Data from: Effects of spatial plant-soil feedback heterogeneity on plant performance in monocultures

1. Plant-soil feedback (PSF) effects have almost exclusively been quantified on homogeneous soils, but as different plant species will influence their local soil differently in reality PSF effects will be spatially heterogeneous. Whether plant performance in soils with spatially heterogeneous PSF can be predicted from pot experiments with homogeneous soils is unclear. 2. In a greenhouse experiment we tested the response of monocultures of six grassland species (two grasses, two legumes, and two forbs) to three spatially explicit treatments (fine-grain heterogeneity, coarse-grain heterogeneity, and homogeneous). Sixteen patches of conditioned soil (~6x6 cm) were placed within each container. For homogeneous treatments all patches contained the same conditioned soil within a container. The fine-grained heterogeneous treatment contained four differently conditioned soils that were applied following a Latin square design, while for the coarse-grained heterogeneous treatment four contiguous square blocks of four cells each were created in each container. 3. In general species grew worse on soil conditioned by conspecifics. However, when the biomass production on all homogeneous soil treatments (own and foreign soils) was averaged and compared to the heterogeneous treatments, we found that biomass production was lower than expected in the heterogeneous soils. This effect of heterogeneity depended on both the conditioning and test species, but most heterogeneity effects were negative. The grain of the heterogeneity (coarse vs. fine: at the chosen spatial scale) did not affect plant performance. 4. We hypothesize that a more diverse soil community is present in spatially heterogeneous soils. This increases i) the chance of plants to encounter its antagonists, which may then rapidly increase in numbers; and ii) the scope for synergistic co-infections. Together this may lead to non-additive responses of plants to spatial heterogeneity in PSF. 5. Synthesis. Plant performance was lower in spatially heterogeneous soils than predicted by spatially homogeneous soils. In natural grasslands that have mixed plant communities conditioning the soil plant-soil feedback (PSF) effects on plant performance may therefore be more negative than what is predicted from pot experiments. Our results emphasise the need to incorporate the spatial dynamics of PSF both in empirical and modelling studies if we are to understand the role of PSF in plant-plant interactions and plant community dynamics.

1. 植物-土壤反馈（Plant-soil feedback, PSF）效应的量化研究几乎均以均质土壤为对象，但现实中不同植物物种对其周边土壤的调控作用存在显著差异，因此PSF效应在空间上具有异质性。目前尚不清楚，能否通过均质土壤的盆栽实验，预测空间异质性PSF土壤中的植物生长表现。
2. 本研究通过温室实验，探究6种草地植物（2种禾草、2种豆科植物及2种非禾本草本植物）的单作种群对3种空间显式处理的响应：细粒度异质性、粗粒度异质性与均质处理。每个培养容器内设置16块经植物预处理的土壤斑块（约6×6 cm）。在均质处理组中，同一容器内的所有土壤斑块均使用同一种经预处理的土壤。细粒度异质性处理组采用拉丁方设计，配置4种不同的预处理土壤；粗粒度异质性处理组则在每个容器内划分出4个相邻的方形区块，每个区块包含4个土壤单元。
3. 总体而言，植物在同种植物预处理的土壤中生长状况更差。然而，当将所有均质处理组（同种及异种预处理土壤）的生物量产量取平均值，并与异质性处理组对比时，研究发现异质性土壤中的植物生物量产量低于预期值。这种异质性效应同时取决于预处理土壤的来源植物与受试植物，但多数异质性效应均为负向。在本研究选定的空间尺度下，异质性粒度（粗粒度vs.细粒度）并未对植物生长表现产生显著影响。
4. 我们提出如下假说：空间异质性土壤中存在更为多样的土壤群落。这将提升两方面的效应：其一，植物接触到自身拮抗生物的概率增加，这类拮抗生物的种群数量可快速增殖；其二，协同复合侵染的发生范围得以拓展。二者共同作用，可能导致植物对PSF空间异质性的响应呈现非加性特征。
5. 研究总结：空间异质性土壤中的植物生长表现低于均质土壤实验的预测结果。在自然草地中，混合植物群落会共同调控土壤环境，因此PSF对植物生长表现的效应可能比盆栽实验的预测结果更为负面。本研究结果强调：若要阐明PSF在植物间相互作用及植物群落动态中的作用，需在实证研究与模型研究中纳入PSF的空间动态特征。