Decline in Net Ecosystem Productivity Following Canopy Transition to Late-Succession Forests |
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Authors: | Anthony R Taylor Meelis Seedre Brian W Brassard Han Y H Chen |
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Institution: | 1. Faculty of Natural Resources Management, Lakehead University, 955 Oliver Road, Thunder Bay, Ontario, P7B 5E1, Canada 2. Natural Resources Canada, Canadian Forest Service - Atlantic Forestry Centre, 1350 Regent Street, PO Box 4000, Fredericton, New Brunswick, E3B 5P7, Canada 3. Faculty of Forestry and Wood Sciences, Czech University of Life Sciences, Kamycka 129, 165 21, Prague, Czech Republic
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Abstract: | Boreal forests are critical to the global carbon (C) cycle. Despite recent advances in our understanding of boreal C budgets, C dynamics during compositional transition to late-succession forests remain unclear. Using a carefully replicated 203-year chronosequence, we examined long-term patterns of forest C stocks and net ecosystem productivity (NEP) following stand-replacing fire in the boreal forest of central Canada. We measured all C pools, including understorey vegetation, belowground biomass, and soil C, which are often missing from C budgets. We found a slight decrease in total ecosystem C stocks during early stand initiation, between 1 and 8 years after fire, at ?0.90 Mg C ha?1 y?1. As stands regenerated, live vegetation biomass increased rapidly, with total ecosystem C stocks reaching a maximum of 287.72 Mg C ha?1 92 years after fire. Total ecosystem C mass then decreased in the 140- and 203-year-old stands, losing between ?0.50 and ?0.74 Mg C ha?1 y?1, contrasting with views that old-growth forests continue to maintain a positive C balance. The C decline corresponded with canopy transition from dominance of Populus tremuloides, Pinus banksiana, and Picea mariana in the 92-year-old stands to Betula papyrifera, Picea glauca, and Abies balsamea in the 203-year-old stands. Results from this study highlight the role of succession in long-term forest C dynamics and its importance when modeling terrestrial C flux. |
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