Ecological Applications最新文献

The prediction of population responses to environmental changes, including the effects of different management scenarios, is a useful tool and a necessary contributor to improving conservation decisions. Empirical datasets based on long-term monitoring studies are essential to assess the robustness of retrospective modeling predictions on biodiversity. These allow checks on the performance of modeling projections and enable improvements to be made to future models, based on the errors detected. Here, we assess the performance of our earlier model to assess the impact of vulture food shortages caused by sanitary regulations on the population dynamics of Spanish vultures during the past decade (2009–2019). This model forecasts the population trends of three vulture species (griffon, Egyptian, and bearded vultures) in Spain (home to 90% of the European vulture population) under various food shortage scenarios. We show that it underestimated bearded and griffon vulture population numbers and overestimated Egyptian vultures. The model suggested that the most plausible food shortage scenario involved an approximate 50% reduction of livestock carcass availability in the ecosystem compared with the previous situation without sanitary carcass removal. However, the observed annual population growth for the period 2009–2019 (7.8% for griffon vulture, 2.4% for Egyptian vulture, and 3.5% for bearded vulture) showed that food shortages had little impact on vulture population dynamics. After assessing the robustness of the model, we developed a new model with updated demographic parameters and foraging movements under different hypothetical food shortage scenarios for the period 2019–2029. This model forecasts annual population increases of about 3.6% for the bearded vulture, 3.7% for the Egyptian vulture, and 1.1% for the Griffon vulture. Our findings suggest that food shortages due to the implementation of sanitary policies resulted in only a moderate impact on vulture population growth, probably thanks to the supplementary feeding network which provided alternative food. Also important was the availability of alternative food sources (intensive farms, landfills) that were used more regularly than expected. We discuss the computational performance of our modeling approach and its management consequences to improve future conservation measures for these threatened species, which provide essential ecosystem services.

Spontaneous plants, such as weeds, are a key component of urban flora that can provide significant ecological benefits like nutrient cycling and soil pollutant removal. Our ability to fully harness these species in urban restoration efforts is hindered, however, due to a lack of understanding of their functional ecology under urban stressors. Here, we analyzed the effects of spatiotemporal urban land dynamics on the functional diversity of spontaneous plants from three life history strategies: colonization, establishment, and nutrient acquisition. Specifically, we measured 11 functional traits of 54 spontaneous plants across 79 sampling sites in Chongqing, a rapidly growing megacity in southwestern China with a population exceeding 16 million. We found that colonization-related traits of spontaneous plants were uncorrelated with nutrient-acquisition traits. When controlled for species richness, functional α- and β-diversity showed clearer responses to urbanization that varied by life history strategy and urban development stage. Spontaneous plant assemblages became more functionally homogeneous in their colonization and nutrient-acquisition strategies within newly urbanized areas than in historically developed areas. Yet, establishment strategies exhibited a neutral response to urbanization. Our findings reveal both challenges and opportunities of utilizing spontaneous plants in urban landscapes, highlighting the need to consider temporal dynamics in urban growth and plant functional diversity across life history strategies. Effective management should focus on controlling high-dispersal spontaneous plants in historically developed areas while retaining those with diverse nutrient acquisition strategies in newly urbanized areas to maximize ecological benefits for sustainable urban development.

Marine foundation species are critical for the structure and functioning of ecosystems and constitute the pillar of trophic chains while also providing a variety of ecosystem services. In recent decades, many foundation species have declined in abundance, sometimes threatening their current geographical distribution. Kelps (Laminariales) are the primary foundation species in temperate coastal systems worldwide. Kelp ecosystems are notoriously variable, challenging the identification of key factors controlling their dynamics. Identification of these drivers is key to predicting the fate of kelp ecosystems under climatic change and to informing management and conservation decisions such as restoration. Here, we used in situ data from long-term monitoring programs across 1350 km of coast spanning multiple biogeographic regions in the state of California (USA) to identify the major regional drivers of density of two dominant canopy-forming kelp species and to elucidate the spatial and temporal scales over which they operate. We used generalized additive mixed models to identify the key drivers of density of two dominant kelp species (Nereocystis luetkeana and Macrocystis pyrifera) across four ecological regions of the state of California (north, central, southwest, and southeast) and for the past two decades (2004–2021). The dominant drivers of kelp density varied among regions and species but always included some combination of nitrate availability, wave energy and exposure, density of purple sea urchins, and temperature as the most important predictors. These variables explained 63% of the variability of bull kelp in the northern and central regions, and 45% and 51.4% of the variability in giant kelp for the central/southwest and southeast regions, respectively. These large-scale analyses infer that a combination of lower nutrient availability, changes in wave energy and exposure, and increases in temperature and purple sea urchin counts have contributed to the decline of kelp observed in the last decade. Understanding the drivers of kelp dynamics can be used to identify regional patterns of historical stability and periods of significant change, ultimately informing resource management and conservation decisions such as site selection for kelp protection and restoration.

