Native plant diversity generates microbial legacies that either promote or suppress non-natives, depending on drought history

Diverse native plant communities resist non-native plants more than species-poor communities, in part through resource competition. The role of soil biota in diversity-invasibility relationships is poorly understood, although non-native plants interact with soil biota during invasions. We tested the responses of non-native plants to soil biota generated by different native plant diversities. We applied well-watered and drought treatments in both conditioning and response phases to explore the effects of “historical” and “contemporary” environmental stresses. When generated in well-watered soils, the microbial legacies from higher native diversity inhibited non-native growth in well-watered conditions. In contrast, when generated in drought-treated soils, the microbial legacies from higher native diversity facilitated non-native growth in well-watered conditions. Contemporary drought eliminated microbial legacy effects on non-native growth. We provide a new understanding of mechanisms behind diversity-invasibility relationships and demonstrate that temporal variation in environmental stress shapes relationships among native plant diversity, soil biota and non-native plants.

相较于物种贫乏的植物群落，多样的本土植物群落对入侵外来植物的抵御能力更强，这在一定程度上源于资源竞争作用。尽管外来入侵植物在入侵过程中会与土壤生物群系（soil biota）产生相互作用，但土壤生物群系在物种多样性-可入侵性关系（diversity-invasibility relationships）中所扮演的角色仍鲜为人知。本研究针对不同本土植物多样性所培育的土壤生物群系，探究了外来入侵植物对其产生的响应。我们在土壤生物群系培育与植物响应两个阶段均设置了正常供水与干旱胁迫处理，以此探究“历史”与“当代”环境胁迫的影响效应。当土壤生物群系培育于正常供水的土壤中时，更高本土植物多样性所留下的微生物遗留效应，会在正常供水条件下抑制外来植物的生长。与之相反，当土壤生物群系培育于干旱处理的土壤中时，更高本土植物多样性所留下的微生物遗留效应，会在正常供水条件下促进外来植物的生长。当代的干旱胁迫则会消除微生物遗留效应对外来植物生长的影响。本研究为物种多样性-可入侵性关系背后的作用机制提供了全新的认知，并证实了环境胁迫的时间异质性会调控本土植物多样性、土壤生物群系与外来植物三者之间的相互关系。