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Title: Landscape controls on carbon and nitrogen cycling in boreal forests

Author
item MANIES, KRISTEN - U.S. GEOLOGICAL SURVEY
item HARDEN, JENNIFER - U.S. GEOLOGICAL SURVEY
item MACK, MICHELLE - UNIVERSITY OF FLORIDA
item LAMBERTY-BOND, BEN - UNIVERSITY OF WISCONSIN
item O Neill, Katherine
item NEFF, JASON - UNIV OF COLORADO BOULDER
item TURETSKY, MERRITT - MICHIGAN STATE UNIVERSITY
item CARRASCO, JOHN - UNIV OF COLORADO BOULDER

Submitted to: Ecological Society of America Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 8/1/2007
Publication Date: 8/5/2007
Citation: Manies, K.L., Harden, J.W., Mack, M., Lamberty-Bond, B., O Neill, K.P., Neff, J., Turetsky, M.R., Carrasco, J. 2007. Landscape controls on carbon and nitrogen cycling in boreal forests. In: Ecological Society of America Abstracts, August 5-10, 2007, San Jose, California, CDROM.

Interpretive Summary:

Technical Abstract: Climate change in the boreal forest biome is having a large impact on two of the main controllers of carbon (C) and nitrogen (N) cycling within this region: permafrost and fire. Permafrost, and its effects on soil drainage, controls the inputs and losses of C and N via net primary productivity (NPP), decomposition, and combustion by wildfire. As part of the BOREAS experiment (1994-1996) and a subsequent experiment called FIRES-ExB (2000-2003), we measured C and N stocks in organic soils and woody debris within different soil drainage types as well as used a long-term modeling approach to examine the balance between soil C and N inputs (NPP as well as fire-killed woody debris) and losses (mainly decomposition and combustion) in context of permafrost or soil drainage class. Soil C and N stocks increased as soil drainage became more poorly drained, largely owing to reduced combustion losses in those systems as well as seasonally colder soil conditions that hamper decomposition in deep soil layers. As a result, soil C dynamics are best captured by modeling soil depth and its variation over fire cycles. Our modeling exercises resulted in three major findings. First, the existence of permafrost has contributed significantly to the amount of C and N stocks within the boreal forest today. Second, fire-killed woody debris accounts for 10 to 60% of the C that persists in deeper soil layers. While landscape variations in wood-derived soil C are likely great, the importance in woody debris in the creation of boreal C pools is understudied. Lastly, N combustion by wildfire in boreal ecosystems has resulted in long-term losses that exceed the amount of N stored in the soil today by 2-3 times. Our results suggest that climate change effects on boreal region soils cannot be understood without explicitly measuring and modeling 1) multiple types of organic soil layers, and 2) permafrost and its effects on soil drainage and fire combustion, all of which are underlying controls of C and N storage at the landscape scale.