Predicting the response of a temperate forest ecosystem to atmospheric CO sub 2 increase

All research goals for the current year have been met. We have prepared eight manuscripts reporting these discoveries. Individual projects have determined: Soil volume is not critical to the decline of photosynthetic rates under elevated CO{sub 2}. However, the shape, as well as the size, exerts a strong influence on growth in response to elevated CO{sub 2}, but this response is variable dependent on the species. Elevated CO{sub 2} may increase the growth of shade-tolerant trees to a greater extent than shade-intolerant trees. All birch trees examined responded in a similar positive way to a doubling of CO{sub 2}, but only yellow birch showed an increase in survival. Seedling regeneration in a New England deciduous forest may be altered by future CO{sub 2} levels. Plants grown in a high CO{sub 2} atmosphere altered their physiological functions, growth rates, biomass, and allometric growth patterns, probably influencing individual survival and plant/plant interactions within a community. The changes in photosynthetic rate (Ps) in response to elevated CO{sub 2} may involve alteration of multiple physiological characteristics. Growth enhancement in elevated CO{sub 2} is contingent on soil moisture conditions. Model simulations show increases in plant survival under elevated CO{sub 2} can have unexpected results on population dynamics. Finally, CO{sub 2} levels do not affect the heat shock response. Future experiments are described. 21 refs., 1 tab. (MHB