Ecological Applications最新文献

Increased nitrogen (N) deposition due to industrial and agricultural activities poses a significant threat to global biodiversity, disrupting ecosystem functions and services. Above- and belowground communities are closely interdependent and both respond to N enrichment, yet they are frequently studied separately. Whether the biodiversity of these communities responds similarly or synchronously to N inputs remains underexplored. Using a decade-long N addition experiment in a meadow steppe ecosystem, we explored the effects of a gradient of N addition levels (from 0 to 50 g N m^-2 year^-1) on the diversity of aboveground plants and belowground nematodes at second, sixth, and tenth years after the initiation of the experiment. Our findings revealed asynchronous responses of above- and belowground biodiversity. Plant diversity showed a progressive, time-dependent decline that intensified with both increasing N concentrations and experimental duration. In contrast, nematode diversity exhibited a threshold response: an initial decline at low N levels (<10 g N m^-2 year^-1) followed by stabilization across higher N concentrations, with no significant temporal intensification of this pattern over the course of the decade-long study. Plant richness declined primarily due to rapid species loss, especially among forbs, with little compensatory gain. In contrast, nematode diversity exhibited a more balanced response, driven by species replacements in which gains offset losses. Bacterivores and omnivores-predators were the most negatively affected nematode groups. This study advances our understanding of ecological responses to nitrogen enrichment by revealing the contrasting long-term dynamics of above- and belowground communities in a meadow steppe ecosystem. While plant diversity deteriorates with increased N input, nematode diversity shows signs of resilience via compensatory turnover, highlighting the potential for belowground biota to buffer ecosystem-level biodiversity loss under chronic N deposition. Our findings underscore the critical need to consider both plant and soil biota simultaneously when assessing the impacts of N deposition on biodiversity.

Artificial surface water (ASW), created through dams, impoundments, and other engineered water features, is increasingly deployed in arid protected areas to support wildlife. However, our understanding of how and why ASW shapes the spatiotemporal activity and ecologically relevant biomass of large mammalian herbivores remains limited. We evaluated whether one form of ASW, dammed seasonal drainages that create reservoirs, alters the metabolic biomass, spatial distribution, and seasonal activity patterns of large herbivores. Specifically, we tested whether reservoirs shifted large herbivore use from seasonal pulses to persistent disturbance, modify species activity patterns, and if large herbivore distributions correspond with their theoretical water dependence. Using a paired catchment design, we deployed camera traps around 11 reservoirs and 11 undammed drainages in Kruger National Park. Cameras were placed along 2250-m transects. Species-specific activity and metabolic biomass were modeled as a function of catchment type, season, and distance from the edge of reservoirs or undammed drainage. Reservoirs concentrated large herbivore activity year-round, indicating a shift from seasonal to persistent disturbance regimes. Dammed catchments supported higher large herbivore metabolic biomass in both wet and dry seasons, with effects extending to just over 1 km in the dry season and >2 km during the wet season. Elephants comprised more than 50% of the observed biomass, and other species such as hippopotamus, impala, and zebra also concentrated their activity near reservoirs. In contrast, browsing species like giraffe, duiker, and steenbok were more active in catchments with undammed drainages. Contrary to expectation, species' water dependence scores did not consistently predict species responses. While ASW can enhance wildlife visibility and forage access, it also risks excluding some species and concentrating herbivore impacts, with implications for vegetation change, human-wildlife conflict along park boundaries, and ecosystem resilience. We recommend adaptive ASW management strategies, including the strategic placement and temporal manipulation of surface water, to balance wildlife needs with long-term conservation goals-particularly under increasing climatic variability.

Elton's diversity-invasibility hypothesis, which proposes that diverse communities should be more resistant to biological invasions, has been the focus of much attention. However, little is known about how soil microbes recruited by native plants influence the vulnerability of forest ecosystems to invasion by exotic plants. Here, we present a two-part plant-soil feedback experiment (Part A, diversity effect; Part B, soil inoculation) to examine the effects of soil microorganisms associated with native plant species at different diversity levels on community invasibility of temperate forests, using two invasive plants, Rhus typhina and Phytolacca americana, as test species. Aboveground plant growth and biomass allocation differed significantly between the two invasive plants under simulated diversity, with negative effects on P. americana and positive effects on R. typhina. Both the diversity effects and soil inoculation experiments showed that the growth of P. americana was inhibited, while that of R. typhina was promoted by soil microorganisms. In contrast to the non-mycorrhizal P. americana, the arbuscular mycorrhizal plant R. typhina enhanced its stress tolerance through close associations with soil fungi. Our study suggests that the role of soil microbes in the "diversity-invasibility" relationship might be related to the species identities (e.g., mycorrhizal type) of both invasive and native species. These results shed new light on Elton's diversity-invasibility hypothesis by highlighting the role of plant-soil feedback mechanisms.