As ecosystems face unprecedented change and habitat loss, pursuing comprehensive and resilient habitat restoration will be integral to protecting and maintaining natural areas and the services they provide. Microbiomes offer an important avenue for improving restoration efforts as they are integral to ecosystem health and functioning. Despite microbiomes' importance, unresolved knowledge gaps hinder their inclusion in restoration efforts. Here, we address two critical gaps in understanding microbial roles in restoration—fungal microbiomes' importance in “reconstructive” restoration efforts and how management and restoration decisions interactively impact fungal communities and their cascading effects on trees. We combined field surveys, microbiome sequencing, and greenhouse experiments to determine how reconstructing an iconic landscape feature—tree islands—in the highly imperiled Everglades impacts fungal microbiomes and fungal effects on native tree species compared with their natural counterparts under different proposed hydrological management regimes. Constructed islands used in this research were built from peat soil and limestone collected from deep sloughs and levees nearby the restoration sites in 2003, providing 18 years for microbiome assembly on constructed islands. We found that while fungal microbiomes from natural and constructed tree islands exhibited similar diversity and richness, they differed significantly in community composition. These compositional differences arose mainly from changes to which fungal taxa were present on the islands rather than changes in relative abundances. Surprisingly, ~50% of fungal hub taxa (putative keystone fungi) from natural islands were missing on constructed islands, suggesting that differences in community composition of constructed island could be important for microbiome stability and function. The differences in fungal composition between natural and constructed islands had important consequences for tree growth. Specifically, these compositional differences interacted with hydrological regime (treatments simulating management strategies) to affect woody growth across the four tree species in our experiment. Taken together, our results demonstrate that reconstructing a landscape feature without consideration of microbiomes can result in diverging fungal communities that are likely to interact with management decisions leading to meaningful consequences for foundational primary producers. Our results recommend cooperation between restoration practitioners and ecologists to evaluate opportunities for active management and restoration of microbiomes during future reconstructive restoration.

Delineating a threshold migration rate for demographic independence important for understanding connectivity among fragmented populations and defining management units for conservation and harvest regulation. In turn, defining management units is an essential step in sustainable management to avoid unintentional depletion of resources managed for conservation or harvest. The 10% rule of demographic connectivity is a rule of thumb that delineates the threshold of demographic independence when the behavior of two populations shifts from synchronous at >10% to independent at <10%. However, the accuracy of the 10% rule to real-world scenarios and application to natural resource management is unknown. We evaluated the 10% rule using simulation for two life history types: Pacific cod, Gadus macrocephalus, a gadid with relatively fast growth, and blackspotted rockfish, Sebastes melanostictus, a long-lived rockfish species. Results were obtained by simulating a real-world tool for evaluating demographic connectivity, positive correlation in estimated population sizes. We assessed the effect of migration on demographic connectivity on otherwise independent populations under one- and two-way migration, and with various population sizes and life history parameters. Sensitivity testing showed that positive correlation in population size does not occur in roughly a quarter of simulations, regardless of the migration rate. When positive correlation in population size does occur, mean migration rates over all simulations were between 5% and 10%: 0.089 (8.9%) for blackspotted rockfish and 0.058 (5.8%) for Pacific cod. However, the range of migration resulting in demographic connectivity was large, 0.02–0.44 for blackspotted rockfish and 0.02–0.40 for Pacific cod.

