Ministry of Education Key Laboratory of Western China's Environmental Systems, Research School of Arid Environment and Climate Change, Lanzhou University, Lanzhou, China.
PLoS One. 2013 Nov 12;8(11):e78698. doi: 10.1371/journal.pone.0078698. eCollection 2013.
It has been demonstrated that the interplay between negative and positive interactions simultaneously shapes community structure and composition. However, few studies have attempted to examine the effect of facilitation on compositional changes in communities through time. Additionally, due to the difficulties in collecting the long-term data, it would be useful to indicate the rate of temporal turnover using a readily obtainable metric. Using an individual-based model incorporating plant strategies, we examined the role of facilitation on the temporal turnover of communities located at different positions along an environmental gradient for three model scenarios: CM without facilitation; CFM-U, a unimodal relationship between facilitation and environmental severity; and CFM-L, a positively linear relationship between facilitation and environmental severity. Our results demonstrated that facilitation could increase, decrease or have no remarkable effect on temporal turnover. The specific outcome depended on the location of the focal community across the environmental gradient and the model employed. Compared with CM, the inclusion of positive interactions (i.e. CFM-U and CFM-L), at intermediate environmental stress levels (such as S = 0.7 and 0.8) resulted in lower Bray-Curtis similarity values; at other severity levels, facilitation slowed down (such as S = 0.3 and 0.4 at low to medium stress levels, and S = 0.9 at high stress levels) or had only a subtle effect (such as at S = 0.1) on temporal turnover. We also found that the coefficient of variation (CV) in species abundances and the rate of temporal variability showed a significant quadratic relationship. Our theoretical analysis contributes to the understanding of factors driving temporal turnover in biotic communities, and presents a potential metric (i.e. CV in species abundances) assessing the consequences of ongoing environmental change on community structure.
已经证明，负相互作用和正相互作用的相互作用同时塑造了群落结构和组成。然而，很少有研究试图通过时间来检验促进作用对群落组成变化的影响。此外，由于收集长期数据的困难，如果能够使用易于获得的度量标准来指示时间周转率，那将是很有用的。我们使用包含植物策略的个体基础模型，检验了在三个模型情景下促进作用对沿环境梯度的不同位置的群落的时间周转率的影响：没有促进作用的 CM；促进作用与环境严酷度之间呈单峰关系的 CFM-U；促进作用与环境严酷度之间呈正线性关系的 CFM-L。我们的结果表明，促进作用可能会增加、减少或对时间周转率没有显著影响。具体结果取决于焦点群落在环境梯度上的位置和使用的模型。与 CM 相比，在中等环境压力水平（如 S=0.7 和 0.8）下包含正相互作用（即 CFM-U 和 CFM-L）会导致较低的 Bray-Curtis 相似性值；在其他严重程度水平下，促进作用会减缓（如在低到中等压力水平下的 S=0.3 和 0.4，以及在高压力水平下的 S=0.9）或对时间周转率只有轻微影响（如在 S=0.1 时）。我们还发现，物种丰度的变异系数（CV）和时间变异性的速率呈显著的二次关系。我们的理论分析有助于理解驱动生物群落时间周转率的因素，并提出了一种潜在的度量标准（即物种丰度的 CV）来评估正在进行的环境变化对群落结构的影响。
