Abstract Riparian vegetation and wood play crucial roles in enhancing spatial heterogeneity in rivers. Historical removal of large wood and cutting of streamside forests around the world have simplified rivers and substantially reduced aquatic habitat complexity. To understand how natural rivers sustain geomorphic and hydrologic complexity and support aquatic diversity, we carried out an interdisciplinary field study in a stream flowing through a natural forest in Hokkaido, Japan. We mapped a total of 631 large wood pieces, including 77 log jams, as well as 65 side channels (total 10.1 km) along a 9.2‐km length of the main channel. More avulsions (channel divergence) and side channels were present in stream sections with a greater density of large wood and logjams. At flood stage, 90% of the side channels were inundated with through‐flowing river water, while the other 10% remained disconnected from the main channel and harbored stagnant water. At base flow, only 20% of the side channels had flow from the mainstem river, 46% contained stagnant water, and 34% were dry. The cumulative areas of permanent, transient, and disconnected side channels were 20%, 9%, and 6% of the main channel area, respectively. We estimated the contribution of each habitat type with different hydrological regimes to the entire population of aquatic animals in the study area. The analysis demonstrated that 4 out of 11fish taxa, 5 out of 26 benthic macroinvertebrate taxa, 3 out of 3 plankton taxa, and 2 out of 2 amphibian taxa primarily utilized transient or disconnected channels. Furthermore, cohort analysis of the dominant fish Salvelinus leucomaenis showed that they exhibit ontogenetic habitat shifts from channels with transient flow as juveniles to channels with permanent flow, indicating the need for both types of habitats and for connectivity between these habitats. Our results demonstrate forms and processes characteristic of the mostly lost and forgotten baseline of rivers in Japan; how geomorphologically and hydrologically complex a natural river can be; and how aquatic organisms rely on such complexity. Large wood potentially plays important roles in sustaining such complexity, and further studies should investigate these mechanisms.
Abstract Monarch butterflies have experienced massive population declines and have been proposed to be listed as threatened under the U.S. Endangered Species Act. Milkweeds (Asclepias spp.) are the sole host plant for monarch larvae, and milkweed abundance has dramatically declined in the past 25 years due to increased usage of herbicides and the spread of row crop agriculture that covers 21% of the continental United States. Given the importance of milkweeds to monarch larvae, there has been a major conservation effort to increase milkweed abundance. However, conservation efforts have largely ignored rangeland because of the incorrect assumption that grazers do not consume milkweeds and that milkweed abundance may be near maximum in rangeland. This is an important conservation blind spot because rangeland covers 34% of the continental United States. In 2023, we compared milkweed and juvenile monarch abundance (eggs + larvae) between ungrazed, cattle‐grazed, and bison‐grazed grassland units at six sites in Nebraska, Iowa, Missouri, and Kansas, United States. The sites are owned by conservation organizations and grazed with moderate intensity. Ungrazed and bison‐grazed grassland units did not significantly differ in milkweed abundance, but they had 5.4× more milkweeds than cattle‐grazed grassland units. We found juvenile monarch abundance did not significantly differ between bison‐ and cattle‐grazed grassland units, but that juvenile monarch abundance was 6.4× higher in ungrazed grassland units. We conclude that rangeland grazed by cattle and bison can support more than the current level of juvenile monarchs. Although grazing reduced juvenile monarch abundance, continued grazing is important for monarch conservation because rangeland that is not grazed in this study region is typically converted to row crop agriculture or invaded by eastern redcedar and other trees. We also discuss changes to grazing timing that could increase milkweed and monarch abundance.
