Grassland Community Composition Research Articles

Differential responses of community‐level functional traits to mid‐ and late‐season experimental drought in a temperate grassland

Abstract Extreme precipitation events are becoming more intense and frequent due to climate change. This climatic shift is impacting the structure and dynamics of natural communities and the key ecosystem services they provide. Changes in species abundance under these conditions are thought to be mediated by functional traits, morpho‐physiological characteristics of an organism that impact its fitness. Future environmental conditions may, therefore, favour different traits to those in present‐day communities. After 6 years of manipulated precipitation levels, including drought (−50% of ambient precipitation), irrigation (+50% of ambient precipitation), and control (ambient precipitation), we measured five key functional traits (plant height, leaf dry matter content [LDMC], leaf thickness, specific leaf area [SLA], and leaf phosphorus concentration) in 586 individual vascular plants to study the effects of precipitation changes on community‐weighted functional traits. Additionally, we tested whether the precipitation change effects on the traits depend on the time of the growing season. As expected, reduced precipitation impacted community composition only for the late‐season timing, after the seasonal field mowing, but led to a significant change in all community‐level plant traits between season timings. Under drought, communities shifted towards shorter individuals with thicker but small leaves and lower phosphorous content. Overall, a combination of community reassembly and intraspecific variation contributed to community‐weighted differences between control and drought plots for plant height, SLA, and LDMC traits. Species turnover was the main driver of community‐weighted means (CWMs) shifts in all traits in the late‐season but SLA. Whereas all traits showed variations at the community level with drought, SLA and LDMC were the most responsive traits at the species level. Nevertheless, our results suggest underestimation of intraspecific variation due to sensitive species lower abundance under stress. No differences in CWMs of functional traits were observed between control and irrigated plots. Synthesis: Our findings suggest that functional trait composition of grassland communities may shift under climate change‐induced drought, depending on the growing season timings. Trait‐based attempts to predict ecosystem functioning must account for such temporal variation in community trait values.

The Effects of Infectious Diseases on the Consequences of Interspecific Competition in Grassland Communities

As infectious diseases have a severe impact on the individual survival and competitive ability of host species in grassland communities, competition between relevant species may have different consequences, potentially influencing the species composition of grassland communities and the functioning of grassland ecosystems. Understanding the impact of infectious diseases on competition is thus crucial for the health management of grassland ecosystems. How do infectious diseases affect the competitive coexistence of grassland plant species? In this study, by drawing on Tilman’s multispecies competition model and incorporating the spread characteristics of grassland plant diseases, we built three spatial competition models of two grass species subject to infectious diseases, and we analyzed the invasion conditions of infectious diseases and how they impact the population dynamics and competitive consequences of the species. Our model revealed the following: (1) Diseases with high transmission rates and low virulence are more likely to invade populations, while the presence of non-host species is detrimental to disease invasion. (2) Disease promotes the coexistence of competing species, breaking down the original competition–compromise trade-off mechanism for species coexistence and greatly expanding the range of parameters within which the two species can coexist. (3) Pathogen infections indirectly weaken the suppression of inferior species by dominant species, which is similar to the cascade effect seen in trophic interactions. Our findings highlight the importance of disease in species coexistence and grassland biodiversity maintenance.

Experimental drought reduces the productivity and stability of a calcareous grassland

Abstract Grasslands, which encompass 40% of terrestrial ecosystems, hold global significance for food production, carbon storage and other ecosystem services. However, grasslands across the biosphere are becoming increasingly exposed to both wet and dry precipitation extremes resulting from climate change. Therefore, understanding how grasslands will respond to precipitation extremes is a pressing issue for managing changes to biodiversity and ecosystem service provision. Here, we use experimental manipulations of precipitation (50% increase and 50% decrease in growing‐season precipitation) over 6 years to investigate the stability and resistance of both productivity and community diversity in a calcareous grassland community. We found that decreased growing‐season precipitation led to reductions in mean productivity (25% decrease in peak above‐ground biomass) and its temporal stability (54% increase in the coefficient of variation of biomass across years). Productivity losses were more pronounced for graminoids and legumes, but this was not reflected in species per cent cover. Community composition was resistant to the precipitation manipulations, with no clear differences in overall community compositional turnover, dissimilarity or biodiversity indices. There was also no detectible effect of increased precipitation on productivity or community composition, which may indicate a lack of efficacy of the irrigation treatment in increasing soil moisture. Finally, the precipitation manipulations had no effect on temporal trends of community change, with an overall increase in richness and shift in grassland community composition across the study period independent of treatment. Synthesis. While the diversity and composition of this calcareous grassland was resistant to precipitation extremes (at least in the short term), sustained reductions in growing‐season precipitation reduced productivity and its temporal stability, particularly for graminoids and legumes. Therefore, we highlight that different properties of grasslands can vary in their responses to changes in precipitation.

