The Hydrological Research Of The Soil And Litter Of Different Type Artificial Robinia Pseudoacacia Forests In The Loess Plateau Of Eastern Gansu

The methods of forest structure investigation,indoor immersion method,soil profile survey method and soil moisture-physical property determination were used,and artificial boring forest was used as the research objectin the ditch small watershed of Guanzhan forest farm in Jingchuan County,Gansu Province.The density was divided into 6 densities(750plants/hm2,1227 plants/hm2,1600 plants/hm2,2196 plants/hm2,3780plants/hm2,4563plants/hm2).Analysis the litter Layer and soil layer,revealing the water holding characteristics,soil physical properties,water holding capacity and permeability characteristics of litter layer of artificial density of Robinia pseudoacacia plant in different densities.Deeply understand the ecological and hydrological functions of vegetation and soil and litter.And provide theoretical reference for the rational management of plantation in the region with limited water resources and scientific construction of forest vegetation.The main conclusions are as follows:(1)The total fluctuation range of litter in six densities of Robinia pseudoacacia was between 8.09 and 13.40 t/hm2.With the increasing of stand density,the litterfall increased first and then decreased.And the percentage of undeclounded volume in the forest decreased gradually from 41.00% to 62.83%,while the proportion of semi-decomposed layer decreased gradually,ranging from 37.17% to 59.00%.The water holding process of the undivided and semi-decomposing layers of different litter density litters is similar,and the relationship between the water holding rate of the litter and the immersion time is very significant.The range of the total effective litter storage is 8.03~33.4 t/hm2,and the overall storage capacity increases with the increase of stand density,and the effective storage volume increases first and then decreases.It is higher than the effective storage of semi-decomposed layer.(2)With the change of stand density,the average soil bulk density of different stands was750 plants/hm2> 1227 plants/hm2> 1600 plants/hm2> 2196 plants/hm2> 4563 plants/hm2>3780 plants/hm2;The mean soil total porosity and non-capillary porosity were 3.96~12.00%and 44.60~53.07%,respectively,and the variation trend was opposite to the mean value of bulk density.(P<0.05).There was no significant difference in soil bulk density,total porosity and non-capillary porosity(P<0.05),and there was no significant difference in soil bulk density,total porosity and non-capillary porosity at 0-40 cm,which were 3780 plants/hm2>4563 plants/hm2> 2196 plants/hm2> 1227 plants/hm2> 750 plants/hm2 respectively.(3)The highest average permeation rate was 4563 plants/hm2 and the lowest density was750 plants/hm2 locust plantation at different densities.The soil initial seepage rate was 4563plants/hm2>3780plants/hm2>2196 plants/hm2>1227 plants/hm2>750 plants/hm2>1600plants/hm2.The highest rate of the soil infiltration was 4563 plants/hm2(3.40 mm/min)and750 plants/hm2(0.82 mm/min)was lowest.(4)The soil water content of the artificial plantation of Robinia pseudoacacia was stable in the early stage of the growing season,and increased with the increase of stand density.The soil moisture content gradually increased after the growth season show a loss,and the late growing season in addition to a density of 1600 plants/hm2 plot,several other showed a certain degree of loss,and a density of 4563 plants/hm2 plot even moderately dry soil phenomenon.(5)Based on the comprehensive analysis of the maximum water holding capacity and effective water holding capacity of the litter and the soil layer,the soil layer is more than 96%of the total forest area occupied by the soil layer,so the soil layer is the main place for the forest to regulate precipitation and water retention.The comprehensive evaluation of litter layer and soil layer hydrological function of Robinia pseudoacacia plantation and soil layer was 4563 plants/hm2,3780 plants/hm2 and 2196 plants/hm2.The results were consistent with those of the soil layer,indicating that the soil layer was the main site for the hydrological regulation of forest land.The results showed that the soil layer was the main site of the forest land.