Leaf Litter Decomposition and Nutrient Release Under Nitrogen, Phosphorus and Nitrogen Plus Phosphorus Additions in a Savanna in Central Brazil
The aim of this study was to determine leaf decomposition rates and nutrient release in a cerrado sensu stricto under nitrogen (N), phosphorus (P) and N plus P additions. The experiment was carried out in an area located in the Ecological Reserve of the Instituto Brasileiro de Geografia e Estatística, near Brasília (15° 56’ S, 47° 53’ W). Between 1998 and 2006, 100 kg ha−1 year−1 of N (N treatment), P (P treatment) and N plus P (NP treatment) were applied to 16 225 m2 plots, arranged in a completely randomized design. Litterfall was collected at the end of dry season (September 2006) and oven dried (60 °C) for 72 h. Litter bags with 10 g of leaf litter were incubated in situ for 453 days to determine decomposition rate. Nitrogen and P concentrations and mass loss were measured during the incubation process. Decomposition rates of leaf litter in N plots did not differ in relation to those in control plots. Leaf litter decomposition rates increased in P (+ 18.6 %) and NP (+ 27.4 %) plots, where there was a greater N (in NP plots) and P (in P and NP plots) initial concentration in litter relative to the control plots (p < 0.05). Leaf litter in the N treatment had the highest N mass loss, and together with NP treatment, the smallest P mass loss. Nitrogen addition increased N mass loss, while the combined addition of N and P resulted in an immobilization of N in leaf litter. When the nutrients are supplied separately, there is greater mass loss of N with N addition, and greater mass loss of P with P addition compared to that observed when N and P are supplied together. The results indicate that if the availability of P is not increased proportionally to the availability of N, the losses of N are intensified during the decomposition process.
KeywordsBiogeochemical cycling Cerrado Nutrient limitation Woody plants
We would like to thank Regina Sartori, Gilberto B. Cosak and UnB Ecology Lab staff for valuable help. We also would like to thank the administration and staff of RECOR-IBGE. This study was funded by the Graduate Program in Ecology of the UnB, CNPq and LBA-NASA (ND-07).
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