Abstract:The laws of nutrient cycling in Paulownia plantation ecosystems were studiedfor 2 years. The results show: the contents of nutrient elements in each Paul-ownia tree organs change monthly. In the ecosystem the total uptake of nutrientelements was 545.3772kg/ha in 1987, comprising N 175.6543kg/ha, P95.5802kg/ha, K 100.2737kg/ha, Ca 140.0955kg/ha, Mg 33.7735kg/ha. In 1988,the total uptake was 471.9595kg/ha, among which N was 155.1429kg/ha, P80.0821kg/ha, K 87.0394kg/ha, Ca 119.4603kg/ha, Mg 30.2348kg/ha. Annualcirculation rates of nutrient elements in 1987 and 1988 were 71.71% and 70.26%respectively, with the circulation rates for each element being N 66.25%, P57.83% K 74.77%, Ca 83.01%,Mg 83.36% in 1987, and N 66.11%, P54.06%,K 73.13%, Ca 81.50%, Mg 81.84% in 1988. According to the quantities ofrecention and loss the national fertilization rates are determined.