Arrangement of protective forest system in gulled-hilly loess area based on water balance.
Zhu Jinzhao; Wei Tianxing; Zhang Xuepei. College of Soil and Water Conservation, Beijing For. Univ., 100083, P.R.China.
This paper studies the rainfall and topography which influence the soil erosion in the gulled hilly loess area, and analyses the sediment source and regularity of soil erosion according to the field monitoring data,puts forward arrangement patterns and techniques of protective forest system which is based on soil and water conservation function and moisture balance. ①When slope degree 25°,agroforestry system is adopted,including terraces separated by slopes,level channels separated by slopes and level terraces. Slope length and farmland width are designed in the light of the eco economic principles.② When slope degree 25°,the lands may be used for forestry and husbandry,the measures include combination of trees and grass planting,closing the land for reforestation and artificial tree planting.③Building a protective forest pattern in valleys and channels to stabilize channels, hold up sediments and filter water,decrease flood peak and reduce velocity of flow.The concrete measures are combinations of forest and grass,closing hill and at forestation as well as artificial planting, also the combination of biological and engineering measures.The arrangement of protective forest system should base on the rational distribution of moisture ecological environment,that is the planting of protective forest system on different topography considering the permission biomass of specific site condition and the balance between forest and moisture,so as to reach the rational planting arrangement pattern and stable stand structure.