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Seasonal variation in animal activity influences fitness and the intensity of ecological interactions (e.g., competition, predation), yet aspects of global change in the Anthropocene may catalyze shifts in seasonal activity. Invasive plants are components of global change and can modify animal daily activity, but their influence on animal seasonal activity is less understood. We examined how invasive woody shrubs (Autumn olive [Elaeagnus umbellata] and Amur honeysuckle [Lonicera maackii]) affect seasonal activity of three common small-mammal species by coupling experimental shrub removal with autumnal camera trapping for two consecutive years at six paired forest sites (total 12 plots). Eastern chipmunks (Tamias striatus) foraged more, and foraging was observed at least 20 days longer, in shrub-invaded forests. White-footed mice (Peromyscus leucopus) foraged more in invaded than cleared plots in one study year, but P. leucopus autumn activity timing did not differ between shrub-removal treatments. Fox squirrel (Sciurus niger) activity displayed year-specific responses to shrub removal suggesting intraannual cues (e.g., temperature) structure S. niger autumnal activity. Our work highlights how plant invasions can have species-specific effects on seasonal animal activity, may modify the timing of physiological processes (e.g., torpor), and could generate variation in animal-mediated interactions such as seed dispersal or granivory., (© 2024 The Ecological Society of America.)

Identifying and clearly communicating the drivers of ecosystem function is a crucially important goal for both basic and applied ecology. This has proven difficult because the putative causes (e.g., environment, species identity, biodiversity, and functional traits) are numerous and correlated. The problem is exacerbated by a lack of a formal framework for unambiguously relating theoretical language to precise, quantitative expressions of that language. Using a formal framework for the graphical expression of complex causal hypotheses, we developed a causal diagram of the concepts required to comprehensively test whether hypothesized sets of functional traits mediate the relationship between community structure and ecosystem function. We then used causal analysis, simulations, and field data to develop and test analytical strategies for understanding how community structure influences ecosystem functions via functional traits. Formal causal analysis showed that biodiversity-ecosystem function correlations are noncausal associations. Using simulations, we showed how biodiversity correlations and species identity effects can arise from misspecification or incomplete mediation by functional trait composites. We also found that different types of model misspecification result in different patterns of residuals, which may be used to diagnose gaps in functional trait hypotheses. Treating the model misspecifications eliminated associations between species identity or biodiversity and ecosystem function. Finally, we provide an example of the analysis of field data to demonstrate how to use these insights to conduct a research program that has the goal of understanding the mechanistic trait relationships that link community structure to ecosystem function., (© 2020 by the Ecological Society of America.)

Establishment and persistence are central to community assembly and are determined by how traits interact with the environment to determine performance (trait-environment interactions). Community assembly studies have rarely considered such trait-environment interactions, however, which can lead to incorrect inferences about how traits affect assembly. We evaluated how functional traits, environmental conditions, and trait-environment interactions structure plant establishment, as a measure of performance. Within 12 prairie restorations created by sowing 70 species, we quantified environmental conditions and counted individuals of each seeded species to quantify first-year establishment. Three trait-environment interactions structured establishment. Leaf nitrogen interacted with herbivore pressure, as low leaf nitrogen species established relatively better under higher herbivory than species with high leaf nitrogen. Soil moisture interacted with root mass fraction (RMF), with low-RMF species establishing better with low soil moisture and higher-RMF species better on wetter soils. Specific leaf area (SLA) interacted with light availability, as low-SLA species established better under high light conditions and high-SLA species under low light conditions. Our work illustrates how community assembly can be better described by trait-environment interactions than correlating traits or environment with performance. This knowledge can assist species selection to maximize restoration success., (© 2020 by the Ecological Society of America.)

There is strong evidence for a positive relationship between biodiversity and ecosystem functioning at local spatial scales. However, how different aspects of biodiversity relate to multiple ecosystem functions (multifunctionality) across heterogeneous landscapes, and how the magnitude of biodiversity, dominant species, and environmental effects on functioning compare, remain poorly understood. We compared relationships between plant phylogenetic, functional, and taxonomic diversity and ecosystem multifunctionality across 29 restored grasslands. Functional diversity was positively associated with multifunctionality, more strongly than other diversity measures; however, landscape composition explained nearly four times more variation in multifunctionality than did functional diversity, with plots within human-modified landscapes supporting lower multifunctionality. Individual functions were typically more strongly correlated with environmental variables than with diversity. We also found that abundance of the dominant species, Andropogon gerardii, was positively correlated with multifunctionality. Plant diversity, dominant species, and underlying environmental conditions underpin ecosystem multifunctionality in grasslands, but how biodiversity is measured matters for the strength and direction of biodiversity-ecosystem function relationships. Finally, in natural systems environmental variation unrelated to local biodiversity is important for determining ecosystem functioning., (© 2019 by the Ecological Society of America.)