基于大比例尺数据库的福建省耕地土壤固碳速率和潜力研究

Study of Soil Organic Carbon Sequestration Rate and Potential of Farmland Soil in Fujian Province Based on the Large Scale Soil Database

明确土壤固碳速率和潜力是制定耕地固碳减排措施的基础。以我国典型亚热带地区—福建省不同地理位置的闽侯、浦城、同安、武平和永定5个县为研究区,运用生物地球化学过程模型DNDC(DeNitrification and Decomposition),模拟这5个县在目前区域尺度最详细的1︰5万土壤数据库下1980—2009年和2010—2039年有机碳动态变化,并运用尺度上推的方法估算出全省耕地土壤固碳速率和潜力。结果表明,福建省耕地土壤1980—2009年的固碳总量为7.37 Tg,而2010—2039年的固碳潜力为7.04 Tg,两个时段的年均固碳速率分别为190 kg·hm^(–2)和176 kg·hm^(–2),说明目前的农田管理措施有利于研究区长期固碳。其中,水稻土和盐渍水稻土分别在土类和亚类级别中固碳速率最大,不同时段均大于175 kg·hm^(–2)·a^(–1);而红壤在土类和亚类级别中固碳速率皆最小,不同时段均小于3 kg·hm^(–2)·a^(–1)。总体来看,1980—2009年和2010—2039年水稻土的固碳总量均占全省耕地固碳总量的92%以上,是今后制定固碳减排措施的重点。

【Objective】Farmland soil organic carbon pool is one of the most important soil carbon pools and its sequestration and emission have a huge impact on global climate change.It is essential to estimate the soil carbon sequestration rate and potential of farmland soils accurately for managing soil fertility and the ecological environment.Fujian Province is characterized by a large population and small land use and strong spatial heterogeneity of soil.It is of great significance to identify the dynamic evolution trend of soil organic carbon and future carbon sequestration potential of cultivated land in this region for formulating the national strategy of“carbon neutrality”and food security in subtropical regions of China.【Method】This study covered five counties including Minhou,Pucheng,Tongan,Wuping and Yongding,located in different geographical locations in Fujian Province.Soil attributes data based on the data of field measurements at 30211 sampling sites in 1980 and 15948 sampling sites in 2008,scattered in these five counties were analyzed.The 1980 soil spatial database was digitized during the Second Soil Survey 1:50000 soil map and the 2008 soil spatial database was extracted from the annual 1:50000 land-use status map.Through ArcGIS software and the Ordinary Kriging method,we related the soil spatial data and soil attributes to obtain a high-precision farmland soil database.Based on the most detailed soil database of 1:50000 at the regional scale,we used the biogeochemical process model DNDC(DeNitrification and Decomposition)to simulate the organic carbon changes in these five counties from 1980 to 2009 and to get predicted value from 2010 to 2039.Also,we estimated the soil carbon sequestration rate and potential of farmland soil in the province by the method of scaling up.【Result】Results show that the carbon sequestration amount of the cultivated land in Fujian Province from 1980 to 2009 was 7.37 Tg,and the carbon sequestration potential from 2010 to 2039 was 7.04 Tg.The average annual carbon sequestration rate for the two periods was 190 kg·hm^(–2) and 176 kg·hm^(–2),respectively.Among them,paddy soil and saline paddy soil showed the highest carbon sequestration rate in soil type and soil subgroup,respectively,and was greater than 175 kg hm^(–2) in different periods.The carbon sequestration rate of the red soil group and soil subgroup was the lowest,with an average rate between-29-3 kg·hm^(–2).Generally,the total carbon sequestration of paddy soil was higher than 6.5 Tg in different periods,accounting for more than 92%of the province's total carbon sequestration,which is the key to formulating carbon sequestration and emission reduction measures in the future.【Conclusion】Results of this study indicate that the cultivated soil in Fujian province showed a weak"carbon sink"effect from 1980 to 2009 and 2010 to 2039.This indicates that the current farmland management measures in this area are conducive for carbon sequestration of cultivated soil and should continue to be promoted.Meanwhile,due to the high variability in soil properties,the soil organic carbon(SOC)change in Fujian province was strongly influenced by soil type,soil subgroup and soil genus.Therefore,in future"carbon sink"policy formulation,it is necessary to formulate corresponding management measures for specific soil types.