| The experiment was based on the mixed stands with R.pseudoacacia and F.velutina. Two tests were conducted: one by stands survey, cut down sample trees and stem analysis to study the growth law of mixed and pure stands with R.pseudoacacia and F.velutina; Using trees disk, we analyzed the salt ions in the accumulation of the tree and related analysis of tree-ring index and meteorological factors; Single tree sap flow of pure and mixed stands of R.pseudoacacia and F.velutina and the environmental factor were measured by means of TDP((Thermal Dissipation Probe) and Portable-Meteorological Station; testing the water and salt contents of five soil layers (0-20cm, 20-40cm, 40-60cm, 60-80cm, 80-100cm) in pure and mixed stands; The leaf photosynthesis was tested by photosynthesis system. The other by continual adding NaCl solution to study the growth,photosynthesis,sap flow,osmotic,soil enzyme and soil nutrient of R.pseudoacacia and F.velutina. The main results were as follows:Test I: By the survey of forest growth, mixed stands was better than pure stands in the forest form,canopy density. Mixed stands have promoted the growth of both species, especially the growth of ash more evident; the pure stands of black locust dieback rate of 51%, mixed forest of black locust dieback was lower than pure forest, to 43%.Stem analysis showed that, volume growth curve of locust and ash with the conventional condition tree growth curves of different. Volume growth curves showed that the mixed locust,ash material accumulated volume growth was significantly higher than their respective pure stand. Annual volume increment despite all as the age decreased, but the mixed locust,ash is less than the decline in their pure. Although the mixed stands of R.pseudoacacia and F.velutina into recession, but compared to their pure forest , the decline of the mixed forest to a lesser extent.The salt ions in the locust,ash body of mixed and pure forest displayed spatial distribution inconsistent.The average sap flow of pure and mixed forest in May was greater than September. The average sap flow of locust in mixed forest was 145% of pure forest in May, 109%in September. The average sap flow of ash in mixed forest was 209% of pure forest in May, 192% in September. The sap flow restricted the transpiration, so mixed locust,ash was more vigorous than their respective pure forest.Sap flow rate and environment factors were significantly related. The soil water and salt content showed that: the soil water content in September was larger than in May. Soil water content (0~40cm) of mixed forest was larger than their respective pure forest. Soil salt content in May was higher than in September, this was because the soil salt content and water contend was relevant. Surface soil salt content of mixed forest smaller than the pure of locust,ash forest.Test II: The salt resistant between mixed planted and pure planted were differences. Result as follows:The salt stress significantly limited the growth of black locust and ash, but the mixed planted showed higher growth in salt stress, indicating that the mixed planted had a certain resistance to salt stress.With salt stress increasing, the net photosynthetic capacity of locust,ash declined. The net photosynthesis of mixed planted locust same with the pure, and the mixed ash was higher than the pure. Salt stress reduced the stomata conductance. Chla,Chlb,Chla+b and Chla/b of mixed and pure planted locust with the deepening of salt stress decreased, while the mixed and pure ash increases. The change of photosynthetic capacity of locust,ash is the result of various factors.Control(CK) and low salt treatment, the sap flow peak of locust with mixed planted turn bigger ,but the average flow rate decreases, and the high salt treatment, there is no difference between mixed and pure planted; After the mixed planted ,both in the control or salt stress, the average flow rate of ash was large.The locust and ash unchanged conductivity in control and salt stress, and increased rapidly in high salt stress. Leaf MDA content of locust,ash in response to the salt concentration, under salt stress, leaf MDA content of mixed with locust,ash was much greater than pure plant; Pro content of locust and ash increased with salt stress strengthened gradually increased, but ash leaf Pro content increased only slightly; The content of SOD of locust and ash leaf showed a different trend, and SOD content of the mixed plant with locust little difference with pure planted, but the mixed with ash was more than pure .SOD content of mixed planted leaf was smaller than in pure.Protease activity in rhizosphere soil has been improved after mixed planted under salt stress;Ash mixed planted increased the rhizosphere and non-rhizosphere soil urease activity, and mixed planted locust was higher than pure planted; Increased mixed planted the rhizosphere and non-rhizosphere soil phosphatase activity in the subject remains the same when salt stress; Catalase did not change the law, locust and ash rhizosphere catalase activity were increased with the degree of salt stress while the larger , pure planted locust and ash non-rhizosphere soil catalase activity increased the level of salt stress larger, mixed planted non-rhizosphere soil catalase activity increased with the degree of stress gradually decreased.Under salt stress, it was complex that mixed planted influenced soil total N, showing a different variation;Mixed planted can significantly improve the locust rhizosphere and non-rhizosphere hydrolysable N content, as salt concentration increased, the hydrolysable N content increased and then showed a downward trend; It was complex that mixed planted influenced soil total P, under low salt stress, the rhizosphere soil total P content of mixed planted more than pure planted. under the high salt stress, the rhizosphere soil total P content of mixed planted less than pure planted; The mixed planted can significantly improve the effective P content of rhizosphere soil; Mixed planted increased effective K content of rhizosphere soil, and the effective K content of non-rhizosphere soil is higher than that pure planted with ash.
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