Divergent shift of normal alpine meadow exacerbated soil loss of hillslope alpine meadows based on field experiments

Global climate change and overgrazing are driving shifts in the plant composition of grassland communities, which may profoundly affect the function of grassland ecosystems in regulating runoff and soil erosion. Here, we examined the shift effects of normal hillslope alpine meadow to shrub and severely degraded meadow states on runoff and sediment generation under natural rainfall conditions, and determined the contributions of plant and soil properties changes to soil erodibility, runoff and sediment generation by in situ rainfall experiment and monitoring on the hillslope of Qinghai-Tibetan Plateau. The results showed that normal meadow shift into severely degraded meadow state, mean weight diameter, soil saturated hydraulic conductivity, soil cohesion and soil erodibility K-factor at the topsoil decreased by 70.3%, 73.1%, 80.3% and −13.1%, respectively, and when normal meadows shift into shrub meadow state, they reduced by 49.1%, −1.3%, 49.4%, and −8.3%, respectively. Runoff and soil loss significantly changed by - 40.0% and 177.8% when normal meadow shifted into a severely degraded meadow state, while runoff and soil loss significantly changed by + 65.0% and +77.8% when normal meadow shifted into a shrub meadow state. Our findings highlight that the two divergent shifts both increased soil loss compared to the normal hillslope alpine meadows. Overall, our results indicate that the divergent shifts of normal alpine meadows exacerbated soil erodibility and soil loss of hillslope alpine meadows. These results obtained here offer a novel perspective on the regulation of runoff and soil erosion in the alpine meadow ecosystem.

Changes in bud bank and their correlation with plant community composition in degraded alpine meadows.

Bud banks are considered a crucial factor in regulating the species composition of grassland communities and maintaining the ecological function of alpine grasslands. However, few studies have paid attention to the dynamic changes of bud banks from undisturbed to severely degraded alpine meadows. Therefore, this study examined the correlations between plant diversity and bud bank traits at different stages of alpine meadows degradation. Grass biomasses and plant diversity were found to be highest in moderately degraded meadows, and sedge biomasses were highest in lightly degraded meadows. Lack of disturbance and moderate disturbance by herbivores increased the bud bank density of alpine meadows. Consistent with the changes in bud bank density, bud bank diversity was highest in undisturbed meadows. The structural equation model indicated that the densities of rhizome and the densities and diversities of tiller buds play crucial roles in facilitating the greater diversity of the plant community. Our findings suggest that the diversities and densities of rhizome and tiller buds in the degradation stages are synchronized with changes in plant diversity, and in the regenerative ability of bud banks, which largely determine the outcome of restoration in degraded meadows. These findings could provide a frame of reference for effectively restoring degraded alpine regions by regenerating bud banks. The potential driving force and renewal capacity of bud banks should be taken into account in restoring the Qinghai-Tibet Plateau's degraded meadow.

Shifts in dominant species modulate nitrogen effects on community temporal stability along a degradation gradient in Tibetan alpine grasslands

Grassland degradation is a widespread concern globally. Nutrient addition is widely recognized as an important management measure for degraded grassland restoration, but nutrient inputs may have important effects on temporal stability of communities. However, it is unclear how the degradation degrees regulate the impacts of adding nitrogen (N) on temporal stability of communities due to large variations in community composition and soil nutrient content. Herein, long-term experimental study was used to identify the N influences on temporal stability of community and driving factors of alpine grasslands at three degradational stages (none (ND), moderate (MD), and heavily degraded grassland (HD)). Elevated N could significantly enhance the aboveground biomass of ND, while there was no notable effect on MD and HD. However, N addition significantly lowered the temporal stability of all these three grasslands, although species richness was only pronouncedly reduced in MD. Our most conspicuous outcome is the major mechanism of temporal stability of community varied with degradation stages. N addition decreased temporal stability of the community predominantly by decrease in the richness of species and the stability of dominant species in ND and MD while decrease in dominant species stability, asynchrony, and richness of species in HD. This study highlights that impacts of N enrichment on temporal stability of community are potentially intermediated via community composition of alpine grasslands, which can offer guidance for scientific management and rehabilitation of degraded alpine grasslands.

