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LEAF AREA INDEX (LAI) CHANGE DETECTION ON LOBLOLLY PINE FOREST STANDS WITH COMPLETE UNDERSTORY REMOVAL
Citation:
Iiames, J., D Pilant, T E. Lewis, AND R. O. Congalton. LEAF AREA INDEX (LAI) CHANGE DETECTION ON LOBLOLLY PINE FOREST STANDS WITH COMPLETE UNDERSTORY REMOVAL. Presented at American Society for Photogrametry and Remote Sensing (ASPRS), Denver, CO, May 23-28, 2004.
Impact/Purpose:
Our research objectives are to: (a) develop new methods using satellite remote sensor data for the rapid characterization of LC condition and change at regional to national scales; (b) evaluate the utility of the new NASA-EOS MODIS (Moderate Resolution Imaging Spectrometer) leaf area index (LAI) measurements for regional scale application with landscape process models (e.g., biogenic emissions and atmospheric deposition); (c) provide remote sensor derived measurement data to advance the development of the next generation of distributed landscape process-based models to provide a predictive modeling capability for important ecosystem processes (e.g., nutrients, sedimentation, pathogens, etc.); and (d) integrate in situ monitoring measurement networks with UAV and satellite based remote sensor data to provide a continuous environmental monitoring capability.
Description:
The confounding effect of understory vegetation contributions to satellite derived
estimates of leaf area index (LAI) was investigated on two loblolly pine (Pinus taeda) forest stands located in the southeastern United States. Previous studies have shown that understory can account from 0-40% of the total LAI values. The primary factors influencing the near infrared (NIR) and visible (VI) spectral responses within forest stands are canopy closure, understory contribution, and soil types. The confounding issue in evaluating spectral vegetation indices is the near flat response of the NIR band occurring over a wide range of LAI values. Thus, forest stands with varying vertical profiles, i.e. differing understory contributions, could have similar LA! values due to horizontal homogeneity.
The two 1.0 ha study plots contained planted loblolly pine stands (ages 19 and 23) with similar crown closure estimates (70% and 71 %, respectively). Understory vegetation was removed from both stands via mechanical harvest and herbicide application in late July and early August 2002. Ikonos and Landsat ETM+ data were collected both prior and subsequent to understory removal and were evaluated for NIR and VI wavelength response. Total vegetative biomass removed under the canopies was estimated using the Tracing Radiation and Architecture of Canopies (TRAC) instrument combined with hemispherical photography. Initial results of ground-based measurements indicate significant differences in LAI before and after harvesting treatment. Preliminary satellite derived LAI results from Ikonos and Landsat ETM+ data will be presented.