Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta, T6G 2E3, Canada.
Department of Biological Sciences, University of Alberta, Edmonton, Alberta, T6G 2E9, Canada.
Ecol Appl. 2018 Mar;28(2):541-556. doi: 10.1002/eap.1669. Epub 2018 Feb 12.
Remote sensing has been used to detect plant biodiversity in a range of ecosystems based on the varying spectral properties of different species or functional groups. However, the most appropriate spatial resolution necessary to detect diversity remains unclear. At coarse resolution, differences among spectral patterns may be too weak to detect. In contrast, at fine resolution, redundant information may be introduced. To explore the effect of spatial resolution, we studied the scale dependence of spectral diversity in a prairie ecosystem experiment at Cedar Creek Ecosystem Science Reserve, Minnesota, USA. Our study involved a scaling exercise comparing synthetic pixels resampled from high-resolution images within manipulated diversity treatments. Hyperspectral data were collected using several instruments on both ground and airborne platforms. We used the coefficient of variation (CV) of spectral reflectance in space as the indicator of spectral diversity and then compared CV at different scales ranging from 1 mm to 1 m to conventional biodiversity metrics, including species richness, Shannon's index, Simpson's index, phylogenetic species variation, and phylogenetic species evenness. In this study, higher species richness plots generally had higher CV. CV showed higher correlations with Shannon's index and Simpson's index than did species richness alone, indicating evenness contributed to the spectral diversity. Correlations with species richness and Simpson's index were generally higher than with phylogenetic species variation and evenness measured at comparable spatial scales, indicating weaker relationships between spectral diversity and phylogenetic diversity metrics than with species diversity metrics. High resolution imaging spectrometer data (1 mm pixels) showed the highest sensitivity to diversity level. With decreasing spatial resolution, the difference in CV between diversity levels decreased and greatly reduced the optical detectability of biodiversity. The optimal pixel size for distinguishing α diversity in these prairie plots appeared to be around 1 mm to 10 cm, a spatial scale similar to the size of an individual herbaceous plant. These results indicate a strong scale-dependence of the spectral diversity-biodiversity relationships, with spectral diversity best able to detect a combination of species richness and evenness, and more weakly detecting phylogenetic diversity. These findings can be used to guide airborne studies of biodiversity and develop more effective large-scale biodiversity sampling methods.
遥感技术已被用于探测多种生态系统中的植物生物多样性，其依据是不同物种或功能群具有不同的光谱特征。然而，探测多样性所需的最适宜空间分辨率仍不明确。在粗分辨率下，不同光谱模式之间的差异可能过于微弱而无法探测到。相反，在细分辨率下，可能会引入冗余信息。为了探究空间分辨率的影响，我们在美国明尼苏达州雪松溪生态系统科学储备研究了草原生态系统实验中的尺度依赖性，研究中比较了经过人为处理的多样性处理中高分辨率图像内合成像素的定标。使用地面和机载平台上的几种仪器收集高光谱数据。我们将光谱反射率的空间变异系数（CV）作为光谱多样性的指标，然后将不同尺度（从 1 毫米到 1 米）的 CV 与包括物种丰富度、香农指数、辛普森指数、系统发育物种变异和系统发育物种均匀度在内的常规生物多样性指标进行比较。在这项研究中，物种丰富度较高的样地通常具有较高的 CV。CV 与香农指数和辛普森指数的相关性高于与单一物种丰富度的相关性，表明均匀度有助于光谱多样性。与具有可比空间尺度的物种丰富度和辛普森指数的相关性通常高于与系统发育物种变异和均匀度的相关性，这表明光谱多样性与系统发育多样性指标的关系弱于与物种多样性指标的关系。高分辨率成像光谱仪数据（1 毫米像素）对多样性水平具有最高的敏感性。随着空间分辨率的降低，不同多样性水平之间的 CV 差异减小，生物多样性的光学可探测性大大降低。在这些草原样地中，区分 α 多样性的最佳像素大小似乎在 1 毫米到 10 厘米之间，这一空间尺度与单个草本植物的大小相似。这些结果表明，光谱多样性与生物多样性关系具有很强的尺度依赖性，光谱多样性最能检测物种丰富度和均匀度的组合，而对系统发育多样性的检测较弱。这些发现可用于指导生物多样性的航空研究，并开发更有效的大规模生物多样性采样方法。
