Quantifying methane emissions from rice fields in the Taihu Lake region, China by coupling a detailed soil database with biogeochemical model

Abstract

Abstract. As China has approximately 22% of the world's rice paddies, the regional quantification of CH 4 emissions from these paddies is important in determining their contribution to the global greenhouse gas effect. This paper reports the use of a biogeochemical model (DeNitrification and DeComposition or DNDC) for quantifying CH 4 emissions from rice fields in the Taihu Lake region of China. For this application, the DNDC model was linked to a 1:50 000 soil database derived from 1107 paddy soil profiles compiled during the Second National Soil Survey of China in the 1980s-1990s. The simulated results showed that the 2.3 Mha of paddy rice fields in the Taihu Lake region emitted the equivalent of 5.7 Tg C from 1982-2000, with the average CH 4 flux ranging from 114 to 138 kg C ha −1 y −1 . As for soil subgroups, the highest emission rate (660 kg C ha −1 y −1 ) was linked to gleyed paddy soils accounting for about 4.4% of the total area of paddy soils. The lowest emission rate (91 kg C ha −1 y −1 ) was associated with degleyed paddy soils accounting for about 18% of the total area of paddy soils. The most common soil in the area was hydromorphic paddy soils, which accounted for about 53% of the total area of paddy soils with a CH 4 flux of 106 kg C ha −1 y −1 . On a regional basis, the annual averaged CH 4 flux in the Taihu Lake plain soil region and alluvial plain soil region were higher than that in the low mountainous and hilly soil region and the polder soil region. The model simulation was conducted with two databases using polygons or counties as Correspondence to: D. Yu (dshyu@issas.ac.cn) the basic units. The county-based database contained soil information coarser than the polygon system built based on the 1:50 000 soil database. The modeled results with the two databases found similar spatial patterns of CH 4 emissions in the Taihu Lake region. However, discrepancies exist between the results from the two methods. The total CH 4 emissions generated from the polygon-based database is 2.6 times the minimum CH 4 emissions generated from the county-based database, and is 0.98 times the maximum CH 4 emissions generated from the county-based database. The average value of the relative deviation ranged from −20% to 98% for most counties, which indicates that a more precise soil database is necessary to better simulate CH 4 emissions from rice fields in the Taihu Lake region using the DNDC model.

Quantifying methane emissions from rice paddies in Northeast China by integrating remote sensing mapping with a biogeochemical model

“…In contrast, other soil properties like bulk density and soil pH, were less sensitive to the CH 4 emission from rice paddy. The regional average was around 400 kg CH 4 -C ha −1 in 2006, which was higher than that (15-198 kg CH 4 -C ha −1 yr −1 ) observed in the Southeast China such as Taihu Lake region (Zhang et al, 2009a) and also higher than the default emission factors of 200 kg CH 4 -C ha −1 season −1 suggested by the IPCC guidelines (IPCC, 1997). The simulated data attributed the high CH 4 emission rates to the SOC rice soils (averagely 0.31 kg C kg −1 soil) in combination with the continuous flooding management in the Sanjiang Plain.…”

“…The major models that are able to simulate CH 4 production include MEM (Cao et al, 1995a), MERES (Matthews et al, 2000), InfoCrop (Aggarwal et al, 2004), DNDC (Li et al, 1992a) and so on. In recent years, these models played an important role in describing CH 4 production and oxidation process in paddies and estimating the CH 4 emissions at regional or global scales (Cao et al, 1995b(Cao et al, , 1996Bachelet and Neue, 1993;Li et al, 2004;Pathak et al, 2005;Zhang et al, 2009a). Among the candidate models, DNDC has been tested for the rice paddies in China and other Asian countries.…”

“…Recently, Pathak et al (2005) applied the DNDC model to estimate total GHG emissions from Indian rice paddies based on agricultural census data. And also, Zhang et al (2009a) quantified CH 4 emissions from rice fields in the Taihu Lake region in China using DNDC. These studies proved that DNDC is applicable for estimating CH 4 emissions from rice paddies at regional scale.…”

Influence of rice varieties, nitrogen management and planting methods on methane emission and water productivity

“…Methane standard of 5 ppmV was used. The gas emission flux was calculated from the difference in gas concentration according to the equation of Zhang et al (1998). Total gas emissions during the study period were calculated by integrating gas emissions on sampling days and cumulative gas emissions on the sampling days.…”

The development of the DNDC plant growth sub-model and the application of DNDC in agriculture: A review

“…(3) DNDC has been widely verified in food crop research, and some crop-specific models (e.g., DNDC-CSW and DNDC-Rice) have also been developed Liu et al, 2006;Tonitto et al, 2007a,b;Zhang et al, 2009;Li et al, 2012b).…”