Grazing effect on grasslands escalated by abnormal precipitations in Inner Mongolia

Linking biodiversity to ecosystem processes and functions is crucial for understanding and predicting the impacts of global change on the conditions that sustain life and human wellbeing on Earth. However, most often the Journal of Vegetation Science publishes articles relating plant communities to environmental drivers, and seldom on the effects of plant communities on ecosystems, i.e., on questions concerning the biodiversity–ecosystem function debate (Eisenhauer et al., 2016). Research topics could include, for instance, relating the functional structure of plant communities to biomass productivity or to certain ecosystem functions linked to herbivores or decomposers, or to their stability, as conceptually depicted in Figure 1. How does Journal of Vegetation Science compare to other ecological journals in this respect? To answer this question, we did a bibliographic survey using the Scopus database. We searched for specific words to identify articles linking plant communities to ecosystem processes and functions (Figure 2). A total of 2,429 articles were retrieved, published between the founding of our journal in 1990 and 2017. Among these, 33 articles were published in the Journal of Vegetation Science. By expressing these numbers as a proportion to the total number of articles published by each journal, we found that Journal of Vegetation Science holds an intermediate position compared to other ecological journals (Figure 2, left). Interestingly, considering as a benchmark the total number of articles on vegetation science or on ecosystem studies across all journals, vegetation science has become much more ecosystem-based over time, while ecosystem science has not increased by including proportionally more plant community level phenomena (Figure 2, right). Given the high relevance of scientific questions on the links between biodiversity–ecosystem function for the future of humanity (Díaz et al., 2015), we believe these numbers will continue to increase. Indeed, research on terrestrial ecosystem functioning can advance substantially if grounded on patterns and processes studied at the plant community level (Figure 1). Examples include predicting productivity stability from plant species diversity (Isbell et al., 2015) or from functional diversity and species traits (Fischer et al., 2016), or linking soil processes to plant community dynamics after invasion (Castro-Díez, Pauchard, Traveset, & Vilà, 2016), or studying feedbacks between community dynamics and resource availability after abandonment (Neuenkamp, Lewis, Koorem, Zobel, & Zobel, 2016). Such studies can also contribute to understanding the reciprocal effects of plant communities and grazing (Pillar et al., 2013; Rota, Manzano, Carmona, Malo, & Peco, 2017), and these effects on below-ground processes (Oñatibia, Reyes, & Aguiar, 2017). In this respect, our bibliographic analysis indicates that the Journal of Vegetation Science has an underused potential, which we hope will improve. Our journal is accepting articles developing new concepts and methods, testing theory, identifying general patterns and predicting effects of different aspects of plant communities on ecosystem functioning, as well as on their reciprocal feedbacks. If these topics are studied with an applied focus, e.g., ecosystem services (Gerken Golay, Thompson, & Kolka, 2016), then our associate journal, Applied Vegetation Science, would be an adequate choice for submission. Nevertheless, both journals focus on plant community ecology; therefore ecosystem studies that do not consider diversity or structure of plant communities remain out of the journals' scope. Every year we select the Editors' Award among the articles published in the last volume of Journal of Vegetation Science. This time the choice was not easy, for our journal published several equally strong candidates. However, we had to choose one article for the Editors' Award, which is given to Oñatibia et al. (2017). Gastón Oñatibia and colleagues studied how different long-term grazing disturbance regimes are related to plant communities in the Patagonian grasslands in Argentina by looking at both above-ground and below-ground components. Below-ground processes remain an underexplored topic in vegetation science. In their paper, they assessed species diversity and biomass of roots and found decoupled responses to grazing of below- and above-ground community structure. As we said, this is a research topic with increasing relevance in biodiversity–ecosystem function science, and such papers are welcome in the Journal of Vegetation Science, being clearly within scope. We should also mention Daleo et al. (2017), which was runner-up in our voting for the Editors' Award. They used a methodical experimental approach involving manipulation of communities by removal to study over 4 years the interactive effects of plant competition and herbivores in a salt marsh in Argentina. This is a classic question in ecology, but the approach they used is not common, and their paper adds a particularly well-executed empirical study, which we welcome in our journal. We also mention the paper of Ibanez et al. (2017). By gathering an impressive data set, and a combination of trait-based, community and phylogenetic analyses, they offer important insights into the role of wood density for plant community ecology. It was commented on by Swenson and Zambrano (2017). Readers familiar with Journal of Vegetation Science have undoubtedly noticed that this Editorial and other papers in this issue use a new style, which is currently being adopted by several journals published by Wiley. Although homogenizing the format across journals, this style maintains distinct graphical elements that identify our journal as an official publication of the International Association for Vegetation Science (IAVS). The adoption of the common style with other Wiley journals will facilitate development of new useful functions, especially in online publishing. It has also several advantages for authors, who will not need to cope with different reference styles among journals. In addition to the change in style, we have also changed the roles of the Chief Editors. Since July 2017, the Chief Editors chiefly responsible for Journal of Vegetation Science are Meelis Pärtel and Valério Pillar, while Milan Chytrý acts as the Chair of the Editors. Alessandro Chiarucci, who was responsible for Journal of Vegetation Science for several years, has accepted new responsibilities in our sister journal Applied Vegetation Science. Journal of Vegetation Science, together with Applied Vegetation Science, are the official journals of IAVS. Our teams of editors, authors and readers meet every year during the annual symposia of IAVS. We had a very good and well-attended meeting during the Palermo symposium in June 2017, and we invite everyone interested in our journals to attend the next symposium, to be held in Bozeman, Montana, USA, on July 22–27, 2018.

