The effect of land-use related diversity on plant-soil feedbacks and plant-community coexistence

我们之前利用生物多样性实验所土壤群落进行的温室实验结果表明，土壤-生物群效应沿土地利用强度梯度通过影响草地群落中植物-物种优势度来促进物种共存。在我们的实验中，与土地利用相关的土壤生物群效应在草地上的差异尤其明显，这表明土地利用对草地植物群落组成和共存具有生物遗留效应。然而，当比较温室和田间条件下的植物-土壤反馈（PSF）时，我们在最近的一系列实验中发现了PSF效应之间的一致差异。在野外，我们观察到植物多样性对生物反馈的总体积极影响。这强调了考虑与土地利用有关的多样性效应的重要性，因为植物多样性可能会对自然植被产生间接和非传递的竞争效应。生物多样性探索项目先前的研究结果清楚地表明，土地利用强度影响了不同营养水平（植物、草食动物和病原体）的多样性。因此，我们希望利用生物多样性探索的框架来明确测试(1)土地利用和与土地利用相关的生物多样性对物种特异性psf的直接影响。(2)通过建立不同土地利用强度下植物竞争与土壤多样性联合试验，在全因子设计中明确排除地上和地下食草动物，我们将提供与土地利用相关的土壤微生物群落多样性以及地上和地下食草动物对psf强度和方向的影响以及它们对植物物种性能和植物群落多样性的影响的额外机制解决方案。在我们的实验方法中，我们将计划(3)调查自然田间条件下施肥或土壤压实等非生物因素对psf的个别影响。由于土地利用强度影响植物多样性，由于植物多样性在之前的田间试验中对植物生长产生了正反馈效应，由于植物生长影响非生物和生物土壤性质，我们将通过一系列温室实验(4)，通过实验测试75个MIPs（3个区域，25个MIPs）的生物土壤遗产和PSF效应，筛选大量常见植物物种，研究与土地利用相关的土壤生物群对土地利用梯度植物丰度的影响和重要性。这些数据将提供与土地利用有关的土壤生物群对植物物种丰度和群落组成的贡献的重要信息，并将为其他土壤生物群和植物相关类群（例如，为进一步研究的物种选择）提供大量信息。通过我们的实验，我们希望对植物物种共存机制的研究做出实质性的贡献。

Results from our previous greenhouse experiments using soil communities from the Biodiversity Exploratories indicate that soil-biota effects along a land-use intensity gradient contribute to species coexistence by influencing plant-species dominance in grassland communities. Land-use related soil-biota effects in our experiments differed especially between grasses and herbs, suggesting a biotic legacy effect of land use on plant-community composition and coexistence in grasslands. However, when comparing plant-soil feedbacks (PSFs) under greenhouse and field conditions, we detected in a recent series of experiments consistent differences between PSF effects. In the field, we observed a generally positive effect of plant diversity on biotic feedbacks. This underlines the importance to consider land-use related diversity effects as plant diversity might drive indirect and intransitive competitive effects in natural vegetation. Previous results from the Biodiversity Exploratories clearly show that land-use intensity affects the diversity across trophic levels (plants, herbivores, pathogens). Therefore, we would like to use the framework of the Biodiversity Exploratories to explicitly test (1) the impact of land-use and land-use related biodiversity on species specific PSFs directly in the field. (2) By setting up a combined plant competition and soil diversity experiment at the different land-use intensities and by explicitly excluding above-and belowground herbivores in a fully factorial design, we will provide additional mechanistic resolution regarding the impact of land-use-related diversity of soil microbial communities as well as of above and belowground herbivores on the strength and direction of PSFs and their consequences for plant-species performance and thus plant-community diversity. Within our experimental approach, we will plan (3) to investigate the individual effects of abiotic factors such as fertilization or soil compactions on PSFs under natural field conditions.As land-use intensity affects the diversity of plants, as the diversity of plants resulted in positive feedback effects on plant growth in a previous field experiment, and as plant growth affects abiotic and biotic soil properties, we will investigate in a series of greenhouse experiments (4) the effect and importance of land-use related soil biota on plant abundance along the land-use gradient by experimentally testing biotic soil legacy and PSF effects of 75 MIPs (3 regions à 25 MIPs) in grasslands screening a large set of common plant species. These data will yield important information on the contribution of land-use related soil biota on plant species abundance and community composition, and will be provide substantial information for other soil biota and plant related groups (e.g., for species selection for further studies). With our experiments we hopefully substantially contribute to the study of mechanisms enabling plant-species coexistence.