Ecosphere最新文献

Many ungulates migrate between distinct summer and winter ranges, and identifying, mapping, and conserving these migration corridors have become a focus of local, regional, and global conservation efforts. Brownian bridge movement models (BBMMs) are commonly used to empirically identify these seasonal migration corridors; however, they require location data sampled at relatively frequent intervals to obtain a robust estimate of an animal's movement path. Fitting BBMMs to sparse location data violates the assumption of conditional random movement between successive locations, overestimating the area (and width) of a migration corridor when creating individual and population-level occurrence distributions and precluding the use of low-frequency, or sparse, data in mapping migration corridors. In an effort to expand the utility of BBMMs to include sparse GPS data, we propose an alternative approach to model migration corridors from sparse GPS data. We demonstrate this method using GPS data collected every 2 h from four mule deer (Odocoileus hemionus) and four elk (Cervus canadensis) herds within Wyoming and Idaho. First, we used BBMMs to estimate a baseline corridor for the 2-h data. We then subsampled the 2-h data to one location every 12 h (a proxy for sparse data) and fitted BBMMs to the 12-h data using a fixed motion variance (FMV) value, instead of estimating the Brownian motion variance empirically. A range of FMV values was tested to identify the value that best approximated the baseline migration corridor. FMV values within a species-specific range (mule deer: 400–1200 m²; elk: 600–1600 m²) successfully delineated migration corridors similar to the 2-h baseline corridors; overall, lower values delineated narrower corridors and higher values delineated wider corridors. Optimal FMV values of 800 m² (mule deer) and 1000 m² (elk) decreased the inflation of the 12-h corridors relative to the 2-h corridors from traditional BBMMs. This FMV approach thus enables using sparse movement data to approximate realistic migration corridor dimensions, providing an important alternative when movement data are collected infrequently. This approach greatly expands the number of datasets that can be used for migration corridor mapping—a useful tool for management and conservation across the globe.

Management interventions are pivotal in shaping the ecosystems, particularly grassland habitats. This study examines the effects of cutting and burning treatments on vegetation composition, physical properties, and herbivore utilization patterns in Baghaura grassland, situated within Bardia National Park, Nepal. The study considers three treatment plots: cutting only, both cutting and burning, and burning only. Vegetation composition is evaluated using the point intercept method within 1 × 1 m quadrats. Grass samples are collected and weighed for fresh weight determination. Subsequently, samples are separated into green leaf, green stem, dead leaf, and dead stem components, and biomass and leaf-stem proportion are calculated. The burned plots, characterized by Imperata cylindrica dominance, exhibit the highest species diversity. Furthermore, the burned-only plots demonstrate significantly greater species height. Cut-only plots display a higher proportion of green leaves and green stems, while the burned-only plots exhibit higher mean dry biomass in dead leaves and dead stems. Grazing intensity is notably higher in the cut-and-burned plots. The regression model (y = −1.4095x + 98.4948) indicates a subtle, statistically nonsignificant relationship (R² = 0.0395, p = 0.3205) between grazing intensity and grass height with low grazer diversity (H′ = 0.7). The study suggests that implementing small-scale cutting followed by controlled burning during the dry season can provide herbivores with fresh, high-quality forage throughout the year, thereby meeting their nutritional needs. These findings enhance our understanding of the effects of management interventions on grassland ecosystems and can inform the development of sustainable conservation strategies for similar habitats.

