Leaf litter manipulations alter soil physicochemical properties and tree growth in a Neotropical savanna

Abstract

This study was aimed to assess the role that leaf litter play in nutrient cycling, nutrient soil availability and ecosystem processes in an oligotrophic tropical savanna. A four year experiment was performed in a Neotropical savanna from the Brazilian plateau (cerrado), in which litter levels were modified, and the resulting changes in biophysical and chemical soil properties were studied. Changes in organic matter decomposition, soil respiration and stem growth of the six most common tree species were also monitored. Compared to litter removal plots, double litter plots had lower maximum soil temperature and higher soil water content, and litter decomposition rates in one of three species studied, consistent with higher soil respiration rates observed in this treatment. With the exception of Ca, there were no significant differences in nutrients between the removal, natural and double litter plots, even though most nutrients tended to increase in the double litter plots by the end of the experimental period, while in the control plots nutrient levels remained relatively constant. Of the six tree species used for growth analysis, only one, Sclerolobium paniculatum, a fast growing species with shallow roots, had a significant increase in stem growth due to litter addition. Preliminary results over four years indicate that litter removal and addition resulted in some significant changes and tendencies that indicate that litter is effectively altering ecosystem processes. The information obtained also suggest that nutrient cycling in plots with natural litter levels (control plots) was in a closed loop; most nutrients released by litter decomposition and mineralization were absorbed and reutilized immediately by the plants, thus minimizing nutrient leakage outside the system.