Abstract:

The mixed plantation of poplar (Populus spp.) and black locust (Robinia pseudoacacia L.) is one of the successful mixed stands of nitrogen-fixing and non-nitrogen-fixing species on poor sandy sites along the river and besides sea in the north of China. The growth and yield of the mixture is briefly introduced in this paper. The soil amelioration and the interaction of mutual supplement of nutrient between tree species are mainly discussed in this paper. It shows that the yield improvement is mainly due to the soil nutrient amelioration (especially nitrogen nutrient) and the interaction of mutual supplement of N and P nutrient. The main reason of the soil nitrogen nutrient improvement is the high speed of litter decomposition and high ammonification and nitrification intensity because of the increased activity of soil microorganism. The interaction of mutual supplement of N and P nutrient between tree species is realized mainly through the mechanism that poplar trees can transfer phosphorus to black locust trees by root-contacting and black locust can transfer nitrogen to poplar trees also by root-contacting. The transfer intensity of N and P is very high. This kind of marvelous interaction between tree species in very important to the yield improvement in the young mixtures.

Key words: Poplar (Populus spp.), Black locust (Robinia pseudoacacia L.), Mixed plantation, Soil amelio ration, The interaction of mutual supplement of nutrient between tree species