Abstract Restoration and conservation efforts often aim to reduce predation, particularly by reducing interactions with nonnative predators in heavily disturbed and invaded ecosystems. For Chinook salmon Oncorhynchus tshawytscha, a highly valued but declining fishery, potentially useful freshwater rearing habitat restoration strategies may include elimination of deep‐water features, shallow off‐channel habitat enhancement, or provisioning cover such as large woody material features. However, reducing predation on target species requires a detailed understanding of existing variation in predation rates and context‐dependent effects of restoration techniques. In a series of stationary predation tethering assays, we found variation in relative predation rates on juvenile salmon across local and habitat level gradients of habitat suitability for juvenile salmon and nonnative fish predators in existing main channel habitats. Counter to expectations, relative predation rates were higher at locations characterized by small‐scale cover and near large woody material. Our results demonstrate that restoration efforts to shift habitat suitability to favor juvenile salmon would be expected to improve salmon survival during rearing and outmigration. However, not all restoration strategies are universally applicable, as large woody material and other forms of cover can produce counterproductive results under some conditions, possibly due to abundant nonnative predator species advantaged by heavily altered environments. Additional studies of spatiotemporal variation in predation risk and context‐dependent restoration impacts on predation rates are needed to inform restoration strategies and avoid unintentionally increasing risk to fragile populations.
Abstract In the Himalayan region, habitat loss from infrastructure development and land use changes threatens biodiversity by degrading biological corridors. Despite increased protected areas (PAs), maintaining connectivity between them remains challenging. A pilot study in Himachal Pradesh, India, aimed to map biodiversity corridors (landscape linkages between isolated protected areas) to support wildlife habitats and guide development planning. A total effort of 120 camera traps over 3605 trap nights and 94 trails covering 918 km recorded 20 species, with 8 species listed as threatened. Using transect surveys and camera‐trapping data along with ensemble species‐distribution models, we generated multispecies habitat‐suitability maps. Additionally, connectivity tools such as Circuitscape, Core Mapper, and Linkage Mapper were utilized to map potential biodiversity corridors and connectivity between protected areas. High species richness areas were located between Inderkilla National Park (NP) and Kias Wildlife Sanctuary (WLS); Kanawar WLS and Khirgana NP; and Dhauladhar WLS and Nargu WLS. We identified 1722.16 km2 of multispecies suitable habitat across the landscape and it is influenced by temperature and elevation. A total of four high connectivity blocks were identified, where the strongest connectivity was found between Inderkilla and Kais national parks, suggesting these areas should be regarded valuable for gene flow. Least‐cost path and cost‐weighted distance analyses mapped valuable wildlife movement routes and quantified resistance to movement across linkages. Several pinch points were identified, especially between Inderkilla NP and Kais WLS, and within Dhauladhar WLS, indicating zones of movement constriction critical for maintaining landscape connectivity. This modeling technique offers a robust and scalable approach for designing ecological networks in mountain regions, enabling policymakers and land use planners to integrate connectivity into landscape‐level conservation strategies for effective conservation under ongoing developmental pressures.
Abstract Understanding the ecological and anthropogenic drivers of habitat selection in native species is critical for biodiversity conservation, particularly in arid ecosystems experiencing rapid land use change. We investigated the burrow density and occurrence of the Indian desert gerbil in the Thar Desert. Factor analysis of mixed data and Akaike information criterion indicated that habitat use by this rodent is structured by land cover, availability of food and shelter‐providing native shrubs, and predator presence. Grazing activity is positively associated with burrow density but did not significantly influence gerbil presence. Zero‐inflated Poisson and resource selection function revealed that gerbils are strongly associated with mixed vegetation land cover, shrubland habitats, and agricultural land with native vegetation. Contrary to expectations, predator presence was positively correlated with both burrow density and gerbil occurrence. This pattern likely suggests the importance of gerbils as a key prey for desert predators, as well as the spatial confinement of native fauna within remnant patches of viable habitats. These findings emphasize prioritizing the conservation of fragmented habitats within transformed landscapes and the preservation of native vegetation. Our study identifies the Indian desert gerbil as a potential indicator species of suitable habitats within the degraded Thar Desert landscape. It further highlights the significance of selecting and modeling appropriate ground covariates to identify critical ecological interactions shaping species distributions in dryland ecosystems subject to anthropogenic land conversion.
