Effects Of Neighbor Desalination On Physiological And Ecological Characteristics Of Populus Euphratica Seedlings With Different Reproduction Modes

Populus euphratica is the main constructive tree species in the Tarim River Basin.Because its growth is restricted by soil,salt and other conditions,the regeneration and reproduction of Populus euphratica is facing many difficulties,which is manifested in the single means of seedling regeneration and the difficulty of vegetation restoration,resulting in the continuous degradation trend of the whole population.Based on this,this experiment takes 2-year-old Populus euphratica with different propagation modes as the research object,uses Suaeda glauca（Bunge）Bunge and Salicornia europaea as companion plants,carries out desalination experiment on Populus euphratica with different propagation modes,and determines the three parameters of soil under Populus euphratica seedlings with different propagation modes under the effect of neighbor desalination,The pH value,photosynthetic parameter index and growth index are comprehensively evaluated by using the membership function value method of fuzzy mathematics,so as to explore the adjacent desalination plants suitable for different propagation modes of Populus euphratica seedlings,so as to provide scientific reference for the cultivation and field regeneration and rejuvenation of Populus euphratica seedlings in the lower reaches of Tarim River.The results are as follows:（1）Neighbor desalination effect had significant desalination effect on the soil under Populus euphratica seedlings with two propagation modes.In general,the soil desalination effect under Populus euphratica seedling forest is better than that under natural Populus euphratica seedling forest,and the desalination effect of Salicornia salina is better than that of Suaeda salsa.The soil conductivity decreased with the extension of desalination time,and the soil volume moisture content increased significantly with the extension of desalination time.The desalination effect of soil conductivity and soil pH value is the best when the depth is 0cm to 15cm.（2）The effect of neighbor desalination had significant differences in the diurnal changes of photosynthesis of Populus euphratica seedlings under the two propagation modes,and water use efficiency had different degrees of inhibition on Populus euphratica seedlings under the two propagation modes.The net photosynthetic rate of Populus tomentosa seedlings under salt horngrass desalination treatment was better than that of Suaeda salsa treatment,and it was found that the water use and efficiency of Populus tomentosa seedlings under neighbor desalination treatment 90d were significantly higher than that under treatment 45d.The net photosynthetic rate of natural seedlings under Suaeda salsa treatment was better than that under Salicornia salina treatment.Combined with water use efficiency,the growth advantage of Populus euphratica under the influence of Suaeda salsa desalination is stronger and more conducive to its growth.（3）The characteristic parameters of photosynthesis light response of Populus euphratica seedlings under two propagation modes under the effect of neighbor desalination were fitted by the right angle hyperbola correction model.It was found that Populus euphratica seedlings under the treatment of salt horn grass could make more effective use of light energy.The photosynthetic utilization ability of natural Populus euphratica seedlings under Suaeda salsa treatment was better,and it was not easy to inhibit photosynthesis.（4）Fitting the photosynthetic CO₂ response characteristic parameters of Populus euphratica seedlings under two propagation modes under the effect of neighbor desalination by using the right angle hyperbola correction model,it is concluded that the maximum photosynthetic capacity,photorespiration rate and CO₂ compensation point concentration of Populus euphratica seedlings under Suaeda salsa desalination treatment are significantly higher than those under Suaeda salsa treatment,and the 90d natural Populus euphratica seedlings under Suaeda salsa treatment use the most CO₂,The photorespiration rate was also much higher than that of other treatments.（5）There were significant differences in the growth characteristics of Populus euphratica seedlings under the effect of neighbor desalination.The plant height and ground diameter of root sprouting Populus euphratica seedlings were the largest after 90d treatment;The plant height and ground diameter of natural Populus euphratica seedlings were the largest at 45d and 90d,respectively.However,on the whole,the growth of plant height and ground diameter of root seedlings under the treatment of salt horn grass is the largest in the treatment cycle,and the growth of plant height and ground diameter of natural Populus euphratica seedlings under the treatment of Suaeda salsa is the largest in the treatment cycle.（6）The desalination effect of two propagation modes of Populus euphratica seedlings was comprehensively evaluated according to the membership function method of fuzzy mathematics.Under the experimental conditions of root sprouting Populus euphratica seedlings,the adaptability of root sprouting Populus euphratica seedlings with salt horngrass as neighbors was better.Under the experimental conditions of natural real Populus euphratica seedlings,the adaptability of natural real Populus euphratica seedlings treated with Suaeda salsa as neighbors for 90d was stronger.To sum up,it is suggested that salt horned grass should be used as the adjacent desalination plant of root sprouting Populus euphratica seedlings,and desalted 90d Suaeda salsa should be used as the adjacent desalination plant of natural seedling Populus euphratica seedlings,in order to promote the probability of establishment and growth of Populus euphratica seedlings.