Reversing the Trend: Year‐Round Grazing Promotes Species‐Rich Grasslands in Natura 2000 Sites

Wetland plant communities in the plateau lakes of Yunnan Province, China, have decreased significantly over the past decades. To better understand this degradation, we analyzed the processes and characteristics of changes in wetland plant communities in two of the largest lakes in Yunnan Province, Dianchi and Erhai lakes. We collected records of native and alien plant communities in the two lakes from literature published from the 1950s to current period. We calculated plant community types and their area in some historical periods when related data were reported, and analyzed the relationship between changes in plant communities and water pollution. In Dianchi Lake, 12 community types of native plant communities, covering over 80% of the surface in the 1950s and 1960s, were reduced to four types covering 2.4% by the late 2000s. Alien plant communities started to appear in the lake in the late 1970s, and have since come to cover 4.9% of the lake surface, thereby becoming dominant. In Erhai Lake, 16 community types of native plant communities, covering 47.1% of the lake surface in the late 1970s, declined to 10 community types, covering 9.3% of the surface, by the late 2000s. Alien plant communities appeared in the middle 1980s, and at present cover 0.7% of the surface area. It was indicated that changes in plant communities were significant related to water eutrophication. The area occupied by native and alien plant communities was, respectively, negatively and positively related to the content of nutrients in water. This showed lacustrine pollution played an important role in native plant loss and alien plant invasion in the two plateau lakes.

Human influence on the environment is so extensive that virtually all ecosystems on the planet are now affected by biological invasions. And, often, ecosystems are invaded by multiple co‐occurring non‐native species. Hence, it is important to understand the impacts these invasions are producing on biodiversity and ecosystem processes.Here, we present results of a 2‐year long field experiment where we tested the effects of co‐occurring invasive C4African grasses in a Cerrado area in central Brazil. We compared plant and arthropod communities, plant biomass, and soil nitrogen dynamics and soil chemical characteristics across five experimental treatments:Urochloa decumbensremoval;Melinis minutifloraremoval; bothU.decumbensandM.minutifloraremoval;U.decumbensandM.minutiflorainvaded plots; and uninvaded Cerrado. We hypothesized that selective removal of invasive grasses would have distinct effects on the native ecosystem structure and functioning. We expected that each invasive grass would produce a different type of impact on the native ecosystem and that their impacts would be synergistic when co‐occurring.Removal ofM.minutifloradoubled native plant diversity and biomass when compared to invaded plots, whereas removal ofU.decumbensdid not alter these parameters. Cerrado plots had four times more plant species than plots cleared of invasives. Removal of invasive grasses did not affect the species richness or community composition of soil epigeal fauna. Cerrado soils had lower fertility, organic matter content and pH than invaded soils. The effects were generally higher when both invasive grasses were removed, suggesting impacts were synergistic, butM.minutiflorahad greater effects on plants and soils thanU.decumbens. Both invasive species produced negative impacts, but a single species was the main driver. We also detected persistent effects of the invasive grass species on the ecosystem after 2 years of removal.We conclude that invasive species of the same functional group have similar types of effects in native ecosystems, but the magnitude of impact was largely dependent on invasive species biomass and cover. Where multiple invasive species are present, research and management of invaded ecosystems should tackle the interacting effects of co‐occurring invaders.

