A constitutive model for the stress-strain relationship of single forest root system was developed in order to provide theoretical foundations for the mechanisms of soil-reinforcement by root system and offer a reliable basis for the analysis of root tensile strength character. This study started a general form of linear and non-linear stress-strain relation that was mathematically defined by four boundary conditions observed in typical tensile tests of single roots. The parameters of the model were determined by experiment data and had definite physical meaning. The model was verified by experiment data, which showed that the calculated values were in good agreement with the experimental single root tensile test results. The constitutive model was validated and found to be feasible for modeling single root tensile stress.

Preferential flow indicates that an ordinary phenomenon of rapid and non-equilibrium transport of water and solutes happens in most of soil. It causes a latent pollution of ground and surface waters and affects runoff yield and concentration. This paper studies the preferential flow movement of the dark coniferous ecosystem of Gongga Mountain, sets up the classification of the preferential flow and discusses the types of preferential flow in the reached area. Results show that the perceptible type of the preferential flow in the young, mid-aged and over-mature is macroporous flow; it is finger flow or funnel flow in the mature forest soil and will gradually transform to macroporous flow as the soil layer is deeper. The purpose of this research is to analyze systemically the law of soil water movement of dark coniferous forest ecosystem of Gongga Mountain and to provide theoretical basis for the effective watershed management.

Meteorological factors are one of the natural factors, which affect ecosystem services value(ESV). Influence of meteorological factors was studied in Beijing-Tianjin-Hebei region using odinary least square (OLS) with geographical weighted regression (GWR). The main aim of this study was to reveal the differences in the influence mechanism at the global and local levels. The main meteorological factors influencing ESV were temperature and precipitation, followed by humidity. Days with annual daily precipitation≥0.1mm, annual minimum precipitation and annual average relative humidity were three important meteorological factors. Annual temperature range, annual minimum precipitation, days with annual daily precipitation≥0.1mm, in particular, the last one had an obvious positive effect. The positive and negative effects of annual average relative humidity were coexisting, and the negative effect was the main. It was obvious that the spatial distribution characteristics of the local influence mechanism. The local model of GWR can better solve the spatial non-stationarity of the dependent and independent variables, thus it was better than the global model of OLS. The results also provide detailed field information on the different effects of meteorological factors at different locations.