A Study on Nutrient Dynamics and the Relative Increment Rate in Different Types of Poplar Intercropping

Through the intercropping of poplar with legume,arbors and shrubs and the rotational cropping of poplar,the effects of different treatments on the soil nutrient elements and the forest land productivity were studied quantitatively.The experimental stands in Henan Province and Beijing cover an area of 3.2 hm2 and 1.8 hm2 respectively,where the same experimental design with five treatments and three replications were adopted.The results from 1992 to 1995 showed that the relative increment rates of height and diameter at breast height(DBH)were significantly different between treatments at 0.01,0.05 and 0.10 level.At the site in Beijing,the relative increment rates of DBH and height were significantly different between treatments at 0.05 level(F =3.916)and at 0.10 level(F=2.423)respectively,at the Minquan site in Henan Province,the relative increment rates of DBH and height were significantly different at 0.01 level(F=28.769)and 0.05 level(F=3.39).The soil nutrient elements of different types of mixed poplar stands varied regularly;poplar mixture and black locust can improve the soil fertility of the forest land;in the poplar continuous cropping forest land,all the amount of soil nutrient elements declined and the land productivity degranded significantly.