Grazing is one of the prevalent human activities that even today are taking place inside protected areas with direct or indirect effects on ecosystems. In this study we analyzed the effects of grazing on plant species diversity, plant functional group (PFG) diversity and community composition of shrublands. We analyzed plant diversity data from 582 sampling plots located in 66 protected areas of the Greek Natura 2000 network, containing in total 1102 plant species and subspecies. We also classified a priori all plant species in seven PFGs: annual forbs, annual grasses/sedges, legumes, perennial forbs, perennial grasses/sedges, small shrubs and tall shrubs. For each site, grazing intensity was estimated in four classes (no grazing, low, medium and high grazing intensity). We found that, at the spatial and temporal scale of this study, as grazing intensity increased, so did total species richness. However, each PFG displayed a different response to grazing. Short-lived species (annual grasses or forbs and legumes) benefited from grazing and their species richness and proportion in the community increased with grazing. Perennial grasses and forbs species richness increased with grazing intensity, but their dominance decreased, since their proportion in the community declined. Short shrub species richness remained unaffected by grazing, while tall shrub diversity decreased. Finally, in sites without grazing the spatial pattern of species richness of the different PFGs was not congruent with each other, while in grazed sites they were significantly positively correlated (with the exception of tall shrubs). This finding may imply that grazing is a selective pressure organizing the community structure, and imposing a certain contribution of each PFG. So, in Mediterranean shrublands in protected areas with a long historical record of grazing, it seems that grazing promotes species diversity and its continuation on a portion of the landscape may be a necessary part of an effective management plan.

Summary Overgrazing has resulted in widespread decline in biodiversity and ecosystem functioning in grasslands world‐wide in recent decades. However, few studies have examined the patterns and thresholds of grazing‐induced changes in community structure and ecosystem functioning along a grazing gradient and based on species‐level responses and plant functional traits. To identify the thresholds of grazing intensity (GI) at both species and community levels, we conducted a grazing manipulation experiment with seven levels of GI (0–9 sheep ha−1) and two topographies (flat vs. slope) in a typical steppe. Four plant functional traits were measured, including specific leaf area (SLA), plant height, leaf nitrogen content (LNC) and stem: leaf ratio. The threshold of GI that significantly altered community composition was at 3·75 sheep ha−1 for the flat system and 3·0 sheep ha−1 for the slope system. For both flat and slope systems, the threshold GI for changes in primary productivity was at 3·0 sheep ha−1, beyond which the productivity decreased substantially. At the species level, the abundances of common species, most of which are perennial grasses, declined at moderate grazing intensities (3·0–4·5 sheep ha−1). The abundances of most rare species, which are perennial forbs, declined at low grazing intensities (1·5–3·0 sheep ha−1). SLA and LNC are good predictors of species‐level responses to grazing. Low SLA and high LNC species are negatively affected by high GI, while high SLA and low LNC species are little affected by grazing. The negative effect of GI on species’ abundance was greater in the slope system than in the flat system. Synthesis and applications. Our results indicate that the structural and functioning thresholds of grazing intensity depend on plant traits and species composition, which is mediated by topographic location. These findings, integrating plant functional traits and threshold approaches, have important implications for determining sustainable grazing intensity in grassland management and biodiversity conservation in semi‐arid regions.

