Evaluating relationships of standing stock, LAI and NDVI at a subtropical reforestation site in southern Taiwan using field and satellite data

In this study, we evaluate the relationships between the standing stock, field-measured LAI, and NDVI from remotely sensed images and in situ measurements at plantation forests in the subtropics–tropics region of southern Taiwan. The purpose is to facilitate assessing the biomass of reforestation sites in large areas applying the possible stock-LAI-NDVI relationships analyzed in this study. 15–16 years old forest in one square kilometer area with 14 tree species was tested at different spatial scales. In addition, we also assess the relationship of plots with pure tree species for the effect mixed tree species. By long-term monitoring, intensive measurement for 5 years and analysis at different spatial scales, the results show the correlation coefficient of stock-LAI is not significant while that of stock-NDVI is 0.5639, 0.7230 and 0.9283 as the spatial scale enlarges. Negative stock-LAI correlations found for three tree species but all the stock-NDVI correlations for six specific tree species are positive. If the multi-regression is applied, the correlation coefficient of stock-LAI-NDVI is higher than that of the stock-LAI and stock-NDVI, which reaches to the 0.6470, 0.7680 and 0.9995 at the plot, block and site level, respectively; the correlation coefficients of six specific tree species are also larger at the plot level.