Project Funding: 2015 - 2019

NRA: 2014 NASA: Terrestrial Ecology   

Funded by NASA

Abstract:
Depth of burning of the soil organic layer (SOL) and resultant carbon (C) emissions from wildfire is an important component of net ecosystem C balance in the ABoVE Domain. The SOL sequesters the majority of ecosystem C in layers that can be hundreds to thousands of years old. Deeper burning could rapidly shift ecosystems across a C cycle threshold: from net accumulation of C from the atmosphere over multiple fire cycles, to net loss. Yet deeper burning must release C that escaped one or more previous fires-which we term legacy C-to shift ecosystems into the domain of accelerating feedback between warming climate and fire. The proposed research will combine widely used and scalable SOL consumption metrics with radiocarbon techniques for aging soil C to address the first key question: What are the ecosystem, landscape and regional controls over the combustion of legacy C in forest and tundra regions of the ABoVE Domain? Combustion of legacy C indicates that a larger proportion of the SOL was combusted in the current fire than in the previous fire, providing historic context for the current fire's severity. New fires that are greater in severity than past fires are expected to be to push ecosystems across thresholds in permafrost and plant composition, rendering C cycling vulnerable to state change after fire. The proposed research will combine a mechanistic understanding of legacy C loss with observations of ecosystem response to address our second key question: What are the consequences of legacy C loss for post-fire permafrost and vegetation dynamics? Proposed research for the Field Campaign will address these key questions by linking field based, process-level studies of legacy C combustion and post-fire responses with geospatial data products in two regions: moist acidic tundra near treeline on the North Slope of the Alaska Range, Alaska, and boreal conifer forest in the Taiga Plains and Shield ecoregions of Northwest Territories, Canada. These regions provide stark contrast in vegetation structure, yet both occur on warm permafrost soils that could be vulnerable to rapid change following fire. Recent extreme fire activity in both regions provides natural gradients in depth of burning across multiple, spatially independent burn scars, making them ideal for addressing these questions. Specific research objectives are to: (1) develop a mechanistic understanding of the ecosystem, landscape and fire characteristics that control legacy C loss from tundra and boreal forest wildfires in the ABoVE Domain; (2) examine the generality of the mechanistic understanding by synthesizing results with combustion and radiocarbon data collected in other regions; (3) estimate the magnitude of legacy C loss across landscapes within fire scars by linking the mechanistic understanding with geospatial data products; (4) determine ecosystem response to legacy C loss and fire severity, focusing on ecosystem vulnerability to state change in permafrost and vegetation; and (5) project ecosystem response to legacy C loss and fire severity across fire scars and identify the ecosystems, landscape positions, and regions at the greatest risk of state change under an intensifying fire regime. The proposed research fits within the overarching focus of the Field Campaign because it focuses on the impacts of an environmental change-intensifying fire regime-on ecosystem function in the ABoVE Domain. The aim to define a novel dimension of fire disturbance, the combustion of legacy C, directly addresses Tier 2 Science Question 3.2 regarding processes contributing to changes in disturbance regimes. Focus on the ecosystem consequences of this loss contribute to other questions, including the direct contribution of emissions to long-term ecosystem C balance (Q 3.6), and how losses may indirectly alter physical and biological controls over C cycling (Q 3.6), permafrost state (Q 3.3), soil drainage (Q 3.4), and vegetation composition (Q 3.5).

Publications:

Baltzer, J. L., Day, N. J., Walker, X. J., Greene, D., Mack, M. C., Alexander, H. D., Arseneault, D., Barnes, J., Bergeron, Y., Boucher, Y., Bourgeau-Chavez, L., Brown, C. D., Carriere, S., Howard, B. K., Gauthier, S., Parisien, M., Reid, K. A., Rogers, B. M., Roland, C., Sirois, L., Stehn, S., Thompson, D. K., Turetsky, M. R., Veraverbeke, S., Whitman, E., Yang, J., Johnstone, J. F. 2021. Increasing fire and the decline of fire adapted black spruce in the boreal forest. Proceedings of the National Academy of Sciences. 118(45). DOI: 10.1073/pnas.2024872118

Schuur, E. A., Mack, M. C. 2018. Ecological Response to Permafrost Thaw and Consequences for Local and Global Ecosystem Services. Annual Review of Ecology, Evolution, and Systematics. 49(1), 279-301. DOI: 10.1146/annurev-ecolsys-121415-032349

Turetsky, M. R., Baltzer, J. L., Johnstone, J. F., Mack, M. C., McCann, K., Schuur, E. A. G. 2016. Losing Legacies, Ecological Release, and Transient Responses: Key Challenges for the Future of Northern Ecosystem Science. Ecosystems. 20(1), 23-30. DOI: 10.1007/s10021-016-0055-2

Walker X J, Rogers B M, Veraverbeke S, Johnstone J F, Baltzer J L, Barrett K, Bourgeau-Chavez L, Day N J, de Groot W J, Dieleman C M, Goetz S, Hoy E, Jenkins L K, Kane E S, Parisien M, Potter S, Schuur E A G, Turetsky M, Whitman E, Mack M C. 2020 Fuel availability not fire weather controls boreal wildfire severity and carbon emissions. Nature Climate Change. 10(12), 1130-1136. DOI: 10.1038/s41558-020-00920-8

Walker, X. J., Baltzer, J. L., Cumming, S. G., Day, N. J., Ebert, C., Goetz, S., Johnstone, J. F., Potter, S., Rogers, B. M., Schuur, E. A. G., Turetsky, M. R., Mack, M. C. 2019. Increasing wildfires threaten historic carbon sink of boreal forest soils. Nature. 572(7770), 520-523. DOI: 10.1038/s41586-019-1474-y

Walker, X. J., Baltzer, J. L., Cumming, S. G., Day, N. J., Johnstone, J. F., Rogers, B. M., Solvik, K., Turetsky, M. R., Mack, M. C. 2018. Soil organic layer combustion in boreal black spruce and jack pine stands of the Northwest Territories, Canada. International Journal of Wildland Fire. 27(2), 125. DOI: 10.1071/wf17095

Walker, X. J., Howard, B. K., Jean, M., Johnstone, J. F., Roland, C., Rogers, B. M., Schuur, E. A. G., Solvik, K. K., Mack, M. C. 2021. Impacts of pre-fire conifer density and wildfire severity on ecosystem structure and function at the forest-tundra ecotone. PLOS ONE. 16(10), e0258558. DOI: 10.1371/journal.pone.0258558

Walker, X. J., Rogers, B. M., Baltzer, J. L., Cumming, S. G., Day, N. J., Goetz, S. J., Johnstone, J. F., Schuur, E. A. G., Turetsky, M. R., Mack, M. C. 2018. Cross-scale controls on carbon emissions from boreal forest megafires. Global Change Biology. 24(9), 4251-4265. DOI: 10.1111/gcb.14287

More details may be found in the following project profile(s):

• NASA Terrestrial Ecology (TE) Project Profile
• North American Carbon Program (NACP) Project Profile
• NASA Arctic-Boreal Vulnerability Experiment (ABoVE) Project Profile