| Terrain is the key factor affect the growth of vegetation in the loess hilly region.Tiny terrain influence the pattern of light radiation, the temperature and humidity and soil nutrient, further influence the distribution and composition of plant community. In order to analyze the impact of tiny terrain on grassland plant community structure and function, species composition, aboveground and belowground biomass, and annual fine root production at different slope aspect(sunny slope and shady slope) and different slope position(top, upper, middle and lower) were investigated in the hilly Loess Plateau region. The main points as follows:(1)The results showed that grassland communities were mainly composed of plants species belonging to Compositae, Poaceae and Leguminosae in research region. The aboveground and belowground biomass and annual fine root production of community were 164.12 g?m-2, 1044.87 g?m-2 and 731.77 g?m-2?a-1, respectively. Aboveground biomass, belowground biomass and annual fine root production of community were in the order of shady slope>sunny slope>top slope. Fine root mainly concentrated in the 0~20 cm top soil layer and decreased with soil depth.(2) The average soil organic carbon(1.20~12.78 g?kg-1), total N(0.14~0.94 g?kg-1),total P(0.14~0.63 g?kg-1),total K(8.32~11.53 g?kg-1), available K(40.82~86.75 mg?kg-1), ammonium N(3.53~7.23 mg?kg-1), nitrate N(12.25~27.91 mg?kg-1), available P(0.43~0.92 mg?kg-1) and soil water content(3.9~12.2%) are basicly greater in shady slope than sunny slope, and lower in the upper slope than lower slope. Soil C/N(4.85~19.38), C/P(3.64~27.66), N/P(0.50~1.78), the C/K(0.22~1.13) also changes with the tiny terrain. Variance analysis showed that slope direction and slope position and their interactions all had a significant effect on soil nutrients and soil water content. Correlation analysis showed the soil nutrients and soil moisture correlated with the community productivity.(3) The average leaf C, N, P, K content were 433.47, 24.84, 1.61, 16.15 g?kg-1 respectively, the average root C, N, P, K content were 380.05, 9.07, 0.31, 5.46 g?kg-1respectively. Leaf C/N, C/P, N/P and C/K stoichiometric were 18.18, 320.36, 17.41, 29.69 respectively, Leaf N/P ratio shows that plants restricted by P in loess hilly region. root C/N, C/P, N/P stoichiometric were 49.61, 1326.64, 30.73 respectively. Leaf and root C, N, P content in different slope aspect were in the order of shady slope > sunny slope > top slope.(4)Plant and soil as the different part of biogeochemical cycle, there must exist the contact. Correlation analysis showed that between 0~20, 20~50, 50~80, 80~100 cm soil nutrient and leaf and root stoichiometric characteristics were correlated. Especially the soil C, N, P, K content in 0~20 cm with leaf and root C, N, P, K content are significantly positive correlation(P < 0.05).(5) The aboveground biomass significantly increased and the belowground biomass decreased after fertilizing, the leaf N, P content also increased after fertilizing, and fertilization also changed the leaf N/P value. Root C and K content are not significantly changed after fertilizing. Fertilization also changed the soil nutrient content and soil chemical characteristics, especially significantly increased soil available N, P nutrient content. |
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