Termite mounds are keystone structures in African savannas, affecting multiple ecosystem processes. Despite the large size of termite mounds having the potential to modify conditions around them, patterns of mound-induced ecosystem effects have been assumed to be isotropic, with little attention given to how effects might vary around mounds. We measured soil nitrogen content, grass species composition, and mammalian grazing on and off termite mounds in the four cardinal directions, and across wet and dry seasons at three savanna sites varying in mean annual rainfall in South Africa's Kruger National Park. Evidence of directional effects (anisotropy) on ecosystem properties around termite mounds varied with site. Grass species composition differed between north- and south-facing slopes at the two drier sites where mounds were taller. However, differences in grazing extent and soil nitrogen content around mounds were only present at the intermediate rainfall site where mammalian herbivore biomass was highest, and mounds were of medium height. Our results suggest that termite mound effects display significant variation with direction, but that the emergence of directional effects is context dependent. Our results further suggest that such context-dependent directional effects can lead to positive feedback loops between termites, abiotic conditions, and mammalian herbivores.

Consumers can play critical roles in ecosystem resilience by modifying community resistance and recovery rates. In coral reefs, grazers can increase reef resilience by controlling algae and maintaining open space for coral recruitment, but can also erode the reef framework critical for coral recovery. Here we examine the context-dependent effects of herbivores on reef persistence in Caribbean Panamá. Using a series of lab and field experiments, we found that the erosional effects of the herbivorous reef urchin (Echinometra viridis) were 2 orders of magnitude greater on dead corals than live corals, and surveys across multiple similarly overfished reefs revealed a positive relationship between urchin densities and percent cover of bare dead coral with urchin densities exceeding 150 m⁻² in some reefs. However, we observed that a mat-forming zoanthid (Zoanthus pulchellus), found exclusively on dead corals, had an inverse spatial relationship with urchins. Through a series of field experiments, we found that zoanthid overgrowth repelled urchins, increased dead coral persistence, and decreased erosion of dead corals making up the reef framework by more than 50% over a 22-month period. Our findings reveal that zoanthids can provide associational refuge to dead corals by enhancing their persistence under high urchin grazing pressure. We suggest that secondary space-holders, such as zoanthids, may play increasingly important functional roles in degraded reef systems by shielding coral skeletons from external bioeroders. Moreover, the Stress Gradient Hypothesis, which predicts that the importance of positive interactions such as associational refuges increases with consumer pressure, extends to dead foundation species such as coral skeletons crucial for ecosystem recovery.

Distributions of both native and invasive species are expected to shift under future climate. Species distribution models (SDMs) are often used to explore future habitats, but sources of uncertainty including novel climate conditions may reduce the reliability of future projections. We explore the potential spread of the invasive annual grass ventenata (Ventenata dubia) in the western United States under both current and future climate scenarios using boosted regression tree models and 30 global climate models (GCMs). We quantify novel climate conditions, prediction variability arising from both the SDMs and GCMs, and the agreement among GCMs. Results demonstrate that currently suitable habitat is concentrated inside the invaded range of the northwest, but substantial habitat exists outside the invaded range in the Southern Rockies and southwestern US mountains. Future suitability projections vary greatly among GCMs, but GCMs commonly projected decreased suitability in the invaded range and increased suitability along higher elevations of interior mountainous areas. Climate novelty did not appear to undermine the prediction reliability in many cases where the climate–species relationship was fully represented by the occurrence data. GCM-derived variability resulting from variation in future cool season precipitation and temperature seasonality was greatest in the Rocky Mountains. SDM-derived variability was higher in currently suitable habitat, and few GCMs projections agreed that these areas would contain future suitable habitat. However, while prediction variability was high, many GCM projections agreed that parts of the Rocky, Wasatch, and Uinta Mountains would contain highly suitable habitat in the future. As disturbances in the interior mountains occur in coming decades, reducing some natural barriers to invasion, land managers, and conservationists will need to monitor for ventenata in post-disturbance environments. Changes to invasion potential may not play out for several decades, but results related to current potential may have applications for early detection and rapid response planning.

