Alteration of North American Streams by Beaver

The role of plant diversity, plant functional groups, and mineral nitrogen for soil microbial functioning and soil mesofauna in temperate grassland

Summary Plant species persistence in natural communities requires coping with biotic and abiotic challenges. These challenges also depend on plant community composition and diversity. Over time, biodiversity effects have been shown to be strengthened via increasing species complementarity in mixtures. Little is known, however, whether differences in community diversity and composition induce rapid transgenerational phenotypic adaptive differentiation during community assembly. We expect altered plant–plant and other biotic interactions (mutualists or antagonists) in high vs. low diverse communities to affect immediate within‐ and between‐species trait differentiations due to competition for light and nutrients. Three years after the initiation of a large‐scale, long‐term biodiversity experiment in Jena, Germany, we tested for effects of varying experimental plant community diversity (1–60 plant species; one to four plant functional groups) and composition (with or without legumes and/or grasses) on phenotypic differentiation and variation of the tall herb Knautia arvensis. We measured reproduction at different diversity levels in the Jena Experiment (residents hereafter) and, in an additional common garden experiment without competition, recorded subsequent offspring performance (i.e. growth, reproductive success and susceptibility to powdery mildew) to test for differentiation in phenotypic expression and variability. We observed phenotypic differences among diversity levels with reduced fecundity of K. arvensis residents in more diverse communities. In the next generation grown under common garden conditions, offspring from high‐diversity plots showed reduced growth (i.e. height) and lower reproduction (i.e. fewer infructescences), but increased phenotypic trait variability (e.g. in leaf width and powdery mildew presence) and also tended to be less susceptible to powdery mildew infection. Community composition also affected Knautia parents and offspring. In the presence of legumes, resident plants produced more seeds (increased fecundity); however, germination rate of those seeds was reduced at an early seedling stage (reduced fertility). Synthesis. We conclude that rapid transgenerational effects of community diversity and composition on both mean and variation of phenotypic traits among offspring exist. In addition to heritable variation, environmentally induced epigenetic and/or maternal processes matter for early plant community assembly and may also determine future species coexistence and community stability.

Long‐term ecosystem development involves changes in plant community composition and diversity associated with pedogenesis and nutrient availability, but comparable changes in soil microbial communities remain poorly understood. In particular, it is unclear whether the diversity of plants and microbes respond to similar abiotic drivers, or become decoupled as resources change over long time‐scales. We characterized communities of archaea, bacteria and fungi in soils along a 2‐million‐year chronosequence of coastal dunes in a biodiversity hot spot in Western Australia. The chronosequence involves marked changes in soil pH and nutrient availability that drive major shifts in plant community composition and diversity as soils age. Patterns of α‐diversity for microbial groups differed along the chronosequence. Bacterial α‐diversity was greatest in intermediate‐aged soils; archaeal diversity was greater in young alkaline or intermediate‐aged soils, while fungal α‐diversity—like plant diversity—was greatest in old, strongly weathered soils where phosphorus is the limiting nutrient. Changes in microbial community composition along the chronosequence were explained primarily by the long‐term decline in soil pH, with a smaller influence of the relative abundance of plant nutrient‐acquisition strategies. However, changes between the prokaryote and fungal communities, and between fungal and plant communities, became increasingly decoupled along the chronosequence, demonstrating that the coordination of change in biological communities by abiotic drivers becomes weaker during long‐term ecosystem development. Several bacterial taxa, including DA101 (Verrucomicrobia), “Candidatus Solibacter” (Acidobacteria) and Gaiella (Actinobacteria), were particularly abundant on the oldest dunes, indicating that they are adapted to acquire phosphorus from extremely infertile soils. However, we cannot disentangle the influence of phosphorus from the long‐term decline in soil pH along the chronosequence. Synthesis. These results provide evidence for contrasting patterns of plant and microbial community composition and α‐diversity in response to acidification and nutrient depletion during long‐term pedogenesis.

