The Effect Of Water And Soil Conservation Of Two Economical Forestry Disposal Modes

Since the operated cycle of the economic forest is short, the economic profits are high, become one of main forest kind in converting farmland to forest engineering construction in our country. However ,the species choosing, mode disposition and the unreasonable forestry structure has resulted in the bad effect of water and soil conservation .The subject chosen in this study is the mode of converting farmland to forest (grass) and the economic forestry's water and soil conservational effect of two modes was also evaluated in this paper .Through setting up artificial surface flow district and the station observation in farmlands, the water holding characteristic of canopy of the two modes were analyzed based on the experimental data. At the same time, the farmland was the control site, the differences among the soil water dynamics, physical features and the nutrient content was reviewed in this paper .The key aspects of the study were the characteristics of flow and sand production situation and the loss of the nutrient of the two modes and farmland .The result showed as followed:The soil physical features in forestry showed the significant difference compared with the farmland. Total porosity, capillary porosity, non-capillary porosity in 0-10cm soil layers has increased respectively by 11.12%, 6.33%, 35.98%; Soil bulk density has decreased by 4.62%, the moisture capacity has been improved. The bulk density in fruiter-greenstuff, porosity situation and the moisture capacity represented no significant difference compared with the farmland .And there was no difference between the two modes on the moisture dynamics.The canopy interception capacity increased with the increase of rainfall but not increased any more when reaching the max value 4.90mm, then the interception rate became lower generally even showed a negative relationship to the rainfall .The flow in the trunk and stem became higher with the increase of rainfall, but occupied a little propotion in the distribution of rainfall each time. stem flow rate fluctuate ranging 1.26%~3.14% .The interception of the canopy of the two modes was relatively lower, do little to decreasing runoff.There were evidently difference between annual changes of runoff and sand production. The different management of the two modes has most important effect on features of the sand production, In 2003,2004, and 2005, the runoff amount of fruiter-grass was 34.0m~3/hm~2, 782.9m~3/hm~2, 794.5m~3/hm~2, fruiter-greenstuff was 42.9m~3/hm~2, 992.5m~3/hm~2,1401.8m~3/hm~2; and the sediment yield of fruiter-grass was 73.5t/km~2,1021.6t/km~2,770.8t/km~2,fruiter-greenstuff was 127.4t/km~2,7897.0t/km~2,10189.5t/km~2.