Role of fine roots in nutrient uptake and turnover for boreal ecosystems

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A quarter of the biomass in a forest ecosystem can be found belowground but the dynamic production of new roots can account for up to 75% of the carbon allocation in a forest stand in a given year. Thus the turnover of roots is an important contribution to the global carbon cycle, yet relatively little is know how this occurs within the soil profile. This project will investigate the longevity and turnover of fine roots within three jack pine ecosystems located across a 600 km N-S to provide a temperature gradient. Fine root dynamics will be observed with a minirhizotron system which utilizes a small video camera that is placed into clear tubes inserted in the ground. By observing root images on a monthly basis we will be able to determine root production and mortality and estimate root longevity. More importantly, this proposed project will examine the role of different diameter root classes to carbon turnover at different depths in the soil profile in order to understand root functionality for these very small diameter classes. To further understand root functionality, selected roots will be subjected to x-ray microprobe analysis to follow metal profiles on the root surfaces.