ID do Resumo: 374

Litter production and decomposition in response to N, P and N plus P additions in a Brazilian Cerrado

The intensive conversion of Cerrado native vegetation into agricultural lands results in anthropogenic nutrient inputs in a nutrient limited ecosystem, with consequences for ecosystem processes. In order to assess the potential impacts of these inputs, a fertilization experiment was conducted in a cerrado stricto sensu, the most common plant physiognomy of the biome. The study area is located in the IBGE (Brazilian Institute for Geography and Statistics) Ecological Reserve, Federal District, Brazil. The experimental design included four fertilization treatments (control, N, P and N plus P additions) replicated in four 225m2 plots per treatment. Between 1999 and 2005, 100 kg.ha-1.y-1 of N, P and N plus P were added annually in the soil (Oxisol). The litter production was quantified biweekly for two years (2006/7 - 2007/8) using five litter traps per plot, randomly installed at 15 cm from soil surface. Litter samples were oven-dried for 72 hours and weighed. The litter mass loss were determined using litterbags (20cmx20cm) with 10g of leaf litter from each treatment, placed under the litter layer and collected bimonthly for 14 months. The decomposition constant (K) was calculated using the negative exponential model. The comparisons were made between fertilized and the control plots using F and T-tests. In two years of collection, annual litterfall only differ significantly from control plots in the NP plots (p< 0.0005) during the first year. Comparing years, litterfall increased only in P plots (p<0.005) and decreased in NP plots (p< 0.05) in the second year (2007/8). The percentage of mass remaining in litterbags was significantly smaller in P (p<0.05) and NP (p<0.005) plots, with higher K values and smaller half-life of leaf litter (-18.66% in P and -27.44% in NP plots). These results indicate that the Cerrado vegetation responses more significantly of nutrient addiction when these are added associated, evidencing a co-limitation for N and P in Cerrado plants.

Sessão:  Biogeoquímica - Ciclagem de nutrientes em ecossistemas e agroecosssistemas florestais e de cerrado.

Tipo de Apresentação:  Oral