Fluxo de nutrientes em precipitação direta e interna na região Oeste Paraense

Abstract

The objetive of this research was to contribute with the knowledge of one of the components of influence on the sustainability of a forest ecosystem : the deposition of nutrients in rainwater. The nutrients inputs potassium (K+), phosphorus (P), magnesium (Mg2+), calcium (Ca2+), iron (Fe2+), aluminum (Al3+), copper (Cu2+) and zinc (Zn2+) were observed in rain in two forest plots (throughfall) and in two plots of open fields (rainfall) , in order to verify the influence in this deposition by intense agricultural practices near FLONA Tapajós. Sampling was carried out the municipality of Belterra-Pará, in the FLONA Tapajós two points (km’s 67 and 126). In each of these points the throughfall was samples in a transect, starting at the border between FLONA and the Santarém-Cuiabá highway and entering FLONA, a distance of 100 m. Rainfall was samples in open areas around the FLONA, at the two collection points of the throughfall. The site of the km 67 is in the zone of influence of the intense agricultural activities while the km 126 owns to the surrounding community belonging to settlement characterized by activities of familiar agriculture, serving as a controller, that is, area outside the zone of influence of agricultural activities. The collections were carried out in two bases in throughfall area of km 67 of FLONA Tapajós, 25 collectors were used in a range of 10x10m from April/2003 to March/2006, weekly. In the second pause, performed monthly between April 2016 and December 2016, sampling was done both on the transect within the FLONA using 06 collectors/plot, and for the rainfall 4 collectors/plot were used. The forest collectors were installed every 10m distance for each from the edge towards the inside of the forest and those of the open field inserted into groups the edges of the area around the respective points of the forest plots. The same sampling scheme was used in the km 126 site. The K+ flux at the site border 67 was greater than FLONA inside, at the control border and in rainfall. Edge 67 also showed higher P deposition relative to the control border and rainfall. Suggesting that potassium and phosphorus flows are prone to influences from surrounding agricultural activities. Throughfall proved to be an important route of input for nutrients, mainly potassium.