Abstract:Based on the measured data obtained from Anxi, the Curves of the orifical runoff precipitation have been established on various slopes. The results show that the coefficient of surface runoff is below 5% and subsurface and underground flow would be dominant factor to make the flood on the slopes with good vegetation cover, and on the undisturbed bare slopes the coefficient is over 45% and the surface flow would be determinant to form the flood. The relationship between the precipitation loss and intensity f=aib have been set up on various slopes, and the curves of infiltration process f=ae-bt also have been simulated on the basis of analyzing to the process curves of precipitation and runoff. It is point that a would be main influenced by precipitation intensity and the advanced rainfall, and b would be determined by advanced rainfall.

Abstract:This paper made a systematic researches on the determination on the level of soil and water loss in leveling area of development and construction (not being adopted the measurement of soil and water conservation). The determination of criteria of the level of erosion in urbanized development area is different from that of traditional soil and water loss in countryside. Through a large scale of field investigations and experiments, we analyzed the erosion modulus in leveling area correspondent with the characteristics of development area (including the soil type, this paper mainly research the area making up of red granite soil), and the results showed that the soil erosion modulus in serious level of leveling area is average 20 000~60 000 t/(k㎡.a),some erosion modulus may be up to more than 100 000 t/(k㎡.a). The paper reports the results of systematic research on the determination on the level of erosion and erosion modulus in construction development area first time. These results have provided the planning of soil and water conservation in Shenzhen City with scientific basic data, and it will be helpful for the work of soil and water conservation in other urbanized area.

Abstract:The model set up with quantification theory II had the good results in differentiating the grades of soil erosion intensity. When the model was used in distinguishing the soil erosion intensity of 88 samples participating in setting up the model, its differentiating accuracy ratios for intensive, median, slight and insignificant erosion groups were 100%, 91.3%, 83.3% and 93.8% respectively; total accuracy ratio was 92%. When it was used in differentiating the soil erosion intensity of 10 samples without participating in setting up the model, its accuracy degree was 90%.

Abstract:The bio-mechanics of 12 normal grasses root with diameter of 0.1~1.0 mm in Loess Plateau are studied by using of simple device designed by author. The result showed that the grasses root have very strong tensile strength. The grass root, with diameter of 0.1~0.2 mm had the anti-tensile strength of 1. 37N, legumes 0.77N and Artemisia of 0.69N. The tensile strength of hair root increased with its diameter enlarged and the incensement rate is that grass >legumes>Artemisia. The effect of age on root tensile strength vary with the plant species, however, there was no signified difference among the species of Artemisia. It was found that there exist a logarithm relations between stress and strain for Astragalus adsurgens and Medicago sativa in which the strain of hair root had a fast raising rate than the prediction by Hooker s Law, and the rest of hair root follow the law with different modulus of elasticity. The rank of elongation rate were Artemisia>Ispedeza duvurica>Setaria virideis. The sensitiveness of stress-strain to strain decreased with the root diameter increased. The critical strain rate varied with root diameter had three types: increase progressively; decrease successively and one-kurtosis curve. The significance of characteristic of bio-mechanics for plant hair roots in improving soil anti-scourability were discussed in the paper.

Abstract:Taking slope research as a breakthrough point, according to the variation law of runoff and sediment in the middle reaches of Yellow River and on the basis of cause and effect analysis, proposes "calculating sediment by flood" method, and apply this method to the slope measures analysis of the south watershed between Hekou and Longmen. The results show that the method is relatively reasonable, this study direction is a kind of useful exploration to methodology and has broad research prospects for the theory and practice.

Abstract:On the basis of analysing soil and water loss features and soil and water conservation practices arrangement of Nihegou watershed, sediment reduction benefit was calculated making use of soil and water conservation method-rainfall rectification and experience formula of region related to precipitation- flood capacity-sediment discharge. Results prove that sediment reduction benefit is move 90%. Finally we discussed also four problems on soil and water conservation.

Abstract:Taking Guyuan experimental area in southern Ningxia as an example, the comprehensive harnessing benefits of small watershed were studied. The results show: In the comprehensive harnessing, the key of harnessing are adjustment of land use structure and rational arrangement of agriculture-forest-pasture distribution. This structure of land use is seted as 3:2:5, according to the used area above. By the theory of eco-system engineering and combination with practice of the agriculture-forest-pasture structure, the land productivity could be improved by 2~5times as that before, runoff and sediment obviously reduce.

Abstract:With the method of system dynamics, a simulation model about land resources, population and social economy, ecologic environment of Changwu County was established. According to the simulation results, the scheme and its actions of land ecologic design of Changwu from the end of this century to 2020 year were put forward.

