Responses Of Plant Function Traits To Microtopographical Changes And The Evaluation Of Ecosystem Services In The Yanhe River Catchment,Shaanxi, China

The hilly region in the Loess Plateau has drastic topography changes, it is difficult to describe the vegetation pattern caused by the topography changes using rainfall-based vegetable zones, the vegetation pattern shows a mosaic structure: forests can spread into forest steppe north along the gullies, and the herbaceous communities can extend along with the dry hill ridges into the south forest zones. The topography controled microhabitats played in important roles in the formation of the mosaic strucutre. Understanding the responses of plant functional traits, a bridge linking species and environment, to terrain changes is important for clarifing the adaptation strategies and the formation of vegetation pattern. The study selected 6 intact transects in forest-steppe zone and typical steppe zone, and analyzed the response relationships among the plant functional traits of different plant communities and different family and genus plant level with terrain changes and the soil gradient. The analysis help to revealthe causes of the formation of vegetation pattern through the variation of plant functional traits at basin and hillslope scales, and to select the plant traits index for ecological service assessment. The mains results are as follows:The topography change has important impact on the spacial change of soil characters: soil carbon and soil nitrogen has significant differences and surface convergence phenomenon, while soil phosphorus has no consistent change rule in forest-steppe zone. There has no significant differences and surface convergence phenomenon between soil carbon, soil nitrogen and soil phosphorus in typical steppe zone.Plant functional traits of plant communities have significantly correlations. Plants of different vegetation zone have different survival strategies: specific leaf area, leaf carbon and phosphorus have significantly positively related to soil carbon, and leaf density have significantly positive correlation with soil phosphorus in steppe, these showed that in order to improve the ability of photosynthesis and plant life vigor and to maintain the growth of plants, plants will improve the use efficiency of carbon and phosphorus in steppe zone; Specific leaf area and leaf phosphorus having significantly positively relation with the soil phosphorus in forest steppe showed that plants use phosphorus in the soil to improve the plant’s defense capabilities.The function traits of different plant are different, and the response of different family and gDifferent plants hold different funtional traits and their responses to different family and genus plants’ functional traits to the terrain changes have big difference. Leaf phosphorus of gramineae plant and leaf phosphorus of compositae plant have significant difference with root phosphorus respectively on different slope aspects in steppe area,and have no significant difference on different slope positions; Leguminous plants have no significant difference on different slope positions and slope aspersion steppe. Only the root density of gramineous plants has significant difference on different slope positions. Leaf nitrogen and root nitrogen of leguminosae plant in the upper slope, lower slopes and mao top have significant difference; Leaf nitrogen, root nitrogen and carbon of compositae plants have significant differences, Specific root length only has significant difference in the middle and upper slopes.Gramineae and leguminosae are greatly influenced by soil nutrient in steppe area: the main limiting factors affecting the train of function of gramineae plants traits are soil carbon, soil nitrogen and soil phosphor, the soil nitrogen and phosphor are main factors affecting leguminosae and asteraceae plants. In forest-steppe area: the significant positive correlation between leaf nitrogen and root nitrogen with soil nitrogen and soil phosphorus of leguminosae and asteraceae plants. Leaf nitrogen and root nitrogen are significantly positively related to soil nitrogen of gramineae and asteraceae plants. This shows that there is major respone differences between different genera plants and environmental changes. Different species plants have different environmental adaptation strategies.Using analytic hierarchy process to calculate the ecological service function index(IE) and analysis the rule changes with the topography varies, it showed that: hills top and upper slope of south in steppe plant community ecological service function index(IE) is greater than the forest-steppe, but others are less than the forest-steppe. plant community ecological service function index(IE) all show that north upper slope and lower slope are greater than the same slope position of south in steppe and forest-steppe, but show the opposite trend in middle slope.