Parasites as ecosystem modulators: foliar pathogens suppress top-down effects of large herbivores.

Parasites can catalyze or inhibit interactions between their hosts and other species, but the ecosystem-level effects of such interaction modifications are poorly understood. We conducted a large-scale field experiment in temperate grasslands of China to understand how foliar fungal pathogens influenced top-down effects of cattle on plant diversity and productivity. When foliar pathogens were suppressed, cattle grazing strongly reduced biomass of the dominant grass, Leymus chinensis, generating competitive release that significantly increased community-level species richness and evenness. In the absence of grazing, pathogen attack on L. chinensis had no measurable effect on host biomass. However, pathogens disrupted top-down effects of herbivory by inhibiting grazing effects on plant biomass and species richness. Mechanistically, fungal pathogens were linked to increased alkaloid and reduced nitrogen levels in leaf tissue, which appeared to deter cattle grazing on L. chinensis. In conclusion, foliar pathogens can suppress top-down effects of large herbivores on grassland community composition and ecosystem function by modifying the strength of their host's interactions with dominant consumers. Parasites may act as modulators of ecosystem function when their direct effects on host abundance are overshadowed by powerful influences on host traits that modify their interactions with competitors, herbivores, or predators.

How Seasonal Grazing Exclusion Affects Grassland Productivity and Plant Community Diversity

The Sanjiang Plain is famous for its concentrated distribution of natural wet grasslands. These wet grasslands are an important source of seasonal pasture or hay in the area. However, changes in community structure and ecosystem function have already occurred in wet grasslands because of overgrazing and climate change, resulting in severe grassland degradation. Exploring a reasonable grazing management strategy is crucial for improving grassland species diversity, increasing grassland productivity, and maintaining sustainable grassland utilization. We investigated the effects of five grazing management (GM) strategies (no grazing through the growing season (CK), spring grazing exclusion (Spr-GE), summer grazing exclusion (Sum-GE)), autumn grazing exclusion (Aut-GE), and grazing through the growing season (G)) on the productivity, community composition and structure of wet grasslands in the Sanjiang Plain under three grazing intensities (GI) (light (L), moderate (M), and heavy (H)). Results showed that Spr-GE and Sum-GE were beneficial in increasing total aboveground biomass (AGB), but decreased plant community diversity in Spr-GE due to increased intraspecies and interspecies competition. The exclusion of different seasonal grazings changed the composition of plant communities. At the level of functional groups and dominant species, Spr-GE had a significant effect on most functional groups and dominant species’ characteristics, while Aut-GE had little effect on most functional groups and dominant species’ characteristics. However, different functional groups and dominant species had different responses to seasonal grazing exclusion. In addition, under M, there were significantly improved grassland total AGB and PF AGB. The results indicated that Spr-GE with M may be an effective livestock-management strategy to protect grassland vegetation and community diversity, as well as to restore degraded grassland.

Effects of Land Use on the Soil Microbial Community in the Songnen Grassland of Northeast China.

Land use change obviously changes the plant community composition and soil properties of grasslands and thus affects multiple functions and services of grassland ecosystems. However, the response mechanisms of soil microorganisms, key drivers of the nutrient cycle and other soil functions during changes in grassland use type and associated vegetation are not well understood. In this study, Illumina high-throughput sequencing was used to analyze the changes in the soil microbial community structure of four grassland use types: exclosure (EL), mowed land (ML), grazed land (GL), and farmland (FL) in the Songnen Plain of Northeast China. The results showed that the FL and EL had significantly higher soil total nitrogen (TN) and lower soil electrical conductivity (EC) and pH than GL and ML. In contrast, the GL and ML had higher soil bulk density (BD) and organic matter, respectively, than the other land use types. In addition, the values of the Shannon diversity and Pielou’s evenness indexes were highest in the EL of all the land use types. Based on the high-throughput sequencing results, we observed high levels of α diversity in the FL for both bacteria and fungi. A structural equation model (SEM) revealed that pH and EC had a direct and positive effect on the bacterial community structure and composition. In addition, plant taxonomic diversity (according to the Shannon diversity and Pielou’s evenness indexes) indirectly affected the bacterial community composition via soil pH and EC. Notably, fungal composition was directly and positively correlated with soil nutrients and the value of Pielou’s evenness index changed with land use type. In conclusion, soil properties and/or plant diversity might drive the changes in the soil microbial community structure and composition in different grassland use types.

