Patterns of stocks of aboveground tree biomass, dynamics, and their determinants in secondary Andean forests

Abstract

In this study, we aimed to identify the main factors that affect the dynamics and rates of aboveground biomass (AGB) accumulation in secondary forests located in the interandean valleys of Colombia. We used two censuses performed on trees with a diameter at breast height of⩾10cm in 10 1-ha plots to answer the following questions: (1) Does prior use of the land for raising crops (instead of pastureland for cattle ranching) promote an increase in the rate of AGB accumulation? (2) To what extent did climate, soil characteristics, the functional traits of resident species, and/or stand age affect the stocks and dynamics of the AGB in these secondary forests? We did not find any evidence that prior land use for cattle ranching had a negative effect on the tree AGB-accumulation rate, when compared with land previously used for raising crops. Greater AGB stocks at an intermediate fertility point may be associated with a higher abundance of tall, short-lived, fast-growth pioneer species. Tree mortality rates in secondary forests were primarily determined by the forest’s composition and the variation in the amount of rainfall between sites. Soil fertility, which is known to accelerate the growth rate of plant species, was significantly and positively associated with the rate of AGB recruitment. We did not find any evidence for a negative correlation between wood density and growth, as has been reported for primary tropical forests. The net AGB change (%) was primarily associated with the low soil-fertility characteristics of sandy well-drained soils that could, in the presence of steep slopes, increase forest dynamics. Land restoration that restores the natural cycle of secondary forests could assist in the mitigation of global warming by promoting key environmental functions, such as carbon sequestration.