Diversity is one major factor driving plant productivity in temperate grasslands. Although decomposers like earthworms are known to affect plant productivity, interacting effects of plant diversity and earthworms on plant productivity have been neglected in field studies. We investigated in the field the effects of earthworms on plant productivity, their interaction with plant species and functional group richness, and their effects on belowground plant competition. In the framework of the Jena Experiment we determined plant community productivity (in 2004 and 2007) and performance of two phytometer plant species [Centaurea jacea (herb) and Lolium perenne (grass); in 2007 and 2008] in a plant species (from one to 16) and functional group richness gradient (from one to four). We sampled earthworm subplots and subplots with decreased earthworm density and reduced aboveground competition of phytometer plants by removing the shoot biomass of the resident plant community. Earthworms increased total plant community productivity (+11%), legume shoot biomass (+35%) and shoot biomass of the phytometer C. jacea (+21%). Further, phytometer performance decreased, i.e. belowground competition increased, with increasing plant species and functional group richness. Although single plant functional groups benefited from higher earthworm numbers, the effects did not vary with plant species and functional group richness. The present study indicates that earthworms indeed affect the productivity of semi-natural grasslands irrespective of the diversity of the plant community. Belowground competition increased with increasing plant species diversity. However, belowground competition was modified by earthworms as reflected by increased productivity of the phytometer C. jacea. Moreover, particularly legumes benefited from earthworm presence. Considering also previous studies, we suggest that earthworms and legumes form a loose mutualistic relationship affecting essential ecosystem functions in temperate grasslands, in particular decomposition and plant productivity. Further, earthworms likely alter competitive interactions among plants and the structure of plant communities by beneficially affecting certain plant functional groups.

The concurrent increase in drought and atmospheric nitrogen deposition has profoundly impacted multitrophic biodiversity and ecosystem functioning in grasslands. Despite the well‐documented individual effects of reduced precipitation and nitrogen enrichment, their interactive effects, especially on multitrophic cascading responses (e.g. plant, nematode and arthropod communities), remain largely unknown. Using a 4‐year field experiment in a typical steppe of Inner Mongolia, we explored the effects of three drought scenarios (intense drought, excluding 100% of rainfall in June; reduced precipitation frequency, reducing rainfall events by 50% without changing total rainfall from June to August; and chronic drought, excluding 50% of each rainfall event from June to August) and nitrogen addition (+10 g N m −2 year −1 ) on species diversity, functional group abundance and functional group associations within and between trophic levels, including plant, ground‐dwelling arthropod and soil nematode communities, as well as their relationships with grassland productivity. We found that: (1) Drought and nitrogen addition had contrasting effects on multitrophic species diversity, functional group abundance and grassland productivity. Chronic drought significantly reduced productivity independent of nitrogen, while nitrogen addition enhanced it. Intense drought increased the abundance of bacterivorous and fungivorous nematodes, but this trend was absent with nitrogen addition. Reduced precipitation frequency had no significant effect on multitrophic communities or productivity under any nitrogen condition. (2) Drought, particularly chronic drought, enhanced positive associations between ground‐dwelling arthropod and soil nematode functional groups, whereas nitrogen addition was accompanied by a weakening of these functional group interconnections. (3) Increased productivity with nitrogen addition was associated with reduced positive associations within plant functional groups and between arthropod and nematode functional groups, along with increased soil nitrogen availability. Drought was related to lower productivity overall, although it also coincided with reduced associations within plant functional groups, which were related to higher productivity. Synthesis . Our results indicate that nitrogen deposition under drought scenarios is linked to adverse effects on the abundance and interconnections of multitrophic functional components, highlighting the importance of species interactions across trophic levels for understanding grassland responses to environmental change.

Understanding the impacts of biodiversity loss on ecosystem functioning and services has been a central issue in ecology. Experiments in synthetic communities suggest that biodiversity loss may erode a set of ecosystem functions, but studies in natural communities indicate that the effects of biodiversity loss are usually weak and that multiple functions can be sustained by relatively few species. Yet, the mechanisms by which natural ecosystems are able to maintain multiple functions in the face of diversity loss remain poorly understood. With a long-term and large-scale removal experiment in the Inner Mongolian grassland, here we showed that losses of plant functional groups (PFGs) can reduce multiple ecosystem functions, including biomass production, soil NO3 -N use, net ecosystem carbon exchange, gross ecosystem productivity, and ecosystem respiration, but the magnitudes of these effects depended largely on which PFGs were removed. Removing the two dominant PFGs (perennial rhizomatous grasses and perennial bunchgrasses) simultaneously resulted in dramatic declines in all examined functions, but such declines were circumvented when either dominant PFG was present. We identify the major mechanism for this as a compensation effect by which each dominant PFG can mitigate the losses of others. This study provides evidence that compensation ensuing from PFG losses can mitigate their negative consequence, and thus natural communities may be more resilient to biodiversity loss than currently thought if the remaining PFGs have strong compensation capabilities. On the other hand, ecosystems without well-developed compensatory functional diversity may be much more vulnerable to biodiversity loss.

