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| Author(s): |
Carla Daniela Câmara
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | Piracicaba. |
| Institution: | Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC) |
| Defense date: | 1999-04-27 |
| Advisor: | Walter de Paula Lima |
| Abstract | |
The main propose of this monitoring was to find indicators that could help forestry activities in the way to reduce potential effects on water yield and water quality. As part of this watershed project of the ltatinga Experimental Station, this work aimed to investigate the effects of clearcutting of an old growth (50 years) Eucalyptus saligna coppice in the catchment hydrology, in terms of water yield, water quality, and nutrient budgets. For this propose, the average data of the first 6 years calibration period are compared with data of the first year after the clearcutting. lt was observed an annual increase of 94 mm in the water yield during the first year after clearcutting, which correspond to 1,0 % increase in correlation between precipitation and annual water yield. Nutrient lasses as dissolved ians in streamflow showed significant increase for K in relation to the pre-harvest period. Ca, Mg, Fe and Na had no significant annual loss increase, but showed significant monthly increases in relation to the pre-harvest period. ln spite of these losses, the annual geochemical budget was positive for K, Ca, Fe Na and negative for Mg. The most affected water quality parameters were turbidity, color and suspended sediment. For detecting clearcutting impacts in water quality, physical parameters were more efficient than chemical parameters, especially color, electric conductivity and turbidity. Wood harvesting was responsible for the following amount of nutrient lasses: 80.0 kg.ha-1 for N, 10.32 kg.ha-1 for P, 68.41 kg.ha-1 for K, 67.09 kg.ha-1 for Ca and 36.13 kg.ha-1 for Mg. Leaves and small branches, which stayed in the catchment after wood harvest, had a nutrient amount of 44.88 kg.ha-1 for N, 3.2 kg.ha-1 for P, 12.82 kg.ha-1 for K, 12.25 kg.ha-1 for Ca and 7.69 kg.ha-1 for Mg in the leaves and 35.13 kg.ha-1 for N, 2.52 kg.ha-1 for P, 18.72 kg.ha-1 for K, 17.29 kg.ha-1 for Ca and 8.86 kg.ha-1 for Mg in the branches. The catchment biogeochemistry budget from September 1991 to august 1998 showed a total nutrient loss of 56.79 kg.ha-1 for K, 72.92 kg.ha-1 for Ca and 40.89 kg.ha-1 for Mg. The maintenance of the integrity of the catchment riparian zone forest, as well as the forest floor; coupled with a conservative harvesting technique and a rapid Eucalyptus regeneration, were considered important factors which were responsible for the relatively minor impacts of the clearcutting on water quality chemical parameters and nutrient losses from the catchment. (AU) | |