Millions of dollars and countless hours are spent on invasive plant management, and the field of invasion ecology has gained increasing attention in recent decades. Yet, despite these efforts to control and understand plant invasions, successful management is often elusive. Budgetary constraints are a common factor limiting invasive plant management programs, and therefore optimizing control strategies is essential. However, such optimization requires data on management inputs and outcomes, and these data are often missing, lacking, or underutilized. To address this knowledge gap and identify predictors of successful invasive plant control in natural areas, we examined nearly 20 years of invasive plant treatment data in the world's largest urban national park-Santa Monica Mountains National Recreation Area of southern California. We resurveyed 279 sites, which had undergone control in the past two decades, collecting data on the abundance of native and invasive plant species to evaluate long-term management outcomes. We used multiple statistical approaches to identify management inputs and site characteristics that are predictors of eradication, invasive plant cover, and native species recovery. We found that the greater the initial size or percent cover of an infestation, the lower the probability of eradication. We also found that infestations on steeper slopes and in areas that have burned more frequently are less likely to be eradicated. Promisingly, our results also showed that greater reductions in invasives generally benefited native plant communities, though not in all cases. These analyses also highlighted that persistence is key; more frequent treatments (both chemical and nonchemical) and greater investment of labor resulted in larger reductions in invasive plants. Our results highlight how site characteristics and limited resources can complicate invasive plant management, while demonstrating the value of analyzing treatment and monitoring data to identify effective control strategies and guide adaptive management decisions.

Urban environments pose a threat to biodiversity through processes such as habitat degradation and biotic homogenization. Despite this, cities are increasingly recognized for their potential to conserve bees and other pollinators. Planting understory vegetation is one way of providing more floral resources to support urban bee communities and the ecosystem services they provide. However, the influence of vegetation origin and landscape context on urban bee communities is unclear, particularly in the Southern Hemisphere. We sampled the bee communities at 32 understory plantings dominated by exotic or indigenous (native to the local bioregion) vegetation around inner Melbourne, Australia. For each site, we recorded the amount of impervious surface and irrigated turf in 200-m buffers. Indigenous plantings were found to promote significantly greater alpha and beta diversity in bee communities compared to exotic plantings. Particular plant taxa were highly effective at attracting a variety of bees, with a maximum of 19 bee species (including specialists) hosted by indigenous Wahlenbergia capillaris (Campanulaceae). Apis mellifera was highly dominant and strongly associated with exotic plantings, whereas many indigenous bee species were positively associated with indigenous plantings. This study shows indigenous understory plants have a positive influence on indigenous bee communities relative to exotic plantings which tend to attract only A. mellifera. Planting indigenous plants in cities is therefore recommended as a conservation action for local bee species.

Despite the ecological expression and conservation importance of diverse behavioral tactics in animals, there is often friction associated with conventional analytical approaches and inference concerning variation in spatial behavior. Implicitly or explicitly, population-level inferences are generally the main objective of studies, but interpretations can be ambiguous in the presence of divergent behavioral tactics across individuals or cohorts, as with generalist species. We pursued a novel analytical approach and assessed the underlying mechanisms driving variation in spatial behaviors of generalist species using the American black bear (Ursus americanus) as our focal species. We quantified individual variation in habitat selection expressed by black bears using individual models for 35 collared bears across four study areas in Wyoming, USA. We modeled how state-dependent factors (age, sex, δ¹⁵Nitrogen, and body fat) and resource availability influenced behavioral variation in resource selection. We observed vast variation among individuals, demonstrating patterns consistent with a generalist species. Black bear resource selection differed with changes in state dependence and resource availability. Specifically, traits uniquely important to black bear success, body fat and carnivory, explained variation in selection for forage indexed by normalized difference vegetation index (NDVI), forests, and riparian areas. Environmental heterogeneity via differences in resource availability magnified behavioral variation in resource selection by black bears. Selection trends for NDVI and deciduous shrubs were explained by resource availability, indicating black bears exhibited functional responses in habitat selection. These insights emerged from our analytical approach; had we implemented a more conventional, population-level assessment, we would have simply concluded that black bears displayed behavioral neutrality with respect to forage resources. Acknowledgment of behavioral variation when considering spatial behavior of generalist species provides a more representative understanding of individuals within a population, and our analytical approach offers a solution to uncovering drivers of individual variation in spatial behavior.

