Ecosphere最新文献

Population declines of the monarch butterfly (Danaus plexippus plexippus) in North America have largely been attributed to the distribution and condition of species-specific preferred nectar sources. In 2020, the US Fish and Wildlife Service (USFWS) listed the monarch butterfly in the US Federal Register as a candidate species under the Endangered Species Act of 1973. The USFWS ranked the availability, quality, and spatial distribution of nectar plants during autumn migration as the fourth most contributing factor to US monarch population declines. During the autumn migration through the Great Plains, monarchs seek nectar plants to accumulate lipid reserves for further migration to and overwintering in Mexico. We applied vegetation and rangeland health data from the US Department of Agriculture, Natural Resources Conservation Service, National Resources Inventory (NRI) to quantify species density and richness of monarch-preferred nectar plants, associated rangeland conditions, and diversity of nectar sources along this autumn migration pathway. We focused specifically on longitudinal gradients W-095-100 and W-100-105 and discrete 5° latitudinal–longitudinal cells within those gradients. The respective NRI dataset spans 8211 rangeland sites sampled between 2009 and 2018. Approximately 84.4% of sites in W-095-100 and 72.5% of sites in W-100-105 contained monarch-preferred nectar plants. Preferred nectar plants made up 7.4% of 2438 identified plant species in W-095-100 and 6.1% of 2371 identified plant species in W-100-105. For W-095-100, preferred nectar plant densities were highest for the 5° cell covering portions of US states Oklahoma and Kansas and lowest for the 5° cell at the US–Mexico border. In W-100-105, preferred nectar plant densities decreased linearly from north to south. Preferred nectar plant densities were greater for 5° cells in W-100-105 (50.5 billion plants) as compared with W-095-100 (44.4 billion plants). Consistent with trends in preferred nectar source density, rangeland conditions assessed by similarity indices and rangeland health protocols were generally lowest for 5° cells spanning the US–Mexico border. The results provide the most comprehensive assessment to date for preferred nectar sources of the monarch butterfly along the Great Plains autumn migration to Mexico and document generally decreasing nectar sources and habitat conditions at southern latitudes in this ecologically important pathway.

While habitat loss and hunting remain the major drivers of biodiversity declines, sublethal disturbances, such as human presence, recreation, and noise also impact wildlife. In response, wildlife often adjust their spatiotemporal behaviors. This study assesses how terrestrial wildlife responds to sublethal disturbances associated with sustainable logging activities. Using camera traps, we conducted a 2-year continuous survey of two logging compartments within an active, sustainably logged forest reserve in central Sabah, Malaysian Borneo. The survey encompassed periods before, during, and after logging activities, and we obtained daily felling data. Using generalized linear mixed models, we assessed the impact of logging on the spatiotemporal activity of 10 terrestrial mammal and galliform species, considering spatial factors like logging intensity and distance from logging activity, and temporal factors such as days since logging. Four species had a significant and strong response to logging intensity, with varied directions of effect. Only for one species, the response to logging intensity was mediated by time since logging. Though only descriptive, we found no evidence of diel activity shifts, and, for all other species detected during our survey, general patterns in the number of records across each logging period were mixed. Our results highlight the variable and species-specific responses to logging activity. At a local scale, many species exhibit resilience in their spatiotemporal activity patterns, but for affected species, the effects of logging appear to linger over time. The overall limited response could be due to the relatively low disturbance nature of reduced-impact logging.

Lake water level fluctuations are an important factor driving variation in many ecosystem processes. The nearshore sediments that are periodically exposed and re-inundated can develop distinct physical and chemical characteristics, especially in relationship to the organic matter content of the sediments and the particle size distribution. These sediment characteristics in turn can alter the flux of nitrogen (N) and phosphorus (P) from sediments into the water column when sediments are inundated. Here, we used intact sediment core experiments across a range of sediment inundation frequencies to estimate the effect of inundation frequency on sediment nutrient flux in Kabetogama Lake, Minnesota, USA. We observed associations between elevation or inundation frequency and some sediment characteristics, but in a structural equation model, inundation frequency and the sediment properties we measured were poorly related to inorganic nutrient flux. On the other hand, inundation frequency did have a moderate association with organic N and P flux from sediments, which could be due to decay of terrestrial organic matter that accumulates on exposed sediments. We used our parameterized structural equation model to estimate how three different water level management regimes employed over the past 50 years could influence organic N and P flux from sediments. The models suggested more recent water level management regimes reduced organic N and P flux by 9%–13% and 5.9%–9.8%, respectively. Nearshore sediment flux could sustain and influence harmful algal blooms that occur in this lake, and these fluxes could be influenced by water level management.

