An official website of the United States government
Abstract Arid ecosystems are strongly limited by water availability, and precipitation plays a major role in the dynamics of all species in arid regions, as well as the ecosystem processes that occur there. However, understanding how biotic interactions mediate long‐term responses of dryland ecosystems to rainfall remains very fragmented. We report on a unique large‐scale field experiment spanning 25 yr and three trophic levels (plants, small mammal herbivores, predators) in a dryland ecosystem in the northern Chilean Mediterranean Region where we assessed how biotic interactions influence the long‐term plant community responses to precipitation. As the most persistent ecological changes in dryland systems may result from changes in the structure, cover, and composition of the perennial vegetation, we emphasized the interplay between bottom‐up and top‐down controls of perennial plants in our analyses. Rainfall was the primary factor affecting the dynamics of, and interactions among, plants and small mammals. Ephemeral plant cover dynamics closely tracked short‐term annual rainfall, but seemed unaffected by top‐down controls (herbivory). In contrast, the response of the perennial plant cover to precipitation was mediated by (1) a complex interplay between subtle top‐down (herbivory) controls that become more apparent in the long‐term, (2) competition with ephemeral plants during wet years, and (3) an indirect effect of predators on subdominant shrubs and perennial herbs. This long‐term field experiment highlights how climate‐induced responses of arid perennial vegetation are influenced by interactions across trophic levels and temporal scales. In the face of global change, understanding how multi‐trophic controls mediate dryland vegetation responses to climate is essential to properly managing the conservation of biodiversity in arid systems.
more »
« less
What's going to be on the menu with global environmental changes?
Abstract Ongoing anthropogenic change is altering the planet at an unprecedented rate, threatening biodiversity, and ecosystem functioning. Species are responding to abiotic pressures at both individual and population levels, with changes affecting trophic interactions through consumptive pathways. Collectively, these impacts alter the goods and services that natural ecosystems will provide to society, as well as the persistence of all species. Here, we describe the physiological and behavioral responses of species to global changes on individual and population levels that result in detectable changes in diet across terrestrial and marine ecosystems. We illustrate shifts in the dynamics of food webs with implications for animal communities. Additionally, we highlight the myriad of tools available for researchers to investigate the dynamics of consumption patterns and trophic interactions, arguing that diet data are a crucial component of ecological studies on global change. We suggest that a holistic approach integrating the complexities of diet choice and trophic interactions with environmental drivers may be more robust at resolving trends in biodiversity, predicting food web responses, and potentially identifying early warning signs of diversity loss. Ultimately, despite the growing body of long‐term ecological datasets, there remains a dearth of diet ecology studies across temporal scales, a shortcoming that must be resolved to elucidate vulnerabilities to changing biophysical conditions.
more »
« less
- Award ID(s):
- 2140322
- PAR ID:
- 10442226
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Global Change Biology
- Volume:
- 29
- Issue:
- 20
- ISSN:
- 1354-1013
- Page Range / eLocation ID:
- p. 5744-5759
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract Climate change interacts with local processes to threaten biodiversity by disrupting the complex network of ecological interactions. While changes in network interactions drastically affect ecosystems, how ecological networks respond to climate change, in particular warming and nutrient supply fluctuations, is largely unknown. Here, using an equation-free modelling approach on monthly plankton community data in ten Swiss lakes, we show that the number and strength of plankton community interactions fluctuate and respond nonlinearly to water temperature and phosphorus. While lakes show system-specific responses, warming generally reduces network interactions, particularly under high phosphate levels. This network reorganization shifts trophic control of food webs, leading to consumers being controlled by resources. Small grazers and cyanobacteria emerge as sensitive indicators of changes in plankton networks. By exposing the outcomes of a complex interplay between environmental drivers, our results provide tools for studying and advancing our understanding of how climate change impacts entire ecological communities.more » « less
-
Abstract Temperature and biodiversity changes occur in concert, but their joint effects on ecological stability of natural food webs are unknown. Here, we assess these relationships in 19 planktonic food webs. We estimate stability as structural stability (using the volume contraction rate) and temporal stability (using the temporal variation of species abundances). Warmer temperatures were associated with lower structural and temporal stability, while biodiversity had no consistent effects on either stability property. While species richness was associated with lower structural stability and higher temporal stability, Simpson diversity was associated with higher temporal stability. The responses of structural stability were linked to disproportionate contributions from two trophic groups (predators and consumers), while the responses of temporal stability were linked both to synchrony of all species within the food web and distinctive contributions from three trophic groups (predators, consumers, and producers). Our results suggest that, in natural ecosystems, warmer temperatures can erode ecosystem stability, while biodiversity changes may not have consistent effects.more » « less
