Study On Coordinated Control Of Soil Erosion In Chestnut Forest In Yanshan Mountainous Area

The distribution area of chestnut in Yanshan was a typical mountain area,with high mountains and steep slopes,and less arable land,more forest land,mountain land utilization occupies an important position in the development of local agriculture and forestry.In the cultivation and management of chestnut forest,the ground surface under chestnut forest was lack of shrub grass and litter layer.The soil was mostly weathered,the structure is loose and the resistance is poor;in addition to the slope of the ground was steep,every case of rain forest ditch down clouds,surface erosion and gully erosion were serious,a large area of soil became gravel.With the development of chestnut plantation in recent years,the problem of chestnut soil erosion was becoming more and more obvious.On the basis of a large number of field investigations and experiments in the study area,the paper put forward a partition-cooperative prevention and control model to decrease soil and water loss:(1)With the increase of the chestnut plantation operation period,comparing the initial soil infiltration rate: chestnut forest slope manage for many years(10mm/min)> chestnut forest level ditch manage for many years(8mm/min)>chestnut forest slope newly cultivated(6mm/min)= horizontal ditch of new reclamation chestnut forest(6mm/min),their soil stability infiltration rate were match;the average soil water stability index of newly cultivated chestnut forest was 4.9 times than the chestnut forest manage for many years,newly cultivated chestnut forest had soil cover,which could effectively reduce surface erosion,because of chestnut forest manage for many years without grass coverage,the soil erosion resistance was poor.(2)With the increase of the operation period,the soil anti-permeability and anti-erosion ability of chestnut forest decreased significantly.For the chestnut forest which had been operating for many years,the remedial measures should be taken to maintain the horizontal ditch;for the newly cultivated chestnut forest,it was necessary to plan and operate reasonably according to the critical slope length of rill erosion.(3)The partition-collaborative control measures on the straight slopes of the chestnut forest were to cut runoff and sediment,the two years regulation rate of interval 8m lay concrete sill reached 61.70% and 97.41%,while the two years regulation rate of interval 6m lay concrete sill were 54.15% and 85.31%,the erosion intensity of Chinese chestnut under two measures were much lower than the erosion intensity of area background value.By comprehensive comparison,8m was more suitable for the prevention and control of soil erosion under the straight slope chestnut forest.(4)The runoff of straight slope chestnut forest was affected by the characteristics of each rainfall factor,and the single rainfall factor did not show the dominance of hillslope runoff;The sediment yield was not determined by a single rainfall factor,but compared with the control area,the correlation of measure area rainfall sediment and rain intensity were weakened.(5)During the heavy rainstorm(greater rainfall intensity),the runoff regulation effect of partition-collaborative prevention measures for Chinese chestnut is significant,but the effect of runoff control is less than that of heavy rain under the condition of larger rainfall but lower average rainfall intensity.Through the analysis of runoff and sediment regulation rate of different rain patterns,and the partition-collaborative control model of different underlying surface,the runoff and sediment regulation rate on the slope of chestnut forest could achieved better under the case of strong rainfall.(6)The runoff and sediment yield of the control area of the partition-collaborative control model showed a decreasing trend with the increase of the average rainfall intensity and I30;in case of measures area,the runoff of the partition-collaborative control model was increased with the average rainfall intensity and I30,and showed reduced trend,the sediment yield was increased with the increase of the average rainfall intensity and I30,and showed an increasing trend,decreasing with the increase of the rainfall.(7)From the view of engineering cost,the project cost of the partition-collaborative control model was much lower than the cost of slope modification project in northern Rocky Mountain area,which had good economic applicability.