Seasonal patterns of spectral diversity at leaf and canopy scales in the Cedar Creek prairie biodiversity experiment

Abstract

The relationship between biodiversity and spectral diversity is highly scale-dependent, and temporal variation in leaf morphological, biochemical traits and canopy structure can alter this relationship. However, the temporal dependence of the spectral diversity – biodiversity relationship is poorly understood, in part due to the difficulties of obtaining consistent measurements across space and time. Using leaf pigments and leaf and canopy reflectance throughout a growing season in the Cedar Creek prairie biodiversity experiment, we explored phenological effects on the scale dependence of the spectral biodiversity – biodiversity relationship. Leaf reflectance spectra displayed larger among-species variation than leaf pigments, indicating that leaf reflectance contained more information for distinguishing species than some leaf trait measurements. At the canopy scale, spectral variation derived using reflectance was mainly driven by among-species variation. The canopy scale spectral diversity was also influenced by changing vegetation percent cover, key phenological events (e.g., flowering), and disturbance (drought). Our results revealed that contrasting phenological patterns of spectral diversity metrics emerged at leaf and canopy scales. Because a misunderstanding of these contrasting temporal effects across spatial scales can lead to possible misinterpretations of the spectral diversity – biodiversity relationship or of their underlying causes, more research effort is needed to understand these cross-scale temporal effects.