HETEROGENEITY OF SAVANNA CANOPY STRUCTURE AND FUNCTION FROM IMAGING SPECTROMETRY AND INVERSE MODELING

Abstract

Arid and semiarid ecosystems cover >40% of the earth’s terrestrial surface. Woody plants and herbaceous species, each with distinct allocation and phenological characteristics, respond to and constrain ecosystem function and biogeochemistry in these regions. High-resolution estimates of vegetation extent, aboveground allocation, and phenology are needed to improve regional links between ecosystem structure and function, especially under conditions of changing land use. We used a combination of imaging spectrometry and radiative transfer inverse modeling techniques to quantify the structural and biophysical attributes of plant canopies and land-cover types in a South Texas savanna. Estimated canopy structural attributes were used to calculate the fraction of photosynthetically active radiation (PAR; 400–700 nm) absorbed by plant canopies and the live foliage and nonphotosynthetic components of the canopies. A landscape analysis of these variables revealed the complexity of the biotic, abiotic, and anthropogenic factors involved in land-cover change in the region. The accuracy in estimating these plant canopy structural and functional attributes has significant implications for range management, fire forecasting, physiological ecology, biogeochemistry, and analyses of landscape structure and diversity.