Estimation of Vegetation Net Primary Productivity of a Typical Karst Area in Central Guizhou
喀斯特地区植被净第一性生产力遥感动态监测及评价——以贵州省中部地区为例

Simulation models are needed to study primary production of ecosystems with complex biological and environmental interactions at various temporal and spatial scales. The karst region in Guizhou has unique environmental conditions. Reestablishment of appropriate vegetation coverage is recognized as a fundamental measure for prevention of soil and water loss and restoration of degraded ecosystems. The primary productivity of different vegetation types and plant species under various environments reflects their adaptability to the environment. The study of primary productivity is an important basis for vegetation reconstruction and ecosystem restoration. Based on the Light Use Efficiency model and the soil water equilibrium model, we integrated actual field conditions into a coupling model. Soil moisture is introduced as a direct variable to the NPP model, so a direct relation between NPP and soil moisture can be established to predict the change in NPP when soil moisture changes. The comparisons with observed data illustrate that the coupling model can validly simulate the variation trends of net primary production (NPP) for typical karst ecosystems. We then used the model to study net primary productivity and its spatio-temporal pattern in a typical karst area of Guizhou Province from October 2006 to May 2007 using TM data, meteorological data and experimental observation data along with vegetation and soil texture information. Results show that there is a trend of NPP rising as vegetation cover increases in spatial distribution, and the mean value of vegetation NPP rises as plant activity increases. Different vegetation types have different NPP characteristics. The mean NPP of different vegetation types are in the following order: forest> shrub>grass>cropland. The mean value of forest is 19.89 gC/m2, shrubland is 19.01 gC/m2, and grass and cropland values are 16.71 gC/m2 and 16.54 gC/m2, respectively. The seasonal change in NPP is basically congruent with local temperature and terrestrial solar radiation. The mean value of seasonal NPP is in the following order: Spring>Autumn>Winter, as is the seasonal change of NPP of the different vegetation types.