苏北沿海不同林龄杨树林土壤活性有机碳特征

Characteristics of soil labile organic carbon in poplar plantations of different ages in coastal area of North Jiangsu

为阐明苏北沿海不同林龄杨树(黑杨派无性系I-72杨)人工林土壤活性有机碳变化特征及其影响机制,选择5种不同林龄(4、8、12、15、20年生)的杨树人工林,测定其0～10、10～25、25～40cm土层土壤总有机碳、水溶性有机碳、微生物生物量碳及其主要理化性质。结果表明:不同林龄的土壤总有机碳、水溶性有机碳和微生物生物量碳含量均随着土层加深而递减,随着林龄的增加,土壤总有机碳含量呈现先增大后减小的变化趋势,其中,15年生最大,4年生最小;水溶性有机碳、微生物生物量碳含量总体趋势与总有机碳一致,二者占总有机碳的比例随林龄增加而增大;2种活性碳之间、活性碳与总有机碳、全氮、C/N、pH、土壤容重存在显著相关,与土壤全硫、土壤湿度关系不显著。研究表明,苏北沿海地区杨树人工林随着林龄的增大,其活性碳含量的变化存在不确定性,在一定程度上影响了不同林龄杨树人工林的碳汇功能。

To understand the characteristics of soil labile organic carbon and its correlations with soil physical and chemical properties in the poplar （Populus euramericana cv. San Martino） plantations of different ages in coastal area of North Jiangsu, five poplar plantations of 4-, 8-, 12-, 15-, and 20 years old were selected, with the total organic carbon （TOC）, water-soluble organic carbon （WSOC）, microbial biomass carbon （MBC）, and physical and chemical properties in 0-10, 10-25, and 25-40 cm soil layers analyzed. In the five plantations, the contents of soil TOC, WSOC, and MBC all decreased with soil depth, and the soil TOC content had a trend of decreased after an initial increase with increasing plantation age, being the maximum in the 15 years old plantation and the minimum in the 4 years old plantation. Overall, the contents of soil WSOC and MBC had the same variation trend as soil TOC content, and the soil WSOC/TOC and MBC/TOC ratios increased with increasing plantation age. There was a significant correlation between soil WSOC and MBC, and the soil WSOC and MBC were significantly correlated with soil TOC, TN, C/N, pH, and bulk density but not correlated with soil total S and soil moisture. This study indicated that with the increasing age of the poplar plantations in the coastal area of North Jiangsu, soil labile organic carbon content had no definite variation pattern, which affected the plantations acting as a carbon sink to a certain extent.