Response To Simulated Foraging And Adaptation Mechanism In Three Elymus Species On Songnen Plain

Plants are often foraged by various herbivores during their life history process.The aboveground parts of plants,such as leaves or inflorescences are generally foraged by herbivores.It causes the removal of apical dominance or loss of photosynthetic production organization.During the long-term evolution,plants have developed protective mechanisms and ecological adaptation strategies to cope with animal foraging.The compensatory growth of plants after damage is not only related to individual’s structural characteristics,but also related to the time and strength of damage and the recovery time after damage.There was great significance of theoretical and practical to study the effect of simulated animal foraging on the growth and adaptive regulation mechanism of cluster grass.This experiment used defoliation and clipping treatments to simulate herbivores foraging,and there species from the same genus,Elymus tangutorum,Elymus dahuricus and Elymus excelsus were chosed as research object.The same experimental design and treatments were carried out in two-year old cohort of the three species.The change of ramets number and biomass,number of buds,vegetative capability,productivity and leaf physiological characteristics were analyzed.The common adaptability and interspecific difference of three species under foraging disturbance were compared and analyzed.The compensation coefficient estimation method of ramets or buds number and bud flow analysis model were established in this study.The following research results and conclusions are obtained:（1）The responses of ramet number and biomass from three Elymus species to simulate foraging were various among different treatment stage.Defoliation at heading stage significantly increased the number and biomass of ramets in E.tangutorum,but the treatment stage had no significant effect on the number of ramets in E.dahuricus and E.excelsus.Defoliation at jointing stage significantly reduced the total biomass of ramets in E.dahuricus,and there was no significant effect of treatment stages on the number and biomass of ramets in E.excelsus.In terms of treatment intensities,the 50%defoliation treatment significantly increased the number of ramets in E.tangutorum and E.dahuricus;the 75%defoliation level significantly increased the number of ramets in E.excelsus and increased the biomass of ramets in E.dahuricus.25%and 50%clipping level significantly increased the number and biomass of ramets in E.tangutorum and E.dahuricus;100%clipping significantly decreased the number and biomass of ramets in E.excelsus.The responses of ramet number and biomass of three species to growth time after treatment were consistent.They showed over-compensatory and equal-compensatory growth at the mature stage and equal-compensatory or under-compensatory growth at the vegetative stage after mature.（2）The responses of the number of juvenile ramets and buds in three Elymus species to treatment stage of simulated foraging were different.Defoliation stage had no significant effect on the number of juvenile ramets in E.tangutorum,but defoliation at heading stage significantly increased the number of buds.Defoliation stage had no significant effect on the number of buds in E.dahuricus,but defoliation at heading stage significantly increased the number of juvenile ramets.Defoliation at jointing stage significantly declined the number of juvenile ramets in E.excelsus,and defoliation at heading stage significantly increased the number of buds.Treatment intensity had no significant effect on the number of juvenile ramets and buds in E.tangutorum.50%defoliation significantly declined the number of juvenile ramets in E.dahuricus,but the treatment degree had no effect on the number of buds in the cohort.100%defoliation significantly declined the number of juvenile ramets and buds in E.excelsus.25%and50%clipping significantly increased the number of juvenile ramets and buds in E.tangutorum and E.dahuricus,respectively.100%defoliation significantly declined the number of juvenile ramets and buds in E.excelsus.The responses of the number of juvenile ramets and buds of three species to growth time after treatment were inconsistent.The number of juvenile ramets and buds in E.tangutorum and E.dahuricus showed over-compensatory growth at the mature stage,and showed equal-compensatory growth at the vegetative stage after mature.They showed equal-compensatory growth for E.excelsus at the mature stage,and showed the equal-compensatory or under-compensatory growth at the vegetative stage after mature.（3）The responses of the bud movement in three Elymus species to treatment stage and degree of simulated foraging were different.Under the medium-degree defoliation at the heading stage in E.tangutorum,the proportion of vegetative ramets and their buds decreased by 1.8%and 6.68%,respectively,and the proportion of buds on sexual ramets increased 2.69%.The proportion of vegetative ramets reduced 1.31%in E.dahuricus,and the proportion of buds on vegetative and sexual ramets were increased by 1.51%and 0.17%,respectively.With the medium-degree defoliation at the jointing stage in E.excelsus,the proportion of vegetative ramets and their buds,buds on sexual ramets increased by 1.53%,2.41%and 3.78%,respectively,and the proportion of juvenile ramets declined 5.41%.（4）The responses of the vegetative capability and productivity in three Elymus species to treatment stage and intensity of simulated foraging were different.Defoliation stage had no effect on vegetative capability in E.tangutorum,but defoliation at jointing stage significantly decreased productivity in the cohort.Defoliation stage had no effect on productivity in E.dahuricus,but defoliation at jointing stage significantly declined vegetative capability.Defoliation at heading stage significantly declined vegetative capability in E.excelsus,and defoliation at jointing stage significantly declined productivity in the cohort.In terms of treatment intensity,25%defoliation significantly declined vegetative capability in E.tangutorum.50%defoliation significantly declined vegetative capability in E.dahuricus and E.excelsus.Defoliation degree had no effect on productivity in E.tangutorum and E.dahuricus.100%defoliation significantly decreased productivity in E.excelsus.75%clipping significantly declined vegetative capability in E.tangutorum;25%clipping significantly increased vegetative capability in E.dahuricus;clipping degree had no effect on vegetative capability and productivity in E.excelsus.In terms of vegetative capability,they showed under-compensatory or equal-compensatory growth in E.tangutorum at the mature stage,and equal-compensatory growth at the vegetative stage after mature.They kept equal-compensatory in E.dahuricus.They showed equal-compensatory in E.excelsus at the mature stage,and were equal-compensatory or under-compensatory growth at the vegetative stage after mature.In terms of productivity,they showed equal-compensatory growth or under-compensatory growth all the time in three Elymus species.（5）Medium defoliation and clipping significantly increased intercellular CO₂ concentration,stomatal conductance and transpiration rate,and significantly declined net photosynthetic rate in E.excelsus.After clipping 5h,the soluble sugar in plant leaves and root significantly increased,but it significantly decreased in plant stem;the content of chlorophyⅡand the proline significantly increased;the soluble protein significantly declined;the protective enzymes significantly increased.This study showed that,E.excelsus could quickly regulate photosynthesis,antioxidant content,osmotic regulator content and antioxidant enzyme activity to improve adaptability after clipping.The response of three Elymus species to simulated foraging,including the number and biomass of ramets,the number of buds,bud flow structure,vegetative capability and productivity,have both convergence and divergence adaptations.