下拉秀剖面有机碳赋存特征

以位于青藏高原三江源地区的下拉秀剖面为对象,按剖面自然分异的颜色层次分层采集样品,研究了三江源腹地沉积土壤的有机碳。结果表明:各层位有机碳含量差异显著(P<0.05),现代生草层总有机碳(TOC)、易氧化碳(LOC)、胡敏素(HM)碳含量最高。全剖面可见LOC和水溶性物质(WSS)存在,WSS和45cm以下的LOC的相对含量随剖面深度的增加总体呈上升趋势。富里酸(FA)和HM含量在各层位间差异显著(P<0.05),胡敏酸(HA)在个别层位存在绝对含量差异不显著(P>0.05)的现象。HA/FA在0.14～2.72范围内变化,总体表现为剖面上半部分大于1,下半部分小于1,最大值未出现在现代生草层。FA的E4/E6变化幅度大,HA的E4/E6波动小。综合表现为剖面有机物质腐殖化程度各层异质各向的特征,现代生草层的腐殖质化程度所代表的年代在剖面各层位当中既不是最高的时期亦不是最低的时期。

Features of Organic Carbon Occurrence of Xia Laxiu Profile

Xia Laxiu region is located in the hinterland of "Three Rivers" area of Qinghai-Tibet plateau.The profile of Xia Laxiu was selected for organic carbon research purpose.Soil samples were collected vertically from different natural color layers and organic carbon deposited in the soil were tested and analyzed.Results showed that contents of organic carbon in different layers were significantly different(P<0.05).Of all layers,contents of total organic carbon(TOC),labile organic carbon(LOC),humin(HM) carbon were highest in grass-growing layer.LOC and water-soluble substances(WSS) were found in all layers of the profile.WSS and relative contents of LOC in layers of 45 cm below showed an overall increasing trend with depth increased.Contents of fulvic acid(FA) and HM were significantly different between layers(P<0.05).Absolute content of humic acid(HA) was not significant between several layers(P>0.05).HA/FA values ranged from 0.14 to 2.72 and maximum HA/FA was not found in grass-growing layer.On the whole,HA/FA values of the upper part of the profile were >1,while the lower half were <1.The E4/E6 of FA varied largely,E4/E6 of HA fluctuated slightly.In conclusion,humification degree of organic substance in Xia Laxiu profile characterized by heterogeneity of components and their different contents.The period which humification degree of the grass-growing layer represented is neither the maximum one nor the minimum one.