Litter Decomposition of Pinus Caribaea and Pinus Oocarpa in a Tropical Climate: Effects of Pure and Mixed Plantation and Native Forest Environments

Abstract

ABSTRACT Although the litter deposition and decomposition dynamics of the Pinus genus is relatively well known, the effects of the mixture of needles from different species and the influence of the microenvironmental condition of the forest system have rarely been investigated. The objective of this work was to evaluate the decomposition of needles of two Pinus species (Pinus caribaea and Pinus oocarpa) and the needle-mixing of these species when exposed to a planted forest condition (one pure and one mixed of these two species) and a natural tropical forest condition. Senescent needles were collected from the base of the treetops. Next, 10 g samples of the dry needles were placed in litterbags: for the pure plantation, 100% samples of P. caribaea were used, while the samples for the mixed plantation were composed of 50% P. caribaea +50% P. oocarpa. The litterbags were placed in the planted forest environment and in the natural forest environment. Litterbag collections were performed after 60, 120, 180, 240, 300 and 360 days after installation. The dry needle material (before and after decomposition) was chemically characterized. The litter composition and the microenvironment influenced the decomposition dynamics. The decomposition rate of mixed needle litter was higher than the rate of pure litter, being even more expressive when in the native forest condition.