Abstract The recovery of the Canada goose (Branta canadensis) is one of North America's greatest conservation success stories. Today, continental abundance of temperate‐breeding Canada geese (those breeding in southern Canada and lower 48 states in the United States) greatly exceeds historical levels. As a result of increased abundance, human–goose conflicts have also increased, ranging from private and agricultural property damage to human health concerns. Managers have primarily attempted to lower Canada goose populations using hunter harvest via liberalized hunting regulations (increased bag limits and total hunting days). To evaluate the effectiveness of harvest strategies for temperate‐breeding Canada geese, managers need a better understanding of how liberalized hunting regulations affect population dynamics. We estimated survival and harvest probabilities, abundance, and recovery distribution of temperate‐breeding Canada geese banded in Arkansas, USA, during 2005–2020. We found that adult harvest probabilities declined overall during the study and adult survival probabilities increased. Annual abundances of juvenile geese (≤1 year old) declined during the study, whereas there was no detectable trend in abundance of the adult population over time. Most Canada geese breeding in Arkansas were shot in Arkansas, indicating potential for population dynamics to be influenced largely by state‐specific harvest regulations. However, our results suggest that harvest liberalization as a management tool may have limited capacity to further influence population dynamics of Canada geese. Declines in productivity and recruitment likely had a greater influence on the similar observed declines in juvenile and adult abundances, respectively, during our study. More research is needed to better understand the ecological mechanism affecting the population dynamics of Canada geese in both urban and rural environments.
Abstract Fuel treatments are implemented across large spatial scales in sagebrush (Artemisia spp.) ecosystems of the US Intermountain West to limit wildfire risk and spread, but treatment effects on ecosystem carbon storage remain poorly understood. Fuel treatments can reduce aboveground carbon storage and may also influence belowground carbon storage either directly through disturbance (e.g., disruption of soil surface) or indirectly through altered plant community composition over time (e.g., increases in invasive annual grasses that can impact plant–soil feedbacks and thus soil carbon storage). We analyzed above and belowground carbon stock estimates before and 10 years after treatment to determine whether woody fuel treatments had measurable effects on ecosystem carbon storage in the Sagebrush Steppe Treatment Evaluation Project (SageSTEP) plot network, which includes both pinyon pine and/or juniper‐encroached woodland sites and sagebrush‐dominated shrubland sites. We also assessed whether cheatgrass (Bromus tectorum L.) invasion, which occurred throughout the study region, impacted soil organic and inorganic carbon storage in the top meter of soil. In woodland sites, prescribed fire and mechanical treatments reduced live tree carbon stocks by 87%–97% and tree litter carbon stocks by 92%–96% compared to starting values, and increased perennial herbaceous carbon stocks by 146%–169%. Prescribed fire also increased annual herbaceous carbon stocks seven‐fold, while mechanical treatments increased shrub carbon stocks by 89% and coarse woody debris carbon stocks five‐fold. In shrubland sites, prescribed fire reduced shrub carbon stocks by 66%. Mowing and woody herbicide treatments reduced shrub carbon stocks between 37% and 46% from pre‐treatment levels, but changes did not differ from those in untreated controls. Belowground carbon stocks were unaffected by treatment, though additional change may occur over time if differences in perennial or annual vegetation are persistent. Regardless of treatment type, cheatgrass invasion correlated with decreases in deep (30–90 cm) soil organic carbon stocks in woodland sites and deep soil inorganic carbon stocks in shrubland sites. While fuel treatments have clear impacts on carbon storage aboveground, their effects belowground (where most dryland ecosystem carbon is stored) appear small compared to the impacts of cheatgrass invasion.