Relationships between vegetation, site type and stand structure in coniferous plantations in Britain

Overgrazing substantially contributes to global grassland degradation by decreasing plant community productivity and diversity through trampling, defoliation, and removal of nutrients. Arbuscular mycorrhizal (AM) fungi also play a critical role in plant community diversity, composition, and primary productivity, maintaining ecosystem functions. However, interactions between grazing disturbances, such as trampling and defoliation, and AM fungi in grassland communities are not well known. We examined influences of trampling, defoliation, and AM fungi on semiarid grassland plant community composition for 3yr, by comparing all combinations of these factors. Benomyl fungicide was applied to reduce AM fungal abundance. Overgrazing typically resulted in reduced dominance of Stipa Krylovii, contributing to degradation of typical steppe grasslands. Our results indicated trampling generally had little effect on plant community composition, unless combined with defoliation or AM fungal suppression. Defoliation was the main component of grazing that promoted dominance of Potentilla acaulis over Stipa krylovii and Artemisia frigida, presumably by alleviating light limitation. In non-defoliated plots, AM fungi promoted A.frigida, with a concomitant reduction in S.krylovii growth compared to corresponding AM suppressed plots. Our results indicate AM fungi and defoliation jointly suppress S.krylovii biomass; however, prolonged defoliation weakens mycorrhizal influence on plant community composition. These findings give new insight into dominant plant species shifts in degraded semiarid grasslands.

SummaryNutrient additions typically increase terrestrial ecosystem productivity, reduce plant diversity and alter plant community composition; however, the effects ofPadditions and interactions betweenNandPare understudied.We added bothN(10 g m−2) and three levels ofP(2.5, 5 and 10 g m−2) to a native, ungrazed tallgrass prairie burned biennially in northeasternKansas,USA, to determine the independent and interactive effects ofNandPon plant community composition and above‐ground net primary productivity (ANPP).After a decade of nutrient additions, we found few effects ofPalone on plant community composition,Nalone had stronger effects, andNandPadditions combined resulted in much larger effects than either alone. The changes in the plant community were driven by decreased abundance ofC4grasses, perhaps in response to altered interactions with mycorrhizal fungi, concurrent with increased abundance of non‐N‐fixing perennial and annual forbs. Surprisingly, this large shift in plant community composition had little effect on plant community richness, evenness and diversity.The shift in plant composition withNandPcombined had large but variable effects onANPPover time. Initially,NandNandPcombined increased above‐ground productivity ofC4grasses, but after 4 years, productivity returned to ambient levels as grasses declined in abundance and the community shifted to dominance by non‐N‐fixing and annual forbs. Once these forbs increased in abundance and became dominant,ANPPwas more variable, with pulses in forb production only in years when the site was burned.Synthesis. We found that a decade ofNandPadditions interacted to drive changes in plant community composition, which had large effects on ecosystem productivity but minimal effects on plant community diversity. The large shift in species composition increased variability inANPPover time as a consequence of the effects of burning. Thus, increased inputs ofNandPto terrestrial ecosystems have the potential to alter stability of ecosystem function over time, particularly within the context of natural disturbance regimes.

Multiscale partitioning effects of livestock grazing management on plant community composition and diversity in arid rangelands.

Geological factors are fundamental determinants of plant community structure and diversity, shaping not only physical terrain but also the chemical and physical properties of the soil. While climate and biotic interactions are crucial, geology often acts as a first-order filter, establishing baseline conditions for other ecological processes. This study investigated the profound influence of geological heterogeneity on soil physicochemical properties and, consequently, plant community composition and diversity within a region encompassing diverse bedrock types (igneous, sedimentary, metamorphic). We systematically collected high-resolution geological data, comprehensive soil samples (analyzing pH, nutrient content, texture, and trace elements), and detailed plant community data (species identification, cover, abundance). Our results demonstrate significant variations in soil properties directly linked to underlying geological units, such as higher pH and calcium in limestone-derived soils versus low Ca:Mg ratios and high nickel in serpentine soils. These edaphic differences imposed strong selective forces on plant species, leading to distinct community structures and biodiversity levels. Plant diversity, including species richness and Shannon-Wiener diversity, was significantly lower on serpentine substrates compared to limestone. Non-metric Multidimensional Scaling (NMDS) ordination clearly separated plant communities based on their geology, with Permutational Multivariate Analysis of Variance (PERMANOVA) confirming geology as a significant driver, accounting for 38.5% of total variation. Redundancy Analysis (RDA) identified soil pH, Ca:Mg ratio, and nickel concentration as key environmental factors correlated with community shifts. Variance partitioning analysis further emphasized the pervasive impact of geology, both directly and indirectly through soil attributes, in shaping plant community composition and diversity. These findings underscore the critical importance of incorporating geological context into ecological research, conservation strategies, and natural resource management, particularly in the face of increasing anthropogenic stress and climate change.

