Characterizing Spatiotemporal Dynamics of Methane Emissions from Rice Paddies in Northeast China from 1990 to 2010

Yuan Zhang,Runhe Shi,Wei Gao,Feng Zhang,Shiliang Su,Julian Clifton

doi:10.1371/journal.pone.0029156

Abstract

BackgroundRice paddies have been identified as major methane (CH4) source induced by human activities. As a major rice production region in Northern China, the rice paddies in the Three-Rivers Plain (TRP) have experienced large changes in spatial distribution over the recent 20 years (from 1990 to 2010). Consequently, accurate estimation and characterization of spatiotemporal patterns of CH4 emissions from rice paddies has become an pressing issue for assessing the environmental impacts of agroecosystems, and further making GHG mitigation strategies at regional or global levels.Methodology/Principal FindingsIntegrating remote sensing mapping with a process-based biogeochemistry model, Denitrification and Decomposition (DNDC), was utilized to quantify the regional CH4 emissions from the entire rice paddies in study region. Based on site validation and sensitivity tests, geographic information system (GIS) databases with the spatially differentiated input information were constructed to drive DNDC upscaling for its regional simulations. Results showed that (1) The large change in total methane emission that occurred in 2000 and 2010 compared to 1990 is distributed to the explosive growth in amounts of rice planted; (2) the spatial variations in CH4 fluxes in this study are mainly attributed to the most sensitive factor soil properties, i.e., soil clay fraction and soil organic carbon (SOC) content, and (3) the warming climate could enhance CH4 emission in the cool paddies.Conclusions/SignificanceThe study concluded that the introduction of remote sensing analysis into the DNDC upscaling has a great capability in timely quantifying the methane emissions from cool paddies with fast land use and cover changes. And also, it confirmed that the northern wetland agroecosystems made great contributions to global greenhouse gas inventory.

Highlights

Methane (CH4) is a major greenhouse gases (GHG)
With the introduction of Remote sensing (RS) analysis into the Denitrification and Decomposition (DNDC) upscaling, this study aims at characterizing the spatiotemporal patterns of the CH4 emissions from rice fields in the Three-Rivers Plain (TRP) over the past two decades, and further for quantifying the contribution of the rice paddies within the TRP to global methane
Validation results and sensitivity factors analysis The measured CH4 fluxes at the three treatments mentioned above were compared with modeled results

Summary

Introduction

Methane (CH4) is a major greenhouse gases (GHG). According to the Intergovernmental Panel on Climate Change (IPCC) report, atmospheric CH4 concentrations have risen to 1774 ppb in 2005 [1]. To estimate the national inventory of CH4 emission, a number of site-specific observations were conducted for measuring CH4 flux at field sites in the major rice producing areas in Southern and Southeast of China [7,8,9,10]. These ground-based measurements were reliable for understanding the mechanics of CH4 emission at local scale. Accurate estimation and characterization of spatiotemporal patterns of CH4 emissions from rice paddies has become an pressing issue for assessing the environmental impacts of agroecosystems, and further making GHG mitigation strategies at regional or global levels

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Conclusion