Department of Natural Resources and Environmental Sciences, University of Illinois, 1102 South Goodwin Avenue, Urbana, Illinois, 61801, USA.
Illinois Natural History Survey, University of Illinois, Champaign, Illinois, 61820, USA.
Ecol Appl. 2019 Jan;29(1):e01827. doi: 10.1002/eap.1827. Epub 2018 Dec 6.
The anthropogenic degradation of natural ecological communities can cause biodiversity loss in the form of biotic homogenization (i.e., reduced β-diversity). Biodiversity offsetting practices, such as compensatory wetland mitigation, may inadvertently cause biotic homogenization if they produce locally homogenous or regionally recurring communities. The fact that compensation wetlands often resemble degraded wetlands suggests that potential impacts to β-diversity are likely. Yet, it is unknown how high-quality, low-quality (degraded), and compensation wetlands compare in terms of β-diversity. We compared the β-diversity of high-quality, low-quality, and compensation wetlands at local and regional scales. β-diversity was quantified as the average distance to group centroids in multivariate space based on pairwise comparisons of community composition. The local spatial structure of β-diversity was assessed using species turnover across plots. Indicator species analysis was used to describe compositional differences potentially contributing to differences in β-diversity. Overall, the β-diversity of compensation sites did not differ from high-quality or low-quality natural wetlands. However, compensation wetlands had a high degree of internal turnover along the hydrological gradient, which culminated in homogenous zones in the wettest areas. Compared to high-quality wetlands, low-quality wetlands had significantly lower β-diversity at local scales, but significantly greater β-diversity at regional scales. Indicator species results showed that compensation wetlands were distinguished by low conservation value species typically found in old fields and waste areas. This analysis also indicated that the invasive grass Phalaris arundinacea was indicative of low-quality and compensation wetlands. This species is likely contributing to differing patterns of β-diversity between high-quality and low-quality wetlands. These results indicate that conclusions regarding β-diversity depend on scale and scope of analysis. Particularly, the unique architecture of compensation wetlands makes conclusions regarding within-site β-diversity dependent on the observer's position along the hydrological gradient. Additionally, while we conclude that compensation wetlands are not contributing to biotic homogenization at the regional scale, these wetlands are distinct from both high-quality and low-quality wetlands in their composition and structure. Therefore, assessments of the overall success of wetland mitigation programs should acknowledge the reality of these differences.
自然生态群落的人为退化可能导致生物多样性丧失，表现为生物均质化（即β多样性降低）。如果补偿湿地产生局部同质或区域重现的群落，生物多样性补偿实践可能会无意中导致生物均质化。事实上，补偿湿地往往类似于退化湿地，这表明对β多样性的潜在影响可能很大。然而，我们不知道高质量、低质量（退化）和补偿湿地在β多样性方面有何不同。我们比较了高质量、低质量和补偿湿地在本地和区域尺度上的β多样性。β多样性通过基于群落组成的成对比较的多元空间中的组质心平均距离来量化。本地β多样性的空间结构通过跨斑块的物种周转率来评估。指示物种分析用于描述可能导致β多样性差异的组成差异。总的来说，补偿地点的β多样性与高质量或低质量自然湿地没有差异。然而，补偿湿地在水文梯度上具有很高的内部周转率，最终在最潮湿的区域形成同质区。与高质量湿地相比，低质量湿地在本地尺度上的β多样性显著降低，但在区域尺度上的β多样性显著增加。指示物种结果表明，补偿湿地的特征是通常在旧田地和废物区发现的低保护价值物种。这一分析还表明，入侵草类雀麦是低质量和补偿湿地的指示物种。该物种可能是导致高质量和低质量湿地之间β多样性差异的原因之一。这些结果表明，关于β多样性的结论取决于分析的尺度和范围。特别是，补偿湿地的独特结构使得关于场内β多样性的结论取决于观察者在水文梯度上的位置。此外，尽管我们得出结论认为补偿湿地在区域尺度上没有导致生物均质化，但这些湿地在组成和结构上与高质量和低质量湿地明显不同。因此，湿地缓解计划整体成功的评估应该承认这些差异的现实。