The national Fire and Fire Surrogate (FFS) study was initiated more than two decades ago with the goal of evaluating the ecological impacts of mechanical treatments and prescribed fire in different ecosystems across the United States. Since then, 4 of the original 12 sites remain active in managing and monitoring the original FFS study which provides a unique opportunity to look at the long-term effects of these treatments in different regions. These sites include California (Blodgett Forest Research Station), Montana (Lubrecht Experimental Forest), North Carolina (Green River Game Land), and Ohio (Ohio Hills). Although regions differed in ecosystem type (e.g., conifer- vs. hardwood-dominated), the overall goals of the FFS study were to promote desirable, fire-adapted species, reduce fire hazard, and improve understory diversity. Our study uses multivariate techniques to compare how these desired outcomes were maintained over the last 20 years and discusses whether we would modify the original treatments given what we know now. Our findings indicate that mechanical treatments and prescribed fire can promote desired tree species, mitigate potential fire behavior by reducing fuels and retaining larger-sized trees, decrease tree mortality, and stimulate regeneration—effects that are still apparent even after 20 years. However, we also found that maintaining desired outcomes was regionally specific with western sites (California and Montana) showing more desirable characteristics under mechanical treatments, while the eastern sites (North Carolina and Ohio) showed more desirable characteristics after prescribed burning. The beneficial effects of treatment were also more apparent in the long term when sites followed up with repeated treatments, which can be adapted to meet new objectives and conditions. These findings highlight the FFS study as an invaluable resource for research and provide evidence for meeting long-term restoration goals if treatments can be adapted to ecosystem type, be maintained by repeated treatments, and accommodate new goals by adapting treatments to changing conditions.

Near-term, iterative ecological forecasts can be used to help understand and proactively manage ecosystems. To date, more forecasts have been developed for aquatic ecosystems than other ecosystems worldwide, likely motivated by the pressing need to conserve these essential and threatened ecosystems and increasing the availability of high-frequency data. Forecasters have implemented many different modeling approaches to forecast freshwater variables, which have demonstrated promise at individual sites. However, a comprehensive analysis of the performance of varying forecast models across multiple sites is needed to understand broader controls on forecast performance. Forecasting challenges (i.e., community-scale efforts to generate forecasts while also developing shared software, training materials, and best practices) present a useful platform for bridging this gap to evaluate how a range of modeling methods perform across axes of space, time, and ecological systems. Here, we analyzed forecasts from the aquatics theme of the National Ecological Observatory Network (NEON) Forecasting Challenge hosted by the Ecological Forecasting Initiative. Over 100,000 probabilistic forecasts of water temperature and dissolved oxygen concentration for 1–30 days ahead across seven NEON-monitored lakes were submitted in 2023. We assessed how forecast performance varied among models with different structures, covariates, and sources of uncertainty relative to baseline null models. A similar proportion of forecast models were skillful across both variables (34%–40%), although more individual models outperformed the baseline models in forecasting water temperature (10 models out of 29) than dissolved oxygen (6 models out of 15). These top performing models came from a range of classes and structures. For water temperature, we found that forecast skill degraded with increases in forecast horizons, process-based models, and models that included air temperature as a covariate generally exhibited the highest forecast performance, and that the most skillful forecasts often accounted for more sources of uncertainty than the lower performing models. The most skillful forecasts were for sites where observations were most divergent from historical conditions (resulting in poor baseline model performance). Overall, the NEON Forecasting Challenge provides an exciting opportunity for a model intercomparison to learn about the relative strengths of a diverse suite of models and advance our understanding of freshwater ecosystem predictability.

