土壤数据源和制图比例尺对旱地土壤有机碳储量估算的影响

明确不同来源土壤剖面数据建立的大、中、小系列制图比例尺对旱地有机碳储量估算的影响对于全球碳循环研究具有重要意义。以江苏北部(简称"苏北地区")3.9×106多hm2旱地为例,系统分析了我国目前常用《县级土种志》、《地级市土种志》、《省级土种志》和《中国土种志》中记录的土壤剖面数据分别建立的1∶5万、1∶25万、1∶50万、1∶100万、1∶400万和1∶1 000万数据库对有机碳储量估算的影响。结果表明,与数据最详细、记录有983个土壤剖面的《县级土种志》1∶5万尺度有机碳密度和储量相比,其他土壤数据源建立的不同制图尺度数据库相对偏差分别在1.94%~23.53%与0.02%~22.86%之间,T检验表明大多数制图尺度土壤数据库的估算结果与《县级土种志》1∶5万尺度之间存在极显著差异(p0.001),这说明在今后国家或区域尺度土壤有机碳储量估算中选择适宜的土壤数据源和制图尺度是非常重要的。

Impacts of Source of Soil Data and Scale of Mapping on Assessment of Organic Carbon Storage in Upland Soil

Accurate assessment of soil organic carbon storage based on the database established on the basis of the attribute data of soil profiles is the basis of the research on global carbon cycling and improvement of soil fertility for agriculture. However,it is still unclear how source of soil profile data and scale of mapping affects assessment of soil organic carbon storage. In this study,a total of 3.93×106 hm2 of upland in the 29 counties(or cities)of North Jiangsu was cited as a case for study. Systematic analysis was performed of how the four sources of soil profile data,namely,"Soils of County","Soils of Prefecture","Soils of Province"and"Soils of China",and the six scales,i.e. 1:50 000,1:250 000,1:500 000, 1:1 000 000,1:4 000 000 and 1:10 000 000,used in the 24 soil databases established for the four soil journals,affected assessment of soil organic carbon. Results show that the soil organic carbon density (SOCD)and storage(SOCS)in the top layer(0~20 cm)of the uplands in the region in the 1:50 000, 1:250 000,1:500 000,1:1 000 000,1:4 000 000 and 1:10 000 000 scaled databases was estimated to be 1.56 kg m-2 and 61.20 Tg,1.53 kg m-2 and 61.32 Tg,1.51 kg m-2 and 61.22 Tg,1.44 kg m-2 and 55.19 Tg,1.60 kg m-2 and 65.08 Tg,1.59 kg m-2 and 63.11 Tg,respectively,based on 983 upland soil profiles in the"Soils of County",1.63 kg m-2 and 63.92 Tg,1.71 kg m-2 and 68.78 Tg,1.64 kg m-2 and 66.37 Tg, 1.62 kg m-2 and 62.06 Tg,1.70 kg m-2 and 69.25 Tg,1.72 kg m-2 and 68.24 Tg,respectively,based on the 209 upland soil profiles in the"Soils of Prefecture",1.27 kg m-2 and 49.88 Tg,1.25 kg m-2 and 50.06 Tg, 1.72 kg m-2 and 69.64 Tg,1.43 kg m-2 and 54.84 Tg,1.40 kg m-2 and 56.99 Tg,1.52 kg m-2 and 60.18 Tg,respectively,based on 64 upland soil profiles in the"Soils of Province",and 1.74 kg m-2 and 68.31 Tg, 1.70 kg m-2 and 68.08 Tg,1.81 kg m-2 and 73.52 Tg,1.75 kg m-2 and 66.78 Tg,1.75 kg m-2 and 71.33 Tg, 1.19 kg m-2 and 47.21 Tg,respectively,based on 21 upland soil profiles in the"Soils of China". Compared with the most detailed 1:50 000 soil database based on 983 upland soil profiles containing 17 024 polygons, the other five databases varied from 1.94% to 23.53% and from 0.02% to 22.86%,respectively,in relative deviation of the assessment of SOCD and SOCS. T test shows that extremely significant differences existed between the assessment based on the 1:50 000 database of"Soils of County"and the assessments based on the databases of other scales(p<0.001),indicating that it is essential for scientists to use soil data from proper sources and of proper mapping scales when trying to assess SOCS of the country or a region in future.