Study On Soil Water Dynamics And Vegetation Carrying Capacity Of Main Vegetation Types In Former Area Of Daqing Mountain

In this paper, the mian forest vegetation vegetation characteristics, soil water dynamic, stomatal conductance, transpiration, photosynthesis of main species, and the response of photosynthetic indexes to light intensity and soil water content were studied in Guluban and ShuiMo test areas of Daqing former mountain. Based on the environment characteristics of the area, BROOK90 was used to simulate the water balance of different vegetation types. Furthermore, vegetation carrying capacity of soil water was studied. The main results were as following:(1) The result of main physical properties of soil showed that the gravel content and soil bulk density of arbor forest were lower than that of shrub land. But the field capacity and maximum water capacity of arbor forest were higher. Soil saturated hydraulic conductivity of Ostryopsis davidiana Decaisne. was the highest(40.14 mm/h). Water conservation capacity of arbor forest was better than shrub land.(2) Soil water annual variation and seasonal variation had a consistent trend with precipitation. The vertical distribution showed a decline trend with the soil depth increased. It indicated that rainfall controlled soil water. In the growing season, soil water content of Populus davidiana Dode.was the highest(23.16%), but soil water content of Pinus tabulaeformis Carr. was the lowest. Water content of arbor forest was better than shrub land.(3) At the similar site condition and tree age, stem biomass of Populus davidiana was the biggest and branch biomass of Quercus liaotungensis Koidz. was the biggest. Equation y=1/(k+a×e-bx)can be used to express the relationship between aboveground biomass and stand density of Pinus tabulaeformis Carr.(x represented stand density, y represented aboveground biomass). Leaf area index of 30a Pinus tabulaeformis Carr. plantation, Betula platyphylla Suk. secondary forest and Ostryopsis davidiana Decaisne. shrub were 4.88—10.95 m2/m2 , 2.80—4.80 m2/m2 and 1.21—4.22m2/m2.(4) Stand extinction coefficient had a similar trend with stem sap flow rate and stomatal conductance daily variation. Stand extinction coefficient of Ostryopsis davidiana Decaisne. was the biggest. Stand extinction coefficient change range of Pinus tabulaeformis Carr. plantation was during 0.10—0.21.(5) Photosynthetic characteristics, chlorophyll fluorescence characteristics and light intensity, soil water content can be simulated by equation y=a+b(1-e-kx) (y represented photosynthetic or fluorescence; x represented light intensity or soil water content).(6) Rainfall under tree crown, canopy interception, stem flow and surface runoff showed positive correlation with rainfall outside of stands. Canopy interception rate of arbor forest were higher than that of shrub land. Canopy interception rate of Populus davidiana was the highest and canopy interception rate of Ostryopsis davidiana Decaisne. was the lowest. Stem flow rate of Populus davidiana secondary forest was 2.81%, which was higher than other tree species. Stem flow rate of Pinus tabulaeformis Carr. was in the range of 1.69% to 4.94%. The water balance result showed that year water supply and consumption showed linear correlation with maximum leaf area index. Maximum leaf area index of Ostryopsis davidiana Decaisne. shrub forest, Betula platyphylla Suk. secondary forest, Pinus tabulaeformis Carr. plantation were 2.99m2/m2, 4.75m2/m2 and 10.65m2/m2. The corresponding densities were 557266 stock/hm2, 2916 stock/hm2 and 3250 stock/hm2, which provided evidence for silviculture and management.