The Experimental Study Of The Relationship Between The Functional Traits Of Peatland Plants And Interspecific Competition

The plant functional traits can reflect the response and adaptation of the plant to the changed environmant,linking the environment,plant individual and ecosystem.In recent years,the response of plant functional traits to the environment is the hot issue of functional ecology.The variation law of palnt above-ground and below-ground functional traits along the intensity of root and shoot competition are very important to understand the species coexistence in the natural community and the adaptation mechanism of plants to the competitive environment.At present,many studies show that competition and plant functional traits have a certain relationship,and more and more functional traits has been commonly used to explore plant strategies in competitive environments.The competition-trait similarity hypothesis and competition-trait hierarchy hypothesis have been widely discussed to explain the relationships between functional traits and competitive abilities.However,the two forms of competitive ability,competitive effect and competitive response were confounded in most of these studies,which limits our understanding on the role of functional traits in community structure.Therefore,the study of the differences of the competitive effect and competitive response in the relatioship between the competitive ability and functional traits is very important to understand the community structure and composition and its relationship with plant functional traits.So that,the main purpose of this research is to study the response of plant functional traits to competitive intensity and to discuss the relationship between plant functional traits and competition(competitive ability and competitive intensity)based on the above two hypotheses.Five common species in Jinchuan peatland were selected :Carex angustior Mackenzie,Comarum palustre Linn,Geranium erianthum DC,Lysimachia davurica Ledeb,Saussurea amurensis Turcz.We conducted a greenhouse experiment to determine the response of the functional traits of these peatland plants to the intensity of competition and the relationship between competition and functional traits.The main results of this study include :(1)The abiotic stress intensity has little influence on the growth of the plants,while the competitive intensity will significantly affect the growth of plants.The above-ground,below-ground and full competition will not only affect the biomass allocation of plants,but also affect the plant functional traits.With the increase of abiotic stress intensity,only shoot ratio increased significantly.However,whether it is above-ground,below-ground competition or full competition,with the increase of the intensity of the competition,the root / shoot ratio,the specific leaf area and the root diameter increased significantly,while the plant height,themaximum root length,the total root length and the specific root length were reduced significantly.The response of the functional traits to the competitive intensity in different competitive treatments are consistent,and the effect of competitive treatments on the relationship between competitive intensity and functional trait is small.(2)The functional traits of the neighbour plants will affect the competitive ability of plants.With the root/shoot ratio,the specific leaf area and the root diameter increase,the competitive effect and response of the plants significantly decreased;while with the plant height,the maximum root length,the total root length and the specific root length increase,the competitive effect and response significantly increased.For most of the traits measured,the absolute value of the slope and the R2 in the regression equation between competitive response and traits is bigger than competitive effect.It shows that the changes of plant traits have a greater impact on competitive response.(3)Both competitive effect and competitive response were significantly correlated with all plant functional traits hierarchical distance.That is to say,the competitive ability of the plants were significantly related to the differences of the functional traits hierarchy.The species interaction will increase with the increase of plant traits hierarchical difference,that is,the results showed that the ‘competition-trait hierarchy' hypothesis could explain the species interaction.The competitive ability was significantly negatively correlated with the traits absolute distance,with the increase of plant traits similarity,the competitive effect and response are significantly improved.As competitive effect and competitive response ability can express the competitive intensity,so the ‘competition-trait similarity' hypothesis can explain the species interaction when the competitive effect is expressed as competitive intensity,whlie the ‘competition-trait similarity' hypothesis can't explain the species interaction when the competitive response is expressed as competitive intensity.This result indicates that the ‘competition-trait similarity' hypothesis is only suitable for explaining the competitive effect.(4)Although the relationship between competitive ability and the traits of the neighbour plant and the plant functional traits distance were consistent in both competitive effect and competitive response.For all the traits,the absolute value of the slope of the linear regression equation in the relationship between competitive response and plant functional traits or traits distance is bigger than competitive effect.This indicates that competitive response is more sensitive to the plant functional traits or functional traits.The size of plant traits and the traits distance between species are more reflecting the response ability of competition,that is,reducing the negative effects of competition.so the competition response may be better to predict the species competition when studing the competitive ability of the plants(5)Water flooded environment will not only affect the influence of the competitive intensity on the functional traits,but also affect the relationship between plant functional traits and competitive ability.Whether it is root,shoot competition or full competition,the absolute value of the slope of the linear regression equation in the relationship between competitive intensity and plant functional traits under waterlogging condition is smaller than under non-waterlogging condition.It shows that the competition between plants will weaken in the waterlogging environment.The absolute value of the slope of the linear regression equation in the relationship between competitive ability and the plant traits or traits distance in waterlogging condition is bigger than in non-waterlogging condition,the results indicate that the effect of the plant traits on the competition will be amplified in waterlogging environment.