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）效应的量化几乎全部基于均质土壤开展，但现实中不同植物物种对其局域土壤的影响存在差异，因此PSF效应本应具有空间异质性。目前尚不清楚，在具有空间异质性PSF的土壤中，植物的生长表现能否通过均质土壤盆栽实验进行预测。
2. 本研究通过温室实验，测试了6种草地物种（2种草本、2种豆科植物及2种非禾本草本植物）的单种栽培植株对3种空间显式处理的响应：细粒度异质性处理、粗粒度异质性处理与均质处理。每个栽培容器内设置16个驯化土壤斑块（约6×6厘米）。对于均质处理组，容器内所有斑块均使用同一种驯化土壤。细粒度异质性处理组采用4种不同的驯化土壤，按照拉丁方设计排布；而粗粒度异质性处理组则在每个容器内设置4个连续方形区块，每个区块包含4个土壤斑块。
3. 总体而言，植物在经同种植物驯化的土壤中生长状况更差。然而，将所有均质处理组（同种与异种驯化土壤）的生物量产出平均值与异质性处理组进行比较后发现，异质性土壤中的生物量产出低于预期值。该异质性效应同时受驯化物种与受试物种的影响，但多数异质性效应均为负向。异质性粒度（即本次研究选定空间尺度下的粗粒度与细粒度）并未对植物生长表现产生影响。
4. 我们提出假说：空间异质性土壤中存在更为多样的土壤群落，这将带来两方面影响：i) 植物接触到自身拮抗生物的概率提升，进而使拮抗生物种群数量快速增长；ii) 协同复合侵染的发生范围扩大。上述两方面共同作用，可能导致植物对PSF空间异质性产生非加和响应。
5. 综合讨论：空间异质性土壤中的植物生长表现低于均质土壤盆栽实验的预测结果。在以混合植物群落进行土壤驯化的天然草地中，PSF对植物生长表现的效应可能比盆栽实验的预测结果更负向。本研究结果强调：若要阐明PSF在植物间相互作用与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。