Ecosphere最新文献

As cities grow, lakes are often assumed to suffer from increasing non-point pollution. Many waterbodies have become more eutrophic in recent decades, as expected—but many others became less eutrophic, especially in urban/suburban areas. What policies, practices, and ecosystem processes have helped some lakes stay stable or become less eutrophic even in a growing city? Identifying and understanding success stories are important to continue protecting these lakes and improving other urban/suburban lakes. We found one such success story when we examined water-quality trends over the past 25 years (1998–2022) in Lake Washington, a well-studied large lake in the Seattle metro area. The watershed population grew rapidly during that time (34% from 2000 to 2020), yet Lake Washington became substantially less eutrophic and indicators of development impacts stabilized or decreased. Chlorophyll concentrations during the main spring bloom decreased sharply (−25% per decade), and water clarity and near-bottom dissolved oxygen both increased (8.5% and 17% per decade, respectively). Alkalinity and specific conductance had increased during the 1970s–1990s, but in recent decades, they held stable. Peak winter/spring nitrogen and phosphorus concentrations decreased (−4.9% and −5.6% per decade, respectively), indicating decreased watershed inputs. The type of development during this time was likely a key contributor: we found no net loss of forest area and little increase in developed land area (4.7% from 2001 to 2021). Instead of expanding into new areas, redevelopment increased density on already-developed land and likely drove improvements in stormwater treatment and other environmental protections. Future work comparing stream watersheds could help discern which specific aspects of redevelopment helped reduce nutrients and other impacts. However, nutrient reductions were not the only factors controlling the lake's trophic state; chlorophyll decreased much more strongly than phosphorus did. Lake Washington is a complex ecosystem governed not only by water chemistry but also by interactions with physical and biological factors such as stratification, warming, phytoplankton community shifts, or food-web interactions. A better understanding of all these factors is essential to provide sound scientific guidance and ensure that Lake Washington and other lakes can thrive in a growing city.

Lagomorphs are selective herbivores that can strongly influence rangeland condition if their population densities increase through predator release. However, the effect size of lagomorph herbivory has not previously been quantified for the semiarid rangelands of the southwestern United States, where their predators are suppressed. We used a differential exclosure experiment replicated across 20 sites in a public rangeland in southern Utah to quantify the effect of lagomorph herbivory (jackrabbits and cottontails) for comparison with ungulate herbivory (cattle and bison). Across our 11-year study, we measured aboveground net primary productivity (ANPP; 3 × 1-year data sets) and long-term standing crop (SC; 1 × 8-year data set). We also measured nutrient concentrations in grass and soil samples in plots with complete exclosure (lagomorphs and ungulates out), partial exclosure (lagomorphs in and ungulates out), and no exclosure (open control plots) for 8 years. From the grass data, we calculated the effect size of lagomorph grazing as a 26.6% reduction in ANPP and an 11.3% reduction in SC, compared to ungulate grazing as a 24.9% reduction in grass ANPP and a 72.2% reduction in SC. We found lagomorphs had no effect on forb ANPP but actually increased forb SC, which is consistent with previous evidence that lagomorphs facilitate noxious weeds on these rangelands. There were no significant effects of either lagomorph or ungulate herbivory on plant and soil nutrient levels. Using the effect sizes of lagomorph herbivory on grass ANPP and SC, applied to the animal unit months (AUMs) prescribed for that rangeland, we calculated that lagomorphs currently impose an annual economic cost of between US$30.16 km⁻² (SC) and US$70.64 km⁻² (ANPP) in the Henry Mountains region of southern Utah, USA. We recommend that managers consider the lagomorph effect on rangeland resources in relation to the costs and benefits of conserving their predators, which are currently suppressed indirectly through various anthropogenic effects (raptors) and directly by agency-funded control programs (coyotes).

Subalpine coniferous forest ecosystems are sensitive to climate change. However, the community formation mechanisms of subalpine coniferous forests in northeastern Asia remain poorly understood. In this study, we assessed the factors controlling the phylogenetic community structure in different strata (whole strata, upperstory, and understory) of Abies nephrolepis and Abies koreana forests in the subalpine zone in South Korea. Piecewise structural equation modeling (pSEM) was performed based on terrain, climate, taxonomic diversity, stand structure characteristics, and disturbance factors. The controlling factors presented different responses for each species depending on the stratum and phylogenetic community structure indices (net relatedness index and nearest taxon index). A. nephrolepis showed a unique community formation mechanism and formed climate refugia through high rock exposure, whereas A. koreana showed niche conservation at high elevations and a community overdispersion trend when forest gaps appeared due to overstory vegetation loss. The Mantel test and partial Mantel test were performed to examine the impact of turnover and nestedness on phylogenetic β-diversity, as well as to establish their correlations with climatic, geographic, and environmental distance. Turnover was a major contributing factor to β-diversity and strongly correlated with environmental distance. Further, geographical and climatic distance presented differential contributions to each species depending on the community characteristics. Integrated analyses of phylogenetic community structure and β-diversity provided detailed insights into the mechanisms underlying community formation and biodiversity patterns. This reveals that biodiversity patterns are driven by interactions between community structure and inter-community characteristics, with internal structure as a key mechanism influencing β-diversity.

