Soil bulk density and soil porosity's spatiotemporal variation under typical secondary forest in hilly regions of North Jiangsu

With the ecological environment problems becoming increasingly acute,how to use,protect,and improve the forest's soil resources to increase its productivity rationally has become the focus of forestry and soil ecology.Six typical secondary forests: Japanese red pine,black pine trees,platycladus orientials forest,oak forest,spinneys and locust forest in hilly regions of North Jiangsu are chosen for the study.By determining the soil bulk density of the six sample plots and comparing them with the bare land,we have found that the soil bulk density of the six sample plots is lower than that of the bare land and that it becomes greater with the increase of the depth in different periods.Moreover,the soil porosity gets smaller with the increase of the depth.Different forests can change the soil bulk density from high to low as follows: platycladus orientials forest,black pine trees,Japanese red pine,locust forest,spinneys,and oak forest.