SOIL LOSSES FROM FIRE BREAKS AND Pinus taeda COMMERCIAL PLANTATION IN SOUTHERN BRAZIL.
CARLA M. CAMARGO CORR╩A1, RENATO A. DEDECEK2, and JORGE R. MALINOVSKI1. (1) FOREST SCIENCE DEPT. - FEDERAL UNIVERSITY OF PARAN┴, RUA: LOTHARIO MEISSNER, 3400 - NCAMPUS III, CURITIBA, Brazil, (2) EMBRAPA CNPFlorestas, Caixa postal 319, COLOMBO, Brazil
In forest areas, fire breaks are the basic forest road system and at logging they are used to complement forest road system and it is common the occurrence of erosion on this place during this period. This work aimed to evaluate, during the period of one year, the losses of sediments originated from fire breaks on a clayey and on a loamy soils with different slopes and from Pinus taeda commercial plantation areas adjacent to fire breaks with 8 and 6 years old, respectively. This work was set on the northern plateau of the state of Santa Catarina in South Brazil. The section of the fire breaks consist 100 m length and 4 m wide, and the adjacent area measuring 100 m length and 50 m wide (0,5 ha). On both areas, runoff were sampled at lower end using a Coshocton wheel device and stored in plastic buckets. Samples of the runoff were collected every fifteen days to separate sediment and water. Sediments were analyzed for nutrients and texture determination. Annual rainfall was 1454 mm on a clayey soil area and 1496 mm on a loamy soil area, resulting on values of rainfall erosivity of 1098 MJ mm ha-1 h-1 and 992 MJ mm ha -1 h -1, respectively. Soil losses from fire breaks on clayey soil, gentle relief were 0,144 t km -1, and from fire breaks located on a loamy soil with 13 to 17 % slope, soil losses were equal to 1,401 t km -1. Considering in the clayey soil area that the fire break density was 11,91 m ha-1, total soil losses could reach 0.002 t ha-1. In a sandy soil area that the road density was 35,61 m ha-1, producing soil losses equal to 0.005 t ha-1. In adjacent areas there were not soil and water losses. Pinus taeda needles annual contribution of nutrients both areas a showed on Table 1.
Key words: water erosion, soil nutrient losses, litter decomposition