In an era marked by accelerating climate change, habitat loss, and shifting land use patterns, it is crucial to understand the intricate effects of multiple stressors on ecosystems. This long-term study sheds light on the complex interplay between grazing and habitat characteristics on pasture dynamics and offers insights into how various stressors affect ecosystems facing environmental challenges. Our experimental study documents that manipulation in restricting reindeer grazing and trampling through fencing led to higher ground-lichen biomass, volume, height (particularly in one habitat), and cover compared with open-control plots. The effect of fencing varied depending on habitat, and for lichen biomass, volume, and height, the lowest values were observed in windswept exposed ridges and mountain heaths (exposed/mountain), and the highest values were observed in forested and leeward-heath (forest/leeward) habitat. The average (past five years) number of reindeer per square kilometer had indirect effects that varied across habitats. We observed negative density dependence in the open plots for height in the exposed/mountain habitats. Fencing reduced this effect, which was also valid for biomass except that habitat did not affect the effect of density. Surprisingly, in the forest/leeward areas, the estimated effects of reindeer density on biomass, volume, and height were positive for the fenced plots. Negative density dependence was evident for lichen cover irrespective of habitats and manipulation, even though this effect had little biological significance, whereas cover at the initiation of the experiment positively affected later recordings (particularly for the controls). Our models showed high explanatory power, highlighting the significance of reindeer density and habitat as predictors of ground-lichen dynamics. Overall, negative density-dependent effects were observed in the open plots in the most exposed areas, and fencing mitigated the negative impact of reindeer on lichens, particularly in less exposed areas. We challenge the “equilibrium” and “nonequilibrium” frameworks for explaining livestock-pasture dynamics. We propose future studies to estimate the relative importance of density-dependent and density-independent factors, such as climate, using models considering both mechanisms simultaneously.

The Upper Gulf of California (UGC) hosts a rich marine biodiversity. Complex climatic processes generate high biological productivity enabling the use of resources in a complex socio-ecological processes (SEPs). Through a literature review, evolution and aggravation of the SEP over 50 years are analyzed. The crisis peaked in the last decade related to vaquita, an endangered marine porpoise at the blink of extinction, and the illegal catch of totoaba, an endangered fish species, both endemic. Over the first three decades, stakeholders defined positions, while disorder in fisheries and reduction of vaquita population occurred. Corrective actions were implemented during the last two decades including diversification of markets for local fisheries, development of fishing technologies, and environmental regulations. Most actions failed, consolidating an ill governance aggravated by poaching of totoaba and drug trafficking. The evolution of the conflict includes (1) transition from community passivity to conservation efforts, to resistance and collective violence against them; (2) transition in the design and implementation of conservation actions from civil organizations to the government, facilitated by the disengagement of philanthropic donors for conservation, and reduction of support for civil organizations; (3) interventions by the Mexican Navy coordinated with the Sea Shepherd Conservation Society; and (4) weakening of the International Committee for the Recovery of Vaquita an international scientific moral authority to propose vaquita conservation. The federal government and the local fishing sector currently discuss scenarios that aim to authorize use of driftnets and gillnets, contrasting with the predominant conservation logic.

Increasing anthropogenic emissions of nitrogen (N) and carbon (C) are major threats to ecosystems globally. Although atmospheric N deposition is likely affecting N cycling and community composition in California's serpentine ecosystems, a historical record of N inputs to vegetation has yet to be reconstructed for these nutrient-limited biodiversity hotspots. For leather oak (Quercus durata var. durata), a foundational, serpentine-endemic species, we investigated leaf N and C isotopic composition (δ¹⁵N and δ¹³C) and leaf %N of herbarium and modern leaf samples collected from 1899 to 2009 from serpentine ecosystems in two study areas in California: Santa Clara County, and Lake and Napa Counties combined. We also evaluated tree ring growth over a similar time period in long-lived leather oak individuals. Leaf δ¹⁵N and δ¹³C values decreased over time in both study areas, likely reflecting changes in the regional and local atmospheric N and C pools caused by human perturbation. However, leaf %N values and stem growth did not change over time with increasing N deposition, indicating that increasing atmospheric N deposition and CO₂ concentration may not translate to increased N uptake or productivity in plants with conservative growth strategies, even in ecosystems thought to be N-limited. In serpentine systems, this could competitively advantage nitrophilic invasive annual grasses and accelerate trends toward native species loss. While the rates of decline in leaf δ¹⁵N values were similar between study areas, rates of decline in leaf δ¹³C values were steeper in Santa Clara County, possibly reflecting its more urban environment. Herbarium samples combined with tree ring data can provide a valuable opportunity to explore the historical record of human-induced changes in N and C cycling and their biotic impacts.

Estimating spatiotemporal patterns of population density is a primary objective of wildlife monitoring programs. However, estimating density is challenging for species that are elusive and/or occur in habitats with limited visibility. In such situations, indirect measures (e.g., nests, dung) can serve as proxies for counts of individuals. Scientists have developed approaches to estimate population density using these “indirect count” data, although current methods do not adequately account for variation in sign production and spatial patterns of animal density. In this study, we describe a modified hierarchical distance sampling model that maximizes the information content of indirect count data using Bayesian inference. We apply our model to assess the status of chimpanzee and elephant populations using counts of nests and dung, respectively, which were collected along transects in 2007 and 2021 in western Uganda. Compared with conventional methods, our modeling framework produced more precise estimates of covariate effects on expected animal density by accounting for both long-term and recent variations in animal abundance and enabled the estimation of the number of days that animal signs remained visible. We estimated a 0.98 probability that chimpanzee density in the region had declined by at least 10% and a 0.99 probability that elephant density had increased by 50% from 2007 to 2021. We recommend applying our modified hierarchical distance sampling model in the analysis of indirect count data to account for spatial variation in animal density, assess population change between survey periods, estimate the decay rate of animal signs, and obtain more precise density estimates than achievable with traditional methods.