The return of large carnivores to areas with strong anthropogenic impact often results in conflicts among different interest groups. One cause of conflict is that large carnivores compete with humans for wild game species. In Scandinavia, the recolonization of wolves (Canis lupus) and brown bears (Ursus arctos) has important ramifications for the harvest of an ungulate species with high economic and recreational value, the moose. We estimated wolf and brown bear predation rates on moose (Alces alces) relative to harvest, natural causes of death, and vehicle collisions within 20 wolf territories. We used data on multi-season kill rates of wolves and brown bears on moose combined with wolf territory sizes and estimates of the population density of brown bears and moose. Wolf predation rate on moose was not related to the density of moose, wolf pack size, nor kill rate but was positively related to wolf density and strongly negatively related to the abundance of moose within wolf territories. Estimated annual wolf and brown bear predation rates averaged 8.6% (range 2.8%–16.9%) and 2.3% (range 0%–12.7%) respectively, among wolf territories, whereas estimated annual harvest rates averaged 17.5% (range 8.1%–33.1%). In wolf territories with relatively high bear densities, the combined predation rates from wolves and brown bears exceeded harvest rates. Across wolf territories, harvest rates were not related to wolf predation rates or to the combined predation rates from wolves and brown bears, indicating that large carnivore predation and harvest were not compensatory to each other at this spatial level. The recolonization of these large carnivores in the Scandinavian boreal forest ecosystem may have small to significant consequences for the sustainable management of moose populations depending on the local conditions of both wolves, brown bears, and moose. Comparison of annual mortality rates for moose in our study in Scandinavia with corresponding data from areas with lower anthropogenic impact (Alaska) shows lower total mortality rates in Scandinavia. This likely results from a different age and sex composition of moose killed by wolves and brown bears versus harvest, in combination with a significant difference in the relative importance of these mortality factors between areas.

Annual mowing, a main management strategy of grasslands, would reduce primary productivity, though might increase plant diversity. Nitrogen (N) fertilization is widely used to raise productivity in global pastures, but always results in biodiversity losses. It is thus a challenge to balance the divergent impacts of mowing and N fertilization on biodiversity and productivity. Here, we examine 9-year responses of aboveground net primary productivity (ANPP) and species richness to mowing across a N addition gradient (0, 2, 5, 10, 20, and 50 g N m⁻² year⁻¹) in a temperate steppe. The negative impacts of mowing on ANPP were exacerbated over time under N fertilization with rates at or lower than 10 g N m⁻² year⁻¹ but were reversed by higher N fertilization rates. Such responses of community-level ANPP were largely driven by the dominant grass, Leymus chinensis (L.c.), instead of species richness. Nitrogen fertilization reversed the negative impacts of mowing on the contribution of L.c. to community-level production over time, with less time being needed for the critical reverse under higher fertilization rates. A “win–win” pattern of biodiversity and production could be reached in the mown grasslands under the N fertilization rate of 5 g N m⁻² year⁻¹, as evidenced by no temporal variation in both production and biodiversity over time in comparison with grasslands under ambient conditions (unmown and non-fertilization). Our results highlight the role of dominant species instead of species diversity in driving the fundamental functioning of mown grasslands and thus facilitate adaptive grassland management.

Grazing by large mammalian herbivores influences ecosystem structure and functions through its impacts on vegetation and soil, as well as by the influence on other animals such as arthropods. As livestock progressively replace native grazers around the world, it is pertinent to ask whether they have comparable influence over arthropods, or not. We use a replicated landscape-level, long-term grazer-exclusion experiment (14 years) to address how ground-dwelling arthropods respond to such a change in grazing regime where livestock replace native grazers in the cold deserts of the Trans-Himalayan ecosystem of northern India. We analyze spatial and temporal variation in the abundance of 25,604 arthropods sampled using pitfall traps across 2765 trap-days through the duration of the growing season spanning spring, summer, and autumn. These were from 88 operational taxonomic units covering six orders from 33 families (ants, wasps, bees, ticks and mites, spiders, grasshoppers, and beetles). We find that grazer assemblage—whether livestock or native herbivores—had a strong influence on both vegetation and arthropods. Partial redundancy analysis (RDA) showed that 53.6% of the spatial and temporal variation in arthropod communities could be explained by grazing and by grazer assemblage identity, alongside covariation with vegetation composition and soil variables. Structural equation models revealed that grazing and grazer assemblage identity have direct effects on arthropods, as well as indirect effects that are mediated through vegetation. Importantly, spiders (predators) were less abundant under livestock, whereas grasshoppers (leaf eaters) and ticks and mites (parasitic disease vectors) were more abundant, compared with native grazers. Reduction in spiders can fundamentally alter material and energy flow through the cascading effects of losing predators, and an abundance of grasshoppers may even contribute to vegetation degradation that is often associated with livestock. Parallelly, increases in ticks and mites lead to concerns over vector-borne disease that require planned interventions to align animal husbandry with One Health. Thus, losing native grazers to livestock expansion can have wide-ranging repercussions via arthropods. This may not only affect ecosystem structure and functions, but also offer challenges and opportunities to mitigate risks from vector-borne disease.