Miyun Reservoir provides more than 70% drinking water resources for Beijing, it is very important that to study the hydrological properties of canopy of water resources protection forests, which to help managing and cultivating the water resources protection forests. In this paper, the stands of Robinia pseudoacacia, Pinus tabulaeformis and Castanea mollissima were studied from 1999 to 2000. The total precipitation amount was 545 mm in the 2 main rain periods from 1999 to 2000, distribution in canopy interception, through-fall and stem-flow in the R. pseudoacacia stand were 97.73 mm, 434.78 mm and 12.49 mm,respectively, that in the P. tabuleaeformis were 131.54 mm, 397.98 mm and 15.48 ram, respectively, and in the C.mollissima stand were 110.73 mm, 422.07 mm and 12.20 mm, respectively. The canopy interception and stem-flow amount of P. tabulaeformis stand, the through-fall amount of R. pseudoacacia stand was the biggest among the three stand respectively.The elements content of N, P, K, Na, Ca, Mg, Fe, Zn, Cu and Mn were monitored for the precipitation, canopy interception,through-fall and stem-flow of the three forest types. The total amount of weighed average content of ten chemical elements in precipitation was 12.001 1 mg·L-1. The sequence of the chemical elements weighted average content of the precipitation is followed: Ca > N > K > Mg > Na > P > Fe > Zn > Cu > Mn. The concentration of chemical elements of through-fall and stem-flow varied in differently for three forest types in comparison with the precipitation' s.
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