Influência da cobertura vegetal na ciclagem de nutrientes e nos atributos do solo, em áreas da Floresta Nacional Mário Xavier, Seropédica, RJ

Abstract

The object of this work was to evaluate soil characteristics, litter production, soil fauna, cycles and the rate of litter decomposition in tree different areas: a secondary forest, Mimosa caesalpiniifolia plantation (sabiá), followed by natural regeneration and Carapa guianenses plantation (andiroba), followed by natural regeneration, located in the district of Seropédica-RJ. It was appraised Ca, Mg, C, Al, P, K and Na of the soil. For evaluation of litter composition, 10 conical collectors were installed in each area in September of 2003. The material was collected during various seasons until September of 2004. After the collection the material was separated in leaves, branches, flowers, seeds, peels and others. They were analyzed for N, P, K and the levels of poliphenois, lignin, suberin, tannin and holocelulose. The fauna of the soil was studied with traps of the type "pit-fall" with 10 traps by area in each season, during 7 days. The individuals were separated and identified. Samples were collected in the layer of 0-5 cm and the microbial biomass was investigated by the method fumigação-extraction. The decomposition was studied in vitro through the evolution of CO2. The evaluation of the decomposition rate was made using the method of the "litter bags ", that were disposed on the forest floor. The areas of sabiá planting followed by natural regeneration and andiroba planting followed by natural regeneration presented higher levels of carbon in the layer of 0-5 cm and of phosphorus in 0-5, 5-10 and 10-20 cm layers, in comparison with area of forest spontaneous secondary succession. The area of andiroba plantation (Carapa guianenses) followed by natural regeneration contributed with the largest amount of litterfall (9,20 t. ha-1 year). The area of sabiá plantation (Mimosa caesalpiniifolia) followed by natural regeneration presented MFS of 9,06 t. ha-1 year and the area of forest spontaneous secondary succession 7,63 t. ha-1 year. The litter of the areas of sabiá plantation (Mimosa caesalpiniifolia) followed by natural regeneration and of the andiroba plantation (Carapa guianenses) followed by natural regeneration were richer in nutrients than the area of forest spontaneous secondary succession. The area of sabiá plantation (Mimosa caesalpiniifolia) followed by natural regeneration presented larger proportion of the saprophytes group which suggests a larger decomposition speed. The area of sabiá plantation (Mimosa caesalpiniifolia) followed by natural regeneration presented larger speed of liberation of CO2 and the smallest microbial biomass what it can be caused by the use of the microbial biomass as source of nutrients for the vegetation. The andiroba plantation (Carapa guianenses) followed by natural regeneration and the sabiá plantation (Mimosa caesalpiniifolia) followed by natural regeneration presented a similar litter decomposition. The liberation of P and K during the decomposition process had a similar behavior among the areas.