Abstract Climatic seasonality plays an important role in shaping ecological interactions, including those between bats and their ectoparasitic bat flies. Although previous studies have acknowledged the influence of climate on the structure of bat–bat fly interaction networks, the existence of biogeographical patterns driven by climatic seasonality remains largely unexplored. Because biogeographic patterns reflect recurrent structural changes along environmental gradients, identifying them can provide valuable insights into host–parasite interactions and their responses to environmental variation. Here, we investigated the effects of climatic seasonality on the structure of bat–bat fly interaction networks across the Neotropics, while accounting for host assemblage composition and bat functional traits. We analyzed interaction networks previously compiled from a published paper on bat–bat fly interactions throughout the Neotropics. We obtained climatic variables from WorldClim models, and bat functional traits from published databases. We quantified network structure using network size, niche overlap, modularity, and nestedness. To assess the influence of climate and host traits on network structure, we fitted generalized linear models including mean annual temperature, temperature seasonality, annual precipitation, and precipitation seasonality as explanatory variables. Network size was also included as a predictor to account for its influence on niche overlap, modularity, and nestedness. In addition, we incorporated the proportion of cavity‐roosting bats, frugivorous bats, and phyllostomid bats as controls for functional and taxonomic composition of host assemblages. Our results show that higher annual precipitation is associated with larger network size and reduced niche overlap, whereas increasing network size leads to lower nestedness. The proportion of phyllostomid bats further increased niche overlap and reduced nestedness, highlighting the importance of host assemblage composition. In contrast, neither temperature seasonality nor precipitation seasonality had a direct effect on network structure. Overall, our findings emphasize the dominant role of annual precipitation and host assemblage, rather than climatic seasonality, in shaping bat–bat fly interaction networks. These results advance our understanding of parasitism dynamics and the structural organization of antagonistic host–parasite networks at broad biogeographical scales.
Abstract Patch‐burn grazing uses the interactive effects of prescribed fire and herbivory to increase heterogeneity in aboveground ecosystem properties. Understanding how management that targets aboveground heterogeneity translates to soil properties and processes provides an important whole‐system context for practitioners. In this study, we investigated how the combination of patch‐burning and livestock grazing aligned with soil nutrients, decomposition activity, and microbial abundance and composition on semi‐arid post‐Conservation Reserve Program rangelands in southwestern North Dakota. We collected soil samples during the 2018–2020 summer grazing seasons in three patch‐burn pastures grazed by cow‐calf pairs and three patch‐burn pastures grazed by sheep. In each year, we measured ammonium, nitrate, calcium, magnesium, phosphorus, potassium, total carbon, and total nitrogen. In 2019 and 2020, we measured soil moisture, decomposition activity, and microbial abundance and community composition. We tested for differences between patches with varying time since fire, between grazer type, and between ecological sites using mixed‐effect models with Tukey post hoc tests and ordinations with post hoc factor and vector fitting. There were no significant differences in any properties between cattle and sheep pastures. Measured nutrients and microbial abundances were not lower in recently burned patches than not yet burned or patches with three years since fire. Bacterial groups comprised the largest proportion of the microbial community across years, ecological sites, and times since fire. Soil moisture, calcium, phosphorus, potassium, total carbon, total carbon:nitrogen ratio, time since fire, and ecological site were significantly correlated with microbial community composition. The lack of negative responses in soil biota and properties under patch‐burn grazing is promising for the continued use of these disturbances in low diversity rangelands.
Abstract In the face of accelerating biodiversity loss, conservation strategies require effective tools to identify species of high conservation priority. In this context, the index of evolutionary distinctiveness (ED), which quantifies the unique contribution of individual species to the overall phylogenetic diversity of a given assemblage, has played a pivotal role. In this paper, we propose a general mathematical framework for ED based on the notion of specificity, a type of non‐probabilistic uncertainty derived from fuzzy set theory. This new perspective allows ED to be extended to other forms of distinctiveness, such as functional distinctiveness, provided that an appropriate pairwise (dis)similarity matrix between species is available. It also enables the development of new measures that capture aspects of species distinctiveness not accounted for by the ED index. Our formulation further connects species‐level distinctiveness with traditional community‐level metrics, such as alpha and beta diversity. We demonstrate how beta diversity, traditionally used to measure species turnover among sites, can be reframed as the average specificity of the sampled sites. Overall, linking ED to fuzzy specificity opens new directions for biodiversity measurement and conservation planning.