Phenological patterns of herbaceous Mediterranean plant communities in spring: is there a difference between native and formerly-cultivated grasslands?

Background and aims – Plant phenology, defined as the timing of recurring life events like leaf flushing, flowering, or fruiting, is highly sensitive to environmental factors such as photoperiod, temperature, and moisture. Phenological synchrony between interacting species – such as plants and their pollinators – is of major importance to the structure and functioning of ecosystems. Plant phenology might also be affected by changes in edaphic conditions. However, whether former agricultural activities may shift phenological patterns of plant communities remains poorly understood. In this study, we evaluated the impact of past agricultural practices on herbaceous plant community phenology in the protected Mediterranean xeric grassland of La Crau (France). Material and methods – We compared (1) species composition, and (2) phenological patterns of annuals, perennials, Bromus rubens (annual), and Lobularia maritima (perennial), in formerly-cultivated plots – abandoned for 30 years – and intact native grassland plots (steppe), both subjected to itinerant sheep grazing. Key results and conclusion – Our results suggest that former agricultural activities can affect species composition of Mediterranean xeric grassland communities with differences visible after 30 years of abandonment, but only altered phenological patterns slightly. We suggest that climatic factors and sheep grazing acted as strong habitat filters constraining community assembly at the phenological level.

Community leaf dry matter content predicts plant production in simple and diverse grassland

AbstractPlant growth correlates with values of collinear (covarying) traits from the leaf economics spectrum. Environmental variation and differences in community composition may alter contributions of these traits to plant production and thereby limit the consistency of trait‐based growth predictions among years and plant communities. We tested effects of interannual variation in precipitation and differences in grassland community composition (planted monoculture of switchgrass, Panicum virgatum, and mixture of perennial herbaceous species) on the utility of two traits from the leaf economics spectrum (leaf dry matter content [LDMC] and plant [N]) to predict aboveground net primary production (ANP) during spring of 6 years. Spatial and temporal variation in spring production correlated with community‐scale (species abundance‐weighted) values of both traits, but community LDMC explained 66% of the variance in production and accounted for ≥89% of the variance explained by the two traits combined. The ANP response to trait variation and the variance in ANP explained by trait values differed with precipitation and between communities. Greater precipitation increased the production response to trait variation by increasing slopes of ANP–trait regression relationships and increased the variance in ANP explained by trait values. Communities differed in response to precipitation variation and in the role of annual variation in the [N]–LDMC relationship in explaining variance in ANP. Results indicate that mean trends in grassland production can be predicted using community‐scale values of LDMC. Trait‐based predictions of grassland production could be improved, however, by accommodating precipitation and community effects on production–trait relationships.

Patterns of grassland community composition and structure along an elevational gradient on the Qinghai–Tibet Plateau

Abstract Grasslands in the Qinghai–Tibet Plateau play an important role in preserving ecological security and high biodiversity in this region. However, the distribution of the composition and structure of plant community and the mechanism by which it maintains itself in this region are still poorly understood. Here, we designed 195 grassland plots in 39 grassland sites along an approximately 1700 m elevation gradient on the Northeastern Qinghai–Tibet Plateau. We found that the grassland community height decreased significantly with increasing elevation, whereas community coverage did not significantly change. With increasing elevation, plant species richness (α diversity) increased significantly, but the community variability (β diversity) decreased significantly. The constrained clustering analysis suggested that the α- and β-diversity in the grasslands transformed gradually with elevation, and that three discontinuous points (based on community structure) were observed at elevation of 3640, 4252 and 4333 m. Structural equation modeling (SEM) indicated that the increase in precipitation and the decrease in temperature significantly positively influenced α diversity, which was negatively correlated with β diversity. These results demonstrate a quantitative-to-qualitative change in the community composition and structure along this elevational gradient on the Qinghai–Tibet Plateau.

