Abstract: 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.

Key words: farmer, climate change, perception, adaptation ability, adaptation strategy.