Leaf Area of Overstory and Understory in Pine Plantations in the Flatwoods

Leaf area index (LAI) was measured in summer and winter for the overstory and understory in 7- and 10-year-old loblolly and slash pine plantations on poorly drained, somewhat poorly drained, and moderately well-drained soils. LAI and vegetation indices (simple ratio [SR], normalized difference vegetation index [NDVI], vegetation index, and enhanced vegetation index) were also calculated using Landsat imagery. LAI values observed for the overstory were low in most of the plots (around 2 m2 m−2 in slash pine and around 3 m2 m−2 in loblolly pine), whereas the understory LAI was very high (around 2 m2 m−2), which can be attributed to the lack of canopy closure observed in all plots. No significant differences were found in the understory LAI values across soil drainage classes. Total LAI (overstory LAI plus understory LAI) values were weakly correlated with the vegetation indices. The LAI values estimated using Landsat data were typically half of the values estimated on the ground. Significant correlations were observed between the vegetation indices (SR and NDVI) and stand and site factors, suggesting that the satellite-derived indices were more related to the stand biophysical parameters than to in situ LAI estimates.