Grasslands half‐full: investigating drivers of spatial heterogeneity in ungulate occurrence in Indian Terai

AbstractGrassland ecosystems have declined in their extent globally, driving declines in wild ungulate populations. Even within the remnant grasslands, ungulate distribution is highly heterogeneous for reasons that are not well understood. This in turn undermines both local and landscape level conservation efforts for these often‐neglected ecosystems and the herbivores they support. We investigated grassland‐ungulate relationships in the Terai region of North India, where wild ungulates are patchily distributed across alluvial grasslands, a besieged ecosystem. Specifically, we posited that spatial variation in grassland habitat use by swamp deer (Rucervus duvaucelii duvaucelii), hog deer (Axis porcinus) and spotted deer (Axis axis) would be explained by community composition, palatability of key grasses, and fire and flooding regimes in grasslands. Hierarchical clustering and multivariate ordination revealed that three dominant tall‐grass communities and the narrowly distributed and more palatable short grass Cynodon‐Oryza community were only marginally influenced by fire and flood histories. Ungulate habitat use, assessed using occupancy models for spatially correlated data, indicated that hog deer were ubiquitously distributed across the grasslands in the park (habitat use probability, ᴪ = 0.92, se = 0.05) utilizing a diverse range of grassland types, while spotted deer (ᴪ = 0.80, se = 0.17) and swamp deer (ᴪ = 0.45, se = 0.10) occurrence within grasslands was relatively lower. Grass height and grassland extent positively influenced habitat use of swamp deer and spotted deer, respectively. However, grassland community composition, fire history, flood history and palatability were relatively uninformative predictors of fine‐scale habitat use. Our study provides a robust baseline for future monitoring of grasslands and ungulates as well as insights for the design and implementation of grassland management interventions.

Understory shading exacerbated grassland soil erosion by changing community composition

The importance of understory herbs for soil erosion controlling in forests is well accepted, but its effectiveness was rarely reported. Understanding how understory shading affects herbs growth and soil erosion controlling benefits is essential for better policy management. Here, we investigated grassland characteristics and soil erosion process before and after grasslands placed beneath the forest canopies. Four typical grasslands (Trifolium repens, Medicago sativa, Elymus dahuricus and Bromus inermis) of the Loess Plateau were selected, and bare land was used as the control. Total fifteen plots (three replicates for each treatment) with a slope of 20° were constructed. All plots were placed outdoor (open areas) in the first year, and were moved to the undergrowth and remained in the Sophora japonica and Populus cathayana forests over the next five years. Time to runoff, runoff volume and sediment yield were examined by two simulated rainfall experiments before and after understory shading. Results showed that understory shading promoted the disappearance of the original grass species, increasing weeds with poor roots. Further, these changes led to more soil loss in all understory grassland treatments. After understory shading, the runoff volume (67.0–125.5 L) and biological soil crust coverage (1.0–15.7%) significantly decreased for all plots, whereas the sediment yield (5.0–1650.5 g), species richness (>5) and litter mass (75.8–241.0 g) significantly increased. Therefore, understory shading changed the community composition and structure of understory grasslands. Besides, we found that herb species difference, but not species richness difference, more determined understory soil erodibility. Our findings indicate that the shade-tolerant herb species application could effectively reduce soil erosion in forest-grassland complex ecosystem will help to achieve the sustainability of understory grassland during vegetation restoration.

Season of prescribed fire determines grassland restoration outcomes after fire exclusion and overgrazing

