黄土高原区不同植物凋落物可溶性有机碳的含量及生物降解特性

以黄土高原区刺槐、小叶杨、沙棘、沙柳、苜蓿和长芒草等6种植物凋落物为研究对象，利用2种浸提剂(水和0.01 mol·L^-1CaCl₂)浸提了不同大小(2 mm粉碎样和1 cm长)植物凋落物，测定了其中可溶性有机碳(SOC)的含量，并利用室内培养试验(25℃)评价了可溶性有机碳的生物降解特性.结果表明，不同植物凋落物可溶性有机碳含量在4.21～76.25 g·kg^-1之间，占其全碳的比例在0.99%～19.84%之间.平均来看，乔木凋落物可溶性有机物含量及其占全碳的比例大于灌木，而灌木又高于草本.经过7 d的培养，不同凋落物可溶性有机碳的生物降解率在34.7%～75.1%之间，平均56.3%，不同种类凋落物的生物降解率相比为乔木＞灌木＞草本.紫外及荧光光谱法测定法表明，培养结束后SOC溶液中结构较为复杂的可溶性有机物的比例呈显著上升，这与其中易降解组分的降解有关.

Contents and Biodegradation of Soluble Organic Carbon in Different Plant Residues from the Loess Plateau

Soluble organic carbon (SOC) in plant residues extracted by water or different extractants is an active component, and has important roles in carbon and nitrogen biogeochemical process in soil ecosystem. Reestablishing the vegetation on the Loess Plateau is changing the types and amounts of the plant residues into soil ecosystem. Therefore, our objective was to evaluate the contents and biodegradation of SOC of residues of different species from this region. Six species of plant residues were sampled from Shenmu, North of the Loess Plateau, and the contents of SOC in two sizes residues (2 mm and 1 cm length) was extracted with two extractants (distilled water and 0.01 mol x L(-1) CaCl2). And a 7-day incubation experiment (25 degrees C) was conducted to compare the biodegradability of SOC of the different plant residues. The contents of SOC in the different plant species ranged from 4.21 g x kg(-1) to 76.25 g x kg(-1), and the rates of SOC to total carbon (SOC/TC) of the plant residues were in range of 0.99% and 19.84%. The order about the average content of SOC and SOC/TC of the different plant species was trees > shrubs > grasses. After 7-day of incubation, rates of biodegradation of SOC in different plant residues ranged from 34. 7% to 75. 1% (averaged 56.3%). The proportion of complex structure SOC increased significantly in solution at the end of incubation, indicated the rapid biodegradation of labile composition in the residues.