Climate Change Ecology最新文献

Tropical ecosystems are expected to experience climate warming, with predicted increases in drying and heat extremes in the coming years. Understanding how these changes will affect terrestrial vertebrates such as amphibians is limited. The Tropical Responses to Altered Climate Experiment in the Luquillo Experimental Forest in northeastern Puerto Rico allows us to study how the tropical forest responds to warming within a replicated plot design. From September 2018 to August 2019, we used mark-recapture sampling to investigate how the spatial population ecology of the common coqui frog (Eleutherodactylus coqui) is impacted by experimentally increasing surface temperatures by 4 °C above ambient. We compared estimates of baseline detection, space use, and the density of frogs in control and warmed plots. Coqui space use and population density did not differ between control and warmed plots. However, coqui detection probabilities were higher in warmed plots, suggesting an increased level of activity relative to individuals in the control (unwarmed) plots. Frog detection increased in all plots with increased precipitation. Our results suggest that, at least in the short-term, the density of an ecological generalist frog like E. coqui does not change as a response to increased surface temperatures. However, short-term responses to warming such as changes in behavior may lead to changes in population dynamics in the long-term. Our research highlights the need to consider mutiple repsonses in order to understand the effects of climate warming on tropical vertebrates.

Organic matter (OM) dynamics determine how much carbon is stored in ecosystems, a service that modulates climate. We synthesized research from across the US Long-Term Ecological Research (LTER) Network to assemble a conceptual model of OM dynamics that is consistent with inter-disciplinary perspectives and emphasizes vulnerability of OM pools to disturbance. Guided by this conceptual model, we identified unanticipated patterns and long-term trends in processing and transport of OM emerging from terrestrial, freshwater, wetland, and marine ecosystems. Cross-ecosystem synthesis combined with a survey of researchers revealed several themes: 1) strong effects of climate change on OM dynamics, 2) surprising patterns in OM storage and dynamics resulting from coupling with nutrients, 3) characteristic and often complex legacies of land use and disturbance, 4) a significant role of OM transport that is often overlooked in terrestrial ecosystems, and 5) prospects for reducing uncertainty in forecasting OM dynamics by incorporating the chemical composition of OM. Cross-fertilization of perspectives and approaches across LTER sites and other research networks can stimulate the comprehensive understanding required to support large-scale characterizations of OM budgets and the role of ecosystems in regulating global climate.

Ecological interactions are the backbone of biodiversity. Like individual species, interactions are threatened by drivers of biodiversity loss, among which climate change operates at a broader scale and can exacerbate the effects of land-use change, overharvesting, and invasive species. As temperature increases, we expect that some species may alter their distribution towards more amenable conditions. However, a warmer and drier climate may impose local effects on plants and animals, disrupting their interactions before noticeable changes in distribution are observed. We used a mutualistic trio from the temperate forests of South America to theoretically illustrate how climate change can disrupt ecological interactions, based on our current knowledge on this system. This study system comprises three generalist species with intersecting roles: a keystone mistletoe, a pollinator hummingbird, and a frugivorous marsupial that disperses the seeds of many species. On the one hand, drought causes water stress, increasing mortality of both mistletoe and host plants, and reducing the production of flowers and fruits. These resource shortages negatively impact animal's foraging opportunities, depleting energy reserves and compromising reproduction and survival. Finally, warmer temperatures disrupt hibernation cycles in the seed-dispersing marsupial. The combined result of these intersecting stressors depresses interaction rates and may trigger an extinction vortex if fail to adapt, with deep community-wide implications. Through negatively affecting generalist mutualists which provide resilience and stability to interaction networks, local-scale climate impacts may precipitate community-wide extinction cascades. We urge future studies to assess climate change effects on interaction networks rather than on singular species or pairwise partnerships.

