Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10114214 | Remote Sensing of Environment | 2005 | 12 Pages |
Abstract
The Hawaiian Islands contain more than two-thirds of the life zones delineated by Holdridge, L.R., 1947. Determination of world plant formations from simple climate data. Science, 105, 367-368, and is thus an ideal testing ground for remote sensing studies of ecosystem function and structure. We tested the generality of imaging spectroscopy with “tied” red-edge and shortwave-infrared (RE-SWIR2) spectral mixture modeling for automated analysis of the lateral distribution of plant tissues and bare substrate across diverse bioclimatic gradients in Hawai'i. Unique quantities of the fractional cover of photosynthetic and non-photosynthetic vegetation (PV, NPV) and bare substrate identified fundamental differences in ecosystem structure across life zones. There was a â¼20-fold increase in fractional PV cover with a 10-fold increase in mean annual precipitation (â¤Â 250-2000 mm yearâ 1). This rate of increase diminished from 2000 to 3000 mm yearâ 1 of rainfall, suggesting that photosynthetic canopy cover may be limited by water saturation at 3000 mm yearâ 1. The amount of exposed surface senescent material (NPV) remained nearly constant at â¼50% in ecosystems with a mean annual precipitation < 1500 mm yearâ 1. Thereafter, NPV steadily declined to a minimum of â¼20% at 3000 mm yearâ 1 of rainfall. Bare substrate fractions were highest (â¼50%) at precipitation levels < 750 mm yearâ 1, then declined to < 20% in the 750-1000 mm yearâ 1 zones. The combination of low bare substrate and high NPV cover in the 750-1000 mm yearâ 1 rainfall zones identified these areas as high fire risk. Remotely sensed fractional cover of PV + NPV was poorly correlated with canopy leaf area index (LAI), showing the uniqueness of the lateral structural measurement afforded by automated RE-SWIR2 spectroscopy approaches. The results indicate the accuracy, precision and applicability of imaging spectroscopy for ecological research across a wide range of bioclimatic conditions.
Keywords
Related Topics
Physical Sciences and Engineering
Earth and Planetary Sciences
Computers in Earth Sciences
Authors
Gregory P. Asner, Andrew J. Elmore, R. Flint Hughes, Amanda S. Warner, Peter M. Vitousek,