Biodiversity across the Greater Cape Floristic Region

Aim: With plant biodiversity under global threat, there is an urgent need to monitor the spatial distribution of multiple axes of biodiversity. Remote sensing is a critical tool in this endeavor. One remote sensing approach in detecting biodiversity is based on the hypothesis that the spectral diversity of plant communities is a surrogate of multiple dimensions of biodiversity. We investigated the generality of this "surrogacy" for spectral, species, functional, and phylogenetic diversity across 1,267 plots in the Greater Cape Floristic Region (GCFR), a hyper-diverse region comprising several biomes and two adjacent global biodiversity hotspots. Location: The GCFR centered in southwestern and western South Africa. Time Period: All data were collected between 1978–2014. Major taxa studied: Vascular plants within the GCFR. Methods: Spectral diversity was calculated using leaf reflectance spectra (450–950 nm) and was related to other dimensions of biodiversity via linear models. The accuracy of different spectral diversity metrics was compared using ten-fold cross-validation. Results: We found that a distance-based spectral diversity metric was a robust predictor of species, functional, and phylogenetic biodiversity. This result serves as a proof-of-concept that spectral diversity is a potential surrogate of biodiversity across a hyper-diverse biogeographic region. While our results support the generality of spectral diversity as a biodiversity surrogate, we also find that relationships vary between different geographic subregions and biomes, suggesting that differences in broad-scale community composition can affect these relationships. Main Conclusions: Spectral diversity was shown to be a robust surrogate of multiple dimensions of biodiversity across biomes and a widely varying biogeographic region. We also extend these surrogacy relationships to ecological redundancy to demonstrate the potential for additional insights into community structure based on spectral reflectance.

研究目的：在全球植物生物多样性面临威胁的背景下，亟需对多维度生物多样性的空间分布开展监测，遥感技术是该工作的关键工具。其中一类生物多样性遥感检测方法基于如下假设：植物群落的光谱多样性可作为多维度生物多样性的替代指标。本研究在开普植物区（Greater Cape Floristic Region, GCFR）的1267个样地中，探究该“替代效应”在光谱、物种、功能及系统发育多样性维度上的普适性；该区域为超多样生物地理区，涵盖多个生物群区以及两处相邻的全球生物多样性热点地区。
研究区域：以南非西南部及西部为核心的开普植物区（GCFR）。
研究时段：所有数据均收集于1978年至2014年期间。
研究类群：开普植物区（GCFR）内的维管植物（vascular plants）。
研究方法：光谱多样性通过450~950 nm波段的叶片反射光谱（leaf reflectance spectra）计算得到，并通过线性模型与其他维度的生物多样性建立关联；采用十折交叉验证（ten-fold cross-validation）对比不同光谱多样性指标的预测精度。
研究结果：本研究发现，基于距离的光谱多样性指标可稳健预测物种、功能及系统发育生物多样性，该结果为“光谱多样性可作为超多样生物地理区域内生物多样性的潜在替代指标”提供了概念验证。尽管本研究结果支持光谱多样性作为生物多样性替代指标的普适性，但同时也发现不同地理亚区域及生物群区间的关联存在差异，这表明大尺度群落组成差异会影响此类关联关系。
主要结论：本研究证实，在涵盖多个生物群区且环境异质性极高的生物地理区域中，光谱多样性可作为多维度生物多样性的稳健替代指标。此外，我们还将此类替代关系拓展至生态冗余性分析，证明了基于光谱反射特性可进一步深入解析群落结构。