Natural ecosystems are threatened by climate change, fragmentation, and non-native species. Dispersal-limitation potentially compounds impacts of these factors on plant diversity, especially in isolated vegetation patches. Changes in climate can impact the phenology of native species in distinct ways from non-natives, potentially resulting in cascading impacts on native communities. Few empirical studies have examined the combined effects of climate change and dispersal limitation on community diversity or phenology. Using a five-year dispersal-restriction experiment in an invaded semi-arid annual plant system in Western Australia, we investigated the interactive effects of dispersal-restriction and inter-annual rainfall variation on community composition, species dominance and seed production timing. We found inter-annual rainfall variation to be the principal driver of community dynamics. Drought years had long-term, stable effects on community composition, with evidence of shifts from native toward non-native dominance. Surprisingly, community composition remained largely unchanged under dispersal restriction. A subtle ‘dispersal rescue’ effect was evident for a dominant native annual forb and a dominant annual non-native grass but only in average rainfall years. The timing of seed production was primarily driven by annual rainfall with native and non-native grasses having opposite responses. There was no evidence that inter-annual variation in seeding timing affected community diversity over time. Our study demonstrates that dispersal is not a major factor in driving community diversity in this invaded, semi-arid system. Results do suggest, however, that increases in drought frequency likely benefit non-native species over natives in the long term.

Adult males of many migratory species arrive at breeding grounds before females and young. In a 34-year study of the masked shrike, Lanius nubicus, an age- and sex-specific pattern of spring arrival was distinguished. Adult males arrived first followed by juvenile males and adult females, whereas juvenile females appeared last. We hypothesized that these differences in migratory strategies would be reflected in a differential response to climate conditions at the wintering grounds. Testing correlations between spring arrival time and winter climate conditions provided strong support to our hypothesis. Adult males’ arrival time exhibited high associations with climate conditions in early spring, upon migratory take-off, whereas juvenile males responded mostly to conditions in November, upon autumn arrival in Africa. Adult females responded to both parameters in autumn and early spring, whereas young females’ arrival correlated only with a few variables in autumn. GLM models of median spring arrival day for all categories but the young females were highly statistically significant with adjusted R-squared values of 0.81–0.93. The emerging pattern of different associations between timing of spring migration and climate conditions at the wintering grounds sheds new light on existing evolutionary theories regarding age- and sex-specific migratory strategies.

Because short growing seasons severely constrain plant growth and biomass accumulation in high elevation habitats, herbivory can profoundly impact both individual fitness and community dynamics in these settings. All else being equal, climate change is expected to increase the activity of insect herbivores as their metabolic rates rise with temperature. However, montane species may have more complex responses than those in agricultural or lowland ecosystems, since many factors that shape plant-insect interactions, including temperature, shift with elevation. From 2016 to 2018 we conducted field observations of grasshopper herbivory on subalpine lupines in Mt. Rainier National Park and combined these with multiple leaf trait analyses and a set of manipulative feeding trials to explore how insect herbivory varies along a climatic gradient, and whether differences in plant or insect herbivore phenotypes that are influenced by a population's climatic history can explain these patterns. We found a significant increase in herbivory with elevation that was related to both abiotic drivers, particularly snowmelt timing, and population traits, particularly leaf nutrition and grasshopper feeding rates. Our results suggest that some high-elevation plants may already be experiencing ecologically meaningful levels of insect herbivory that could intensify with climate warming. They also highlight the complexity of predicting how species interactions will change with warming in alpine and subalpine ecosystems, where environmental plasticity or local adaptation driven by elevational differences in climate may lend tremendous complexity to ecological dynamics.

Predicted shifts in mean and extreme temperatures associated with climate change can have variable impacts on organisms, and the sign and magnitude of these impacts may depend upon local context. For Hedophyllum sessile, a habitat-forming intertidal kelp, the impacts of warming may vary with local density and position in the intertidal zone. To assess the potential context-dependence of warming, we manipulated H. sessile densities across an intertidal gradient and experimentally imposed periodic thermal stress in the field. The recruitment of H. sessile juveniles was unimodally related to shore level, peaking near the center of the species’ vertical distribution and falling off at the upper and lower distributional limits. Experimental warming tended to have mildly positive effects on recruitment lower on the shore regardless of adult density, and in upper zone, high density plots. However, warming had strongly negative effects on recruitment in upper zone, low density plots. Temperature manipulations also had context-specific effects on adult plant growth; seasonal increases in blade number and canopy cover were slightly enhanced by warming in high-density plots but greatly reduced by warming in low-density plots. Finally, experimental heating had context-dependent effects on an understory herbivore, the chiton Katharina tunicata, which increased in abundance following heating in high density plots but decreased in low density plots. Our results demonstrate that extreme temperature events can affect multiple species and multiple life history stages, and that the impacts of such events can depend upon both environmental (e.g. intertidal height) and biological (e.g. adult density) context.