AbstractFire exclusion and mismanaged grazing are globally important drivers of environmental change in mesic C4 grasslands and savannas. Although interest is growing in prescribed fire for grassland restoration, we have little long‐term experimental evidence of the influence of burn season on the recovery of herbaceous plant communities, encroachment by trees and shrubs, and invasion by exotic grasses. We conducted a prescribed fire experiment (seven burns between 2001 and 2019) in historically fire‐excluded and overgrazed grasslands of central Texas. Sites were assigned to one of four experimental treatments: summer burns (warm season, lightning season), fall burns (early cool season), winter burns (late cool season), or unburned (fire exclusion). To assess restoration outcomes of the experiment, in 2019, we identified old‐growth grasslands to serve as reference sites. Herbaceous‐layer plant communities in all experimental sites were compositionally and functionally distinct from old‐growth grasslands, with little recovery of perennial C4 grasses and long‐lived forbs. Unburned sites were characterized by several species of tree, shrub, and vine; summer sites were characterized by certain C3 grasses and forbs; and fall and winter sites were intermediate in composition to the unburned and summer sites. Despite compositional differences, all treatments had comparable plot‐level plant species richness (range 89–95 species/1000 m2). At the local‐scale, summer sites (23 species/m2) and old‐growth grasslands (20 species/m2) supported greater richness than unburned sites (15 species/m2), but did not differ significantly from fall or winter sites. Among fire treatments, summer and winter burns most consistently produced the vegetation structure of old‐growth grasslands (e.g., mean woody canopy cover of 9%). But whereas winter burns promoted the invasive grass Bothriochloa ischaemum by maintaining areas with low canopy cover, summer burns simultaneously limited woody encroachment and controlled B. ischaemum invasion. Our results support a growing body of literature that shows that prescribed fire alone, without the introduction of plant propagules, cannot necessarily restore old‐growth grassland community composition. Nonetheless, this long‐term experiment demonstrates that prescribed burns implemented in the summer can benefit restoration by preventing woody encroachment while also controlling an invasive grass. We suggest that fire season deserves greater attention in grassland restoration planning and ecological research.

Variation of foliar silicon concentrations in temperate forbs: effects of soil silicon, phylogeny and habitat

Silicon (Si) accumulation is known to alleviate various biotic and abiotic stressors in plants with potential ecological consequences. However, for dicotyledonous plants our understanding of Si variation remains limited. We conducted a comparative experimental study to investigate (1) interspecific variation of foliar Si concentrations across 37 dicotyledonous forbs of temperate grasslands, (2) intraspecific variation in foliar Si concentration in response to soil Si availability, the influence of (3) phylogenetic relatedness, and (4) habitat association to moisture. Foliar Si differed markedly (approx. 70-fold) across the investigated forbs, with some species exhibiting Si accumulation similar to grasses. Foliar Si increased with soil Si availability, but the response varied across species: species with higher Si accumulation capacity showed a stronger response, indicating that they did not actively upregulate Si uptake under low soil Si availability. Foliar Si showed a pronounced phylogenetic signal, i.e., closely related species exhibited more similar foliar Si concentrations than distantly related species. Significant differences in foliar Si concentration within closely related species pairs nevertheless support that active Si uptake and associated high Si concentrations has evolved multiple times in forbs. Foliar Si was not higher in species associated with drier habitats, implying that in dicotyledonous forbs of temperate grasslands high foliar Si is not an adaptive trait to withstand drought. Our results demonstrated considerable inter- and intraspecific variation in foliar Si concentration in temperate forbs. This variation should have pervasive, but so far understudied, ecological consequences for community composition and functioning of temperate grasslands under land-use and climate change.

N deposition may accelerate grassland degradation succession from grasses- and sedges-dominated into forbs-dominated in overgrazed alpine grassland systems on Qinghai-Tibetan Plateau

Alpine grasslands are sensitive to grazing and atmospheric nitrogen (N) deposition. Despite increases in N deposition, few field studies have assessed the effects of grazing in conjunction with increased N deposition on alpine grassland vegetation.In this two-year field study, we examined the effects of overgrazing and overgrazing plus N deposition on eco-physiological processes of alpine grassland plants at the functional group level. We found that both overgrazing and overgrazing plus N deposition altered species composition and the dominance of three plant functional groups (grasses, sedges, and forbs) in an alpine meadow and alpine steppe.In the overgrazing and overgrazing plus N deposition treatments, forbs dominated the plant community. Grass and sedge dominance decreased substantially, relative to a ungrazed treatment. The underlying eco-physiological processes that led to the forb-dominated plant community differed between the overgrazing and overgrazing plus N deposition treatments. Overgrazing plus N deposition increased forb dominance both directly by selective herbivory and indirectly by enhancing forb photosynthetic rates.Our results suggest that overgrazing concomitant with increases in N deposition will likely shift the plant community composition of alpine grasslands on the Qinghai-Tibetan Plateau from grass/sedge communities to forb-dominated communities in the future.

