摘要
土地利用方式是影响农业土壤碳固持和温室气体减排的关键因子之一,而准确地评价土地利用变化的影响往往因土壤本底的不均一和土地利用历史多变而复杂化。为此,在崇明东滩湿地围垦区选取了本底均匀、利用历史简单的几种土地利用类型(水-旱轮作农田、人工林、鱼塘撂荒地),研究其土壤有机碳库和土壤呼吸的变化及其与土壤环境间的关系,以期评价其各自的固碳和温室气体减排潜力。农田土壤的表层(20cm)有机碳和微生物生物量碳含量最高,分别为12.62g/kg和225.34mg/kg,包括苗圃栾树林、水杉林带以及桔园在内的人工林地次之,鱼塘撂荒地最低;但撂荒地深层土壤(40—100cm)的有机碳含量高于其它类型,反映了围垦前湿地土壤有机碳累积的残留影响。土壤呼吸强度的顺序则为鱼塘撂荒地>农田>桔园>苗圃栾树林>水杉林带。农耕地在前作小麦收割种植水稻后,土壤CO2通量显著下降,不及旱作时的10%。除农田和撂荒地以外,土壤表层5 cm深处温度可以很好地解释土壤呼吸速率的变化,但在高温高湿季节呼吸速率较为离散。研究表明:在有机质含量较低的土壤中,水-旱轮作可增加土壤有机碳的储量;受人类活动干扰较小的林地土壤,有机碳含量反而有可能低于农田土壤。在中国南方湿润亚热带地区,水旱轮作可较好地协调农业土壤的碳固持和释放过程的矛盾,可能具有相当大的农业减排潜力。
Land-use change is a crucial factor in regulating soil C processes with a potential to mitigate green house gases emission by fossil fuel combustion.The assessment of its influence is,however,complicated by the heterogeneity in background and land-use history.The soils in the Chongming Island,located in the estuary of the Yangtze River,have a relatively homogeneous background and short and clear history of soil development and land-use after reclaimed on wetlands.Various sites in eastern Chongming Island of different land uses,including farmland（rotation of barley and paddy rice）,tree nursery（Koelreuteria bipinnata）,Metasequoia glyptostroboides forest shelter belt,orchard（Citrus reticulata） and fallow land（reclaimed in 1999 for fish farming then drained as a fallow land since 2005） were selected.The average contents of soil organic carbon（SOC） and soil microbial biomass carbon（SMBC） in the layer of top 20 cm in farmland,at 12.62 g/kg and 225.34 mg/kg respectively,were significantly higher than others.The fallow land had the lowest SOC and SMBC in the layer of top 20 cm.SOC content in deep soil（40—100 cm）,however,was the highest in fallow land,reflecting the remaining effects of previous wetland soil.Soil respiration rate varied with land use in the order： fallow land 〉farmland〉orchard〉plantationshelter belt.After the harvest of barley,the arable land was turned into paddy rice and soil respiration decreased dramatically,less than 10% of previous barley rotation.Soil respiration increased exponentially with increasing soil temperature at the depth of 5 cm,except farmland and fallow.At high temperature（〉25 ℃） during rainy season,soil respiration data were distinctly scattered.Our results suggest that paddy rice-drying farming rotation can increase both soil respiration and SOC stocks in young soils of relatively low SOC;soils under tree plantations may have a lower SOC content.In moist subtropical regions of south China,the rotation of paddy rice-drying farming can balance processes of C sequestration and release in arable soil,with a potential of mitigating greenhouse gases emission.
出处
《生态学报》
CAS
CSCD
北大核心
2010年第24期6698-6706,共9页
Acta Ecologica Sinica
基金
上海市科委重点项目(07JC14002)
上海市"浦江计划"
教育部高等学校博士学科点专项科研基金
关键词
土地利用
土壤有机碳
土壤微生物量碳
土壤呼吸
农业减排
land use
soil organic carbon
soil microbial biomass carbon
soil respiration
agricultural mitigation
