Predicting effects of interannual variability in climate and drought on plant community outcomes, resilience, and soil carbon using temporally replicated grassland reconstructions

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Grasslands provide services that benefit society and there is growing interest in restoring native grasslands to enhance ecosystem services in targeted areas, such as marginal agricultural land. A goal of restoring agricultural land to grassland is to promote the recovery of diverse native plant communities that can withstand and bounce back from periodic stress, and that improve the health of soil degraded from cultivation. However, the composition of plant communities that develop and rate at which soil recovers in restored grasslands is highly variable and difficult to predict. Forecasting plant community outcomes and soil recovery is further complicated by an increasingly variable climate, especially in the southern Great Plains. This research uses a series of grassland restorations established in an agricultural field every other year for twelve years, encompassing a wide range of climate conditions, to understand of the role of climate variability on plant community composition, the resilience of restored communities to drought, and the rate at which carbon accumulates in the soil. This long-term study provides new insights into the role of climate in achieving conservation goals and reduces uncertainty about the capacity for restored grasslands to sequester carbon in soil. The similarly reconstructed grasslands provide a novel framework to test the hypotheses that stochastic variation in climate has deterministic consequences for restored community states, resilience develops as communities age and interact with community state, and climate-driven differences in plant composition contribute to variation in soil carbon accrual. Previously collected and continued measurements of plant species composition are used to model the effect of planting-year climate on restored community trajectories of change. Climate-influenced community states in these grasslands vary uniquely and widely in the ratio of C4-grasses and C3-forbs. The grasses and forbs produce organic matter that varies in both substrate quality and stable carbon isotopic signatures that are measured to determine whether soil carbon accrual is influenced more by recalcitrant or high-quality inputs, respectively. The occurrence of multiple droughts over the course of establishing this long-term experiment provides a rare opportunity to evaluate whether resilience varies predictably with restoration age and whether it interacts with climate-influenced community state. Ultimately, this research helps to transition long-term studies in community ecology toward prediction, advance understanding of factors influencing resilience in ecosystems, and help resolve competing hypotheses regarding plant-based controls on soil carbon accrual.This project is jointly funded by Ecosystem Science and the Established Program to Stimulate Competitive Research (EPSCoR).This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.