Project Funding: 2014 - 2017

NRA: 2013 NASA: Carbon Cycle Science   

Funded by USDA

Abstract:
There is a great need to accurately quantify the effects of climate change on soil organic carbon and to evaluate strategies for mitigating global warming. Since organic carbon in soils greatly exceeds the atmospheric contents of carbon dioxide, small changes in soil organic carbon have large effects on the climate. One mechanism which has not been included in models to predict soil carbon dynamics and therefore climate, is the influence that added pyrogenic carbon has on the mineralization of existing organic carbon in soil. This has relevance to regions that experience a greater prevalence of vegetation fires, to soil that already contain large amounts of pyrogenic carbon and to the intentional addition of pyrogenic carbon for soil carbon sequestration. This project will develop the fundamental understanding of how different pyrogenic carbon forms affect the soil carbon cycles, quantify the direction and magnitude of these effects and develop the modeling platform to insert the insights into existing prediction models for soil carbon and global climate. The experiments will employ techniques to separately quantify the different soil carbon fluxes and investigate the location of any remaining carbon on mineral surfaces. The model component developed by this project will enable more accurate predictions of future changes in soil carbon, which is important not only for climate change simulations, but also to decide on the most appropriate mitigation strategies for both global warming as well as soil degradation. 'Today’s most widely-used models of the soil organic carbon (SOC) cycle including those that are part of leading Earth system models use a few key environmental and edaphic parameters to determine SOC cycling rates, but do not include mechanisms whereby different pools of SOC may affect the decomposition rate of other pools. This limitation means that so-called “priming” interactions (in which addition of an organic substrate alters the turnover rate of existing SOC) are not readily captured by current models. This restricts us from predicting how existing SOC stocks will be affected by factors such as changing above- vs. below-ground allocation in plants under future climatic scenarios, changing organic matter inputs through agricultural management practices, or pyrogenic carbon (pyC) produced through natural fires or used intentionally in land management or for carbon management. We propose to conduct a systematic program of experiments to isolate and test for key proposed mechanisms of priming due to root-soil interactions, fresh organic matter additions, and pyC additions to soils. We will determine which mechanisms dominate SOC priming interactions in natural soils, across a broad range of globally-applicable environmental conditions, and nutrient statuses, using targeted laboratory and greenhouse studies. Results from these experiments will be used to improve two key soil carbon cycle models (CENTURY and CLM-CN, the carbon-nitrogen cycling module of the CESM’s Community Land Model) to allow for the modeling of priming effects and to calibrate and validate the new models. This model-inspired research will lead to increased understanding about fundamental mechanisms of soil C cycling, and will improve our capacity to predict potentially important effects of priming on soil C stocks now and in the future.'

Publications:

Ahmed, Z. U., Woodbury, P. B., Sanderman, J., Hawke, B., Jauss, V., Solomon, D., Lehmann, J. 2017. Assessing soil carbon vulnerability in the Western USA by geospatial modeling of pyrogenic and particulate carbon stocks. Journal of Geophysical Research: Biogeosciences. 122(2), 354-369. DOI: 10.1002/2016JG003488

Dai, Z., Webster, T. M., Enders, A., Hanley, K. L., Xu, J., Thies, J. E., Lehmann, J. 2017. DNA extraction efficiency from soil as affected by pyrolysis temperature and extractable organic carbon of high-ash biochar. Soil Biology and Biochemistry. 115, 129-136. DOI: 10.1016/j.soilbio.2017.08.016

Sun, T., Levin, B. D. A., Guzman, J. J. L., Enders, A., Muller, D. A., Angenent, L. T., Lehmann, J. 2017. Rapid electron transfer by the carbon matrix in natural pyrogenic carbon. Nature Communications. 8(1). DOI: 10.1038/ncomms14873

Whitman, T., Lehmann, J. 2015. A dual-isotope approach to allow conclusive partitioning between three sources. Nature Communications. 6(1). DOI: 10.1038/ncomms9708

Whitman, T., Pepe-Ranney, C., Enders, A., Koechli, C., Campbell, A., Buckley, D. H., Lehmann, J. 2016. Dynamics of microbial community composition and soil organic carbon mineralization in soil following addition of pyrogenic and fresh organic matter. The ISME Journal. 10(12), 2918-2930. DOI: 10.1038/ismej.2016.68

Woo, S. H., Enders, A., Lehmann, J. 2016. Microbial mineralization of pyrogenic organic matter in different mineral systems. Organic Geochemistry. 98, 18-26. DOI: 10.1016/j.orggeochem.2016.05.006

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

• North American Carbon Program (NACP) Project Profile