively. Defoliation enhanced phosphorus acquisition by soil microorganisms, further strengthening the microbial regulation of plant productivity. Overall, we provide novel insights on how defoliation enhances the positive effects of soil microbial diversity on above‐ and below‐ground net primary productivity. Our findings highlight that soil microorganisms associated with phosphorus cycling are mobilized to play a more active role in promoting productivity after defoliation. It may provide a new perspective on how to better utilize the role of soil microorganisms in grazed or managed grasslands. Read the free Plain Language Summary for this article on the Journal blog.

Plant provenance can influence the impacts of temperature and moisture on intraspecific competition in Pseudoroegneria spicata.

Warming and changing precipitation can alter the performance of native grasses that are essential to grassland ecosystems. Native grasses may respond to changing climate by phenotypic plasticity or lose their current ranges. Establishing plant species from southern, warmer provenances may reduce the likelihood of biodiversity loss and improve restoration success in cool, northern locations that are undergoing warming. We conducted competition trials for Pseudoroegneria spicata (bluebunch wheatgrass), a native grass commonly found in western North American grasslands, to understand the impact of temperature and moisture on plant-plant interactions. We obtained seeds from three locations along a latitudinal gradient in North America, two in British Columbia (BC), Canada, and one in California, USA. We compared the effects of warming, changing water inputs, and competitor provenance on pairwise competitive interactions among Pseudoroegneria spicata plants grown from seeds obtained from the three locations. We quantified interactions using the relative interaction intensity, which has values from -1 (complete competition) to +1 (complete facilitation). Target plants from northern British Columbia, the location with the coldest summer temperature, were generally more competitively suppressed when competing with plants from California, which had the warmest summer temperature and lowest summer precipitation. Competitive suppression of target plants from northern British Columbia and southern British Columbia was more intense when competitor provenance was more geographically distant from target plant provenance. Finally, plants from northern British Columbia and southern British Columbia were more suppressed at higher temperatures, indicating some local adaptation, while plants from California were not affected by competitors, temperature, or water input. Plants grown from seeds obtained from warm and dry locations appear to be more tolerant to competition at higher temperatures, compared to plants from cooler regions. Native plant diversity and restoration success in grasslands subjected to climate change may be preserved or improved by assisted migration of seeds from warm to cooler but warming locations.

Higher plant colonisation and lower resident diversity in grasslands more recently abandoned from agriculture

Abstract Rates of species colonisation and extirpation are increasing in plant communities world‐wide. Colonisation could potentially help compensate for, or compound, resident diversity loss that results from global environmental change. We use a multifactorial seed addition grassland experiment to examine relationships between plant colonisation, resident species diversity and key community assembly factors over 3 years. By manipulating colonist seed rate, imposing disturbance and examining abundance and diversity impacts of 14 formerly absent sown colonists in communities that varied in successional stage and time since agricultural abandonment, we were able to disentangle effects of global change factors (species introduction, novel disturbance and land use change) that are usually confounded. Evidence suggested that cover abundance of sown colonists was most strongly influenced by successional stage of recipient communities, though number of growing seasons was also important for the group of seven colonists with resource conservative ‘slow’ life history traits. Colonist type, seed rate and disturbance had weaker relationships with colonist cover. Factors affecting sown colonist cover were highly conditional. A negative relationship between plot‐level disturbance and colonist cover in early successional communities meant that, despite a positive relationship in late succession, colonisation was negatively related to disturbance overall, defying theoretical expectations. Non‐sown resident diversity was negatively related to colonist cover and positively related to successional stage. Resource acquisitive colonists with ‘fast’ life history traits appeared to limit cover of ‘slow colonists’ when the two groups were sown together, likely reflecting niche pre‐emption. Communities at earlier stages of succession had lower resident diversity and experienced higher levels of colonisation than communities at later stages of succession. Elevated colonisation and lower resident diversity both appeared to be symptoms of human‐induced land use change. However, results suggested that resource competition from plant colonists may also limit resident diversity in grasslands abandoned from agriculture more recently. Synthesis. Our findings point to the importance of resource availability and competition on plant colonisation and colonist impacts on residents. Although colonisation is potentially a source of biodiversity in the short term, our results suggest that plant colonists that reach high abundance may be a further threat to resident plant diversity in secondary grasslands recovering from a recent history of agriculture.

