A MODEL OF REGIONAL VEGETATION DYNAMICS AND ITS APPLICATION TO THE STUDY OF NORTHEAST-CHINA-TRANSECT (NECT) RESPONSES TO GLOBAL CHANGE

We developed a dynamic regional vegetation model to address problems o f responses of regional vegetation to elevated ambient CO2 and climati c change. The model takes into consideration both local ecosystem proc esses within a patch or grid cell, such as plant growth and death, and mass and energy flow, such as plant migration, across adjacent grid c ells. The model is able to couple vegetation structure dynamics and pr imary production processes. The normalized differential vegetation ind ex from meteorological satellite AVHRR was used to parameterize the mo del. Plant migration rates were derived based on effective seedling di stribution around parent plants. The model was applied to Northeast Ch ina Transect at a spatial resolution of 10 min latitude by 10 min long itude per grid cell and a temporal resolution of 1 month. The results indicated that with doubled CO2 concentration, a 20% increase in preci pitation and a 4 degrees C increase in temperature, the model predicte d that net primary productivity (NPP) of Larix forests, conifer-broadl eaf mixed forests, Aneurolepidium chinense steppes, Stipa grandis step pes, and wetland and salty meadows would decrease by 15% to 20%. Howev er, NPP of deciduous broadleaf forests, woodland and shrubs, Stipa bai calensis meadow steppes, and desert grasslands would increase by 20% t o 115%, as predicted by the model for the same climatic scenario. The average NPP of natural vegetation over the whole transect would decrea se slightly, largely because of the compensation between the positive effects of increased CO2 and precipitation and the negative effect of increased evapotranspiration induced by increased temperature.