Soil Communities Promote Temporal Stability and Species Asynchrony in Experimental Grassland Communities

BackgroundOver the past two decades many studies have demonstrated that plant species diversity promotes primary productivity and stability in grassland ecosystems. Additionally, soil community characteristics have also been shown to influence the productivity and composition of plant communities, yet little is known about whether soil communities also play a role in stabilizing the productivity of an ecosystem.Methodology/Principal FindingsHere we use microcosms to assess the effects of the presence of soil communities on plant community dynamics and stability over a one-year time span. Microcosms were filled with sterilized soil and inoculated with either unaltered field soil or field soil sterilized to eliminate the naturally occurring soil biota. Eliminating the naturally occurring soil biota not only resulted in lower plant productivity, and reduced plant species diversity, and evenness, but also destabilized the net aboveground productivity of the plant communities over time, which was largely driven by changes in abundance of the dominant grass Lolium perenne. In contrast, the grass and legumes contributed more to net aboveground productivity of the plant communities in microcosms where soil biota had been inoculated. Additionally, the forbs exhibited compensatory dynamics with grasses and legumes, thus lowering temporal variation in productivity in microcosms that received the unaltered soil inocula. Overall, asynchrony among plant species was higher in microcosms where an unaltered soil community had been inoculated, which lead to higher temporal stability in community productivity.Conclusions/SignificanceOur results suggest that soil communities increase plant species asynchrony and stabilize plant community productivity by equalizing the performance among competing plant species through potential antagonistic and facilitative effects on individual plant species.

背景 近二十年来，诸多研究已证实植物物种多样性可提升草地生态系统的初级生产力与群落稳定性。此外，尽管已有研究表明土壤群落特征能够影响植物群落的生产力与组成，但学界目前对土壤群落是否同样有助于维持生态系统的生产力稳定性仍知之甚少。
方法与主要结果 本研究通过微宇宙（microcosms）实验，在为期一年的时间跨度内探究土壤群落存在与否对植物群落动态与稳定性的影响。实验微宇宙装填灭菌土壤，并分别接种未经灭菌处理的原生野外土壤，或经灭菌以去除本土土壤生物群的野外土壤。
研究结果表明，去除本土土壤生物群不仅会降低植物生产力、降低植物物种多样性与均匀度，还会随时间推移削弱植物群落地上净生产力（net aboveground productivity）的稳定性，该效应主要由优势草种多年生黑麦草（Lolium perenne）的丰度变化所驱动。与之相对，在接种了含土壤生物群的野外土壤的微宇宙中，禾本科与豆科植物对群落地上净生产力的贡献占比更高。此外，在接种未经灭菌处理土壤接种物的微宇宙中，杂类草（forbs）与禾本科、豆科植物呈现补偿性动态变化，进而降低了生产力的时间变异幅度。总体而言，接种未经灭菌处理土壤群落的微宇宙中，植物物种间的异步性更高，这使得群落生产力的时间稳定性更强。
结论与意义 本研究结果表明，土壤群落可通过对单个植物物种产生潜在的拮抗与促进作用，平衡竞争植物物种间的生长表现，从而提升植物物种间的异步性，稳定植物群落的生产力。