Simulating carbon accumulation in northern ecosystems

A model of the carbon balance in arctic and boreal forests has been developed to estimate the effects of higher carbon diox ide levels in the atmosphere on northern ecosystems. The model predicts that northern ecosystems should accumulate 5-10% of the carbon added to the atmosphere each year. Ac cumulation rates should increase by 2-8 times by year 2020 depending on the availability of nutrients. The rates of change in several processes are only estimates. The predictions are subject to large errors because of the complexity of ecosys tems interactions and the absence of data on the long-term ef fects of higher temperature and atmospheric CO₂ levels. More differentiation of plant types, more feedback interactions, and more stochastic variations could improve the model. How ever, the results show that carbon accumulation in northern ecosystems is a significant fraction of the terrestrial carbon flux. The response of these systems is therefore important in predicting global carbon balance.