Abstract:

The parper studies the effect of precipitation on litter decomposition and migration of several chemicals.

1. Diao luo montain in Hannan island is characterized by larger precipitation. Therefore, precipitation is direcly proportional to leak water and soil moisture content but in inverse proportion to element concentration in tropical monsoon forest and rubber plantation. The overall concentration of all 9 elements concentration in water is in the order of ditch water>Well Water>soil seepage water>run off>river water>leak water percipitation. The concentration of each element in all water is in the order of SiO2, K2O, Na2O, CaO, MgO and P2O5, MnO, Fe2O3, Al2O3.

2. Precipitation accelerates the litter decomposition and the element release and promotes material cycle and exchange. Decomposition of leaf litter in rain season is 16. 6–28. 8% faster than that in dry season in the early ninety days. Total element return capacity in dry season is more that in rain season. Return of SiO2 is much more that CaO,N, MgO and K2O. But return of CaO, N is more in rain season, return of SiO2 is more in dry season.

3. Elements migration restricted by precipitation may be attributed to three aspects, i. e. ground migration, soil migration and mixed migration. Ground migration takes up to 51.7–59.3 percent of the total migration capacity; decreasing and enrichment of Fe and A1 is the main feature of element magration; enrichment and lack of nutrient is the results of element migration. Monsoon forest accumulates 172.5kg/ha·yr, rubber plantation lacks 13.6kg/ha·yr. In addition, the bulk of element migration is occurred from August go October when the precipitation and it′s intensity are both high.

4. Element concentration of precipitation and all kinds of water may be expressed and predicted by equation.

5. In planting of tropical economic crops and tree, protected measures must be taken such as building terrace, suitable close planting and reasonable intercropping and so on. Otherwise, nutrient element leach and soil fertility reduction would not be avoided.