Data from: Biomass responses to elevated CO2, soil heterogeneity and diversity: an experimental assessment with grassland assemblages

While it is well-established that the spatial distribution of soil nutrients (soil heterogeneity) influences the competitive ability and survival of individual plants, as well as the productivity of plant communities, there is a paucity of data on how soil heterogeneity and global change drivers interact to affect plant performance and ecosystem functioning. To evaluate the effects of elevated CO2, soil heterogeneity and diversity (species richness and composition) on productivity, patterns of biomass allocation and root foraging precision, we conducted an experiment with grassland assemblages formed by monocultures, two- and three-species mixtures of Lolium perenne, Plantago lanceolata and Holcus lanatus. The experiment lasted for 90 days, and was conducted on microcosms built out of PVC pipe (length 38 cm, internal diameter 10 cm). When nutrients were heterogeneously supplied (in discrete patches), assemblages exhibited precise root foraging patterns, and had higher total, above- and belowground biomass. Greater aboveground biomass was observed under elevated CO2. Species composition affected the below:aboveground biomass ratio and interacted with nutrient heterogeneity to determine belowground and total biomass. Species richness had no significant effects, and did not interact with either CO2 or nutrient heterogeneity. Under elevated CO2 conditions, the two- and three-species mixtures showed a clear trend towards underyielding. Our results show that differences among composition levels were dependent on soil heterogeneity, highlighting its potential role in modulating diversity–productivity relationships.尽管已有大量研究证实，土壤养分的空间分布（即土壤异质性，soil heterogeneity）会影响单个植物的竞争能力与存活能力，同时也会影响植物群落的生产力，但目前关于土壤异质性与全球变化驱动因子如何交互作用，进而影响植物表现与生态系统功能的相关数据仍较为匮乏。为评估高浓度CO2（elevated CO2）、土壤异质性以及植物多样性（物种丰富度与物种组成）对生产力、生物量分配模式及根系觅食精度的影响，本研究构建了由单栽培群落、2物种混播群落及3物种混播群落组成的草地实验组合，所选物种包括多年生黑麦草（Lolium perenne）、长叶车前（Plantago lanceolata）与绒毛草（Holcus lanatus）。本实验为期90天，实验载体为聚氯乙烯（PVC）管材构建的微宇宙培养体系（microcosms），管材规格为长38 cm、内径10 cm。当养分以异质性方式供给（即分布于离散斑块中）时，实验群落展现出精准的根系觅食模式，且总生物量、地上生物量与地下生物量均显著更高。在高浓度CO2条件下，实验群落的地上生物量显著更高。物种组成会影响地下/地上生物量比，且与土壤异质性产生交互作用，共同决定地下生物量与总生物量。物种丰富度未对上述指标产生显著影响，也未与CO2浓度或土壤异质性产生交互作用。在高浓度CO2条件下，2物种和3物种的混播群落均表现出明显的产量低于预期的趋势。本研究结果表明，不同物种组成水平间的差异依赖于土壤异质性，这凸显了土壤异质性在调控多样性-生产力关系中的潜在作用。