Summary Biodiversity conservation of grasslands in the face of transformation and global climate change will depend mainly on rangelands because of insufficient conservation areas in regions suited to agriculture. Transformed vegetation (pastures, crops and plantations) is not expected to conserve much biodiversity. This study examined the impact of land use on the plant diversity and community composition of the southern Drakensberg grasslands in South Africa, which are threatened with complete transformation to pastures, crops and plantations. The main land uses in this high rainfall region are: ranching or dairy production under private tenure using indigenous grassland, pastures (Eragrostis curvula, kikuyu and ryegrass) and maize; plantation forestry; communal tenure (maize and rangelands); and conservation. Plant diversity and composition were assessed using Whittaker plots. Transformed cover types were depauperate in species and ranged from kikuyu (1·4 species m−2) and ryegrass (2·9), to pine plantation (3·1), E. curvula pasture (3·1), commercial maize (3·2) and communal maize (7·8). With the exception of pine plantations, these communities supported mostly exotic (50 of 70 species) or ruderal indigenous species and made little contribution to plant species conservation. Abandoned communal cropland reverted to an indigenous grassland almost devoid of exotic species within c. 20 years. It was predicted that frequently cultivated sites (maize and ryegrass) would support less diversity than long‐lived pastures (kikuyu and E. curvula). This was contradicted by the relatively high species diversity of communal maize fields, which was attributed to a lack of herbicides, and the depauperate communities of kikuyu and of E. curvula pasture, which were attributed, respectively, to a dense growth form and a severe mowing regime. Pine plantations harboured fourfold more indigenous species per plot (27) than other transformed types. Species were mostly shade‐tolerant grassland relics that had persisted for 12 years since planting, and some forest colonizers. Indigenous species were unlikely to be maintained because of aggressive invasion by the exotic Rubus cuneifolius and severe disturbance associated with tree harvest and replanting. The richness of indigenous grasslands was expected to differ in response to grazing pressure but they differed only in composition. Grasslands were dominated by grasses, despite the richness of herbaceous species. The dominance of Themeda triandra was reduced under livestock grazing in favour of more grazing‐tolerant species. Exotic species were inconspicuous except for the dicotyledon Richardia brasiliensis, a subdominant under communal grazing. Southern Drakensberg grasslands are probably now stocked with livestock six‐ to 35‐fold higher than during pre‐settlement times. A grassland protected for c. 50 years supported twofold greater richness (101 species plot−1) than grazed grasslands, suggesting that a 150‐year history of increased mammalian grazing had already reduced plant diversity. Synthesis and applications. Land acquisition is costly, thus conservation of plant diversity in the southern Drakensberg requires a policy that inhibits transformation of rangelands. This can be achieved by enhancing their economic viability without changing the vegetation composition. Their inherent value must be recognized, such as for water production. The viability of commercial ranches can be improved by increasing their size. Conservation efforts need to be focused on plant taxa that only occur on unprotected rangelands.

