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Stochastic modelling of soil moisture dynamics in a grassland of Qilian Mountain at point scale

Science China Earth Sciences 2007年第12期50卷 1844-1856页

作者： liu hu,zhao wenzhi he zhibin & zhang lijie linze inland river basin research station,chinese ecosystem research network Laboratory of Watershed Hydrology and Ecol-ogy,Cold and Arid Regions Environmental and Engineering research Institute,chinese Academy of Sciences,Lanzhou 730000,China 1. linze inland river basin research station Chinese Ecosystem Research Network China 2. Laboratory of Watershed Hydrology and Ecology Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou 730000 China

Stochastic modeling of soil moisture dynamics is crucial to the quantitative understanding of plant responses to water stresses,hydrological control of nutrient cycling processes,water competition among plants,and some other ecological dynamics,and thus has become a hotspot in ecohydrology at *** this paper,we based on the continuously monitored data of soil moisture during 2002―2005 and daily precipitation date of 1992―2006,and tried to make a probabilistic analysis of soil moisture dynamics at point scale in a grassland of Qilian Mountain by integrating the stochastic model improved by Laio and the Monte Carlo *** results show that the inter-annual variations for the soil moisture patterns at different depths are very significant,and that the coefficient of variance(CV) of surface soil moisture(20 cm) is almost continually kept at about 0.23 whether in the rich or poor rainy ***,it has been found that the maximal CV of soil moisture has not always appeared at the surface *** of the analytically derived soil moisture probability density function(PDF) with the statistical distribution of the observed soil moisture data suggests that the stochastic model can reasonably describe and predict the soil moisture dynamics of the grassland in Qilian Mountain at point *** extracting the statistical information of the historical precipitation data in 1994―2006,and inputting them into the stochastic model,we analytically derived the long-term soil moisture PDF without considering the inter-annual climate fluctuations,and then numerically derived the one when considering the inter-annual fluctuation effects in combination with a Monte-Carlo *** was found that,though the peak position of the probability density distribution significantly moved towards drought when considering the disturbance forces,and its width was narrowed,accordingly its peak value was increased,no significant bimodality was observed in the soil moistur

关键词： soil moisture dynamics, stochastic modelling, Monte Carlo method, probability density function, grassland ecosystem

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Response of tree-ring growth to climate at treeline ecotones in the Qilian Mountains,northwestern China

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research in Cold and Arid Regions 2011年第2期3卷 103-109页

作者： zhibin he wenzhi zhao lijie zhang hu liu ZhenXing Tang linze inland river basin research station Chinese Ecosystem Research Network Heihe Key Laboratory of Ecohydrology and Integrated River Basin Science Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou Gansu 730000 China University ofWuzhou Wuzhou Guangxi 543002 China

Climate constitutes the main limiting factor for tree-ring growth in high-elevation forests, and the relationship between tree-ring growth and climate is complex. Based on tree-ring chronology and meteorological data, the influence of precipitation, mean temperature and mean minimum temperature at yearly, seasonal and monthly scales on the tree-ring growth of Picea crossifolia was studied at treeline ecotones in the Qilian Mountains, northwestern China. The results show that growing season temperatures of previous and current years are important limiting factors on tree-ring growth, particularly June mean temperature and mean minimum temperature of current year. The precipitations in the previous winter and current spring have a positive correlation, and in the current fall has a negative correlation with tree-ring growth, but these correlations are not significant. Our results suggest that temperature controls tree-ring growth more strongly than precipitation at treeline ecotones in the Qilian Mountains.

关键词： Qilian Mountains treeline ecotones climate tree-ring growth

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Study on vegetation ecological water requirement in Ejina Oasis

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Science China Earth Sciences 2007年第1期50卷 121-129页

作者： zhao wenzhi CHANG XueLi he zhibin zhang Zhihui Laboratory of Watershed Hydrology and Ecology Cold and Arid Regions Environmental and Engineering Research InstituteChi-nese Academy of SciencesLanzhou 730000China linze inland river basin Comprehensive research station Chinese Ecosystem Research NetworkLanzhou 730000China Geography and Resource Management College Ludong UniversityYantai 264025China

The Ecological Water Requirement (EWR) of desert oasis is the amount of water required to maintain a normal growth of vegetation in the special ecosystems. In this study EWR of the Ejina desert oasis is estimated through the relational equation between normalized difference vegetation index (NDVI), productivity and transpiration coefficient, which was established by a combination of the RS, GIS, GPS techniques with the field measurements of productivity. The results show that about 1.53×108 m3 water would be needed to maintain the present state of the Ejina Oasis, and the ecological water requirement would amount to 3.49×108 m3 if the existing vegetation was restored to the highest productivity level at present. Considering the domestic water requirement, river delivery loss, oasis vegetation water con-sumption, farmland water demand, precipitation recharge, etc., the draw-off discharge of the heihe river (at Longxin Mount) should be 1.93×108―2.23 ×108 m3 to maintain the present state of the Ejina Oasis, and 4.28×108―5.17×108 m3 to make the existing vegetation be restored to the highest productiv-ity level at present.

关键词： Ejina Oasis NDVI productivity pattern vegetation ecological water requirement.

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