农业工程学报2016，Vol.32Issue(21)：170-176,7.DOI:10.11975/j.issn.1002-6819.2016.21.022
黄土丘陵区不同退耕还林地土壤颗粒结合态碳库分异特征
Variances of carbon storage in soil particle-sized fractions following conversion of cropland to forest in Loess Hilly Region
摘要
Abstract
With the implementation of Grain for Green Project in the Loess Hill region of China, a large amount of arable land has been replaced by shrubs and trees, resulting in increased storage of soil organic carbon (SOC). To elucidate the mechanisms of change in the SOC and differences in the storage of SOC among the afforested lands, we separated the whole SOC into three particle-sized fractions: sand associated carbon (sand-C,≥53-2000µm), silt associated carbon (silt-C,≥ 2-53µm) and clay associated carbon (clay-C, <2µm). Soils were collected from cropland land and from areas with five tree species, robinia (Robiniapseudoacacia L), apricot(Armeniacasibirica), poplar (Populustomentosa), buckthorn (Hippophaerhamnoides L) and caragana (Caraganakorshinskii), which have grown on former cropland for 15 years. The result showed that compared with cropland, the content of SOC in whole soil at all afforested lands were significantly increased by 1.9-1.0 g/kg from top soil of 0-10 cm to soil depth of >40-60 cm, while the content of silt-C, clay-C and sand-C was increased by 1.0-0.6, 0.4-0.3, 0.5-0.1 g/kg, respectively. As a result, the stock of whole SOC and silt-C in 0-20 cm soil depth followed the increased ordercaragana = poplar< buckthorn < apricot <robinia, and increased 2.4-5.8 and 1.2-3.5 Mg/hm2, respectively. Carbon in the clay-C and sand-C fraction in the shallow soil layer was not significant differences among the afforested lands, and averagely increased 0.7 and 0.9 Mg/hm2, respectively. Moreover, the stock of whole SOC, silt-C and clay-C in soil depth of 0-60 cm was in the order caragana = poplar = buckthorn < apricot <robinia, and increased by 7.1-12.1, 3.8-6.8 and 1.8-3.2 Mg/hm2, respectively. There were no differences for sand-C stock in the 0-60 cm soil layer among the afforested sites, and the sand-C averagely increased 1.5 Mg/hm2 compared with cropland. However, the variation of sand-C stock was 1.6 times higher than the variation in silt-C and clay-C stock, implying that the sand-C was more sensitive when farmland was converted to forest than organic carbon associated with silt and clay. Additionally, the mass percentage of soil fraction was only increased by average 49.3% in the fraction of sand plus soil organic matter in 0-60 cm soil depth at all afforested lands. The particle-sized carbon fractions accounting for whole SOC followed the order silt-C (56.8%) >Clay-C (29.3%) >Sand-C (13.8%). There was only 4%-8% of the whole SOC lost because that dissolved organic carbon and trace amounts of soil was lost during the process of fractionation. In conclusion, our results indicated that carbon absorbed by silt fraction was the major mechanism for SOC change and accumulation during conversion of cropland to forest. The afforestation of former arable land with robinia and apricotcould increase more SOC in whole soil and particle-sized fraction that other afforested lands. Thus planting robinia and apricot at former arable land could be the best ecological technology for carbon sequestration in the soils of the region.关键词
土壤/有机碳/颗粒/黄土丘陵区/退耕还林/黄绵土Key words
soils/organic carbon/particles/Loess Hill Region/conversion of cropland to forest/loessial soil分类
农业科技引用本文复制引用
佟小刚,韩新辉,李娇,杨云芬,王健..黄土丘陵区不同退耕还林地土壤颗粒结合态碳库分异特征[J].农业工程学报,2016,32(21):170-176,7.基金项目
国家自然科学基金（41301602）；国家林业公益性行业科研专项（201304312）；中央高校基本科研业务费专项 （）