Soil biota could have a significant impact on plant productivity and diversity through benefiting plants and mediating plant–plant interaction. However, it is poorly understood how soil biotic factors interaction with abiotic environments affect plant community diversity and composition. Here, we investigate the community‐level consequences of arbuscular mycorrhizal fungi (AMF) interactions with multiple nutrients and their ecological stoichiometry. We conducted a greenhouse experiment manipulating nitrogen (N) and phosphorus (P) to create soil nutrient availability and N:P gradients for microcosm communities with and without AMF. We found that AMF suppressed plant diversity at low P levels, whereas it did not alter the diversity at high P levels because of trade‐offs in the abundance of the dominant and subordinate species. AMF reduced plant diversity at the intermediate N:P ratios, while AMF did not affect the diversity at low and high N:P ratios. P addition decreased the mycorrhizal contribution to community productivity, whereas N addition reduced the negative effects of AMF on productivity at high P levels. AMF decreased community productivity at low N:P ratios but increased it at high N:P ratios. AMF increased the stoichiometric homoeostasis of plant communities, which was positively correlated with the stability of productivity under variations in soil N:P ratios. Our study demonstrates that both resource availability and stoichiometry influence the effect of AMF on plant community productivity and diversity and suggests that AMF may increase the stability of plant communities under variations in the soil nutrients by increasing the stoichiometric homoeostasis of the plant community.

Fungal symbionts commonly occur in plants influencing host growth, physiology, and ecology (Carlile et al., 2001). However, while whole-plant growth responses to biotrophic fungi are readily demonstrated, it has been much more difficult to identify and detect the physiological mechanisms responsible. Previous work on the clonal grass Glyceria striata has revealed that the systemic fungal endophyte Epichloë glyceriae has a positive effect on clonal growth of its host (Pan & Clay, 2002; 2003). The latest study from these authors, in this issue (pp. 467- 475), now suggests that increased carbon movement in hosts infected by E. glyceriae may function as one mechanism by which endophytic fungi could increase plant growth. Given the widespread distribution of both clonal plants and symbiotic fungi, this research will have implications for our understanding of the ecology and evolution of fungus-plant associations in natural communities.

AimClimate change and an increase in human disturbance are major drivers of global biodiversity loss. Yet it is not clear to what extent their effects on animal communities are direct or indirectly mediated by changes in biotic factors, such as plant diversity. Here, we disentangle the direct and indirect effects of climate, human disturbance, vegetation structure and plant functional traits on the functional diversity of avian frugivore communities across a large environmental gradient.LocationMount Kilimanjaro.Time periodSampling between November 2013 and October 2015.Major taxa studiedFleshy‐fruited plants, frugivorous birds.MethodsWe sampled plant and bird communities along an elevational and a human disturbance gradient and measured corresponding morphological traits of plants and birds to calculate indices of functional identity and functional diversity of plant and bird communities. We used structural equation models to disentangle direct and indirect effects of all variables on functional identity and diversity of frugivorous bird communities.ResultsBoth functional identity and diversity of frugivorous bird communities were consistently related to the functional identity and diversity of plant communities. Climate had almost exclusively indirect effects on functional identity and diversity of bird communities mediated through effects on plant functional identity and diversity. In contrast, human disturbance also had direct negative effects on bird diversity.Main conclusionsWe show that plant functional identity and diversity are the most important drivers of functional identity and diversity of frugivorous birds. Although effects of climate on bird communities are almost exclusively mediated indirectly through plant communities, human disturbance resulted in a direct reduction of bird diversity. The high degree of trait matching between interdependent trophic levels over a large environmental gradient demonstrates the importance of biotic drivers for animal communities and shows that biodiversity models need to consider such bottom‐up effects in future conditions.

