Data from: Additive effects of nurse and facilitated plants on ecosystem functions

1. Nurse plants drive the assembly of facilitated communities and commonly promote plant-soil feedbacks, and are thus recognized as key engineers in abiotically stressful ecosystems. The literature neglects however, the role of the communities which benefit from the presence of the nurse as contributors to soil ecosystem functions. We hypothesized that the nurse and its beneficiaries synergistically enhance essential ecosystem functions mediated by soil microbiota. 2. To track how plant-plant facilitation impacts plant-soil feedbacks, we selected three nurse species in semi-arid mine tailings and defined three microsites (open space, nurse canopy, nurse + facilitated canopy). In each microsite, we quantified 18 abiotic and biotic variables associated with four functions: reduction of climatic stress, reduction of edaphic stress, soil fertility and soil microbial productivity (decomposition and nutrient cycling). 3. Litter biomass increased from open spaces to the microsite beneath the nurses, and further beneath the nurses and their beneficiaries. Litter biomass was a good predictor of both the reduction in climatic stress and increase in edaphic stress (likely owing to metal bioaccumulation). We attributed increments in soil organics and heterotrophic respiration beneath the nurses and their beneficiaries, compared to nurses alone, to biomass effects through increased litter deposition. Variation in fertility and microbial productivity among microsites shaped by the nurses and their facilitated communities was attributed to both diversity and biomass effects. In particular, fertility was promoted beneath phenotypically diverse facilitated communities, as inferred from ten above- and belowground traits. However, microbial productivity increased at low levels of root biomass likely due to reduced plant-microbe competition for nutrients. 4. Synthesis. Our results show that facilitated plant communities sheltered by nurse species relieve local abiotic stress and promote plant-microbe interactions, both through biomass and biodiversity effects. These observations shift the conception of facilitated species from simple beneficiaries of the nurse’s effects, to co-drivers of essential ecosystem functions.1. 保育植物（nurse plants）主导促生群落（facilitated communities）的组装过程，且通常可促进植物-土壤反馈（plant-soil feedbacks），因此被认为是非生物胁迫生态系统（abiotically stressful ecosystems）中的关键生态系统工程师。然而现有研究往往忽视了受益于保育植物的群落对土壤生态系统功能的贡献。本研究提出假说：保育植物与其受益物种可通过协同作用，增强由土壤微生物群（soil microbiota）介导的核心生态系统功能。 2. 为探究植物间促进作用对植物-土壤反馈的影响机制，本研究在半干旱矿山尾矿（semi-arid mine tailings）生境中选取3种保育植物物种，并设置3类微生境（microsites）：裸露空间、保育植物冠幅下区域、保育植物+促生植物冠幅下区域。针对每类微生境，本研究量化了与4项生态系统功能相关的18项非生物与生物变量：气候胁迫缓解、土壤胁迫（edaphic stress）缓解、土壤肥力以及土壤微生物生产力（soil microbial productivity，包括分解与养分循环）。 3. 枯落物生物量（litter biomass）从裸露空间到保育植物冠幅下区域逐渐升高，在保育植物与其促生植物共同覆盖的区域进一步提升。枯落物生物量可较好预测气候胁迫的缓解程度与土壤胁迫的加剧程度（这一现象可能与金属生物富集有关）。相较于仅保育植物覆盖的区域，保育植物与促生植物共同覆盖区域的土壤有机质含量与异养呼吸（heterotrophic respiration）水平的提升，可归因于枯落物输入量增加带来的生物量效应。由保育植物及其促生群落塑造的不同微生境间，土壤肥力与微生物生产力的差异，同时受到多样性效应与生物量效应的影响。具体而言，通过对10项地上与地下性状（above- and belowground traits）的分析可知，表型多样的促生群落可提升土壤肥力。然而，当根系生物量处于较低水平时，土壤微生物生产力反而升高，这可能是由于植物与微生物间的养分竞争减弱所致。 4. 综合分析与结论。本研究结果表明，受保育植物庇护的促生植物群落，可通过生物量效应与生物多样性效应双重途径，缓解局地非生物胁迫并促进植物-微生物互作。本研究结论将促生物种的定位从单纯的保育植物受益方，拓展为核心生态系统功能的共同驱动者。