Abstract Most ecological knowledge about carbon recovery during natural regeneration in tropical regions has focused on individuals exceeding 10 cm in diameter. However, the contribution of smaller individuals to aboveground carbon (AGC) across successional gradients remains poorly quantified, despite their potentially substantial role during early stages of forest regeneration. While remote sensing technologies provide powerful tools for large‐scale carbon monitoring, their effectiveness in capturing contributions from different size classes across successional gradients requires validation with detailed field data. To understand the role of individuals smaller than 10 cm in diameter in carbon recovery, we conducted two sets of analyses. First, we compared the contribution of small and large individuals along the successional gradient using 126 plots (0.25 ha each) distributed across 16 municipalities in the Eastern Amazon, Brazil. Second, we evaluated the sensitivity of remote sensing‐based carbon estimates from the European Space Agency Climate Change Initiative (ESA CCI‐AGB) to capture these variations across size classes and successional gradients. Smaller individuals played a key role in carbon stocks, storing up to 75% of the total carbon in early succession. This contribution declined to 50% after 10 years and to 18% after 25 years. At 10 years of regeneration, the mean total AGC stock was 24.3 ± 2.3 Mg C ha−1 (mean ± SE), increasing to 41.5 ± 2.0 Mg C ha−1 at 25 years, reflecting the progression of ecological succession. The ESA CCI‐AGB estimates tended to systematically overestimate AGC stocks, with a mean error of approximately 39 Mg C ha−1. Convergence with field‐measured stocks was 33% when all individuals were included, compared with 29% when only large individuals were considered. Our findings highlight the crucial role of small individuals in AGC stocks, emphasizing the need to include them in carbon recovery estimates, especially in younger secondary forests that make up most of the Amazonian regrowth.
Abstract Resource subsidies, or the flow of energy across ecosystem boundaries, can influence community structure and function and act as important nutrient sources to less productive ecosystems, particularly in marine and coastal zones. Coastal dunes, connected to the nearshore through sandy beaches, likely depend on the delivery of marine subsidies to regulate the dune building biophysical feedback between vegetation and sand. Here we consider the role of marine subsidies to foliar nitrogen and dune grass production along the US Outer Banks coastline and ask: (1) Do macrophyte wrack biomass and composition, sand nitrate concentration, and dune grass production vary at local and regional scales? (2) Do dune grasses utilize marine‐derived nitrogen (15N) and, if so, how does δ15N and %N vary across species, foredune profile locations, and islands? and (3) What factors, including macrophyte wrack biomass, sand nitrate, sand supply, and dune morphology, are important to foliar nitrogen (δ15N and %N) and dune grass production? We found that sand nitrate concentrations increased with latitude along the Outer Banks coastline but were unrelated to macrophyte wrack biomass. Dune grass δ15N was highest at the foredune toe and decreased landward, suggesting that grasses closer to the beach are using marine‐derived nitrogen. Although dune grass %N content and production (density and biomass) did not vary across the foredune profile, they did increase with latitude. Moreover, sites with slightly negative shoreline change rates, steeper backshore slopes, and taller foredunes had greater sand nitrate concentration, foliar %N and δ15N, and dune grass production at the seaward side of the foredune. At the back dune, foliar δ15N and dune grass production were not correlated with sand supply or sand nitrates, indicating other factors at play on the landward side of the foredune. Given the important role of dune grasses in sand capture and dune building, any shifts in marine‐derived nutrients from changes in ocean productivity or sand flux could have landscape‐level consequences for dune building, coastal protection, and carbon storage services.
Abstract Rangelands provide ecosystem services that support approximately 30% of the human population. To maintain sustainable forage resources for animals in grasslands, it is essential to manage grazing pressures by adapting to changes in the quantity and nutritional quality of vegetation affected by climate change and subsequent shifts in plant interactions. To investigate how climate change and altered plant composition interact to impact forage quantity and quality, we conducted a field experiment involving warming and dominant plant removal treatments. We measured changes in the abundance and crude protein content of key forage species. Our results showed a 12% reduction in community‐level protein content due to warming. In contrast, plant species removal and the interaction between warming and removal treatments had only minor effects on community‐level crude protein content. Warming did not significantly affect the total abundance of palatable plant species, but it caused a decline in evenness in the forage plant community. Additionally, the relative cover of the high‐value forage species decreased slightly, while low‐quality forage species saw a modest increase under warming conditions. To prevent overgrazing and the long‐term degradation of rangelands in a warmer world, managers may need to reduce livestock stocking rates if forage nutritional quality declines, even without a reduction in forage quantity. This study highlights how even a single aspect of global change, such as warming, can lead to significant losses in forage quality—an effect that is expected to worsen as these ecosystems continue to dry.