Seabirds are chemical and physical engineers that are capable of transforming terrestrial vegetation by altering edaphic conditions, generating physical disturbance, and affecting seed dispersal. Substantial changes in seabird populations are occurring worldwide and are likely to have important consequences for plant community composition on islands and coastal areas. This review focuses on the impact of seabirds on plant biomass, species richness and community composition. A total of 57 publications (42 studies) were selected for review. Of the 42 studies represented in the publications, 55% were descriptive. Most studies took place in Australia, New Zealand, the British Isles, Japan, North America, and sub-Antarctic islands. A few studies showed that aboveground plant biomass in seabird colonies increased with sufficient rainfall and moderate temperatures. The majority of studies on plant species richness showed a decrease in seabird colonies compared to areas unaffected by birds. However, species richness was higher in areas of intermediate seabird disturbance, compared to undisturbed areas. Moreover, the effects of seabirds on species richness varied with respect to island size. Most studies of plant community composition indicated that annuals, ȁ8ruderals”, and cosmopolitan species increased in abundance in seabird colonies. Changes in plant communities in seabird colonies appear to result mainly from altered soil nutrient concentrations and pH, increased physical disturbance, and seed dispersal by seabirds and humans. However, few studies have rigorously studied the relative importance of these alterations. Both the direction and magnitude of seabird effects are modified by: (1) density of birds, (2) temperature and precipitation, and (3) proximity to human habitation. A reduction in seabird populations is likely to have negative consequences for native plant species that rely on seabird disturbance for their persistence. However, seed dispersal by nesting seabirds, especially gulls, frequently leads to invasion by cosmopolitan plant species and declines of native species. Further studies that incorporate both quantitative sampling and manipulative experiments would go a long way in improving our understanding of how seabirds affect plant communities.

Using GPS technology and community research methods for plant communities, we investigated the distribution patterns of aquatic plant communities in the high plateaus of the Napahai Wetlands, Yunnan, China, as well as the species changes of plant communities compared with that of 24 years ago since 2005. We found that the types and numbers of aquatic plant communities have changed. Some pollution-tolerant, nutrient-loving plant communities such as Scirpus tabernaemontani, Zizania caduciflora, Myriophyllum spicatum, and Azolla imbricata flourished, while the primary aquatic plant communities were reduced or even disappeared. The number of aquatic plant communities were increased from nine to 12 with the addition of two new emergent plant communities and one new floating-leaved plant community. The increase in emergent plant communities was significant. From east to west and from south to north, various types of plant communities were continuously distributed, including floating-leaved plant communities, emergent plant communities and submerged plant communities. The composition of the communities became more complicated and the number of accompanying species increased, while the percentage ratio of dominant plant species declined. In 2005, the coverage of emergent plant communities was the largest (528.42 hm2) followed by submerged plant communities (362.50 hm2) and the floating-leaf plant communities was the smallest (70.23 hm2). The variations in the distribution of aquatic plant communities in the Napahai Wetlands reflect the natural responses to the change of the wetland ecological environment. This study indicates that human disturbances have led to an inward movement of the wetland shoreline, a decrease in water quality and a reduction in wetland habitat.

Wildlife trade is a key driver of extinction risk, affecting at least 24% of terrestrial vertebrates. The persistent removal of species can have profound impacts on species extinction risk and selection within populations. We draw together the first review of characteristics known to drive species use - identifying species with larger body sizes, greater abundance, increased rarity or certain morphological traits valued by consumers as being particularly prevalent in trade. We then review the ecological implications of this trade-driven selection, revealing direct effects of trade on natural selection and populations for traded species, which includes selection against desirable traits. Additionally, there exists a positive feedback loop between rarity and trade and depleted populations tend to have easy human access points, which can result in species being harvested to extinction and has the potential to alter source-sink dynamics. Wider cascading ecosystem repercussions from trade-induced declines include altered seed dispersal networks, trophic cascades, long-term compositional changes in plant communities, altered forest carbon stocks, and the introduction of harmful invasive species. Because it occurs across multiple scales with diverse drivers, wildlife trade requires multi-faceted conservation actions to maintain biodiversity and ecological function, including regulatory and enforcement approaches, bottom-up and community-based interventions, captive breeding or wildlife farming, and conservation translocations and trophic rewilding. We highlight three emergent research themes at the intersection of trade and community ecology: (1) functional impacts of trade; (2) altered provisioning of ecosystem services; and (3) prevalence of trade-dispersed diseases. Outside of the primary objective that exploitation is sustainable for traded species, we must urgently incorporate consideration of the broader consequences for other species and ecosystem processes when quantifying sustainability.