Abstract:The process of runoff and sediment yield in bareland and Astragulus adsurgens of different coverage were studied by means of artificial simulated rainfall. The results showed; the process of runoff and sediment yield were exponential (ｙ＝ｅａ＋ｂｘ) distribution in bareland, and were power (y=axb) distribution in Astragulus adsurgens grassland. When coverage varied from high to low, the parameter a decreasing, and b increasing.

Abstract:We selected Gaojiagou and Yuanzhishan in Mizhi county as the typical area to the Southern Yulin Hilly and Gully, and built fruit tree introduction and observation plantation. In early 80s, we introduced 114 tree species and 278 varieties, which are fallen into 67 genera and 34 families. Through fourteen years natural selection, 47 species and 106 varieties are selected which are fallen into 16 families and 32 genera and suitable to grow in this area and with good economic benefit. During 1987-1993, soil cannot run off the mountain and water cannot flow out the river in the arboretum, and the sand is decreased by 104 874 t/(k㎡.a). The water con-tent in 0~10 cm forest soil of Pinus tabulaeformis,Robinia pseudoacacia and peach is 6.8%~59.2% more than that farm soil. But below 11 cm the water content is to a decreasing tendency. The water content in 0~10 cm forest soil of apricot, Eleagnus angustifolia and Caragana microphylla is 16.4%~33.8% less than in farm land. Apple s economic benefit is the highest in all species, the per hectare output value of apple was 14579 yuan in 1993-1994, which is 3.86 folds higher than potato.

Abstract:Effective cover rate for soil and water conservation forests is an important index in the construction of forestry. This terminology appeared early, but its value are fluctuating from 30%to 75% for there is not a definite concept and the same method for determining it. In view of this, based on analysis of the system of soil and water conservation forest in detail, the concept of the effective cover rate for soil and water conservation forest is advanced as the cover rate when the amount of soil loss is equal to the permissible amount of soil loss in a given range: ae(-bF)=SLA. And its determining method is concerned with two important aspects and three steps, the effective cover rate is a function of time and space. Finally the soil and water loss region in Loess Plateau was exampled to introduce the determining method of effective cover rate.

Abstract:Field trials were conducted in a manural loessial soil with medium fertility, located in Yangling, Shaanxi, to study the changes of the mineralisable N and the relationship between its contents and biomass N in soil, the soil in different layers being sampled and the mineralisable and biomass N determined at regular interval times. The results show that the distribution of the mineralisable N varied with layer as well as with plant growth stage: being higher in cultivated layer than in deep layer, and lower and stable in early stage while 1 time higher in late stage. Application of N fertilizer had no obvious influence on the mineralisable N whereas application of organic fertilizer increased its contents in late stage of the plant growth. The effects of kinds of plants and plantation systems(i.e., with plantation or with no plantation) on mineralisable N were much less than sampling times. The mineralisable N released during plant growth period was only 12% of the biomass N, and there was no correlation between them. It seemed that the biomass N could hardly reflect the N-supplying capacities of a soil.

Abstract:With the help of a natural watershed, in which the vegetation was the artificial forest of Pinus massoniana with a 10 years old, it had been studied for the hydrological process and the movement of mineral elements. The evaporation in the stand was 4.0% of the annual rainfall, interception 20.8%, runoff 27.8%, throughfall 76.5% and stemfall 2.7%. It was the most concentration of K,P,Ca,Mg, Zn,Cu,Fe and Mn in the throughfall, the surplus of 8 mineral elements in the watershed was 8.528 kg/h㎡ in the average from 1993 to 1994.

Abstract:In the lightest rainfall year, the soil water cycle level was very low (3.05%), the in-filtration of rainfall was the shallowest (30 cm) and the soil water deficit was extremely heavy (-89.51 mm) in Caragana korshinskii forest land; in the heaviest rainfall year, however, the soil water cycle level was the highest (4.88%), the rainfall infiltration was the deepest (310 cm),and the water balance reached the highest (+195.09mm) in the shrub forest. The heaviest rainfall during the annual growing season contributed highly to the restoration of normal soil water cycle. Although the dry layer remained under the layer of rainfall infiltration in C. korshinskii, it was eliminated in Populus hopeiensis and P. simoniiplantitions.

Abstract:Based on investigation of physiography and soil property in Mae Rim catchment, Chiangmai province, Thailand, many factors are analyzed integratedly by remote sensing and Geographic Information System. As a result, the four maps of runoff curve number, runoff coefficient, runoff capacity, and flood inundation are produced.