Project Funding: 2011 - 2014

NRA: 2010 NASA: Carbon Cycle Science   

Funded by NASA

Abstract:
Soils are important sources and sinks of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). Soil moisture can change rapidly, and it is one of the dominant factors controlling soil aeration, and hence the balance between aerobic (CO2 producing) and anaerobic (CH4 producing) microbial respiration. Production and consumption of N2O are also highly dependent on spatial and temporal variation in soil moisture. However, studies of soil fluxes of CH4 and N2O at high temporal frequency have been hampered by lack of appropriate technology for in situ real-time measurements. Flux estimates are subject to large errors when temporal variations are inadequately sampled. Opportunities for mitigation to reduce greenhouse gas emissions could be missed due to lack of understanding of transient spikes in emissions in response to rapidly changing environmental conditions across agricultural and forest landscapes. The proposal responds to research theme #1 “Interactions between land management and land change and the carbon cycle� and is also relevant to mitigation aspects of theme #4. New satellite technologies are arriving to estimate soil moisture, a key driver of soil emissions of CO2, N2O and CH4. The operational Advanced Land Observing Satellite (ALOS) and anticipated Soil Moisture Active Passive (SMAP) mission and Deformation, Ecosystem Structure and Dynamics of Ice (DESDynI) mission all feature microwave instrumentation with this capability. We propose to couple trace gas flux measurements to estimates of seasonal and interannual variation of soil moisture and the area of saturated soils using L-band radar of the ALOS satellite. Our study sites in North Dakota include a commercial-scale agricultural experimental site and a mosaic of upland agriculture that drains to prairie glacial wetlands. Similarly, the Howland Forest, located in a region of actively managed forests of central Maine, includes soils ranging from well drained to very poorly drained over relatively small areas. Hence, the daily, seasonal and interannual variation of soil moisture and of area of saturated soils will likely affect landscape-scale fluxes of CO2, N2O and CH4 in these agricultural and forest systems. The advent of new cavity ring-down spectroscopy is about to transform soil greenhouse gas flux measurement methodology. Here we describe how an existing automated system that measures soil CO2 efflux at half-hourly intervals can be integrated with new instruments to produce simultaneous measurements of soil CO2, N2O, and CH4 fluxes. Given the exceptional stability, sensitivity, and fast response times of the new generation of instruments for detecting changes in N2O and CH4 concentrations, we anticipate not only greatly increasing the frequency of measurements through automation, but also improving sensitivity and reducing uncertainty in flux measurements. The objective of this project is to demonstrate how a combination of nested high and low temporal resolution field measurements of trace gas fluxes and soil moisture can be integrated with soil models and with remotely sensed L-band microwave data for a range of temporal and spatial scales. We will explore the biases and uncertainties of model simulations based on “snapshots� of radar-based soil moisture estimates at spatial scales from 15m (ALOS) to aggregations of ALOS data at 3000m resolution to simulate a SMAP pixel. Using hourly automated chambers at intensively studied sites and a temporally and spatially clustered design of manual measurements across a 3-km landscape, we will compare the temporal variation in measured and simulated fluxes and soil moisture contents to those likely to be captured by future SMAP and DESDynI estimates of soil moisture used to drive soil models. This type of analysis is made possible only by combining new technological developments in both flux measurements on the ground and remote sensing opportunities.

Publications:

Davidson, E. A., de Araujo, A. C., Artaxo, P., Balch, J. K., Brown, I. F., C. Bustamante, M. M., Coe, M. T., DeFries, R. S., Keller, M., Longo, M., Munger, J. W., Schroeder, W., Soares-Filho, B. S., Souza, C. M., Wofsy, S. C. 2012. The Amazon basin in transition. Nature. 481(7381), 321-328. DOI: 10.1038/nature10717

Davidson, E. A., Savage, K. E., Finzi, A. C. 2014. A big-microsite framework for soil carbon modeling. Global Change Biology. 20(12), 3610-3620. DOI: 10.1111/gcb.12718

Richey, J. E., Ballester, M. V., Davidson, E. A., Johnson, M. S., Krusche, A. V. 2011. Land-Water interactions in the amazon. Biogeochemistry. 105(1-3), 1-5. DOI: 10.1007/s10533-011-9622-y

2013 NASA Terrestrial Ecology Science Team Meeting Poster(s)

• Modeling temporal variations in soil moisture across an agricultural landscape using radar-based imagery   --   (Josef Kellndorfer, Jill Derwin, Rebecca Phillips, Eric Davidson, Kathleen Savage)   [abstract]

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

• NASA Terrestrial Ecology (TE) Project Profile