Abstract Ecological stoichiometry emphasizes that mismatches between the elemental composition of organisms and their resources can shape ecological interactions, evolutionary trajectories, and nutrient cycling. For hemiparasitic plants such as mistletoes, which draw water and nutrients from hosts while maintaining their own photosynthesis, such mismatches raise a fundamental question: To what extent do parasites mirror or diverge from the elemental constitution of their hosts, and what ecological and evolutionary consequences emerge from these differences? To address this, we measured concentrations of 14 elements in leaves of 168 mistletoe–host pairs spanning 90 species combinations across Australian bioregions. We used bioconcentration ratios, slopes of log–log relationships, and spatial mixed‐effects models to assess whether mistletoes accumulate or underaccumulate elements relative to their hosts, and to test the influence of host phylogeny, mistletoe identity, and geography on stoichiometric patterns. Mistletoes consistently exhibited higher concentrations of boron, copper, phosphorus, potassium, and sodium, but lower iron and nitrogen than their hosts, while concentrations of other elements were broadly similar. Potassium, in particular, showed evidence of tight homeostatic regulation across diverse hosts, suggesting a physiological requirement potentially linked to water relations and osmoregulation. In contrast, sodium and several other elements tracked host concentrations more closely, indicating context‐dependent accumulation. Variation in mismatches was strongly structured by host family, species pair, and site, underscoring the importance of both evolutionary and geographic context in parasite–host nutrient relationships. These patterns imply that mistletoes are not simply “what they eat” but instead selectively accumulate elements in ways that may underlie their distinctive life history traits, such as extended reproductive phenology and high transpiration rates. At broader scales, stoichiometric mismatches between mistletoes and hosts may influence herbivore foraging, shape plant–animal interactions, and alter nutrient inputs through litterfall, thereby contributing to ecosystem productivity and biodiversity. By linking elemental imbalances across individual, community, and ecosystem levels, our results highlight the integrative role of stoichiometric theory in understanding the biology of parasitic plants and their ecological consequences.
Abstract Global change is accelerating and pushing the planet's ecosystems beyond the range of historical observations, creating increasing uncertainty in future system conditions. Despite general agreement that proactive environmental action is warranted, environmental decision conversations often end by identifying additional data needed to reduce uncertainty before taking novel action. Given the inherent uncertainty in complex issues such as global change, quantitative data alone are likely insufficient to support proactive environmental action. Holistic understanding of uncertainty includes scientific quantification of uncertainty paired with emotional responses and transcendental grounding to help people work together toward proactive action in uncertain decision contexts. Holistic understanding arises from the four ways in which humans perceive the world, termed the Four Realms: Physical (e.g., how I observe), Mental (e.g., how I think), Emotional (e.g., how I feel), and Transcendental (e.g., how I connect to greater meaning or purpose). Environmental scientists and decision makers are generally trained in Physical and Mental Realm observation and analysis, but not in how to apply Emotional and Transcendental Realm understanding. Emotional and Transcendental processing occurs in scientists and decision makers whether it is acknowledged or not and contributes to different people interpreting the same information in different ways. Thus, when the role of Emotional and Transcendental Realms in an individual's interpretation process is not understood, it can derail conversations and perpetuate the status quo. Explicitly recognizing all Four Realms can bring people together across differences and inspire shared, novel decision making even in increasing uncertainty. To illustrate the benefits of holistic understanding, we share stories from our experiences in environmental decision contexts. Because accessing the Four Realms requires experiential and embodied techniques, while still relying on core scientific tenets of observation and analysis, we also present techniques for readers to learn to feel their own emotional understanding and connect to their own transcendental understanding. Holistic understanding can enhance data‐driven decisions by recognizing that human responses to uncertainty inherently include interactions between emotions, thoughts, transcendental connections, and behavior. Ultimately, holistic understanding can help anchor data‐driven decisions in intra‐ and interpersonal connections, inspiring action in the face of uncertainty.