Revegetation is an important restoration strategy for the control of rocky desertification. However, few studies have focused on the effects of different rocky desertification degrees (RDDs) on plant diversity and soil fertility in northern Guangdong over long periods of time. In this study, variance analysis, correlation analysis, and canonical correlation analysis (CCA) were used to examine plant diversity, soil physicochemical properties, and their correlations in various rocky desertification areas in northern Guangdong. The results showed that the Pinaceae, Lauraceae, and Fagaceae species were relatively abundant in the rocky desertification areas of northern Guangdong. Additionally, Cinnamomum camphora, Schima superba, Pinus massoniana, Quercus stewardiana, and Acer camphora could be used as indicators for rocky desertification. There were significant differences in plant community compositions and diversity characteristics between the five RDDs, and the vegetation exhibited the trend of initial destruction and then gradual improvement and stabilization. There were significant differences in soil bulk density, mechanical composition, organic matter, total nitrogen, alkaline hydrolysis nitrogen, and available potassium between the different RDDs. Except for pH, the soil chemical characteristics all had clear aggregation effects. Soil organic matter, total nitrogen, total potassium, and alkaline hydrolysis nitrogen all exhibited degradation–improvement cycles. The correlation analysis revealed that there was a significant correlation between soil physicochemical properties and species diversity. The CCA analysis showed that the most important soil factors affecting plant community structures were total phosphorus and available phosphorus. In conclusion, some achievements have been made in the restoration of rocky desertification in northern Guangdong; while the plant community structure improved, some soil nutrients also improved. Vegetation and soil have a strong coupling relationship. In the later stages of recovery, suitable species for rocky desertification could be considered in varying degrees and P and K could be supplemented appropriately. Our study will have implications for the revegetation of rocky desertification.

Understanding the relationships between diversity and functional traits in plant communities is essential for elucidating ecosystem functions, forecasting community succession, and informing ecological restoration efforts in arid regions. Although the current research on plant functional traits and diversity has improved our ability to predict ecological functions, there are still many problems, such as how environmental changes affect the relationship between species diversity and plant functional traits, and how these interactions affect plant community functions. We examined the relationships among leaf and fine root functional traits, species diversity, and functional diversity at the community level, along with their environmental interpretations, in a plant community within the desert-oasis transition zone of the Hexi Corridor, where habitats are undergoing significant small-scale changes. During dune succession, plant community composition and diversity exhibited significant variation. Plants are adapted to environmental changes through synergistic combinations of above-ground and below-ground traits. Specifically, plants in fixed dunes adopted a "slow investment" strategy, while those in semi-fixed and mobile dunes employed a "fast investment" approach to resource acquisition. A strong coupling was observed between plant community functional traits and species diversity. Soil phosphorus content and compactness emerged as primary factors influencing differences in plant community functional traits and composition. These soil factors indirectly regulated fine root functional traits and diversity by affecting species diversity, thereby driving community succession. Our study elucidates the "soil-diversity-community functional trait" linkage mechanisms in the successional process of desert plants. This research provides scientific support for the restoring and reconstruction of degraded ecosystems in arid zones.

In mountains, current land-use changes are altering plant communities of semi-natural grasslands with potential cascading effects on associated herbivores. Besides vegetation changes, temperature is also a key driver of insect diversity, and in the European Alps is predicted to increase by 0.25 °C per decade. Understanding herbivore responses to temperature and plant composition changes in mountain environments is of increasing importance. Our study aims at investigating the response to temperature and plant diversity and composition of two key herbivore groups (orthopterans and leafhoppers) belonging to contrasting feeding guilds (chewers vs. sap-feeders). We hypothesized that orthopteran diversity would be driven by temperature while leafhoppers by plant community composition. We selected 15 dry calcareous grasslands ranging from 100 to 1330 m a.s.l. along two independent gradients of plant diversity and temperature. We sampled orthopteran and leafhopper species richness and abundance by sweep-netting. Consistent with their low feeding specialisation, orthopteran species richness and community composition were only driven by temperature. By contrast, leafhopper species richness was not affected by temperature nor by plant diversity but leafhopper community composition was strongly influenced by plant species composition. This response can be explained by the higher host feeding specialisation of many leafhopper species. Species rarity and mobility did not change the response of the diversity of both groups, but orthopteran abundance increased with temperature only for highly mobile species. Altogether, our results suggest that future responses of grassland herbivores to vegetation changes and temperature warming are highly variable and depend on the feeding strategy and specialisation of the focal herbivore group.Implications for insect conservationLeafhoppers emerged to be particularly sensitive to potential management or climate-induced change in vegetation composition, while orthopterans are expected to respond directly to temperature warming due to their relaxed association with plant community diversity and composition.