Plant communities on mountain summits are commonly long‐lived, cold‐adapted perennials with low dispersal ability. These characteristics in tandem with limited area to track suitable conditions make these mountain communities potentially highly vulnerable to climate change, and indicators of climate change impacts. We investigated temporal changes in plant communities on 29 arid mountain summits across eight study regions in California and Nevada, USA, over 19 years. We analyzed community dynamics in terms of species richness, turnover, gain and loss of functional groups, and relative abundance of functional groups. First, across all summits and regions, we found no change in species richness over time. Second, there was relatively high species turnover (21.7%) between the five‐year survey intervals, but turnover was not significantly different from random expectation. Within functional groups, forbs had the greatest proportion of gains and cushions had the greatest proportion of losses. Third, qualitative abundance categories presented a small but consistent signal of decrease in the relative abundance of cushions, graminoids, and shrubs/trees over the study period. Across a broad geographic scale and nearly two decades, community patterns were widely similar, suggesting that climate change has not impacted local colonization or extirpation of mountaintop species in this arid region. These findings support observed differences in response to climate change between temperature‐limited and water‐limited regions globally, and highlight the lagged and variable nature of high‐elevation systems. Our findings fill a major data gap on alpine plant community responses to climate change in the western United States and bolster the importance of long‐term ecological monitoring with rapid climate change.

N-driven changes in a plant community affect leaf-litter traits and may delay organic matter decomposition in a Mediterranean maquis

Evidence of the effects of alien plant colonisation on plant communities is often hindered by the fact that similar patterns in community composition can arise through a variety of processes. The objective of this study is to determine whether changes in species composition in coastal dune communities depend on the colonisation of a neophyte plant, Oenothera stucchii, or on concurrent processes that favour its colonisation. We hypothesised two scenarios: 1) a direct impact of O. stucchii on colonised communities, leading to displacement of native species; or 2) no direct impact of O. stucchii, i.e. the species colonises plant communities by exploiting disturbances that lead to the rearrangement of plant communities. We used the species-habitat network approach to identify potential drivers of changes in species composition, assuming that changes in the structure of the species-habitat network depend on the nature of the driving process. We demonstrated that changes in species composition in plant communities were due to species rearrangement, with colonised communities characterised by more homogeneous composition of species. We suggest that changes in plant communities may not depend on colonisation by O. stucchii per se, but on concomitant processes that affect coastal dune communities while promoting colonisation by O. stucchii.

Assessing temporal changes in plant communities is a core aim of temporal ecology and a shared priority of global conservation agendas which is particularly urgent in threatened ecosystems. Mediterranean coastal dunes harbour some of the most threatened habitats in Europe. Yet, surprisingly, studies capturing the recent temporal dynamics of biodiversity in these systems by accounting for multiple diversity facets and different aspects of community structure are missing. Here, using data from a resurveying study, we provide a first comprehensive, habitat‐based, multi‐faceted assessment of recent (10–15 years) temporal changes in threatened Mediterranean coastal dunes. To this aim, we quantified taxonomic and functional changes in plant communities using indices capturing multiple biodiversity features, and we explored trends at both the community level and the species level. We compared observed biodiversity changes across habitats (to look for evidence of generalized biodiversity loss) and across facets (to infer the potential loss of unique functions), and tested their significance using a null model. Overall, we predicted large compositional shifts and biodiversity loss beyond expectations in many communities, although with differences among habitat types. Our results reveal severe shifts in the taxonomic profile of the communities, mostly driven by a non‐random species loss, and little temporal overlap in functional space, implying large changes in both community structure and ecological strategies of the investigated habitats. This, together with the disappearance of c. 23% of historical plots and with substantial losses in focal species, suggests that intense degradation processes are occurring in coastal dune habitats, particularly on the upper beach and on shifting dunes. Synthesis. This study provides the first evidence of large, often non‐random, taxonomic and functional changes occurring in Mediterranean coastal dune plant communities in a surprisingly short time‐span. Along with furthering our knowledge of the recent dynamics affecting these endangered ecosystems, our results also pinpoint the types of habitats that are most at risk, helping to direct future conservation efforts and management. Future research should now be directed at more precisely testing potential drivers of these changes.

