مجله جنگل ایران (Jun 2014)
The relationship between fuel moisture content and leaf spectral reflectance of Quercus brantii in Chahartagh Reserve forest, Chaharmahal Va Bakhtiari province
Abstract
To assess the physiological states, the stress impact and ultimately the overall health condition of living plants, measuring moisture content is a well-known choice. Alteration in plant water is more likely occurs not only after prolonged drought and fire prone forests, but also in more sparse and weaken stands. Hyperspectral remote sensing techniques try to provide means to quantify the leaf moisture content with low cost, high-speed, online and up-to-date information. In this study the relationship between spectral reflectance of Quercus brantii leaves and fuel moisture content, equivalent water thickness and specific leaf weight was estimated. The sampling was done on 40 randomly selected oak trees in southern and western aspects in central Zagros range. To acquire spectral reflectance the leaves were scanned through wavelengths 350 to 2500 nm, using a ASD Fieldspec® field spectrometer. For each tree, leaves were picked up from four canopy directions. Then the leaf wet and dry weights as well as their masses were determined. Water Index (WI) spectral was most significantly correlated to fuel moisture content (P<0/001, r=0/22). In addition, WI and Normalized Difference Vegetation Index (NDVI) showed high correlation coefficient with both fuel moisture content and specific leaf weight. None of the spectral indices could establish significant relationship with equivalent water thickness. On the other hand, there was also no significant difference between fuel moisture content, water equivalent thicknesses, and specific leaf weight with spectral indices in four of the tree crown direction. Nevertheless, there was significant difference between leaf equivalent water thickness and indices NDVI, NDSI [1108, 1242] and NDSI [1108, 1457] in both western and southern aspects.
