Data from: Plant–soil feedbacks promote negative frequency dependence in the coexistence of two aridland grasses

Understanding the mechanisms of species coexistence is key to predicting patterns of species diversity. Historically, the ecological paradigm has been that species coexist by partitioning resources: as a species increases in abundance, self-limitation kicks in, because species-specific resources decline. However, determining coexistence mechanisms has been a particular puzzle for sedentary organisms with high overlap in their resource requirements, such as plants. Recent evidence suggests that plant-associated microbes could generate the stabilizing self-limitation (negative frequency dependence) that is required for species coexistence. Here, we test the key assumption that plant–microbe feedbacks cause such self-limitation. We used competition experiments and modelling to evaluate how two common groups of soil microbes (rhizospheric microbes and biological soil crusts) influenced the self-limitation of two competing desert grass species. Negative feedbacks between the dominant plant competitor and its rhizospheric microbes magnified self-limitation, whereas beneficial interactions between both plant species and biological soil crusts partly counteracted this stabilizing effect. Plant–microbe interactions have received relatively little attention as drivers of vegetation dynamics in dry land ecosystems. Our results suggest that microbial mechanisms can contribute to patterns of plant coexistence in arid grasslands.

阐明物种共存机制，是预测物种多样性格局的核心所在。长期以来，生态学主流范式认为，物种通过资源划分实现共存：当某一物种的多度攀升时，其自身会触发自我限制效应，因该物种专属的资源会随之耗竭。然而，对于资源需求高度重叠的固着生物（如植物）而言，明确其共存机制一直是学界的一大难题。近期研究证据表明，植物共生微生物可产生物种共存所需的稳定化自我限制（负频率依赖，negative frequency dependence）。本研究针对“植物-微生物反馈可引发此类自我限制”这一核心假设开展验证。我们通过竞争实验与模型模拟，评估了两类常见土壤微生物——根际微生物与生物土壤结皮——对两种竞争荒漠草本自我限制的影响。优势竞争植物与其根际微生物间的负反馈放大了自我限制效应，而两种植物与生物土壤结皮间的互利互作则部分抵消了这一稳定化作用。长期以来，植物-微生物互作作为旱地生态系统植被动态的驱动因子，未受到足够关注。本研究结果表明，微生物介导的机制可助力干旱草原的植物共存格局形成。