Abstract Climate change is a leading threat to global biodiversity. Research on climate change impacts on foundational species, which underlie the structure and function of ecosystems, is critical to developing effective conservation responses. To better understand the landscape of existing research and identify research needs, we conducted a scoping review on the gray and peer‐reviewed literature between 1971 and 2023 on climate change impacts on endemic and near‐endemic, foundational trees (N = 31) in California, a biodiversity hotspot. From this review, we quantitatively synthesized studies on spatial/temporal demographic changes (recruitment, mortality, and density) across these species as related to climate change and provided narrative syntheses for each individual species. While research on climate change impacts has grown, significant gaps remain, and research effort was highly variable across species, topic, approach, and focal climate stressor. Many of our focal species are already showing recruitment and mortality patterns consistent with climate change, with particularly strong evidence of spatial/temporal shifts in young life stages in response to a drying environment (86% of species studied). This work provides continuing evidence that species are already responding to climate change and highlights research gaps and opportunities to support climate‐adaptive conservation for key, foundational species of our study region.
Abstract Intraspecific variation in diet is often influenced by geographic location, resource availability, trophic position, or foraging specialization and can result in environmental changes exerting heterogeneous effects across the species' distribution. Managing species under environmental changes therefore requires an understanding of how the species diet differs spatially in order to prescribe locally suitable conservation pathways. The emu, Dromaius novaehollandiae , while secure across much of its wide range, has declined or disappeared from many areas along the east coast of Australia. Its generalist omnivorous diet may allow for re‐establishment in some areas, but to date, no studies have quantified the geographic variability in the species diet or whether any locational diet specialization occurs. Using stable isotope analysis and review of previous dietary studies, we aim to determine whether localized dietary specialization and geographic intraspecific variation in diet exist in emus to inform emu conservation efforts (e.g., source selection for reinforcement or reintroduction programs). Aggregation of previous dietary studies shows the large number of dietary sources which emus consume consists predominately of C 3 plants but also differs across their range. Based on the isotopic signatures of feathers collected opportunistically from across eastern Australia, there appears to be a broad split east to west and south to north in emu diet following the Great Dividing Range. This pattern generally mirrors Australia's δ 13 C isoscape and the longitudinal transition from predominately C 3 to C 4 vegetation cover across the Range. The geographic clustering of samples, based on δ 13 C and δ 15 N, is driven by similar environmental and climatic variables (temperature and rainfall patterns and woodland cover) to that which drives C 3 :C 4 abundance. Our data suggest that although emu show preference for C 3 plants, diet varies geographically in line with those plants most available locally. Emus appear to have a highly adaptable diet, likely allowing them to recolonize areas and move between vastly different habitats.
Land use change alters forest ecosystems by reducing habitat amount and often increasing fragmentation, but the relative importance of these drivers for community dynamics remains debated. It is also unclear whether functional traits consistently predict species' responses to forest change, particularly in tropical dry forests. Using 6 years of camera-trap monitoring and remotely sensed forest metrics from the Chiquitano Dry Forest in Bolivia, we assessed how forest cover (habitat amount) and edge density (fragmentation) interact to shape mammal occupancy, and whether traits (body mass, home range size, activity cycle, diet breadth, and habitat breadth) mediate species' responses to forest change. Community occupancy tended to increase with forest cover, but this association weakened in areas with high edge density, indicating that fragmentation reduces the ecological benefits of greater habitat amount for mammal communities. Edge density added explanatory power for community-level and several species' responses through its interaction with forest cover but showed little evidence for an independent effect. Forest cover showed strong positive associations with occupancy for several species, but the strength of individual species' responses was variable. Wide-ranging, large-bodied mammals consistently showed stronger dependence on high forest cover, while activity cycle, diet, and habitat breadth were poor predictors of species' responses. None of the examined traits was consistently associated with responses to edge density. Although trait models explained only modest variance in species' responses (similar to 15%), our findings suggest that wide-ranging, large-bodied mammals may serve as useful monitoring targets in areas experiencing deforestation. At the same time, the interaction between habitat amount and fragmentation was most clearly supported at the community level, indicating that integrating species- and community-level perspectives can provide a more complete basis for the conservation of intact mammal communities in human-modified tropical forests.
