Clonal Growth Characteristics Of Leymus Chinensis Under Soil Saline-alkali Heterogeneity And Mowing

Clonal plant plays an important role in grassland ecosystem.The unique cloning and reproduction characteristics of clonal plants have a good adaptability to the heterogeneous environment.Therefore,it has important ecological value for the restoration and reconstruction of degraded grassland.Leymus chinensis is a kind of perennial rhizome type clonal plant,with strong grazing resistance and salt tolerance,good palatability and high nutritional value.The Songnen Plain is typical meadow grassland with L.chinensis as the dominant species.In recent 30 years,due to the overuse of grassland(grazing and mowing),the soil salinization has become more and more serious.The population of L.chinensis was distributed in patches.The productivity of grassland decreased significantly,which resulted in the loss of animal husbandry production.The restoration of the ecological environment of Songnen grassland has become an important issue in scientific research and production.In the past,studies on L.chinensis have focused on adaptation strategies in homogeneous saline-alkali environment,but lack of more detailed studies on the changes of functional organs of L.chinensis in soil saline-alkali heterogeneous environment.In this experiment,we selected the seeds of L.chinensis which collected from the Northeast Songnen grassland as the experimental materials,we adopted the pot experiment and two factor interactive experiment design.The purpose is to simulate the heterogeneity of soil saline-alkali in natural grassland by different saline-alkali treatments,simulate the different intensity of animal feeding by different mowing height(mowing plant height 0%,35%,70%).So as to discuss the effects of soil saline-alkali heterogeneity and mowing and their interaction,on the rhizome expansion(rhizome expansion distance,rhizome expansion rate and number of daughter-plant with different expansion distance),biomass distribution(biomass of each organ and time for biomass accumulation),asexual propagation strategy of population(number of daughter-plant and rhizomes buds)and photosynthetic characteristics(photosynthetic stomatal parameters and photosynthetic pigment content)of L.chinensis.Further,it provides some experimental and theoretical basis for the restoration and rational utilization of Songnen grassland in Northeast China.The results show that L.chinensis can maintain photosynthesis when there were only moderate saline-alkali patches in the soil.Under the condition of homogeneous soil without saline-alkali and saline-alkali heterogeneous patches with one side without saline-alkali and the other side with moderate saline-alkali,moderate mowing is good for maintaining photosynthesis of L.chinensis.In addition,heavy mowing and high concentration saline-alkali heterogeneity habitat inhibited the net photosynthetic rate(PN)and transpiration rate(E)of L.chinensis,and reduced leaf area and plant height.However,L.chinensis can cope with extreme soil saline-alkali and strong mowing disturbance by improving water use efficiency(WUE),reducing relative water content(RWC)and changing stomatal conductance(Gsw).Therefore,our results show that moderate grazing or moeing can maintain the productivity and economic benefits of grassland in the homogeneous environment without salt-alkali and in the heterogeneous environment of moderate saline-alkali.Soil saline-alkali heterogeneity and mowing had significant effects on the rhizome expansion of L.chinensis.At the same time,moderate mowing can promote rhizome expansion,the time to reach 20 cm was reduced by 11 days.Under the condition of saline-alkali heterogeneous patches with one side without saline-alkali and the other side with moderate saline-alkali,the rhizome expand faster,but soil saline-alkali heterogeneity and mowing reduced the number of spacers and the distance of rhizome expansion,the number of daughter-plant was reduced from 70 to 40,and the maximum distance of rhizome expansion was reduced from 35 cm to 25 cm.Moreover,soil saline-alkali heterogeneity and mowing will lead to the direction of population expansion of L.chinensis.When there is no mowing,L.chinensis selected to distribute more daughter-plant in the soil patches with moderate saline-alkali.When there is moderate mowing,L.chinensis is more likely to grow in patches of soil with non saline-alkali or moderately saline-alkali.The number of rhizome buds will be reduced under high concentration of saline-alkali and heavy mowing.Moderate saline-alkali and mowing can promote the growth of rhizome expansion,rhizome buds and daughter-plant of L.chinensis.In addition,soil saline-alkali heterogeneity and mowing changed the biomass distribution in the belowground of L.chinensis.Without mowing and moderate mowing,moderate saline-alkali increased the biomass of rhizome.And the rapid growth period of the belowground roots of the L.chinensis is different under different soil saline-alkali heterogeneity conditions.When there is no saline-alkali,it is July and September.When there was moderate saline-alkali,it is September.When there was high saline-alkali,it is August.Moderate mowing and moderate saline-alkali environment are instrumental in maintaining photosynthesis of L.chinensis.And more energy and material are transported to the belowground.It stored in the rhizome,in order to ensure the expansion of rhizome and rhizome buds,and the increase of daughter-plant at the same time,so as to compensate for the damage caused by mowing and saline-alkali.In conclusion,soil saline-alkali heterogeneity,mowing and their interaction have different responses of L.chinensis.Grasslands with non-or moderately saline-alkali habitats,moderately grazing and mowing are beneficial to the growth of L.chinensis population.In addition,grazing or mowing should be prohibited in high saline-alkali grasslands.