Describing patterns of plant phenology through models has been critical for quantifying species responses to climate change and forecasting future vegetation impacts. However, many species remain unincluded in large analyses because they are poorly represented in the large public or citizen science datasets that form the foundation of these efforts. Botanical living collections are often key resources that facilitate study of rare and sparsely observed species, but alone are insufficient to predict species phenology throughout their observed ranges. We investigate whether predictions for rare and data-poor species observed at a single site can be improved by leveraging observations of similar taxa observed at multiple locations. We combined observations of oak (Quercus) budburst and leaf out from one botanical garden with a subset of congeneric species observed in the USA-NPN citizen science dataset using Bayesian hierarchical modeling. We show that including USA-NPN observations into a simple thermal time model of budburst and leaf out did not reduce geographic bias in model predictions over models parameterized only with single-site observations. However, using USA-NPN data to add non-taxonomic spatial covariates to the thermal time model improved model performance for all species, including those only observed at a single site. Living collections at botanical gardens provide valuable opportunities to observe rare or understudied species, but are limited in geographic scope. National-scale citizen science observations that capture the spatial variability of related or ecologically similar taxa can be combined with living collections data to improve predictions of species of conservation concern across their native range.

Prior exposure to variable environmental conditions is predicted to influence the resilience of marine organisms to global change. We conducted complementary 4-month field and laboratory experiments to understand how a dynamic, and sometimes extreme, environment influences growth rates of a tropical reef-building crustose coralline alga and its responses to ocean acidification (OA). Using a reciprocal transplant design, we quantified calcification rates of the Caribbean coralline Lithophyllum sp. at sites with a history of either extreme or moderate oxygen, temperature, and pH regimes. Calcification rates of in situ corallines at the extreme site were 90% lower than those at the moderate site, regardless of origin. Negative effects of corallines originating from the extreme site persisted even after transplanting to more optimal conditions for 20 weeks. In the laboratory, we tested the separate and combined effects of stress and variability by exposing corallines from the same sites to either ambient (Amb: pH 8.04) or acidified (OA: pH 7.70) stable conditions or variable (Var: pH 7.80-8.10) or acidified variable (OA-Var: pH 7.45–7.75) conditions. There was a negative effect of all pH treatments on Lithophyllum sp. calcification rates relative to the control, with lower calcification rates in corallines from the extreme site than from the moderate site in each treatment, indicative of a legacy effect of site origin on subsequent response to laboratory treatment. Our study provides ecologically relevant context to understanding the nuanced effects of OA on crustose coralline algae, and illustrates how local environmental regimes may influence the effects of global change.

Food web rewiring is becoming more likely as climate change continues, yet few experimental studies have focused on it and even fewer have examined the effects of two or more climate variables simultaneously. To help fill this gap the current study examined the effects of warming and drought, both alone and in combination, on herbivore feeding behaviors in a well-known old field food web consisting of two plants (grass and goldenrod), one grasshopper herbivore (Melanoplus femurrubrum), and one arachnid predator (Pisaurina mira). Drought had much stronger effects than warming on goldenrod mortality and flowering, goldenrod nutrient content, herbivore feeding preferences, and live goldenrod biomass remaining at the end of the experiment, while grass was largely unaffected. Drought combined with warming to almost completely suppress goldenrod because of increased goldenrod mortality rates and the drought-stressed grasshoppers’ clear preference for consuming goldenrod with high foliar carbon concentrations. When compared with previous studies that have focused on warming in this system, the current study suggests that food web rewiring is very likely in old fields but the type of rewiring that may occur will be dependent on which climate variables shift more strongly.