Harmony on the prairie? Grassland plant and animal community responses to variation in climate across land‐use gradients

Abstract

Human induced climate and land-use change are severely impacting global biodiversity, but how community composition and richness of multiple taxonomic groups change in response to local drivers and whether these responses are synchronous remains unclear. We used long-term community-level data from an experimentally manipulated grassland to assess the relative influence of climate and land use as drivers of community structure of four taxonomic groups: birds, mammals, grasshoppers, and plants. We also quantified the synchrony of responses among taxonomic groups across land-use gradients and compared climatic drivers of community structure across groups. All four taxonomic groups responded strongly to land use (fire frequency and grazing), while responses to climate variability were more pronounced in grasshoppers and small mammals. Animal groups exhibited asynchronous responses across all land-use treatments, but plant and animal groups, especially birds, exhibited synchronous responses in composition. Asynchrony was attributed to taxonomic groups responding to different components of climate variability, including both current climate conditions and lagged effects from the previous year. Data-driven land management strategies are crucial for sustaining native biodiversity in grassland systems, but asynchronous responses of taxonomic groups to climate variability across land-use gradients highlight a need to incorporate response heterogeneity into management planning.

Consumer roles of small mammals within fragmented native tallgrass prairie

“…As stated, it is possible that increased woody encroachment may generate a positive feedback through small mammal resource consumption that influences the relative interactions of these mammals with native prairies vs. woody habitats. Our data indicate that seasonal and inter‐annual changes in weather impact isotopic niche, including position and size of isotopic ellipses, respectively, of small mammals across all habitats, as has been shown statistically through alternative multivariate community analyses (Bruckerhoff et al 2020). Frequent wildfire is known to temporarily reduce populations of certain grassland small mammal species.…”

“…The North American tallgrass prairie ecoregion is one such area, where remaining fragments of native grassland are experiencing widespread woody encroachment, potentially attributable to extirpation of native mega‐herbivores, cessation of natural fire regimes, and various other yet unresolved factors (e.g., increasing atmospheric CO 2 , Bond and Midgley 2000, Collins and Calabrese 2012). Maintenance of existing grasslands and restoration of historic prairie habitats will depend in part on a greater understanding of linkages between major ecological drivers and the constituent roles and responses of species comprising local communities (Collins 2000, Bruckerhoff et al 2020). Here, we investigate the trophic niche dynamics of small mammal assemblages to assess the bottom‐up responses of small mammals to other major drivers (climate variables and fire) through time (e.g., Báez et al 2006) and to infer their potential roles as consumers (top‐down), within an experimental prairie‐woodland mosaic.…”

Salty, mild, and low plant biomass grasslands increase top‐heaviness of invertebrate trophic pyramids

“…While community structure is often described using a single trophic level (e.g. Srivastava et al., 2009), trophic levels may not track environmental gradients in parallel, suggesting multi‐trophic studies will better capture system dynamics (Bruckerhoff et al., 2020; Soliveres et al., 2016).…”

Sampling frequency, duration and the Southern Oscillation influence the ability of long‐term studies to detect sudden change

“…We had expected inconsistencies in detection ability (Hypothesis 1) to be driven by the different types of temporal patterns the selected species displayed (from low variability with no seasonality or predictable seasonality to highly variable seasonally, from no multi‐year cycles to long cycles). However, distinct differences in detection ability could be observed for the same species between sites, possibly due to differential responses in population dynamics and growth rates to different aspects of SOI or lags (Bruckerhoff et al, 2020; Hewitt & Thrush, 2009; Spurgeon et al, 2020). At AA, small proportional reductions could be detected for species exhibiting both seasonality and multi‐year cycles, while at CB, small proportional reductions could be detected for species with no or unpredictable seasonality.…”