Identification of factors that drive changes in plant community structure and contribute to decline and endangerment of native plant species is essential to the development of appropriate management strategies. Introduced species are assumed to be driving causes of shifts in native plant communities, but unequivocal evidence supporting this view is frequently lacking. We measured native vegetation, non-native earthworm biomass, and leaf-litter volume in 15 forests in the presence and absence of 3 non-native plant species (Microstegium vimineum, Alliaria petiolata, Berberis thunbergii) to assess the general impact of non-native plant and earthworm invasions on native plant communities in northeastern United States. Non-native plant cover was positively correlated with total native plant cover and non-native earthworm biomass. Earthworm biomass was negatively associated with cover of native woody and most herbaceous plants and with litter volume. Graminoid cover was positively associated with non-native earthworm biomass and non-native plant cover. These earthworm-associated responses were detected at all sites despite differences in earthworm species and abundance, composition of the native plant community, identity of invasive plant species, and geographic region. These patterns suggest earthworm invasion, rather than non-native plant invasion, is the driving force behind changes in forest plant communities in northeastern North America, including declines in native plant species, and earthworm invasions appear to facilitate plant invasions in these forests. Thus, a focus on management of invasive plant species may be insufficient to protect northeastern forest understory species.

The effects of spring grazing by sheep and of natural levels of insect herbivory were studied in 1985 on a limestone field abandoned from arable land for four years. A split-plot design was adopted in which paddocks, arranged in Latin squares, were either left ungrazed or heavily grazed by sheep for ten days in April. Within each paddock plots were either sprayed regularly with Malathion-60 or untreated.Natural levels of insect herbivory, compared to the reduced levels in insecticide-treated plots, had effects of similar magnitude to those from the short burst of spring grazing. Many attributes of the grazed/insecticide-treated sward were either increased or decreased by a factor of two within a season. Both types of herbivore caused changes in the direction of plant succession as well as in its rate. Effects on early successional species were large and similar when caused by either type of herbivore. Effects on later successional species were often smaller, but also showed differences in the action of the two herbivore types, as did effects on sward height, species richness and total cover. The effects of sheep and insect herbivory were not always additive or in the same direction.The results suggest that manipulations of both mammal and insect herbivores may be powerful tools for directing changes in plant community composition.

Summary It is well known that plant–soil interactions play an important role in determining the impact of global change phenomena on biodiversity and ecosystem functioning. Little is known, however, about the individual and relative importance for carbon (C) and nitrogen (N) cycling of non‐random changes in plant and soil communities that result from global change phenomena, such as fertilization and agricultural intensification. We set up a field‐based mesocosm experiment in which we re‐inoculated soil with contrasting microbial communities taken from extensively managed and from intensively managed grasslands. In a full‐factorial design, we subsequently established plant communities representative of intensively and extensively managed grasslands and imposed a fertilization treatment. We then measured plant biomass and diversity, and leaching of C and N as key measures of C and N loss. We hypothesized that non‐random changes in both microbial and plant communities would impact C and N leaching, but via different mechanisms. We predicted that plant communities representative of extensively managed grassland would reduce C and N leaching directly through increased water or N uptake, or indirectly via promoting microbial communities that immobilize C and N, whereas plant communities of intensively managed grassland would have the opposite effect. We also hypothesized that microbial communities of extensively managed grassland would feed back positively to plant diversity and that ‘matching’ plant and microbial communities would reduce C and N leaching. We found that both plant and microbial communities from extensively managed grassland reduced C and N leaching, especially when ‘matched’. Plant community effects on C and N leaching operated directly through root C inputs and N uptake, rather than through changes in soil microbial communities. In contrast, microbial communities modified C and N leaching both directly by immobilization and indirectly through modifying plant community composition. Synthesis. Our results show that changes in plant and microbial communities both individually and interactively modify C and N loss from grasslands. Moreover, our results suggest that soil microbial communities typical of extensively managed grassland might counteract, or delay, the negative consequences of fertilization on plant diversity and ecosystem functioning.

