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Global warming is widespread concern that people are giving global environmental problems, leading to the greenhouse effect of greenhouse gases concentrations in the atmosphere continue to grow more and more attention and therefore in all greenhouse gases, CH4 contribution to greenhouse effect second only to the C02, is the second largest emitter of greenhouse gases. CH4 emissions from rice fields leading to rising atmospheric concentrations of CH4 is one of the important reasons, more and more scholars biogeochemical process model used to simulate the complex trace gas emissions from agricultural soils process. During the simulation, using raster data, the nature of the study area into homogeneous discrete estimation unit, help to improve simulation accuracy. But in simulation, excessive grid cells will generalizability important attribute information, too small grid cells will reduce the simulation efficiency. Therefore, in the selection of the appropriate analog simulation unit, the use of the model to carry out agricultural greenhouse gas emissions is of great significance. In this paper, DNDC (DeNitrification-DeComposition) model, based on the Taihu Lake region 1:50,000 soil database conversion integrated 1km, 2km, 4km, 8km, 16km, 32km and 64km seven kinds of grid size database to estimate the 19 years between 1982-2000 paddy CH4 emissions of the model input parameters - soil attribute data, the average annual per unit area of ??CH4 emissions from rice fields and rice paddies CH4 emissions in a single grid size and the variability of different characteristics of the grid size. The results show that: the model input parameters - soil attribute data in a single grid size and grid size under different spatial distribution showed that: in a single grid size, the Taihu Lake region paddy soil texture soil clay content in the Taihu Lake west the lowest in the Taihu Lake east and south east of the regional soil clay content is higher, in the Taihu Lake north and south as well as Shanghai territory clay content centered; and soil texture spatial differentiation of different soil bulk density in the Taihu Lake east lowest soil bulk density in the study area in the southwest southwest of Shanghai soil bulk density and higher in the north of Taihu Lake, west of Shanghai, Zhejiang Province, eastern and northern soil bulk density content centered; soil pH from inland to coastal direction changes gradually the performance in the Taihu Lake region from west to east soil pH increases, the study area in northern and central Zhejiang Province, the soil pH optimum CH4 production, Shanghai, Jiangsu, Zhejiang, the most northern and north is more appropriate for the production of CH4, Shanghai coastal The southwest corner of the study area and other areas, and inhibition of CH4 produced; while spatial variation of soil organic matter present in the side from the east and west ends south of the eastern and central regions growing trend, the performance of the Taihu Lake, east and west of Shanghai, Zhejiang Province of soil organic carbon content is higher, and Shanghai in the north central and northern Taihu soil organic carbon content centered in Jiangsu Province, the western soil organic carbon content is low. At different grid size, the Taihu Lake region paddy soil four kinds of soil attributes describe statistical results showed that soil texture, bulk density and organic carbon showed three kinds of major trends; soil pH, mainly showing two kinds of trends. With the grid size from 1 km to 64 km of gradually increasing paddy soil characteristics raster map plaques showing the trend of constantly being there. Unit area of ??paddy annual CH4 emissions and CH4 emissions in a single grid size and grid size under different variation characteristics showed that: in a single grid granularity, from the regional scale, the average annual per unit area of ??paddy CH4 emissions, showing from south to north, from west to east, gradually rising trend, the study area southwest region, east of Taihu Lake region and the northwest corner of the region the average annual emissions of CH4 per unit area of ??less emission centered central region, the eastern and northern regions of higher emissions; terrain area from a different perspective, per unit area average annual paddy CH4 emissions from small to large order of hilly area in turn lt; low-lying polder areas lt; Taihu Plain lt; alluvial plain; From the county scale, the chuansha CH4 per unit area of ??the average annual emissions of up to 204 kg C / (hm2 · a), Linan minimum 3 kgC / (hm2-a), 54% of CH4 per unit area of ??the county emissions of 100 ~ 200 kg C / (hm2-a) between the majority and these counties located in Jiangsu Province and Shanghai Municipality territory unit area average annual paddy soil CH4 emissions relatively large counties in Shanghai, in Zhejiang counties is relatively small. At different grid size, the size of each grid area error rate, in 16 km grid size at the obvious turning point, showing from 1 km to 16 km grid size of the area the lowest error rate was 0.09%, the highest of 2.28%, a very small amplitude, and in the 32 km and 64 km grid size of the area at the sharp increase in the error rate were 19.93% and 42.14%, an area of ??great error; regional scale from the point of view of the study area, paddy soil CH4 emissions also significantly scale turning point appeared in at 16 km grid size, too large grid cell area error caused a direct result from 16km to 32 km and 64 km grid size at the CH4 emissions increased rapidly. From the county yardstick, 1 km to 16 km 5 种 grid size unit area under paddy annual emissions of CH4 there are obvious differences between, 46% of the county's average annual emissions of CH4 per unit area at 8 km and 16 km 2 种 granularity grid with 1 km, 2km, 4 km 3 种 granularity simulation results vary significantly. Considering the amount of spatial data and the model calculation cycle to 1:50,000 soil database, based on the regional scale, 16 km grid size is best suited to regional greenhouse gas emissions estimates simulation particle size; in the county scale, 4 km grid size is best suited to the county unit area of ??paddy field estimated annual emissions of greenhouse gases analog granularity.
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