Organic matter composition and stabilization in a polygonal tundra soil of the Lena Delta
Organic matter composition and stabilization in a polygonal tundra soil of the Lena Delta
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DOI：
10.5194/bg-10-3145-2013
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发表时间：
2013-01-01
期刊：
影响因子：
4.9
通讯作者：
John, S.
中科院分区：
文献类型：
--
作者：
Hoefle, S.;Rethemeyer, J.;John, S.
采用密度和粒度分馏相结合的固态C-13核磁共振光谱定性分析方法，以及脂质分析相结合的C-14分析方法，研究了俄罗斯勒拿河三角洲多边形苔原土壤活性层中不同稳定土壤有机质组分的土壤有机质组成。块状土壤有机质主要由植物源性、低分解物质组成，随着活性层深度的增加，其表观C-14年龄惊人地高且急剧增加，表明寒冷气候下微生物有机质转化缓慢。土壤有机碳主要分布在粘土和细粉砂质组分（< 6.3 mu m），这些组分由分解程度较低的植物物质组成，主要以长正构烷烃和正脂肪酸化合物为主，烷基/ o -烷基C比值较低。有机矿物组合被认为是温带土壤中有机质稳定的关键机制，但在活动层中似乎不那么重要，因为主要来自植物的粘土和细粉粒大小的有机质出人意料地“年轻”，其C-14含量与大块土壤值相似。此外，与土壤团聚体中封闭的密度分馏有机质相比，这些组分含有更少的有机碳，这是温带土壤中限制微生物可及性的另一个重要有机质稳定机制。这一过程似乎在活性层深度较大的地方很重要，在那里，被土壤团聚体遮蔽的颗粒有机质比自由颗粒有机质“更老”。
This study investigated soil organic matter (OM) composition of differently stabilized soil OM fractions in the active layer of a polygonal tundra soil in the Lena Delta, Russia, by applying density and particle size fractionation combined with qualitative OM analysis using solid state C-13 nuclear magnetic resonance spectroscopy, and lipid analysis combined with C-14 analysis. Bulk soil OM was mainly composed of plant-derived, little-decomposed material with surprisingly high and strongly increasing apparent C-14 ages with active layer depth suggesting slow microbial OM transformation in cold climate. Most soil organic carbon was stored in clay and fine-silt fractions (< 6.3 mu m), which were composed of little-decomposed plant material, indicated by the dominance of long n-alkane and n-fatty acid compounds and low alkyl/O-alkyl C ratios. Organo-mineral associations, which are suggested to be a key mechanism of OM stabilization in temperate soils, seem to be less important in the active layer as the mainly plant-derived clay-and fine-silt-sized OM was surprisingly "young", with C-14 contents similar to the bulk soil values. Furthermore, these fractions contained less organic carbon compared to density fractionated OM occluded in soil aggregates - a further important OM stabilization mechanism in temperate soils restricting accessibility of microorganisms. This process seems to be important at greater active layer depth where particulate OM, occluded in soil aggregates, was "older" than free particulate OM.