Shifts in microbial communities do not explain the response of grassland ecosystem function to plant functional composition and rainfall change

Aims Water and nitrogen (N) are two key resources in dryland ecosystems, but they may have complex interactive effects on the community structure and ecosystem functions. How future precipitation (rainfall vs snowfall) change will impact aboveground net primary production (ANPP) is far from clear, especially when combined with increasing N availability. Methods In this study, we investigated changes in community productivity, abundance and aboveground biomass of two dominant plant functional groups (PFGs), i.e. perennial rhizome grasses (PR) and perennial bunchgrasses (PB) under the impacts of increased precipitation (rainfall vs snowfall) combined with N addition in a semiarid temperate steppe. Important Findings Summer rainfall augmentation marginally increased community ANPP, whereas it significantly increased the abundance and aboveground biomass of PR, but not those of PB. Summer rainfall addition increased the fraction of PR biomass (fPR) while decreased that of PB (fPB). Spring snow addition had no effect on aboveground biomass of either compositional PFG although it marginally increased community ANPP. Nitrogen addition significantly increased community ANPP with greater increase in PR under summer rainfall addition, indicating strong interactive effects on community ANPP largely by enhancing PR biomass. We also found a nonlinear increase in the positive effect of nitrogen addition on productivity with the increased precipitation amount. These findings indicate an amplified impact of precipitation increase on grassland productivity under the accelerated atmospheric N deposition in the future.

Plant diversity drives changes in the soil microbial community which may result in alterations in ecosystem functions. However, the governing factors between the composition of soil microbial communities and plant diversity are not well understood. We investigated the impact of plant diversity (plant species richness and functional group richness) and plant functional group identity on soil microbial biomass and soil microbial community structure in experimental grassland ecosystems. Total microbial biomass and community structure were determined by phospholipid fatty acid (PLFA) analysis. The diversity gradient covered 1, 2, 4, 8, 16 and 60 plant species and 1, 2, 3 and 4 plant functional groups (grasses, legumes, small herbs and tall herbs). In May 2007, soil samples were taken from experimental plots and from nearby fields and meadows. Beside soil texture, plant species richness was the main driver of soil microbial biomass. Structural equation modeling revealed that the positive plant diversity effect was mainly mediated by higher leaf area index resulting in higher soil moisture in the top soil layer. The fungal-to-bacterial biomass ratio was positively affected by plant functional group richness and negatively by the presence of legumes. Bacteria were more closely related to abiotic differences caused by plant diversity, while fungi were more affected by plant-derived organic matter inputs. We found diverse plant communities promoted faster transition of soil microbial communities typical for arable land towards grassland communities. Although some mechanisms underlying the plant diversity effect on soil microorganisms could be identified, future studies have to determine plant traits shaping soil microbial community structure. We suspect differences in root traits among different plant communities, such as root turnover rates and chemical composition of root exudates, to structure soil microbial communities.

Summary The rapid loss of global biodiversity can greatly affect the functioning of above‐ground components of ecosystems. However, how such biodiversity losses affect below‐ground communities and linkages to soil carbon (C) sequestration is unclear. Here, we describe how losses in plant functional groups ( PFG s) affect soil microbial and nematode communities and net ecosystem exchange ( NEE ) in a 4‐year removal experiment conducted on the Mongolian plateau, the world's largest remaining natural grassland. Our results demonstrated that the biomasses or abundances of most components of the two below‐ground communities (microbes and nematodes) were negatively affected by PFG loss and were positively related to above‐ground plant biomass. The removal of dominant PFG s (perennial bunchgrasses and perennial rhizomatous grasses) reduced the biomass or abundance of below‐ground community components while removal of less dominant PFG s (perennial forbs and annuals/biennials) did not change or increased the biomass or abundance of below‐ground community components. The biomass‐based ratio of fungal to bacterial microbes and the number‐based ratio of fungal‐feeding to bacterial‐feeding nematodes decreased with increasing PFG losses. Variation partitioning analyses showed that the identity of PFG s together with above‐ground plant biomass explained most of the total variation in soil microbes and that the identity of PFG s and above‐ground plant biomass together with nematode food resources explained most of the total variation in soil nematodes. The increase in NEE with PFG loss was mainly explained by decreases in above‐ground plant biomass and the ratio of fungi to bacteria. Synthesis . The shift of below‐ground communities from a fungal‐based to a bacterial‐based energy channel as PFG richness decreases indicates that less diverse grassland ecosystems will have lower nutrient retention and hence be more sensitive to land‐use or climate change. The dominant effects of above‐ground plant biomass and below‐ground communities on NEE indicate that PFG loss resulting from land‐use or climate change has the potential to reduce C sequestration in semi‐arid grassland soils. These findings suggest that predictive models may need to consider the composition of above‐ground and below‐ground communities in order to accurately simulate the dynamics of CO 2 fluxes in terrestrial ecosystems.

