Subei Seawall Protection Forest Soil Fertility Characteristics Of Study

This thesis studies the six main coastal protective forest models in northern JiangSu province through measuring soil physical and chemical properties,enzymatic activities and trees growth . The results are described as follows: 1. Except for catalase, the nutrient status in the top was highest. From top to bottom, it decreased gradually. The nutrient status of forest soil was higher than that of beach land, which showed that coastal protective forest could obviously improve the soil fertilities and black locust,poplar were better than water fir and Chinese fir. With the forest soil salt lost, the growth of trees was no longer limited by the salt content in the soil. 2. Soil bulk density,organic matter content,total nitrogen had a good correlation coefficient with other nutrient activities. There also exists close relationship between soil enzymatic activities and physical, chemical properties. So the soil enzymatic activities could be used to evaluate the soil fertilities. 　3. The soil physical properties, nutrient status and enzymatic activities in the two mixed plantation were better than the pure forests. It showed that after different kind of tree species were mixed, the soil enzymatic activities were enhanced, the nutrient status was improved, and the environment in the mixed forests was more fit for trees growth. 　4. Study on the relationship between soil fertility properties and species diversity in grass layer showed that the main factor affecting species diversity was soil PH, then was the soil total phosphorus. The soil water content,available phosphorus,soil bulk density,total porosity,noncapillary porosity,total nitrogen also affected the species diversity. With soil PH decreased in the mixed models, species diversity in grass layer in mixed forests was more than that in the pure forests. Therefore it is necessary to take measures such as mixing different kind of trees to decrease the soil PH, improve the soil fertility condition to increase species diversity in grass layer of coastal forests. 5. Of all the kinds of tree species, black locust was the best. So we should plant black locust and false indigo etc in the new first seawall. After the soil conditions were improved, we could plant other tree species such as poplar etc.　Now the protective forests such as black locust, water fir and Chinese fir were growing very slowly, and most were pure models. They were easily harmed by illness and did no good to trees. Some of them might be cut, then we could plant poplar trees. Thus the forests could still prevent the wind when they were replaced, and also could remedy soil degredation, using the productive power of forest soil better.