Non-linear thresholds in the effects of island area on functional diversity in woody plant communities
Non-linear thresholds in the effects of island area on functional diversity in woody plant communities
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岛屿面积对木本植物群落功能多样性影响的非线性阈值
DOI：
10.1111/1365-2745.13632
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发表时间：
2021
影响因子：
5.5
通讯作者：
Mingjian Yu
中科院分区：
文献类型：
--
作者：
Aiying Zhang;Shilu Zheng;Raphael K. Didham;Robert D. Holt;Mingjian Yu
阈值非线性岛屿面积和物种丰富度之间的关系，可能会导致一个看似小的阈值附近的面积下降，丰富度急剧下降。目前尚不清楚的是，丰富度的阈值下降是否也伴随着功能性状空间的非线性变化和响应面积下降的性状组组成的非随机变化。记录了植物物种丰富度，并根据5个地区76个树种的12个性状计算了4个功能多样性（FD）指数，在浙江千岛湖岛湖区29个岛屿上的082个样地（5 × 5 m）。我们使用分段回归测试了丰富度和FD关系中的阈值非线性，使用空模型进行随机回归以解释潜在的采样伪影。我们将树种聚类到性状组的基础上的性状相异度，并使用多项分段模型来测试是否阈值面积对FD的影响与性状组composition.Species丰富度和四个FD指数的三个变化相关的阈值非线性下降岛屿面积低于阈值约1.16-6.88公顷。K均值聚类确定了两个性状组，反映了性状谱“快”端与“慢”端的物种。特征组组成中的显著区域阈值是由岛屿上具有资源保护特征的物种的相对丰富度增加但相对丰度下降驱动的。我们发现下面的岛屿上的丰富度出现了临界崩溃。1公顷，导致功能特征空间（功能丰富度）显著减少，小岛屿上群落物种间生态位分化程度（功能分化）增加。阈值效应与性状组组成的非随机重组有关，有利于性状谱中“缓慢”资源保护端物种的相对丰富度，但少数具有“快速”资源获取性状的物种的相对丰富度。这些结果表明，扰动驱动的动态可能会在临界阈值处驱动生态系统状态的功能转变。我们表明，一个最小的关键栖息地面积需要保持功能多样性的木本植物群落。
Threshold nonlinearities in the relationship between island area and species richness can result in dramatic declines in richness with a seemingly small decline in area near the threshold. What is not known, is whether threshold declines in richness are also accompanied by nonlinear changes in functional trait space and non‐random shifts of trait group composition in response to declining area.Plant species richness was recorded, and four functional diversity (FD) indices calculated based on 12 traits for 76 tree species in 5,082 plots (5 × 5 m) on 29 islands in the Thousand Island Lake region, Zhejiang, China. We tested for threshold nonlinearities in richness and FD relationships using segmented regression, with randomized resampling using a null model to account for potential sampling artefacts. We clustered tree species into trait groupings based on trait dissimilarity, and used multinomial segmented models to test whether threshold area effects on FD were associated with shifts in trait group composition.Species richness and three of the four FD indices showed significant threshold nonlinearities with declining island area below a threshold of ca 1.16–6.88 ha. K‐means clustering identified two trait groups, reflecting species at the ‘fast’ versus ’slow’ ends of the trait spectrum. Significant area thresholds in trait group composition were driven by increasing relative richness, but decreasing relative abundance, of species with resource‐conservation traits on islands below the threshold.Synthesis. We found a threshold collapse in richness on islands belowc. 1 ha, resulting in a significant decrease in functional trait space (functional richness) and an increase in the degree of niche differentiation among species in the community (functional divergence) on small islands. Threshold effects were associated with non‐random re‐assembly of trait group composition, favouring the relative richness of species at the ‘slow’ resource‐conservation end of the trait spectrum, but the relative abundance of a few species with ‘fast’ resource‐acquisition traits. These results suggest that disturbance‐driven dynamics potentially drive a functional shift in the ecosystem state at a critical threshold. We show that a minimum critical habitat area is required to maintain functional diversity in woody plant communities.