Amount and vertical distribution of foliage of young loblolly pine trees as affected by canopy position and silvicultural treatment

Abstract

Silvicultural practices such as thinning and fertilization can affect both canopy foliage quantity and distribution, altering stand growth. The objectives of this research were to quantify the effects of tree size and silvicultural treatment on the vertical distribution of foliage of individual trees of loblolly pine (Pinustaeda L.) and to estimate foliage quantity and distribution using easily measured tree data. In three stands sampled in North and South Carolina, fertilization and (or) thinning treatments had been applied 2 years prior to sampling. A fourth stand was untreated. Nonlinear and linear regression models were developed to test the effects of silvicultural treatment on individual branch foliage biomass and whole tree foliage biomass. Vertical distributions of foliage and branches were modelled using a Weibull probability density function. Analyses indicated that individual branch foliage biomass was positively related to branch size but negatively related to distance from the top of the tree. Fertilization with nitrogen and phosphorus, or thinning, increased the foliage biomass carried by a given sized branch. Silvicultural treatment effects on individual branches translated into whole-tree foliage biomass with thinning and fertilization increasing the crown size of individual trees. Though treatment affected crown size, the distribution of foliage (and branches) remained unaffected. Because silvicultural treatments change the size of crowns for trees of given dimensions, any estimation of loblolly pine crown biomass must be site and treatment specific.