Responses of boreal trees to rising atmospheric carbon dioxide concentration

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The atmospheric carbon dioxide concentration ([CO2]) has been increasing rapidly since the Industrial Revolution and the increase will continue in the foreseeable future. The rising [CO2] will affect the physiology, growth and distribution of plants and ecosystems.  The boreal forest is the largest terrestrial ecosystem on the earth and its response to rising [CO2] will influence the global climate conditions as well as things that depend on the boreal forest, e.g., wildlife and the forest industry. This research will examine how boreal trees respond to rising [CO2] under both lab and field conditions. The results will enhance our understanding of how boreal trees will respond to rising [CO2] and be used in computer models to predict changes in the growth, structure and distribution of the boreal forest under future climate conditions.There are three common techniques used in CO2 elevation research: enclosures (growth chambers & greenhouses), open top chambers and Free Air CO2 Enrichment (FACE). Each method has its merits and drawbacks, e.g., enclosures control all environmental conditions well and are inexpensive to operate. Because its operation is not limited by the season, it is especially attractive to regions with short growing seasons, e.g., Canada. However, it doesn't permit the investigation on large trees or tree communites. In contrast, FACE permits larger scale field experiments, but is extremely expensive to establish and operate. There are large spatial and temporal variations in [CO2] within a FACE plot, it discharges large amount of CO2 into the atmosphere and it is impossible to control all other environmental factors. The plant responses using different methods generally follow similar trends but differ in magnitude. we will examine mechanisms underlying the response differences and establish quantitative relationships in tree response between enclosure and FACE experiments. The results will help researchers design better enclosure studies and make the results of past enclosure studies more useful. The quantitative relationships will be critical for the development and/or parameterization of ecosystem models for predicting the impact of rising [CO2] on the boreal forest.