| Songnen grassland is located on the eastern edge of the Eurasian grassland.It is a meadow grassland with flat terrain,abundant water and grass,high productivity,and is an excellent pasture and pasture.It is a important animal husbandry bases in China.However,in recent years,large-scale grassland has been degraded,salinized,and the situation has become increasingly serious,making Songnen grassland to be one of the main distribution areas of soil salinization in China.At the same time,artificial utilization such as overgrazing and mowing is also degrading grassland,and the synergistic effect of soil salinization and overgrazing has become an important reason for the difficulty in restoring the ecological environment of Songnen grassland.Because of its excellent resistance to salt and alkali and grazing,Leymus chinensis has excellent forage characteristics such as high nutritional value and good palatability,and it has gradually become a dominant species in the grassland of Songnen grassland.The population reproduction of Leymus chinensis has always been affected by the interaction of salinity and grazing.Therefore,in this study,a field experiment was conducted to Simulate the four salinities(Na Cl,Na2SO4,Na HCO3,Na2CO3)and their salinity(0 mmol/L,50 mmol/L,100 mmol/L)contained in natural grassland soil,using clipping to simulate grazing(clipping above-ground Biomass 0%,35%,70%),the loss of biomass caused by the feeding of simulated animals,the impact on plants,two treatments to study the response mechanism of asexual reproduction strategy of Leymus chinensis to soil salinity and its grazing disturbance,and to analyze sheep by analyzing the distribution pattern of Leymus chinensis biomass,photosynthetic efficiency and plant absorption efficiency of nitrogen and phosphorus The adaptation mechanism of grass to double stress of salinized grassland and grazing disturbance provides theoretical support and practical guidance for the stability and ecological restoration of L.chinensis community in Songnen saline-alkali grassland.The results showed that under the condition of no salt and alkali,with the increase of cutting degree,the growth of various organs on the ground of L.chinensis was significantly inhibited,and the total nitrogen content in the leaves of plants was significantly reduced.Under moderate saline-alkali conditions,leaf growth of L.chinensis was promoted,and stem biomass,leaf biomass and leaf number were significantly higher than that of no salt-alkali and hard saline-alkali treatment under the same clipping conditions.With the increase of soil salinity,under hard saline-alkali treatment,above-ground biomass decreased significantly,and the under-ground biomass increased significantly.This is because the high concentration of saline and alkali significantly inhibited the accumulation of stem and leaf biomass in plants.On the other hand,the net photosynthetic rate of L.chinensis showed a significant decrease under hard saline and hard clipping.Under hard saline-alkali treatment,the transpiration rate and stomatal conductance of L.chinensis were lower than that of no-salt alkali treatment,and the interaction between hard saline-alkali and hard clipping significantly inhibited the growth and development of sheep.In contrast,the leaf biomass and leaf number of L.chinensis under significant moderate cutting increased significantly,indicating that L.chinensis has a certain ability to compensate for growth.The trend of total phosphorus content in soil and plants indicates that the compensatory growth ability of L.chinensis is mainly due to the fact that plant leaves absorb phosphorus from the soil.After being interfered by clipping,the average height of plants per unit time is significantly increased.The interaction between salinity and clipping showed synergy,and the net photosynthetic rate and the fine root biomass,soil total nitrogen,total nitrogen in plants leaf showed a common inhibition,while the stem biomass and leaf biomass leaf number,plant average height,total phosphorus in plant leaves were jointly promoted.In the saline-alkali environment,L.chinensis is clonal integration to achieve grazing resistance.L.chinensis temporarily abandons the supply of nutrients to the aboveground parts,and stores materials and energy in underground rhizomes.When the plants are disturbed or stressed by the outside,the rhizomes will mobilize nitrogen in the body.The element is temporarily stored in the roots for regeneration of the new organs and compensates for the damage taken by the feed.Through this experiment,different grazing or mowing management systems should be adopted for L.chinensis under different salt-alkali stress conditions,which should be moderately grazing under moderate saline-alkali soil conditions,and should be taken under severe saline-alkali soil conditions.A management system that prohibits grazing or stops clipping. |
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