Nutrient resorption and patterns of litter production and decomposition in a Neotropical Savanna

Abstract

1. Deposition of nutrients due to anthropogenic activities has the potential to change nutrient availability in nutrient-limited ecosystems with consequences for plant and ecosystem processes. 2. Species-specific and ecosystem responses to the addition of nutrients were studied in a field experiment conducted in a Savanna (Cerrado sensu stricto) on dystrophic soil in central Brazil. Three fertilization treatments (N, P and N plus P additions) and unfertilized control were replicated in four 15 x 15 m plots per treatment. 3. Five of the dominant woody species were studied. Specific leaf area (SLA) was not affected by the treatments, but species responded differently in terms of foliar nutrient concentration, resorption efficiency and proficiency to the increased soil N and P availability. 4. Responses of N and P resorption suggested different levels of regulation for these two limiting elements, with a decrease in N and P resorption proficiency depending on the treatment. In general, under N fertilization, senesced leaves presented higher N concentration, whereas combined fertilization with N and P resulted in senesced leaves richer in P. The concomitant variation in P resorption efficiency and proficiency indicates a stronger regulation between them compared to N. 5. Results indicated a highly efficient and complete P resorption, while N concentrations in senesced leaves indicated intermediate or incomplete resorption efficiencies, supporting the idea that Cerrado plants might be more limited by P than by N. 6. At the ecosystem level, higher N concentration in the leaf litter was measured at the end of the dry season in the +NP-fertilized plots, resulting in a significantly faster decomposition rate in relation to the control treatment. Responses of litterfall and decomposition rates indicated that the system was generally more responsive to the combined addition of N and P than to fertilization with N or P alone over the relatively short time span of this study. © 2007 The Authors.