Study On Changes Of Water And Salt Movement And Soil Nutrient And Soil Enzyme In Pure And Mixed Stands Of Black Locust Under Salt Stress

Forestry College of Shan Dong Agricultural University, Tai'an 271018The experiment was conducted to study the water and salt movement soil nutrient content and Soil enzyme activity of several mixed forests of black locust (twenty years old) on seashore saline soil, and the object are the pure and mixed forests of black locust (Robinia pseudoacacia) and Tree of heaven (Ailanthus altissima ) and Elm (Ulmus pumila) and Chinese ash(Fraxinus chinensis). Two tests were conducted: One by continual testing the water and salt contents of five soil layers (0-20cm, 20-40cm, 40-60cm, 60-80cm, 80-100cm) for 12 months in pure and mixed stands to study the water and salt year movement in different pure and mixed stands; at the same time, the season difference and correlation of soil nutrient and soil enzyme activity in different pure and mixed stands are also be studied by continual testing soil nutrient content and soil enzyme activity for four months (4, 6, 8, 10) in and off root soil. The other by continual adding NaCl solution to study the growth,photosynthesis and osmotic adjustment of pure and mixed stands of black locust. The main results were as follows:Test I:There are differences on growth,water and salt movement,soil nutrient content and soil enzyme activity in pure and mixed stands of black locust. Results as follows:The growth condition of different mixed stands is: black locust and Chinese ash >black locust and Tree of heaven>pure black locust>black locust and Elm.The total water and salt movement in one year is: the changes of soil water content have two high peaks , one is in 6-8 month and another one is 11-12month, and during those months, the water content is much higher than that of the other months. At the same time, the salt content in these months changes to the low peak. The water content is higher and salt content is lower in mixed stands than that in pure ones. But different mixed stands have differences: black locust and Chinese ash stand was better than that of black...