Disruption of Traditional Grazing and Fire Regimes Shape the Fungal Endophyte Assemblages of the Tall-Grass Brachypodium rupestre.

The plant microbiome is likely to play a key role in the resilience of communities to the global climate change. This research analyses the culturable fungal mycobiota of Brachypodium rupestre across a sharp gradient of disturbance caused by an intense, anthropogenic fire regime. This factor has dramatic consequences for the community composition and diversity of high-altitude grasslands in the Pyrenees. Plants were sampled at six sites, and the fungal assemblages of shoots, rhizomes, and roots were characterized by culture-dependent techniques. Compared to other co-occurring grasses, B. rupestre hosted a poorer mycobiome which consisted of many rare species and a few core species that differed between aerial and belowground tissues. Recurrent burnings did not affect the diversity of the endophyte assemblages, but the percentages of infection of two core species -Omnidemptus graminis and Lachnum sp. -increased significantly. The patterns observed might be explained by (1) the capacity to survive in belowground tissues during winter and rapidly spread to the shoots when the grass starts its spring growth (O. graminis), and (2) the location in belowground tissues and its resistance to stress (Lachnum sp.). Future work should address whether the enhanced taxa have a role in the expansive success of B. rupestre in these anthropized environments.

Proximity to high densities of pastoral settlements reduces grassland regrowth in a protected tropical savanna

AbstractSedentarization of pastoralist communities is reshaping the structure and functioning of tropical savannas. Of particular concern is how permanent pastoral settlements change grassland vegetation inside “protected” areas. In this study, we investigate the spatial impact of pastoral settlements on grassland regrowth in Nech Sar National Park, Ethiopia. Within the National Park, we established herbivore exclosures across the central grassland plains at varying distances from a high concentration of pastoral settlements. Plant species composition, biomass, and regrowth after clipping were measured every 6 months, inside and outside exclosures in close proximity and further away from pastoral settlements. After 18 months, close proximity to high densities of pastoral settlements negatively influenced grassland regrowth compared to further away from pastoral settlements. Excluding herbivores resulted in lower regrowth compared to grazed swards independent of distance from high densities of pastoral settlements. Cover of the dominant grass species Bothriochloa insculpta was lower when grazed and following clipping, whereas Chrysopogon plumulosus cover was higher closer to settlements. These grasses were dominant across the plain; yet further away from settlements there was a higher number of co‐dominant grassland species. These findings suggest that subtle changes in grassland community composition, likely following livestock grazing, contribute to spatial differences in savanna grassland regrowth near to and far from pastoral settlements. Furthermore, specific grassland species may be used as indicators of the wider spatial impact of pastoral settlement sedentarization on savanna regrowth.

Ant community composition and functional traits in new grassland strips within agricultural landscapes.

Ongoing intensification and fragmentation of European agricultural landscapes dramatically reduce biodiversity and associated functions. Enhancing perennial noncrop areas holds great potential to support ecosystem services such as ant‐mediated pest control.To study the potential of newly established grassland strips to enhance ant diversity and associated functions, we used hand collection data and predation experiments to investigate differences in (a) ant community composition and (b) biocontrol‐related functional traits, and (c) natural pest control across habitats in cereal fields, old grasslands, and new grassland transects of three years of age.Ant species diversity was similar between new and old grasslands, but significantly higher in new grasslands than in surrounding cereal fields. Contrary, ant community composition of new grasslands was more similar to cereal fields and distinct from the species pool of old grasslands. The functional trait space covered by the ant communities showed the same distribution between old and new grasslands. Pest control did not differ significantly between habitat types and therefore could not be linked to the prevalence of functional ant traits related to biocontrol services in new grasslands.Our findings not only show trends of convergence between old and new grasslands, but also indicate that enhancing ant diversity through new grasslands takes longer than three years to provide comparable biodiversity and functionality. Synthesis and applications: Newly established grasslands can increase ant species richness and abundance and provide a consistent amount of biocontrol services in agroecosystems. However, three years after their establishment, new grasslands were still dominated by common agrobiont ant species and lacked habitat specialists present in old grasslands, which require a constant supply of food resources and long colony establishment times. New grasslands represent a promising measure for enhancing agricultural landscapes but must be preserved in the longer term to promote biodiversity and resilience of associated ecosystem services.