Spatial overlap between wildlife and related domestic animals can lead to disease transmission, with substantial evidence for viral and bacterial spillover. Domestic and wild animals can also share potentially harmful helminth parasites, many of which have environmental transmission stages that do not require direct contact between hosts. We used camera traps, fecal sampling, and mathematical modeling to evaluate the potential for hookworm parasites to spillover from domestic dogs to wild cats in the Osa Peninsula, Costa Rica. Traditional microscopy was found to be more sensitive than DNA-based diagnostics for parasites, though the methods were complementary. We found high hookworm (Ancylostoma spp.) prevalence in domestic dogs (74.2%, 95% CI: 67.0%–80.7%, N = 155), and considerable spatial overlap with ocelots (Leopardus pardalis) and pumas (Puma concolor), particularly on trails and dirt roads. Pumas had hookworm prevalence of 36.4% (18.6%–57.2%, N = 22), and ocelots had 27.3% (7.6%–56.5%, N = 11); however, molecular identification of these parasites was inconclusive. We developed a macroparasite transmission model to infer the likelihood of spillover, compared with separate parasite cycles, or different parasite species in each host. According to the model, spillover of hookworm from dogs would lead to a prevalence of less than 10% in wild hosts. Low presumed compatibility between wild hosts and parasites adapted to domestic species limits the prevalence that could be reached in wild species, even under potentially higher overlap. The prevalence observed was more consistent with a model that assumes hookworms in wild cats in the Osa are a cat-specific parasite. The combination of parasitology, molecular diagnostics, and mathematical modeling used here could complement wildlife disease monitoring programs worldwide to shed light on understudied helminth–host dynamics at the domestic–wild animal interface.

In the mountainous regions of the Western United States, increasing wildfire activity and climate change are putting forests at risk of regeneration failure and conversion to non-forests. During periods with unfavorable climatic conditions, locations that are suitable for post-fire tree regeneration (regeneration refugia) may be essential for forest recovery. These refugia could provide scattered islands of recovering forest from which broader forest recovery may be facilitated. Spring ecosystems provide cool and wet microsites relative to the surrounding landscape and may act as regeneration refugia, though few studies have investigated their influence on post-fire regeneration. To address this knowledge gap, we quantified coniferous tree regeneration adjacent to and away from springs in mixed-conifer forests in a mountainous region of central Idaho, USA. Our research objectives were to (1) quantify post-fire conifer density near and away from springs, (2) assess the relative importance of distance to a spring compared with other biophysical factors important to post-fire regeneration, and (3) examine the temporal trends of post-fire seedling establishment near and away from springs. In areas burned at high severity from fires in 1988, 2000, and 2006, we sampled transects at 27 springs for the count, age, and height of extant conifer seedlings, as well as topographic factors and distance to surviving seed source. We modeled the relative effects of distance to a spring, topographic variables (slope, heat load index, elevation), post-fire climate, and distance to surviving seed source for the two dominant species, Douglas fir (Pseudotsuga menziesii) and lodgepole pine (Pinus contorta), using a generalized linear mixed-effects model. Our study revealed that proximity to springs resulted in higher conifer density and earlier establishment after high-severity wildfire when conditions for available seeds and topography were also met. Our results demonstrate that springs are important and previously undescribed regeneration refugia with landscape-scale implications for post-fire forest recovery in increasingly water-limited environments. Springs are relatively abundant features of montane landscapes and may offer continued regeneration refugia for post-fire recovery into the future, but additional springs mapping and hydroclimatic considerations are needed.

Course-based undergraduate research experiences (CUREs) are an instructional strategy to help students learn the content and process of science by engaging students in authentic science research. The ESA-endorsed 4-Dimensional Ecology Education framework emphasizes engaging students in authentic ecology scientific practices, and uniquely foregrounds human dimensions as a core tenant of ecological literacy. Model-based CURE instruction may help ecology instructors by giving students a scaffold to better orient their line of inquiry and develop more accurate conceptions of the broader socio-ecological system through the integration of the CURE experimental data to known concepts within the system. We explored how student model accuracy changes throughout the course, what modeling practices students engaged in during collaborative modeling, and how students used CURE data along with social and ecological sciences in their models. We found that students created more accurate models as the course progressed, and all student groups exhibited expert-like modeling practices during the summative collaborative modeling process. Importantly, we also found that students were able to integrate experimental data they generated through the CURE within their broader understanding of the study system. A major benefit of model-based CUREs is to cultivate scientific thinking by helping students connect how individual pieces of research inform larger phenomenon.

