Using Imaging Spectroscopy to Study Ecosystem Processes and Properties

Abstract

ArticlesT he consequences of land use, disturbance, and climate change in the world's ecosystems have created increased demand for remote sensing data at all scales. A wide range of information is needed to predict the consequences of climate change and to monitor carbon, water, and nutrient cycles, from land cover, land-use history, and estimates of standing biomass to succession, biodiversity, and sustainability. Traditional field-based sampling methods are prohibitively expensive and time-consuming at large spatial scales, and such methods are inadequate for today's needs. Satellite observations provide the only practical means to obtain a synoptic view of Earth's ecosystems, including their spatial distribution, extent, and temporal dynamics (Cohen and Goward 2004).Accurate maps of the spatial distribution, percentage cover, and variability of global ecosystems are essential to improve ecosystem process models (Running et al. 2004, Turner et al. 2004. Current vegetation maps contain significant classification errors, and there is little understanding of how to scale mixed land cover, variable stand age, and density classes from local estimates. Normalized difference vegetation index (NDVI) data are used for estimating carbon fluxes, stores, and turnover rates, as well as other land-cover characteristics affecting the carbon budget. However, ecosystem and biogeochemical models could significantly benefit from independently derived information about terrestrial biomes. Several new types of data that could improve model results, including quantitative estimates of canopy and soil biochemistry, canopy structural information, and improved land-cover classifications, can be produced by imaging spectrometers.A wide range of new instrument capabilities are available or planned, based on airborne and satellite platforms that measure all parts of the electromagnetic spectrum, from ultraviolet to radar (Treuhaft et al. 2004). Imaging spectrometers are instruments that measure a detailed spectrum of reflected solar energy for each pixel. Spectroscopy data have already significantly improved theoretical understanding of the interactions of electromagnetic radiation with matter and are changing the way remotely sensed data are analyzed

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