PARENT SESSION
Symposium 1: The boreal forest and global change
Organized by: EA Johnson, K Miyanishi, and K Ruckstuhl
Monday, August 8, 8:00 AM - 11:30 AM, Meeting Room 517 A, Level 5, Palais des congrès de Montréal

How will climate change affect boreal forest carbon dynamics?

Kurz, Werner¹, Stinson, Graham^*,1, ¹ Natural Resources Canada, Canadian Forest Service, Victoria, BC, Canada

ABSTRACT- To understand how boreal forest carbon dynamics might respond to anticipated climatic change, we must consider two important processes. First, projected climatic changes are expected to result in increased frequency of fire and other natural disturbances. Increased rates of stand-replacing disturbances change the forest age class structure and reduce forest carbon stocks at the landscape level. Second, climatic changes may result in increased net ecosystem productivity (NEP). Could higher NEP offset the anticipated carbon losses resulting from increased disturbance frequency? We used the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3) to simulate the impacts of changes in disturbance rates, net primary productivity (NPP) and decomposition rates on a hypothetical boreal forest landscape and to explore the impacts of these changes on the landscape-level forest carbon budget. We found that large increases in NEP are required to balance carbon losses from increased natural disturbance rates. Moreover, these increases in NEP would have to be sustained over several decades and be widespread across the landscape. Increased NEP can only be realised when NPP is enhanced relative to decomposition rates. This study provides further evidence that boreal forest carbon stocks are likely to decline as a result of climate change because it would be difficult to balance the carbon losses resulting from the anticipated increases in disturbance rate through greater NEP.

Key words: boreal forest, carbon, net ecosystem productivity, disturbance