Soil heterogeneity increases plant diversity after 20 years of manipulation during grassland restoration
Soil heterogeneity increases plant diversity after 20 years of manipulation during grassland restoration
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DOI：
10.1002/eap.2014
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发表时间：
2019-11-04
影响因子：
5
通讯作者：
Collins, Scott L.
中科院分区：
文献类型：
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作者：
Baer, Sara G.;Adams, Tianjiao;Collins, Scott L.
“环境异质性假说”预测，资源的可变性促进物种共存，但很少有实验在植物群落中支持这一假说。此前在草原恢复实验中对这一假设进行了15年的测试，结果表明，人为操纵的土壤资源异质性对植物多样性的影响很小。这一反应归因于恢复后补充繁殖枝增加后丰富度的短暂增加，在营养丰富的情况下偶尔增加了多样性，以及在一组土壤处理中优势物种的盖度减少。在这里，我们报告了在同一实验中，对应于16-20年恢复的连续繁殖增加下的群落动态，以响应土壤资源的可用性和异质性的改变。我们还量化了新增加的物种的特征，以确定异质性是否增加了可供新物种利用的生态位的数量和种类。异质处理包含改变养分有效性和土壤深度的因素组合；对照小区没有任何处理。在这项为期5年的研究中，异质处理的总多样性和丰富度较高，这是因为先前建立的杂交种的盖度、多样性和丰富度较高，特别是在富N亚区。所有添加到实验中的新物种都表现出独特的特征空间，但没有证据表明，与对照处理相比，异质地块包含更多种类的新物种，代表更广泛的特征空间。富氮土壤中新物种的丰富度和盖度较高，但响应幅度较小。长期施氮量下群落聚集在接受施氮量不同的样地中以不同物种占优势，导致群落在异质性样地中的分散度高于对照样地。与期望异质性增加多样性的确定性机制相反(新物种可利用的资源的更大变异性)，异质样地中更高的多样性是由于以前以草为主的群落在N丰富的亚样地中的不稳定造成的。虽然我们不主张在大范围内增加土壤有效氮，但我们得出结论，环境异质性对多样性的积极影响可能需要数十年的时间才能实现，并依赖于具有较强建立限制的群落中随机过程的发展。
The "environmental heterogeneity hypothesis" predicts that variability in resources promotes species coexistence, but few experiments support this hypothesis in plant communities. A previous 15-yr test of this hypothesis in a prairie restoration experiment demonstrated a weak effect of manipulated soil resource heterogeneity on plant diversity. This response was attributed to a transient increase in richness following a post-restoration supplemental propagule addition, occasionally higher diversity under nutrient enrichment, and reduced cover of a dominant species in a subset of soil treatments. Here, we report community dynamics under continuous propagule addition in the same experiment, corresponding to 16-20 yr of restoration, in response to altered availability and heterogeneity of soil resources. We also quantified traits of newly added species to determine if heterogeneity increases the amount and variety of niches available for new species to exploit. The heterogeneous treatment contained a factorial combination of altered nutrient availability and soil depth; control plots had no manipulations. Total diversity and richness were higher in the heterogeneous treatment during this 5-yr study due to higher cover, diversity, and richness of previously established forbs, particularly in the N-enriched subplots. All new species added to the experiment exhibited unique trait spaces, but there was no evidence that heterogeneous plots contained a greater variety of new species representing a wider range of trait spaces relative to the control treatment. The richness and cover of new species was higher in N-enriched soil, but the magnitude of this response was small. Communities assembling under long-term N addition were dominated by different species among subplots receiving added N, leading to greater dispersion of communities among the heterogeneous relative to control plots. Contrary to the deterministic mechanism by which heterogeneity was expected to increase diversity (greater variability in resources for new species to exploit), higher diversity in the heterogeneous plots resulted from destabilization of formerly grass-dominated communities in N-enriched subplots. While we do not advocate increasing available soil N at large scales, we conclude that the positive effect of environmental heterogeneity on diversity can take decades to materialize and depend on development of stochastic processes in communities with strong establishment limitation.