Resource fluctuations and niche separation in plant communities: Can land-use effects on soil moisture explain observed patterns in plant diversity?

Silvertown等（1999年《自然》）假设草地系统中的植物多样性分别与植物物种对干旱和水饱和土壤的耐受性有关。他们认为耐旱的物种对积水的土壤特别敏感，反之亦然，这就产生了一种干旱-积水-权衡，解释了植物多样性。这一水文生态假设本身没有经过独立或实验的检验。在这里，我们建议使用生物多样性勘探站收集的独特数据来测试水文生态假设。此外，我们建议调查土地利用和土壤类型对水文条件的影响，并测试水文效应的替代解释（特别是与土壤化学有关）。此外，我们建议进行两个操作实验中围隔测试波动的土壤水分和植物多样性之间的因果关系，并解开养分供应和土壤水分的贡献。最后，我们提出了一个试点研究转移到森林林下植被的水文生态假说。在这里，适应阴影可能权衡对生理耐受性的亮点，因此森林地面植物多样性可以类似地解释为不同的适应波动的资源条件。

Plant diversity in grassland systems has been hypothesised Silvertown et al. (1999 Nature) to be related to the plant species' tolerance to drought and water saturated soil, respectively. They argue that drought-tolerant species are particularly sensitive to water-logged soils and vice versa, yielding a drought-water logging-trade off that explains plant diversity. This hydro-ecological hypothesis has as such not been tested independently or experimentally. Here, we propose to use the unique data collected within the Biodiversity Exploratories to test the hydro-ecological hypothesis. Furthermore, we propose to investigate the effect of land use and soil type on hydrological conditions and to test alternative explanations for the hydrological effect (particularly related to soil chemistry). Also, we propose to carry out two manipulative experiments in mesocosms to test the causal link between fluctuating soil moisture and plant diversity, and to disentangle the contribution of nutrient availability and soil moisture. Finally, we propose a pilot study to transfer the hydro-ecological hypothesis to the forest understorey. Here adaptation to shade may trade-off against physiological tolerance of light spots and thus forest floor plant diversity may be similarly explained by differential adaptation to fluctuating resource conditions.