The gradual accumulation of phosphorus from historical fertilization can contribute to the eutrophication of surface waters by increasing the potential for subsurface leaching losses. Grazing lands areas are a priority for concern, and phytoremediation efforts in grazing lands have prioritized grasses that may be used as forage for cattle. This study investigated the influence of three different forage species—Paspalum notatum, Hemarthria altissima, and Cynodon nlemfuensis—on the loss of phosphorus in leachate from surface soils. The experiment used a nested pot mesocosm design that allowed us to monitor leachate volume and concentration biweekly over the course of 3 months. Pots containing P. notatum plants leached significantly more phosphorus than pots containing C. nlemfuensis or empty pots with no plants growing in them, despite losing an equivalent amount of water. H. altissima lost equivalent amounts of phosphorus in leachate water, but each H. altissima plant removed approximately 33.6 mg of phosphorus, approximately 2.5× that removed by P. notatum (13.4 mg). C. nlemfuensis had lower average leachate phosphorus concentrations at each biweekly sampling than either plant species (C. nlemfuensis-P. notatum, p_adj = 0.001; C. nlemfuensis-H. altissima, p_adj = 0.02), averaging only 0.110 ppm in leachate relative to 0.175 ppm and 0.200 ppm in pots beneath H. altissima and P. notatum, respectively. This, combined with C. nlemfuensis' slightly higher-than-average aboveground P content and overall aboveground biomass expression suggest it is the best possible phytoremediation candidate. As even minor leachate P loads can be critically threatening to neighboring oligotrophic water bodies, if the conservation of downstream environments is the priority, the short-term threat of increased leachate must be considered. Further research is needed to explore the underlying mechanisms and field-scale implications of these findings.

In 2022, a severe outbreak of disease caused by clade 2.3.4.4b Highly Pathogenic Avian Influenza (HPAI) H5N1 virus resulted in unprecedented mortality among wild birds in eastern Canada. Tens of thousands of birds were reported sick or dead, prompting a comprehensive assessment of mortality spanning the breeding season between April 1 and September 30, 2022. Mortality reports were collated from federal, Indigenous, provincial, and municipal agencies, the Canadian Wildlife Health Cooperative, and other nongovernmental organizations, universities, and citizen science platforms. A scenario analysis was conducted to refine mortality estimates, accounting for potential double counts from multiple sources under a range of spatial and temporal overlaps. Correcting for double counting, HPAI is estimated to have caused 40,391 wild bird mortalities in eastern Canada during the spring and summer of 2022; however, this figure underestimates total mortality as it excludes unreported deaths on land and at sea. Seabirds and sea ducks, long-lived species that are slow to recover from perturbations, accounted for 98.7% of estimated mortalities. Our study provides estimates of bird mortality, with Northern Gannets (Morus bassanus; 25,669), Common Murres (Uria aalge; 8133), and American Common Eiders (Somateria mollissima dresseri; 1894) exhibiting the highest mortality figures. We then compare these mortality estimates with recent population estimates and trends and make an initial assessment of whether biologically meaningful population-level impacts are possible. Specifically, we focus on the Northern Gannet, a species that has suffered significant global mortality, and two harvested species, Common Murre and American Common Eider, to inform management decisions. Our analysis suggests population-level impacts in eastern Canada are possible for Northern Gannets and American Common Eiders, but are unlikely for Common Murres. This study demonstrates a comprehensive approach to assessing mortality and underscores the urgent need for further research to understand the broader ecological ramifications of the HPAI outbreak on wild bird populations.