In the C-4-dominated semiarid grasslands of the western Great Plains (Colorado, USA), spring soil moisture (soil volumetric water content, Soil(VWC)) is thought to be a critical determinant of aboveground net primary production (ANPP) and overall carbon cycling. However, because evidence for this is based on observational studies, we attempted to test this sensitivity by experimentally reducing spring (May-June) Soil(VWC) with standard drought shelters. Our goal was to reduce rainfall inputs from May to early July in a native grassland dominated by C-4 Bouteloua spp. and assess ANPP and related carbon cycle responses. Although we were able to reduce ambient rainfall inputs directly into the plots, spring precipitation was unusually high (similar to 40% above average) in the year of this experiment (2021), and our treatments had negligible impacts on Soil(VWC). Indeed, the drought shelters were able to reduce Soil(VWC) below ambient levels for only 2 weeks, after a large natural precipitation event (similar to 65 mm) fell in late June. As expected, by mid-July, we could detect only minor impacts of our treatments on soil CO2 efflux and canopy greenness, and no effect on ANPP, consistent with Soil(VWC) remaining at non-limiting levels throughout most of the first half of the growing season. Despite the seeming ineffectiveness of the spring drought treatments, we challenged these plots with an experimental deluge (60 mm of water addition) after the drought shelters were removed. Surprisingly, in plots subjected to the drier spring treatment, we measured significant reductions in soil CO2 efflux immediately after the experimental deluge as well as reduced canopy greenness throughout much of the remainder of the growing season. Moreover, end-of-season ANPP was reduced by 32%, and regrowth after defoliation ("simulated grazing" at mid-season) was reduced by 45% in the treatment with only minor reductions in Soil(VWC) in the spring. Our largely serendipitous results confirm the strong sensitivity of this grassland to alterations in early season rainfall inputs, even during a wet spring when measurable impacts on soil moisture are minimal.
Synthetic normalized biomass size spectra (NBSS) comprising non-synoptically sampled phytoplankton, meso- and macrozooplankton, and micronekton including mesopelagic fishes were explored to analyze pelagic community structure in seven regions of the tropical and the subtropical Atlantic representative of different water bodies (NE Brazil shelf, NE Brazil oceanic islands, northern and southern offshore Benguela Upwelling System, northern offshore Canary Current Upwelling System, equatorial region, southern Canary Current Upwelling System oxygen minimum zone). For mesopelagic fishes and micronekton, conversions were applied accounting for sampling biases in relation to other ecosystem components. Three main results were obtained. Firstly, NBSS slopes based on biovolume were significantly shallower than slopes based on carbon contents, as revealed in part through pairwise comparisons of linear models and by ANOVA. The ensemble mean slope for six regions combined (one region omitted due to missing zooplankton data) measured in terms of biovolume was -0.866, and the respective value in terms of carbon biomass was -0.894. Secondly, log ratios of spectral densities, that is, contrasts, between consumers and phytoplankton increased with decreasing primary production. Contrasts for total micronekton and mesopelagic fishes relative to phyto- and zooplankton varied with primary production, indicating that below a primary production of 650 mg C m-2 day-1, their spectral densities were higher than predicted by phytoplankton. Above this level, however, the spectral densities were lower. Thirdly, regional population marginal means were positively correlated with primary production in terms of carbon biomass (p = 0.01) but not biovolume (p = 0.48). Biovolume NBSS slopes were negatively correlated with primary production (p = 0.02), if the northern Benguela Upwelling System was not included (else p = 0.11). The increase in biovolume relative to the carbon biomass of gelatinous organisms is discussed as allometric advantage to enhance trophic transfer efficiency. Trophic transfer efficiencies ranged from 28.9% to 36.8% for open-ocean systems and from 36.8% to 49.7% for coastal and oceanic island habitats. The results suggest that synthetic pelagic size spectra provide a powerful framework to detect regional and functional shifts in Atlantic pelagic communities, offering predictive value for future ocean changes under climate scenarios.
