Fine root dynamics of trembling aspen in boreal forest and aspen parkland in central Canada

Fine root responses to potential climate change are relatively unknown in spite of their central role in ecosystem functioning. We quantified fine root length, production, and turnover in boreal forest and aspen parkland of central Canada because the future climate of the boreal site is expected to be similar to the current climate of the parkland site. Root depth distribution and turnover were similar between sites. Fine root mass was 4x greater at the parkland site and root length was 10x greater. Accordingly, the ecosystem level fine root: leaf mass ratio was 1.6 in the boreal site compared to 4.3 in the parkland site. On a per tree basis, however, fine root biomass was similar between sites due to the higher stem density of the parkland site. The parkland site had a greater proportion of very fine roots (62% of the fine roots were < 0.1 mm in diameter) compared with the boreal site (82% of the fine roots were between 0.1-0.5 mm in diameter). These differences indicate a large-scale shift towards increased root allocation at the parkland site associated with decreasing water availability and earlier successional stage.