Data from: Biodiversity-ecosystem function relationships change through primary succession

Ecologists traditionally use environmental parameters to predict successional shifts in compositional characteristics of local species assemblages (environmental control). Another important focus in ecology is to understand functional roles of species assemblages in determining local environmental properties (diversity control). Then, the question emerges: which is the cause, and which is the consequence? To clarify the causal relationships between species assemblages and environmental properties, we focused on seral changes in species/functional diversity of vascular plants in tundra ecosystems of the High Arctic. We found that, although species richness was influenced by soil properties in the earlier stages of primary succession, the causalities were reversed in the later stages. We also found functional differentiation among coexisting species in the later stage, suggesting that the ‘complementarity effect’ of diversity on ecosystem functions likely increased with ecosystem development through time. By contrast, particular species had little disproportional influence on soil properties, suggesting that the ‘selection effect’ as an alternative mechanism was less important. This result was likely attributed to the importance of facilitation in the marginal High Arctic environment. Plant–microsite associations are shaped by feedback mechanisms and therefore, neither plant nor microsite is a single absolute predictor of the other. Although our observational study has limitations, we demonstrates a possibility that the relative magnitude of the influence of one on the other can change in the process of succession, emphasizing that the causalities underlying biodiversity–ecosystem function relationships change through succession.

生态学家传统上会借助环境参数，预测当地物种组合（species assemblages）的组成特征随演替过程的变化，该研究范式被称为环境调控（environmental control）。生态学领域另一重要研究方向，是解析物种组合在调控当地环境属性中发挥的功能角色，该范式被称为多样性调控（diversity control）。由此引出一个核心问题：二者何为因，何为果？为厘清物种组合与环境属性间的因果关系，本研究聚焦高北极地区苔原生态系统中维管植物的物种/功能多样性演替变化。研究发现：尽管原生演替早期阶段的物种丰富度受土壤属性调控，但在演替后期，二者的因果关系发生了逆转。本研究同时发现，演替后期的共存物种间存在功能分化，这表明多样性对生态系统功能的‘互补效应’大概率随生态系统的长期发育而增强。与之相对，特定物种对土壤属性几乎未表现出显著的非均衡影响，这意味着作为另一作用机制的‘选择效应’重要性相对较低。这一结果大概率归因于高北极边缘生境中物种促进作用（facilitation）的核心地位。植物-微生境关联由反馈机制塑造，因此二者均无法单独作为另一方的绝对预测因子。尽管本观测研究存在一定局限性，但我们的研究揭示了一种可能性：二者间的相对影响强度可随演替过程发生动态变化，这也强调了生物多样性-生态系统功能关系背后的因果机制会随演替进程发生改变。