Imaging spectroscopy studies of hawaiian ecosystems, carbon properties, and disturbance

The Hawaiian Islands contain more than two-thirds of the global life zones delineated by Holdridge¹. We used high-fidelity imaging spectroscopy and shortwave-infrared (SWIR) spectral mixture analysis to analyze the lateral distribution of plant tissues and bare substrate across bioclimatic gradients and ecological life zones in Hawai'i. Unique quantities of photosynthetic and non-photosynthetic vegetation (PV, NPV) and bare substrate identified fundamental differences in ecosystem structure across life zones. There was a nearly 20-fold increase in PV fractional cover with a 10-fold increase in mean annual precipitation (≤ 250 to 2000 mm yr^-1). NPV fractional cover remained nearly constant at ∼50% in ecosystems with a mean annual precipitation < 1500 mm yr^-1. Thereafter, NPV steadily declined to a minimum of ∼20% at 3000 mm yr^-1 of rainfall. Bare substrate fractions were highest (∼50%) at precipitation levels < 750 mm yr ^-1, then declined to < 20% in the 750-1000 mm yr^-1 zones. The combination of low bare substrate and high NPV cover in the 750-1000 mm yr^-1 rainfall zones identified these areas as high fire risk. The results verify the applicability of SWIR imaging spectroscopy for ecosystem research on a global scale. They also set the framework for continued studies of ecosystem structure, function and invasive species throughout the Hawaiian Archipelago.