Invasive species alter habitats and biological communities. The giant river prawn Macrobrachium rosenbergii (de Man 1879) was introduced to Brazil for aquaculture, and invasive populations have established in the Amazon Delta region where they are believed to pose a risk to the native aquatic fauna. To assess potential impacts, we performed dietary metabarcoding using generalist COI primers on 105 stomach contents collected from prawns from the southern Amazon Delta. Overall, M. rosenbergii presents an opportunistic and generalist diet that reflects the dominant aquatic and terrestrial fauna of the region, including the orders Diptera, Characiformes, and Lepidoptera as dominant dietary items in terms of both frequency of occurrence and richness. One unidentified congeneric species was identified in the diet, indicating the potential for negative effects on the native prawn fauna. Additionally, while there is a general overlap in the diet for all categories of sex and reproductive phase, smaller immature individuals and molted females showed reduced diversity in their diet, suggesting limitations in prey handling or access. We conclude that dietary metabarcoding of opportunistic generalists and/or detritivores appears to be a potentially useful tool for monitoring biodiversity as well as understanding their role in the food web.

The derivation of biological information—abundance, diversity, movement of organisms—from dual-polarization weather surveillance radars (WSRs) presents an opportunity for novel large-scale biodiversity monitoring. This review takes a systematic approach to ask what degree of taxonomic resolution has so far been achieved in dual-polarization WSR observations. A range of methods are described that can be classified as observational, algorithmic, or modeling-based approaches. While progress toward finer taxonomic resolution (species, genus, family) so far has been limited, machine learning methods demonstrate that the information for at least some degree of taxonomic resolution is present in the data, and electromagnetic modeling provides a valuable research direction. A more systematic, interdisciplinary approach that incorporates zoological understanding, radar physics, and machine learning is recommended for future research.

Tree regeneration underpins forest resilience, but how pathways of postfire tree regeneration will unfold with future climate and fire regimes is difficult to anticipate. We conducted a simulation study in the Greater Yellowstone Ecosystem (GYE; United States) using a process-based model, iLand, to ask how rates, composition, and spatial patterns of postfire tree regeneration vary with 21st-century climate. Subalpine forest and fire dynamics were simulated through 2100 under four climate scenarios, 2 × 2 factorial of aridity (wet and dry) and temperature (warm and hot), in five GYE landscapes. We tallied postfire tree seedling density by species in simulated fires (>400 ha) at five years postfire. To assess changes in regeneration rates (total and by species) to 2100 in each landscape × climate scenario combination, we fit generalized linear models of regeneration versus time and estimated slope coefficients. To analyze spatial patterns of recovery, we compared regeneration to prefire forest state. Postfire regeneration rates were maintained through 2100 in wet scenarios but declined in the hot-dry scenario. Seedling composition was generally consistent throughout the simulations across wet scenarios, except for declines of Engelmann spruce (Picea engelmannii). Regeneration of fire-sensitive species declined in the hot-dry scenario, with Engelmann spruce experiencing the steepest declines (−20% to −71%) and failing by late century. Lodgepole pine (Pinus contorta var. latifolia) and subalpine fir (Abies lasiocarpa) declined in the hot-dry scenario, but regeneration never failed. Regeneration of fire-tolerant Douglas-fir (Pseudotsuga menziesii) and aspen (Populus tremuloides) was sustained or increased in dry scenarios (+4% to +6%). The proportion of burned area where regeneration failed increased in all dry scenarios but never exceeded 20%. Declining tree regeneration and shifts in dominant tree species revealed that changes in forest structure and composition—and not a conversion to non-forest—are the dominant response to future climate across broad swaths of the simulation landscapes. Our results suggest that postfire reorganization may be widespread during the 21st century and enable forests to persist in a warming climate with more fire.

The relationship between a species' growth rate and its size—its growth function—represents essential biological information for supporting sustainable fisheries and wildlife management. Yet, growth functions are known for only a fraction of species. Progress is especially limited in marine invertebrates, including shellfish, due to challenges rearing early life stages in the lab and identifying statolith ring patterns indicative of individual age. We overcome these challenges by deriving a species' growth function using multi-year size-frequency population survey data collected from 71 subtidal sites over 35 years. We fit Gaussian mixture models to the data at each survey site and year to identify cohorts, then tracked cohorts between survey years to estimate cohort growth over time. We then used the estimates of growth to parameterize growth functions containing initial and asymptotic size constraints based on the survey data. We demonstrated our method with the kelp forest gastropod and commercial fisheries species, Kellet's whelk (Kelletia kelletii). The assembled survey data included 28,816 whelks, 9–180 mm in shell length. Through cohort tracking, we generated 297 estimates of cohort growth. We fit seven growth functions to the growth estimates and used information criterion and least squares to select the best-fit model; in this case the Richards, characterized by maximum initial growth at small size that initially declines exponentially and then linearly with size, reaching asymptotic growth by approximately 40 years of age. We also analyzed and compared select portions of the population survey data to test for biogeographic and fisheries management effects on growth. The method we developed can support research on species with size-frequency population survey data, and the function we derived for Kellet's whelk can inform research on its population biology and sustainable fisheries management.

