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

草原提供造福社会的服务，人们越来越有兴趣恢复本土草原，以加强目标地区的生态系统服务，如边缘农地。退耕还草的一个目标是促进能够承受周期性压力并从周期性压力中反弹的各种本土植物群落的恢复，并改善因耕作而退化的土壤的健康状况。然而，在恢复的草原上，植物群落的组成和土壤恢复的速度是高度可变的，很难预测。由于气候变化越来越大，特别是在大平原南部，预测植物群落结果和土壤恢复变得更加复杂。这项研究使用了12年来每隔一年在农业领域建立的一系列草地恢复，涵盖了广泛的气候条件，以了解气候变化对植物群落组成的作用，恢复群落对干旱的恢复能力，以及碳在土壤中积累的速度。这项长期研究为气候在实现保护目标中的作用提供了新的见解，并减少了关于恢复的草原在土壤中固定碳的能力的不确定性。类似的重建草地提供了一个新的框架来检验这样的假设，即气候的随机变化对恢复的群落状态具有确定性的结果，恢复能力随着群落年龄的增长而发展并与群落状态相互作用，气候驱动的植物组成的差异导致土壤碳积累的变化。以前收集的和持续测量的植物物种组成被用来模拟种植年气候对恢复的群落变化轨迹的影响。这些草地受气候影响的群落状态在C4-草和C3-杂草的比例上有独特而广泛的差异。牧草和杂草产生的有机质在底物质量和稳定的碳同位素特征上都不同，通过测量这些特征来确定土壤碳积累分别受到顽固性投入和高质量投入的影响更大。在建立这项长期实验的过程中发生了多次干旱，这为评估恢复力是否可预测地随恢复年龄变化以及是否与受气候影响的社区状态相互作用提供了难得的机会。最终，这项研究有助于将群落生态学的长期研究转变为预测，促进对生态系统中影响弹性的因素的理解，并帮助解决关于基于植物的土壤碳积累控制的相互矛盾的假设。该项目由生态系统科学和既定的刺激竞争研究计划(EPSCoR)共同资助。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.