Study On Water Balance In Small Watershed Of Natural Forests In Upper Of AShe River

This article took the natural secondary forest in small watershed of natural forests in SunRong channel as research object and quantitatively analyzed the water balance in forest ecosystem, the results were as follows:(1) The rainfall mainly intensively covered the July, August, September in the growing season in test area forest. The rainfall comprised 88.45% of that in the whole rainy season with the largest rainfall in July, 169.3mm. With increased rainfall class, penetration rate performance of the overall trend is gradually increasing at each sample field, but growth is easing gradually. The trunk runoff rate is sample 2> sample 1> sample 4> sample 3 in the growing season, this is mainly to the proportion of tree species which is easy to form a trunk runoff, as well as the slope and slope position. The canopy retention rate is greater in July than in other months at each sample. Different stands on the redistribution of rainfall in different.(2) Given the consumption of water, the transpiration rate was relatively higher in August and September in growing season in forest. The evapotranspiration water consumption ranged 68.27% of rainfall during all the growing season. The evaporation intensity in forest land during different spells were in such sequence: early August > late August > late August > late September .The non-decomposed layer where forest land litter existed had weaker potential for water retention than the decomposed layer. Water-holding capacity is relevant to the slope and tree species composition. The soil water storage capacity of sample 4 is the strongest in 0-40cm soil layer, sample 1 and sample 3 is second. Sample 2 is the worst. The differences of each sample field relevant to the slope and slope position.(3) Terrain along with the depth soil layer had relative huge effect on soil water content and soil water physical property. The soil water content decreased as the soil depth deepened in natural secondary forest at distinct terrains. The difference of average water content was largest at each sample field in 0—10cm, reaching up to 20.47% while there was the least water content at each sample field in 30—40cm with just 8.00%. The moisture capacity of natural secondary forest at different terrain mainly depended on the soil structure and pores forming situation at different terrains.(4) The equilibrium of supply and demand in every month during growing season were as follows: July 2.87×10~4 t, August-0.42×10~4 t, September 0.09×10~4 t. The water profit during the whole growing season was 2.54×10~4 t. The water required for forest growing was sufficient and the plant growth indicated that there was no serious water stress there.