AimBiodiversity–ecosystem function (BDEF) experiments commonly group species into arbitrary a priori functional groups, e.g. the grass/forb/legume (GFL) classification. As a result, the causes of functional group diversity effects are often poorly understood. This paper presents a new process that uses functional trait data to create customized plant functional groups that can be tailored to address specific questions. This method is illustrated throughout with an example taken from a temperate mesotrophic grassland in southern England.LocationSilwood Park, Berkshire, UK.MethodsThe method described applies divisive hierarchical cluster analysis to plant functional trait data (from either field or greenhouse conditions) in order to cluster species into a user‐specified number of groups. In our example, this was done using unweighted traits with clear links to C and N cycling. To ensure between‐group variance had been maximized, we used a linear discriminant analysis. ANOVA should also be used to compare the mean trait values of groups, in order to make specific hypotheses regarding the effect that each group has upon ecosystem functioning. We compared the resulting groups with the GFL classification to see which was more likely to deliver functionally distinct groups.ResultsThe resulting groups had discrete functional characteristics, so simple hypotheses could be formulated. These groups also appeared to show stronger trait value differences than the GFL classification. Results from the experiment demonstrate that hypothesized removal effects on function were supported, thus validating our approach.ConclusionsThe method described is applicable to a wide range of communities and is able to recognize functionally distinct groups of species. General use of this approach could result in a more mechanistic understanding of biodiversity–ecosystem function relationships as it can establish experimentally validated links between functional effects traits and ecosystem functioning.

AimsSaprophytic fungi are important agents of soil mineralization and carbon cycling. Their community structure is known to be affected by soil conditions such as organic matter and pH. However, the effect of plant species, whose roots provide the litter input into the soil, on the saprophytic fungal community is largely unknown.MethodsWe examined the saprophytic fungi in a grassland biodiversity experiment with eight plant species belonging to two functional groups (grasses and forbs), combining DNA extraction from plant roots, next-generation sequencing and literature research.ResultsWe found that saprophyte richness increased with plant species richness, but plant functional group richness was the best predictor. Plant functional group was also the main factor driving fungal saprophytic community structure. This effect was correlated with differences in root lignin content and C:N ratio between grasses and forbs. In monocultures, root traits and plant functional group type explained 16% of the variation in community structure. The saprophyte taxa detected in mixed plant communities were to a large extent subsets of those found in monocultures.ConclusionsOur work shows that the richness and community structure of the root-associated saprophytic fungi can largely be predicted by plant functional groups and their associated root traits. This means that the effects of plant diversity on ecosystem functions such as litter decomposition may also be predictable using information on plant functional groups in grasslands.

Grazing reduces the temporal stability of temperate grasslands in northern China

Revealing the role of biodiversity in ecosystem functioning (BEF) has been a major focus of ecological research over recent decades. In general, results from artificially assembled communities point to the important role of biodiversity showing that loss of species has a negative effect on various ecosystem functions (mostly assessed by above‐ground peak biomass). However, the evidence from manipulations of natural communities is scarce, and results are often contradictory between these two approaches. In particular, the importance of species dominance for ecosystem functioning remains poorly understood. We created a gradient of plant species richness in a meadow community following a realistic species loss scenario (removal of less abundant species) to test the effect of diversity on community biomass and assess the importance of subordinate species compared with dominants in a 5‐year experiment. Contrasting with results of BEF experiments with artificial assembly, we did not find any relationship between plant species diversity and above‐ground biomass across the timeframe of the experiment. We provide evidence that dominant species' identity and traits are the main drivers of community biomass because dominant species were able to maintain biomass production after substantial species loss. Furthermore, dominants prevented community biomass from declining and biomass was indirectly influenced not by species richness but through differences in functional diversity. Our results support the mass ratio hypothesis, showing much bigger effect of dominant species on community biomass production and hints to the rather minor importance of the complementarity effect between species. We emphasize that BEF research should more focus on the role of dominant species in maintaining various ecosystem functions. Synthesis . Species diversity is a poor predictor of community above‐ground biomass production and dominant species can effectively compensate the total production after substantial loss of other species in a grassland community.

The responses of soil microbes to climatic and anthropological factors in the Tibetan grasslands