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 Exploring the interactions between carbon cycling, land use and climate change within mixed agricultural, forested, suburban, and urban landscapes

NASA, Carbon Cycle Science, $1,144,441, 2014-2017

PI Jingfeng Xiao, Co-Is Changsheng Li, Alexandra R. Contosta, Ruth K. Varner, Junmei Tang

Human activities (e.g., urbanization, land use planning) have led to complex patterns of urban, suburban, agricultural, and forested landscapes. Ecosystems within these landscapes play an important role in climate regulation by acting as regulators of CO2 and other greenhouse gases and altering surface albedo and other biophysical properties. Although climate change policy initiatives often include incentives for land management activities that can offset warming, most have focused on enhanced carbon storage. Often not considered is the fact that these practices also bear climate consequences through other mechanisms (N2O and CH4 emissions, altered albedo, etc). Better understanding of the processes controlling the uptake, storage, and release of greenhouse gas emissions along urban to rural gradients is essential for evaluating how alternative patterns of land use interact with carbon cycling and climate change and how future land use change will influence carbon sequestration potential within these complex landscapes.

The overarching goal of our work is to examine the interactions among carbon cycling, land use, and climate change in a human-dominated, mixed land use region that includes urban, suburban, agriculture, and forest land uses in southern New Hampshire. We plan to combine field measurements of carbon storage and greenhouse gas emissions (CO2, CH4, and N2O), an improved process-based biogeochemical model - DNDC (DeNitrification and DeComposition) designed to predict C fluxes and trace gas emissions, historical and projected land use change data derived from Landsat imagery and cellular automata/agent-based modeling, and high spectral resolution remote sensing data from NASA Airborne Visible/Infrared Imaging Spectrometer (AVIRIS). Our specific objectives designed to achieve the overarching goal are to: (1) Measure C pools and greenhouse gas emissions (CO2, CH4, and N2O) in urban, suburban, agricultural, and forested landscapes; (2) Improve and parameterize the DNDC (DeNitrification and DeComposition) model and validate model predictions; (3) Develop historical land use change data for the last three decades from Landsat imagery and projections of future land use change; (4) Generate spatially continuous predictions of C pools and greenhouse gas emissions using Urban-DNDC and assess how land use interacts with C cycling and climate change and how future land use change will influence carbon sequestration potential within these complex landscapes; and (5) Determine the net radiative forcing values (in w m-2) for the major greenhouse units using CO2 and climate change scenarios.

Our research is directly responsive to this Carbon Cycle Science program element - Theme 4: Carbon Dynamics within Urban-Suburban-Forested-Agricultural Landscapes, and is highly relevant to the goals and objectives of NASA, USDA, DOE, and NOAA. Our work will reveal how carbon dynamics, non-CO2 greenhouse gases, surface albedo, land use, and climate change interact with each other. It will also elucidate how future land use change will influence C cycling within complex landscapes. Our results will have implications for crafting effective land management policies that balance C sequestration and climate mitigation with food production, forest resources and many other services that these landscapes provide. Results of this activity will highlight tradeoffs among multiple land management strategies in terms of their net climate effect. Information of this nature is of critical importance for preparing sound land management policies and designing strategies to cope with changes in climate.