The effects of grazing and fencing on grassland productivity and diversity in alpine grassland ecosystem in the Tibetan highland

Anthropogenic activities, such as grazing and fencing, have been known to alter the productivity and biodiversity of grassland ecosystems, potentially affecting their functioning. However, the impact of these activities on aboveground biomass (AGB) and plant diversity in alpine grasslands at different altitudes, as well as how they may be affected by soil nutrients and environmental climate, is not well understood. To address this knowledge gap, a study was conducted in the Lhasa Valley of Tibet. In 2013, twelve metal fences were set up at mountainous transects, and field surveys were conducted at twelve paired sites in early August 2021. The results of the study showed that AGB was slightly higher in fenced sites compared to grazed sites at altitudes from 4000 to 5100 m, but decreased with altitude at a slower rate in grazed sites. Plant diversity indices exhibited a unimodal pattern with increasing altitude, with no significant differences between fenced and grazed sites. Soil nutrients and environmental climate were found to be positively correlated with plant diversity indices and AGB at both fenced and grazed sites. Multiple linear regression models revealed that AGB and the Shannon index were largely influenced by soil nutrients (AP and AN) rather than by growing season soil temperature at fenced sites, while AGB and the Shannon index were more impacted by growing season soil temperature than by soil nutrients at grazed sites. These findings provide important insights into the impacts of grazing and fencing on above-ground biomass and plant diversity in mountainous environments.

Nitrogen availability constrains grassland plant diversity in response to grazing

Grassland plant diversity has been observed with divergent responses in grazing experiments around the world. However, the dominant role of nitrogen (N) availability in controlling this global variation has not been well explored, impeding our capacity to formulate effective strategies for preserving grassland plant diversity. Here, we synthesized data from 306 grazing experiments that measured plant diversity and soil N content across global grasslands. Overall, grazing reduced plant diversity by 7.63 %, with substantial variations observed across the dataset. Our study revealed that these contrasting effects were best explained by soil N change. Plant diversity under enhanced soil N showed a strong increase in response to grazing. We found that lower grazing intensity and higher background N deposition could collectively enhance soil N, thereby promoting diversity. These results suggest that while avoiding high grazing intensity is crucial in maintaining biodiversity of grazed grasslands, it alone is not sufficient. In regions with lower N deposition (< 500 mg N m−2 yr−1), additional management strategies that target improving soil fertility are needed. Our analysis propounds that local environmental conditions should be incorporated into decision-making of grassland biodiversity conservation, or ignoring this may lead to counterproductive impacts.

Increasing plant species richness by seeding has marginal effects on ecosystem functioning in agricultural grasslands

Abstract Experimental evidence shows that grassland plant diversity enhances ecosystem functioning. Yet, the transfer of results from controlled biodiversity experiments to naturally assembled ‘real world’ ecosystems remains challenging due to environmental variation among sites, confounding biodiversity ecosystem functioning relations in observational studies. To bridge the gap between classical biodiversity‐ecosystem functioning experiments and observational studies of naturally assembled and managed ecosystems, we created regionally replicated, within‐site gradients of species richness by seeding across agricultural grasslands differing in land‐use intensity (LUI) and abiotic site conditions. Within each of 73 grassland sites, we established a full‐factorial experiment with high‐diversity seeding and topsoil disturbance and measured 12 ecosystem functions related to productivity, and carbon and nutrient cycling after 4 years. We then analysed the effects of plant diversity (seeded richness as well as realized richness), functional community composition, land use and abiotic conditions on the ecosystem functions within (local scale) as well as among grassland sites (landscape scale). Despite the successful creation of a within‐site gradient in plant diversity (average increase in species richness in seeding treatments by 10%–35%), we found that only one to two of the 12 ecosystem functions responded to realized species richness, resulting in more closed nitrogen cycles in more diverse plant communities. Similar results were found when analysing the effect of the seeding treatment instead of realized species richness. Among sites, ecosystem functioning was mostly driven by environmental conditions and LUI. Also here, the only functions related to plant species richness were those associated with a more closed nitrogen cycle under increased diversity. The minor effects of species enrichment we found suggest that the functionally‐relevant niche space is largely saturated in naturally assembled grasslands, and that competitive, high‐functioning species are already present. Synthesis: While nature conservation and cultural ecosystem services can certainly benefit from plant species enrichment, our study indicates that restoration of plant diversity in naturally assembled communities may deliver only relatively weak increases in ecosystem functioning, such as a more closed nitrogen cycle, within the extensively to moderate intensively managed agricultural grasslands of our study.