Organic Matter Production and Distribution in Slash Pine (Pinus Elliottii) Plantations

Abstract

The production and accumulation of total system organic matter (to 100 cm soil depth) in plantations of slash pine were analyzed using three replications of stands 2, 5, 8, 14, 18, 26, and 34 yr old. Maximum leaf area occurred at 5 yr. After this point aboveground net primary production (NPP) continued to increase to a maximum at 26 yr and then declined. After 5 yr stem biomass production composed a constant 50% of NPP. The forest floor increased at a constant rate through 34 yr, although total detritus (forest floor plus soil organic matter) was relatively constant at m160 Mg/ha. Live vegetation mass was less than detritus mass until =m25 yr, the current harvest rotation length. Total system organic matter showed no indication of a decline after site preparation, and was still increasing at 34 yr (340 Mg/ha). During site preparation -30 Mg/ha organic matter were lost through burning and decomposition. This loss was small enough to be completely offset by increases in live vegetation and forest floor over -3 yr following site preparation, which may be important in limiting losses of nutrients from these sites after a disturbance. rently 5.2 x 106 ha of commercial slash pine (Pinus elliottii var. elliottii), with -40% of the total in north- ern Florida. Fifty-two percent of the total is in plan- tations, representing 14% of the forested land area in Florida, and the rest is in naturally regenerated second growth (Scheffield et al. 1981); the proportion in plan- tations is rapidly increasing. Although the conversion of the natural stands to plantations amounts to landscape modification at a tre- mendous scale, we have little idea of the ecological consequences. Delcourt and Harris (1980) proposed