Freshwater ponds host diverse arthropod communities, but conservation frameworks are scarce. Heterogeneous pond mosaics of various sizes and successional stages can develop during raw material extraction in mining sites, acting as refugia for a variety of species. Here, we investigate arthropod diversity and conservation status across lakes and ponds in mining sites; analyze how water body size, age, and vegetation cover affect diversity patterns; and discuss how results can contribute to management actions and conservation schemes. Using environmental DNA metabarcoding, we determine arthropod diversity at 55 pond and lake plots located in active mining sites in Germany. We assess the effect of structural parameters on arthropod species richness, beta diversity, and the occurrence of rare and endangered species. Overall, we detected 436 arthropod species, many of which lacking a threat status evaluation, potentially hampering analyses of conservation aspects. We identify different effects of structural variables on species richness and beta diversity, and variable responses at the order level. Further, results reveal comparable diversity of accumulated pond network area, compared with single large water bodies of similar size, supporting high importance of heterogeneous pond networks for arthropod diversity conservation. Our study shows that systematic biodiversity management concepts both during active mining and at later stages of succession will be needed. Monitoring should go beyond just measuring taxonomic richness, including also assessments of community composition, the presence of rare and endangered taxa, and functional diversity.

Plant trait networks (PTNs) quantitatively describe the trait correlation patterns, which constrain the dynamic responses and individual fitness of plants under climate change. Despite renewed attention directed toward intraspecific trait correlation within trait-based ecology in the last decade, thorough descriptions of how trait correlation patterns within species respond to changing environments ontogenetically and influence ecological strategies are still lacking. In this study, a controlled experiment was conducted on Arabidopsis thaliana wild-type (Columbia), with three treatment groups (control/drought/heat) over three stages of the life cycle (vegetative/inflorescence/reproductive stage). Thirty traits (aboveground biomass and seed biomass were not used in trait correlation analyses) were obtained to investigate how trait correlation patterns in particular life stages (three T-PTNs constructed based on trait variation across treatments within life stages) and during whole-life cycles (three L-PTNs constructed based on trait variation across life stages in particular treatments) respond to stress. The results showed that traits were correlated along an axis within life stages, reflecting an economic trade-off between acquisitive strategies (in control plants) and conservative strategies (in drought/heat plants). With ontogeny, the higher sensitivity of central traits (highly connected with other plant traits in a network) in T-PTNs to stress resulted in more significant separation among treatment groups along the axis. Second, based on life cycles, stress decoupled trait correlations in L-PTNs and decreased the value of central traits (related to carbon assimilation/accumulation) compared with the ambient control, resulting in lower fitness. These results suggested that central traits in PTNs drove the shifts in ecological strategies across changing environments, and the network topology (the connection frequency or clustering degree among traits in a network, describing the correlation patterns) constrained the resource utilization efficiency in plants; both affect plant fitness collectively. These insights will facilitate more accurate and broader applications (e.g., the assessment of plant fitness or sensitivity to stress) of PTNs in trait-based ecology.

Investigating ecological questions at the scale of individual organisms is necessary to understand and predict the biological consequences of changing environmental conditions. For small organisms, this can be challenging because ecologists need tools with the appropriate accuracy, precision, and resolution to record and quantify their ecological interactions. Unfortunately, many existing tools are only appropriate for medium to large organisms or those that are wide-ranging, inhibiting our ability to investigate the spatial ecology of small organisms at fine scales. Here, we tested a novel workflow for recording animal locations at very fine (decimeter) spatial scales, which we refer to as high-resolution orthomosaic location recording (HOLR). The workflow for HOLR combined direct observations with data collection of locations on high-resolution uncrewed aerial vehicle (UAV) imagery loaded on smartphones. Observers identified landscape features they recognized in the imagery and estimated positions relative to these visual landmarks. We found HOLR was approximately twice as accurate as consumer-grade GPS devices, with a mean error of 0.75 m and a median error of 0.30 m. We also found that performance varied across landscape features, with the highest accuracy in areas that had more visual landmarks for observers to use as reference points. In addition to submeter accuracy, HOLR was cost-effective and practical in the field, requiring no bulky equipment and allowing observers to easily record locations away from their own position. This workflow can be used to record locations in a variety of situations, but it will be particularly cost-effective when users simultaneously utilize the high-resolution environmental data contained within UAV imagery. Together, these tools can expand the application of spatial ecology research to smaller organisms than ever before.