Relationships between forest structure and vegetation indices in Atlantic Rainforest

The alliance between remote sensing techniques and biophysical indicators can be valuable to studies on diagnosis and monitoring, especially in threatened habitats, such as the Atlantic Rainforest. This approach may improve monitoring through diagnosing forest fragments instead of quantifying only forest area reduction. This paper aims to evaluate relationships between forest structure and vegetation indices in Atlantic Rainforest fragments, in southeastern Brazil. Two Landsat 7 ETM+ images acquired in humid and dry seasons were used, and measurements of forest structure in nine forest fragments and in a continuous forest area in the Guapiaçú River Basin, in Rio de Janeiro State were taken. Three vegetation indices (normalized difference vegetation index (NDVI), moisture vegetation index using Landsat's band 5 (MVI5) and moisture vegetation index using Landsat's band 7 (MVI7)) were correlated with measurements of forest structure (frequency of multiple-stemmed trees, density of trees, mean and range of tree diameter, mean and range of tree height and average of basal area). Models describing the relationships between forest structure and vegetation indices using linear regression analysis were also developed. MVI5 and MVI7 showed the best performances in dense humid forests, whereas NDVI seems to be a good indicator of green biomass in deciduous and dry forests. Moreover, the saturation matter in vegetation indices and the transferability of relationships between biophysical characteristics and vegetation indices to other sites and times were discussed.