Summary 1. Biotic homogenization (BH), a dominant process shaping the response of natural communities to human disturbance, reflects both the expansion of exotic species at large scales and other mechanisms that often operate at smaller scales. 2. Here, we examined the relationship between BH in plant communities and spatio-temporal landscape disturbance (habitat fragmentation and surrounding habitat conversion) at a local scale (1 km²), using data from a standardized monitoring programme in France. We quantified BH using both a spatial partitioning of taxonomic diversity and the average habitat specialization of communities, which informs on functional BH. 3. We observed a positive relationship between local taxonomic diversity and landscape fragmentation or instability. This increase in local taxonomic diversity was, however, paralleled by a decrease in average community specialization in more fragmented landscapes and in more unstable landscapes around forest sites. The decrease in average community specialization suggests that landscape disturbance causes functional BH, but there was limited evidence for concurrent taxonomic BH. 4. Synthesis. Our results show that landscape disturbance is partly responsible for functional BH at small scales via the extirpation of specialist species, with possible consequences for ecosystem functioning. However, this change in community composition is not systematically associated with taxonomic BH. This has direct relevance in designing biodiversity indicators: metrics incorporating species sensitivity to disturbance (such as species specialization to habitat) appear much more reliable than taxonomic diversity for documenting the response of communities to disturbance.

Rewilding has emerged as a prominent ecological restoration approach in recent decades. It is aimed at restoring natural processes, improving ecosystem functioning, and enhancing biodiversity with minimal human interference necessitated. Different approaches to rewilding exist, including trophic and passive rewilding. Trophic rewilding involves the active introduction of species, most often large herbivores. The latter approach involves passive management with minimal human interference. Being a nascent strategy available to ecosystem managers, comparative empirical research in the context of rewilding is lacking, especially relating to soil functions like carbon (C) and nitrogen (N) cycling and storage.In this study, we investigated whether the choice of trophic versus passive rewilding had an impact on the quantity and cycling of C and N stored in soils. Additionally, we compared these two approaches to annual mowing and removal of biomass, a typical conservation management strategy for grasslands.Permanently fenced passive rewilding and conservation mowing plots were established within a trophic rewilding project at Mols Bjerge, Denmark in spring 2017. Plots delineated adjacent to these represented trophic rewilding. Exmoor ponies and Galloway cattle were introduced the previous year and continue to freely roam the 120 ha site with minimal human intervention. The area has previously been used for sheep and cattle grazing research, primarily on aboveground biodiversity. In August 2024, we collected soil samples from three layers (0-5 cm, 5-10 cm, and 10-20 cm; n = 216) in each treatment replicated at 8 locations within the study site. Additional topsoil (0-5 cm; n=72) samples were retrieved from each plot for analyses of microbial activity.Bulk density, organic carbon (OC), total nitrogen (TN), and pH were determined in samples from all depths. Microbial biomass C and N, respiration, microbial activity and diversity, and net N mineralization rates were analysed in the topsoil samples. Based on preliminary results, trophic rewilding was characterised by the largest stocks of C and N to 20 cm with mean values of 3.62 kg m-2 and 0.27 kg m-2, respectively. Passive rewilding and conservation mowing resulted in mean C stock values 11% and 19% lower compared to trophic rewilding, with similar results for N stocks. In contrast, soil C/N ratios were significantly higher under conservation mowing compared to the rewilding treatments. The lowest levels of microbial biomass C, specific (normalised for OC content) C mineralization, and net N mineralization were associated with trophic rewilding, suggesting that nutrient turnover rates are comparatively suppressed. EcoPlate™ results similarly showed reduced microbial activity, as well as diversity, under trophic rewilding with significantly higher results under mowing. These results demonstrate that the decision to include or exclude animals in land management strategies can have a consequential impact on C and N storage and the driving processes related to their cycling in soil. Therefore, this decision should be considered carefully in land management policy development.

Evaluation of a forage allocation model for Theodore Roosevelt National Park