Research On The Physical And Chemical Properties Of Soil Under The Forest Of Cunninghamia Lanceolata (Lamb.) Hook In The Early Period Of For-grass Intercropping And Soil And Water Conservation

The trail used the matching of Cunninghamia lanceolata(Lamb.)Hook and different spices of pastures as experimental factors, and plot without grass as controls. 5 sample plots are put in the experimental area of Cunninghamia ianceolata (Lamb.) Hook, and the experimental area have an average site type and forest age. Each sample plot is divided into four experimental plots, each was intercropped with one of the four pasture spices: Lolium perenne, Cunninghamia ianceolata(Lamb.)Hook, Trifollumpratense,T.repense with white colour and Medicago sativa, to form four types of for-grass intercropping model with the Cunningham iaianceolatu(Lamb )Hook. As the forest is young, it has little to do with the changing of the physical and chemical properties of the soil, so the main factors that induced the improvement of the physical and chemical properties of the soil and decrement of soil erosion and water loss is the growth of the pasture. So this trail takes not the effect of the young forest, but the effect of the pasture under the forest to the physical and chemical properties of the soil into consideration. Furthermore, six 10m×5m artificial slope runoff experimental plots are put in the experimental area. Each plot grows one of the following pastures: Hemathria compressa (L.F) R.Br, Dactylis glomerata L., Medicago sativa, Cichorium intybus L., using the agricultural land (maize) and the naked-field as control plots, to observe the effect of water and soil conservation of the different types of vegetation, the result showed that:1 Study on the improvement of the physical prosperity of the soil caused by the intercropping of four pastures with Cunninghamia ianceolata(Lamb.)Hook showed that, the sowing of the four pastures improved the soil's physical prosperity effectively. The effects of improvement of the soil's physical prosperity caused by Hemathria compressa (L.F) R.Br and Trifollumpratense,T.repense are better, one year latter, the values of bulk density declined with the decrement of 0.08 and 0.11, the total soil porosity increased by 7.14% and 5.10%, capillary porosity increased by 6.42% and 3.71%, and field moisture capacity increased by 5.33% and 3.48%; secondly, for Lolium perenue, the value of bulk density declined with the decrement of 0.07 after one year , the total soil porosity increased by 2.12%, capillary porosity 1.50% and field moisture capacity 3.48%; for Medicago sativa L., whether the soil's bulk density, soil porosity or the change of the field moisture capacity are less, the value of bulk density declined with the decrement of 0.03, total soil's porosity increased by 1.98%, capillary porosity 1.36% and field moisture capacity 0.83%.2 Study on the improvement of soil chemical property in the early period of intercropping of four pastures with Cunninghamia ianceolata(Lamb.)Hook showed that, grass family consumed more soil organic matter than leguminous grass. To be more concrete: Hemarthria compressa and Lolium perenne consumed 0.332% and 0.228% respectively in one year. Trifollumpratense,T.repense and Medicago sativa's consumption are 0.166% and 0.119%. At the same time, the two grass family pastures made greater impact on total N and available N than the two leguminous grass pastures in a year. Hemarthria compressa, total N declined 0.55% and available N declined 43.11mg/kg. Lolium perenne, 0.047% and 30.67mg/kg. Trifollumpratense,T.repense 0.017% and 9.21mg/kg, Medicago sativa, 0.026% and 8.27mg/kg. Although potassium and phosphatealso changed in a small range, the trend is decrease, however, the effect of improvement is unobvious on the whole. As the time is too short to observe enough, the tendency of the change of soil chemical property is complex.3 Study on the capacity of soil and water conservation of these pastures showed that good vegetation covering could reduce soil and water loss effectively. Different types of vegetations have great impact on the runfall's characteristic and the amount of soil washed away by the rainfall. Among these experimental pastures, plot oiHemarthria compressa (L.F.) R.Br. has the smallest amount of soil washed away in the whole year's rainfall. The order of depth of slope runfall of each small pasture area and area of control is that, agricultural lands >naked-fields>C7c/jor/M/n intybus L.=Dactylis glomerata L.>Medicago satirat>Hemarthia compressa (L.F) R.Br, among them, the effect of Hemarthia compressa (L.F) R.Br. is the best. The order of each plot's soil erosion is that, naked-fields>agricultural lands> Medicago satirat>Cichorium intybus L.> Dactylis glomerata L.> Hemarthia compressa (L.F) R.Br, the of soil erosion of each pasture are less than the agricultural lands and naked-fields, and the of soil erosion of Hemarthia compressa (L.F) R.Br is the best. After 10 minutes when rainfall intensity reached to the climax, the runoff amount of each plot reached to its climax and Hemarthia compressa (L.F) R.Br. is 20 minutes later. During the rainfall, the runoff amount's changes of Hemarthia compressa (L.F) R.Br. are always mild, the others are fluctuate heavily, the impacts which caused by rainfall intensity on the runoff amount of Cichorium intybus L. and agricultural lands (maize) are also relative great, and the naked-fields are the most obvious. The soil and sand content in runoff in plots of runoff is obvious less than the plots of naked-fields. There is not much difference of the soil and sand content in runoff between agricultural lands and each small pasture area. The runoff amounts in all the plots which covered with vegetation are less than plots did not covered with vegetation, but among those areas covered with vegetation, the capacity of preserving water and soil of Hemarthia compressa (L.F) R.Br is obvious better than the others.