-
In an era where human influence pervades every corner of the natural world, improving our understanding the how ecosystems are structured and function has never been more critical. Dryland ecosystems, occupying over 40% of the plant’s land surface area, represent the largest terrestrial biome on earth. Drylands are particularly vulnerable to global change pressures such as rising temperatures, altered precipitation regimes, and the spread of invasive species. The Earth's climate is changing rapidly, exacerbating these pressures and threatening the productivity, biodiversity, and function of dryland ecosystems. The interactions between these shifting pressures and disturbances, both natural and anthropogenic, add layers of complexity that challenge our understanding of these ecosystems. In my dissertation, I used a combination of observational and experimental studies to investigate the impacts of disturbances on vegetation within dryland ecosystems, focusing particularly on the interactions between climate and biological factors known to influence the structure and function of plants. A rainfall manipulation and mechanical disturbance experiment repeated in three climatically distinct North America dryland ecosystems revealed complex, site-specific responses of dominant shrubs to environmental stressors. Findings indicated that individual traits, such as plant size, significantly influence sensitivity to climate changes, highlighting the need for localized management strategies. A study assessing the trophic impacts from a native twig girdling beetle on the above ground biomass of honey mesquite (Prosopis glandulosa) found significant year-to-year variability in beetle activity, with notable reductions in mesquite biomass due to girdling that exceeded estimates for annual net primary production for some years. A study assessing the influence of fire on biodiversity of soil seed bank across the Mojave found increased diversity in burned areas, but highlights the dominance of invasive species, ultimately leading to biodiversity loss and community homogenization. These findings underscore the significant impact of invasive species and the necessity of management practices to mitigate their spread. Collectively, this dissertation provides a nuanced understanding of how natural and novel disturbance regimes affect dryland ecosystems. The differential responses among species and ecosystems suggest that effective management strategies must consider local ecological contexts to preserve productivity and biodiversity amidst rapidly changing global pressures.more » « less
-
Understanding temporal variability across trophic levels and spatial scales in freshwater ecosystemsAbstract A tenet of ecology is that temporal variability in ecological structure and processes tends to decrease with increasing spatial scales (from locales to regions) and levels of biological organization (from populations to communities). However, patterns in temporal variability across trophic levels and the mechanisms that produce them remain poorly understood. Here we analyzed the abundance time series of spatially structured communities (i.e., metacommunities) spanning basal resources to top predators from 355 freshwater sites across three continents. Specifically, we used a hierarchical partitioning method to disentangle the propagation of temporal variability in abundance across spatial scales and trophic levels. We then used structural equation modeling to determine if the strength and direction of relationships between temporal variability, synchrony, biodiversity, and environmental and spatial settings depended on trophic level and spatial scale. We found that temporal variability in abundance decreased from producers to tertiary consumers but did so mainly at the local scale. Species population synchrony within sites increased with trophic level, whereas synchrony among communities decreased. At the local scale, temporal variability in precipitation and species diversity were associated with population variability (linear partial coefficient, β = 0.23) and population synchrony (β = −0.39) similarly across trophic levels, respectively. At the regional scale, community synchrony was not related to climatic or spatial predictors, but the strength of relationships between metacommunity variability and community synchrony decreased systematically from top predators (β = 0.73) to secondary consumers (β = 0.54), to primary consumers (β = 0.30) to producers (β = 0). Our results suggest that mobile predators may often stabilize metacommunities by buffering variability that originates at the base of food webs. This finding illustrates that the trophic structure of metacommunities, which integrates variation in organismal body size and its correlates, should be considered when investigating ecological stability in natural systems. More broadly, our work advances the notion that temporal stability is an emergent property of ecosystems that may be threatened in complex ways by biodiversity loss and habitat fragmentation.more » « less