Foraging plasticity provides a mechanism for long-lived species to adapt to rapidly changing environments. When shifts in food availability occur, individual variation in plasticity can lead to an increase in within-species trophic diversity. We tested for drivers of trophic diversity in Arctic tern (Sterna paradisaea) and common tern (Sterna hirundo) chicks across three years (2017, 2018, 2021) and five seabird breeding islands in the Gulf of Maine. We measured tern chick trophic diversity using two approaches: (1) the Shannon-Wiener diversity index of observed prey feeds and (2) the stable isotope standard ellipse area for blood cell and plasma samples. We hypothesized that individuals would vary in how they responded to declines in food availability and that individual-level dietary responses would influence fitness. Across contexts (islands and years), we predicted that tern trophic diversity would be correlated with sea surface temperature and with the percentage of preferred prey in the diet of tern chicks (P1), which we used as two indicators of food availability. Furthermore, we predicted that individuals would vary in the magnitude and direction of shifts in isotope values over a two-week period (P2) and that the magnitude of these shifts would be correlated with chick growth and survival (P3). Trophic diversity varied across islands, years, and species but was not correlated with either indicator of food availability (P1 Not Supported). Though tern chicks generally shifted to higher δ¹⁵N values and less-enriched δ¹³C values later in the season, the magnitude of these shifts varied across individuals (P2 Supported). Chicks that shifted to relatively high δ¹⁵N values also showed greater magnitude shifts to less-enriched δ¹³C values and, in Arctic terns, had a lower asymptotic mass (P3 Partially Supported). Our study suggests trade-offs in individual-level foraging and diet plasticity in seabirds that should be explored further.

Nonmajors (i.e., undergraduate students not majoring in the natural sciences) constitute a majority of United States college graduates and are a large potential audience for courses with ecology content. However, nonmajors may be unmotivated to learn about ecology because they perceive it to be uninteresting and irrelevant to their everyday lives or career goals. Although the Four-Dimensional Ecology Education (4DEE) framework can be adapted for nonmajors courses as a starting point to improve student engagement, we suggest that nonmajors ecology instructors also use ecology hooks as effective gateways to 4DEE that will motivate and deepen student learning. Selecting and developing meaningful ecology hooks requires knowing your audience, including their chosen majors. In this way, the audience should inform the hook, and the hook then helps to propel the audience's learning. In addition to being relevant to the audience, ecology hooks should be connected to student learning outcomes and multiple dimensions of 4DEE and supportive of inclusive classroom goals. We discuss how to identify and develop authentic ecology hooks and integrate them into 4DEE-aligned courses to engage students. For heterogeneous audiences that comprise a mix of many different majors, we suggest the use of three types of universal ecology hooks: “everyday,” “local,” and “wow” hooks. For specialized audiences of a single major or similar majors, we suggest the additional use of “major-specific” ecology hooks and provide examples for health professions, business, and visual and performing art majors. Although ecology hooks alone are unlikely to be a panacea for all challenges of engaging nonmajors, they are an important teaching tool that can bring new relevance, energy, creativity, thought-provoking ideas, and connections into nonmajors courses.

Disturbances modify the three-dimensional (3D) physical structure of forest canopies, which cascades to influence numerous ecosystem functions. The capacity to model the structural outcomes of disturbance may aid in predicting ecosystem functional responses, especially for novel disturbance types and regimes. Disturbance characteristics, such as severity and spatial patterning, influence 3D canopy structure, but our understanding of structure–disturbance relationships is limited to a small number of empirical studies and experiments that investigate a narrow range of disturbance variables with limited or no replication. We conducted a novel coupled field-modeling experiment using 3D forest canopy models derived from terrestrial laser scanning to evaluate how three different disturbance characteristics interact to affect canopy structure: disturbance severity (proportion basal area removed) and the horizontal and vertical distribution of canopy removal. Our analysis suggested that initial stand structure and the vertical and horizontal distribution of disturbance have an equivalent or greater influence on canopy structure relative to severity. Disturbances affecting smaller stems and with more uniform spatial patterns of stem removal had the most consistently positive effects on structural complexity. The simulation framework developed here is broadly applicable to other forest or vegetation types and could be used to further evaluate the structural effects of a range of disturbances, including novel disturbance types and interactions, across a variety of sites and ecosystem types in a manner that is infeasible through field manipulations alone. In addition, this approach could facilitate opportunities to improve disturbance detection, predictive ecosystem modeling, and assessment and design of forest management approaches in an era of uncertainty and rapid environmental change.