Changes In Catchments Runoff Due To Forest Vegetation Variety In Xiaoxing'an Mountains

Forest variety contains forest cutting and forest restoration。Forest cutting is one of the main measures by which people can exploit and utilize the forest resources, but with the acquisition of some economic interest, loss of various ecology benefits also follow, which is several times higher than economic interest. There are abundant forest and water resources in the region of Xiao Xing'an Mountain, whereas because of excessive cutting, there used to appear some ecology crisis such as water loss, soil erosion, flash flood and riverbed elevation. Combining sample investigation and data statistics, two comparing small watersheds in Xinlin River Catchment and Yulin River Catchment of Xiao Xing'an Mountain was studied to analyze the effect on small watershed runoff of forest vegetation change after cutting, according to the investigation data of meteorology and hydrology during year 1970-2005. Results showed that:Selective cutting manner was adopt to manage Xinlin River Catchment forest during 1970～2005, so that the forest types were predominated by the primitive korean pine and broadleaved forests with complicated stand structure, and the forest coverage rate was stabilized at 70%-80%. Whereas forestation year by year was carried out in Yulin River Catchment after large area clear cutting, so that the coverage rate was raised from 28% to 79% divided to 3 stages with the point of inflection in 1980 and 1990 and the species of forestation was Larch plantation, whose structure was rather single. From the forest soil point of view, the sequence of compacting effect on soil was virgin forestselective cutting forest>clear cutting forest. Although the maximum retention volume sequence of another 3 forest types showed as natural secondary mixed broadleaved forest