Biodiversity is highly affected by ecological processes at the landscape level. To facilitate management decisions at a landscape level, we present an end-user-oriented framework that assesses the biodiversity capacity of individual biotopes in a fragmented landscape and ranks the importance of the biotope patches. The framework can be applied to any biotope and landscape. Analyses can further be done on planned or predicted future scenarios and changes in the landscape structure. There has been continuous exchange with stakeholders and case study testing with the purpose to build a tool that answers the important questions of end users, and provides results that are useful for decision-makers and environmental managers in environmental management and land use planning. The framework is novel in its calculations of the combined effects of connectivity and survival of biodiversity in the biotope patches. It uses land cover data and the concept of umbrella focal species as input. The framework strongly builds on ecological theory and ecological modeling, and produces three outputs of interest: a heatmap visualizing individual patch importance for upholding landscape biodiversity, an indicator metric of the ability of a biotope landscape to support biodiversity, and the number of unsustainable individual patches. The theoretical foundation and structure of the framework are thoroughly explained. The use of its output is further demonstrated by one selected case study where the calculations are applied to a biotope of fragmented old coniferous forest in Sweden. We additionally examine and show how the overall biodiversity potential of the biotope landscape is dependent on which types of species communities are in focus by applying different umbrella focal species. The case study demonstrates the importance of landscape structure for sustainable biodiversity. Results further demonstrate that it is essential to consider the type of species community that is the primary biodiversity conservation target.

The loss of plant diversity in grasslands is implicated as one of the main causes of arthropod decline. The loss of a single plant species can have a cascading effect on specialized arthropod species. It is thus critical to expand our understanding of plant–arthropod interactions. Detecting plant–arthropod interactions, however, has been difficult, as it requires the observation of individual plant visits. A possible solution to this problem is offered by environmental DNA (eDNA) analysis. Here, we test the utility of eDNA to detect fine-scaled community differentiation in grassland arthropods in Germany. Based on eDNA from 13 plant species, we explore community differentiation between plant species, and between flower and green parts of individual plants. We show that eDNA successfully recovers extremely fine-scaled community differentiation. Plant species, as well as plant compartment, emerge as major drivers of arthropod community composition in grasslands, with the differentiation being particularly pronounced in herbivorous arthropods. Terrestrial eDNA on plants thus appears to be deposited in a very localized fashion, making this tool ideally suited to detect very fine-scaled community differentiation. Considering the high specificity we observe in our analysis, our results highlight the necessity of integrating vegetation surveys into future monitoring of arthropod communities.

Ecological impacts of invasive species are mounting as their numbers and geographic extent continue to increase. Across extensive parts of their range, Pacific salmon (Oncorhynchus spp.) smolts face an expanding gauntlet of nonnative predators during their seaward migration. Adopting multispecies, spatiotemporal perspectives is essential for understanding direct and indirect predation risks and prioritizing management actions seeking to reduce impacts. Using quantitative DNA metabarcoding, we investigated trophic interactions of commonly co-occurring nonnative and native fish predators of Pacific Northwest, USA, salmon-bearing rivers, addressing challenges for salmon recovery and questions related to single-species management. Chinook salmon (Oncorhynchus tshawytscha) were frequently consumed by nonnative smallmouth bass (Micropterus dolomieu), largemouth bass (Micropterus salmoides), rock bass (Ambloplites rupestris), and native northern pikeminnow (Ptychocheilus oregonensis). Among the focal predators, Chinook salmon were the largest contributors to smallmouth bass diets, ranking as their second most important prey. Chinook salmon consumption peaked during a year of relatively high smolt abundance, low discharge, and warm stream temperatures. The following year, under opposite conditions, Chinook salmon consumption declined, though predation remained disproportionately high in certain mainstem and tributary regions. Native species of conservation concern were frequently consumed by nonnative predators, including imperiled native lamprey (family Petromyzontidae). Across space and time, native prickly sculpin (Cottus asper) and largescale sucker (Catostomus macrocheilus) were generally the highest contributing prey for nonnative predators. Intraguild predation was prevalent, most notably with smallmouth bass as the top prey for northern pikeminnow. Intraguild predation highlights potential risks of compensatory effects when predators are managed in isolation. Our study provides crucial insights into restoring food webs for native species while minimizing the likelihood of compensatory effects and demonstrates the value of quantitative DNA metabarcoding for understanding novel predator assemblages. As ecosystems worldwide face increasing pressures from co-occurring invasive species, integrating multispecies approaches into management strategies is essential for mitigating impacts and conserving biodiversity.

In theory, increasing sensitivity of primary productivity to precipitation variability is a biophysical symptom of dryland degradation, or “desertification,” but empirical tests of this in the context of biological invasions are scant. To test the potential for exotic grass invasion to exacerbate biophysical symptoms of desertification, we measured the biomass and biodiversity of herbaceous plant assemblages along a 41–248 mm/year precipitation gradient across the Mojave and San Joaquin Deserts within communities at high versus low levels of exotic grass invasion and under shrub canopies versus interstitial space, over 5 years. Exotic grass invasion doubled the conversion rate of precipitation into biomass, and native shrubs increased ecosystem sensitivity to precipitation through strong facilitation of exotic grasses. Invasion-driven increases in biomass production corresponded to significant decreases in native biodiversity. We propose that shrub facilitation of exotic grasses accelerated desertification by promoting a non-native flora that is highly sensitive to precipitation variability and strongly linked to biodiversity degradation. Suppressing exotic grasses and managing facilitated invasion will help mitigate desertification.