Nutrients cycling is one of the fundamental and functional processes that maintain the structure and services produced by forest ecosystems. Many micronutrient elements can be essential to forested ecosystem biomass production. A lack of any of the essential elements can be limiting to biological production and ecological processes, This may be particularly important in karst areas, such as karst regions in southwestern China, where the high permeability of the bedrock and the strong anthropogenic disturbance result in nutrients deficiency and poor soil fertility. In order to understand the effect of urban forest development on microelements cycling in karst areas, we have studied poplar plantations located in Guiyang city, Guizhou Province of China, where the karst area accounts for 85% of the total urban area of the city. The concentration, accumulation, spatial distribution, decomposition and bioloigcal cycling of eight micronutrient elements (Cu, Fe, Zn, Mn, Ni, Pb, Co and Cd) in 25-year old poplar (Populus tremula) plantations were investigated. The results showed that the concentration of Fe was the highest among the eight microelements, following by Mn and Cd had the lowest concentration in the soils. The concentration of the eight micronutrient elements decreased with increasing of the soil depth. Microelements of Pb, Ni, Mn, Cd, Cu, Co and Zn had a higher rate of decomposition than Fe element in litter layer on the stand floor. The concentration of microelements in different organs of poplar trees was in an order of fine root > leaf > coarse root > bark > branch > large root > stake > wood. The concentrations of Cu in leaf were higher than those in other organs. The total storage of microelements in the plantations was 14.086 kg/hm², and the content of eight micronutrient elements in different organs of poplar trees was in the order of Mn>Zn>Cu>Fe>Cd>Co>Pb>Ni. The wood and bark had the highest amount of microelements than other organs, and they accounted for 43.4% of the total microelements in poplar trees. The patterns of biological cycle of micronutrient elements showed that annual uptake amount of microelements was 3.079 kg/hm², annual return 2.663 kg/hm², and annual retention 0.417 kg/hm² in the studied plantations. The utilization coefficient (ratio of the annual uptake amount to the total microelement storage in plantations) and cycling coefficient (ratio of annual return amount to annual uptake amount) of micronutrient elements were 0.219 and 0.865, respectively. The turnover period of the microelements (ratio of the total microelement storage in plantations to the annual return amount) was estimated to be 5.29 year. The poplar plantations had strong ability to absorb Cd from the soils, and the biological decomposition rates of all microelements were higher than their migration rates in the studied forests. Our results indicated that there was a relative high cycling rate and a relative short turnover period of the micronutrient elements in the poplar plantations. The study suggested that the urban poplar forests had a strong ability to keep nutrients stability, to make stand self-adjustment and to improve soil fertility, which might be beneficial to the maintenance of forest productivity.