Abstract: Fine root biomass was studied using the sequential soil coring method in two four-year-old poplar plantations (Populus deltoides cv. 35.), which grew at the 2hm2grid pattern (Pw) and the 2hm2grid dyke pattern (PT), in Suqian, Jiangsu province from March, 2006to 2007. The annual production, mortality, decomposition and turnover rates of the fine roots in the depth of 0--40cm were also estimated and compared using the decision matrix method (DM) and the max-rain method (MM). The results showed that the mean standing pools of fine roots was 1.26--1.86t/htn2in two patterns. The annual net production, mortality, decomposition and turnover rates for fine roots were 2.24t/hm2, 2.34t/hm2, 1.88t/hm2, 1.43times/a (Pw) and 1.43t/hm2, 1.29t/hm2, 1.37t/hm2, 1.31times/a (PT) by the DM method, respectively. Compared with the DM method, about 19% annual net production, 68% mortality, 89% decomposition and 23% turnover rates for fine roots were underestimated by the MM method. Soil nutrient and seasonal water content were the main possible reasons for the differences of fine-root production and turnover rates between Pw and PT patterns.