Study On Growth Decline Mechanism Of Black Locust On Coastal Saline-alkali Soil

The study was based on the pure black locust forest of 23a on the coastal saline-alkali soil, the growth rule of black locust was studied, the correlation of rainfall and temperature between growth rule as well. The salty ions distribution of Na⁺, K⁺, Mg²⁺ and Ca²⁺ was tested at different height. Continual tested the water and salt contents of five soil layers (0-20cm, 20-40cm, 40-60cm, 60-80cm) for 12 months in pure, at the same time, the season difference and correlation of soil enzyme activity in different pure are also be studied by continual testing soil enzyme activity for four months (4, 6, 8, 10) in and off root soil. The leaf transpiration and photosynthesis were tested by photosynthesis system based on forest spot, Delta-T auto-moveable climatic station for all-weather forest air and soil environmental eco-factors measurement, Thermal Dissipation Probe(TDP-30 and TDP-50) for single tree sapwood flow's temporal-and-spatial fluctuation. Analysis of the peroxidase (POD) isozymes of the three degree of Robinia pseudoacacia. L had been conducted by using polyacrylamide gel electrophoresis method, The genetic relationships were also studied based on the genetic molecular levels. Therefore, the decline machnism of black locust on the coastal saline-alkali soil was analyzed systermatically.1 The black locust on coastal saline-alkali soil has been grown deeline for recent 7 years,The growth of 23 year Robinia pseudoacacia. L seedling on coastal saline-alkali soil was studied to analyse the height, diameter at chest height and volume by regression analysis. The optimal simulation equations were that: H=-0.372+3.318* lnt; DH=exp (- 5.518+0.977/t); V=exp (- 13.771-0.938/t). There were different decline degrees of same age black locust that ruled out death possibility of overmature forest. Further demonstrate that the decline of black locust caused by the external disturbance. And the reason maybe was elimate. The precipitation trend on coastal saline-alkali soil was rising, its change among years turnd up variational significantly, and average precipitation of month as well. The distribution of season precipitation was unbalance. The fluctuation of temprerature showed waving trend. But the general trend was up heated.2 Responses of soil enviroment on air factors was the promote agent lead to decline of black locust. The rule of water and salt movement in one year was that the changes of soil water content have two high peaks with the rain season coming, one was in 3-5 month and the other one was in 7-8 month, the water content was much higher than that of the other months. At the same time, the salt content in these months turned up to the low peak. The characteristics of soil salt content was that the salt content followed the water content. The soil salt content influenced water content, it was correlated significantly between soil salt soil water of 0 to 60cm and precipitation. The enzyme activity change of Urease, Phosphatas and Invertase appear in a similar trend that their contents in different depth of soil were decreased as that of the soil depth, but there were differences in different soil. The activity of soil enzyme was the highest in 10Mth and kept stable in other months in low level; The enzyme activity change of Protease and Polyphenoloxidase and Catalase appear in a another similar trend, the sequence of enzyme activity was l0-20cm wood soil >the root soil >20-40cm wood soil. All enzyme activity decreased with the increasing of decline degree, and the wood soil enzyme activity decline more than root soil.3 The decline of black locust leaded to the varietes of tree physiology. Photosynthesis of decline black locust decreased, and the water sap flow velocity as well. There were difference significantly among black locust of different decline degree. The photosynthesis of normal functional leaves decreased with the increasing of decline degree. The sap flow velocity decreased at different height and different opposition of decline black locust. The higher the more decline. There were correlation significantly between decline degree and sap flow velocity. Diurnal variation of healthy tree sap flow velocity was wide peak curve. Following decline degree the curve turned to be narrow, sap flow starting time turned late, decreasing time turned ahead. The northern sap flow velocity was higher than southern, but the difference between them turned smaller following the decline degree. The sap flow velocity of healthy tree was 6m>4m>1.3m, 4m and 6m decreased following the decline degree, and at different height as well. There were different significantly between northern and southern, northern was higher than southern. The sap flow correlated significantly between air enviroment. Enviroment influnced the water sap flow. The intribution of Na⁺, K⁺, Ca²⁺ and Mg²⁺ turned up their curves.4 The diseases and insect pests of gall midge occoured recent years which was the promote factor lead to decline in the leaves photosynthesis area and time reducing.5 Eliminated the possibility that the decline was caused by different in genetic diversity through the analysis of peroxide isoenzyme zymogram.