Bailu Zhao1, Qianlai Zhuang2,3, Narasinha Shurpali4, Kajar Köster5, Frank Berninger6, Jukka Pumpanen7. 1. Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, IN, 47907, USA. 2. Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, IN, 47907, USA. qzhuang@purdue.edu. 3. Department of Agronomy, Purdue University, West Lafayette, IN, 47907, USA. qzhuang@purdue.edu. 4. Production Systems - Milk Production Unit, Natural Resources Institute Finland (Luke), Halolantie 31 A, Maaninka, FI-71750, Finland. 5. Department of Forest Sciences, University of Helsinki, PO Box 27, 00014, Helsinki, Finland. 6. Department of Environmental and Biological Sciences, University of Eastern Finland, PO Box 111, 80101, Joensuu, Finland. 7. Department of Environmental and Biological Sciences, University of Eastern Finland, PO Box 1627, 70211, Kuopio, Finland.
Abstract
Wildfires are a major disturbance to forest carbon (C) balance through both immediate combustion emissions and post-fire ecosystem dynamics. Here we used a process-based biogeochemistry model, the Terrestrial Ecosystem Model (TEM), to simulate C budget in Alaska and Canada during 1986-2016, as impacted by fire disturbances. We extracted the data of difference Normalized Burn Ratio (dNBR) for fires from Landsat TM/ETM imagery and estimated the proportion of vegetation and soil C combustion. We observed that the region was a C source of 2.74 Pg C during the 31-year period. The observed C loss, 57.1 Tg C year-1, was attributed to fire emissions, overwhelming the net ecosystem production (1.9 Tg C year-1) in the region. Our simulated direct emissions for Alaska and Canada are within the range of field measurements and other model estimates. As burn severity increased, combustion emission tended to switch from vegetation origin towards soil origin. When dNBR is below 300, fires increase soil temperature and decrease soil moisture and thus, enhance soil respiration. However, the post-fire soil respiration decreases for moderate or high burn severity. The proportion of post-fire soil emission in total emissions increased with burn severity. Net nitrogen mineralization gradually recovered after fire, enhancing net primary production. Net ecosystem production recovered fast under higher burn severities. The impact of fire disturbance on the C balance of northern ecosystems and the associated uncertainties can be better characterized with long-term, prior-, during- and post-disturbance data across the geospatial spectrum. Our findings suggest that the regional source of carbon to the atmosphere will persist if the observed forest wildfire occurrence and severity continues into the future.
Wildfires are a major disturbance to forest carbon (C) balance through both immediate combustion emissions and post-fire ecosystem dynamics. Here we used a process-based biogeochemistry model, the Terrestrial Ecosystem Model (TEM), to simulate C budget in Alaska and Canada during 1986-2016, as impacted by fire disturbances. We extracted the data of difference n class="Chemical">Normalized Burn Ratio (dNBR) for fires from Landsat TM/ETM imagery and estimated the proportion of vegetation and soil C combustion. We observed that the region was a C source of 2.74 Pg C during the 31-year period. The observed C loss, 57.1 Tg C year-1, was attributed to fire emissions, overwhelming the net ecosystem production (1.9 Tg C year-1) in the region. Our simulated direct emissions for Alaska and Canada are within the range of field measurements and other model estimates. As burn severity increased, combustion emission tended to switch from vegetation origin towards soil origin. When dNBR is below 300, fires increase soil temperature and decrease soil moisture and thus, enhance soil respiration. However, the post-fire soil respiration decreases for moderate or high burn severity. The proportion of post-fire soil emission in total emissions increased with burn severity. Net nitrogen mineralization gradually recovered after fire, enhancing net primary production. Net ecosystem production recovered fast under higher burn severities. The impact of fire disturbance on the C balance of northern ecosystems and the associated uncertainties can be better characterized with long-term, prior-, during- and post-disturbance data across the geospatial spectrum. Our findings suggest that the regional source of carbon to the atmosphere will persist if the observed forest wildfire occurrence and severity continues into the future.
Authors: Egle Köster; Kajar Köster; Frank Berninger; Heidi Aaltonen; Xuan Zhou; Jukka Pumpanen Journal: Sci Total Environ Date: 2017-06-02 Impact factor: 7.963
Authors: Monica G Turner; Erica A H Smithwick; Kristine L Metzger; Daniel B Tinker; William H Romme Journal: Proc Natl Acad Sci U S A Date: 2007-03-02 Impact factor: 11.205
Authors: Neslihan Taş; Emmanuel Prestat; Jack W McFarland; Kimberley P Wickland; Rob Knight; Asmeret Asefaw Berhe; Torre Jorgenson; Mark P Waldrop; Janet K Jansson Journal: ISME J Date: 2014-04-10 Impact factor: 10.302