Study On Phenotypic Traits And Ecophysiological Adaptation Strategies Of Agropyron Mongolicum Under Heterogeneous Habitats

Taking Agropyron mongolicum as the research object,four sample plots were set up in Dashuikeng town(Sitel),Qingshan town(Site2),Huamachi town(Site3)and Gaoshawo town(Site4)in desert steppe in Yanchi County,Ningxia basing on different natural habitats,geographical location and meteorological background.The growth parameters,leaf functional properties,root architecture,biomass and nutrient accumulation and allocation,leaf eco-physiological characteristics of A.mongolicum under different habitat conditions were studied to explore the response of phenotypic plasticity,resource allocation pattern and leaf eco-physiological characteristics to habitat changes.The main results are as follows:(1)Habitat changes had significant effects on the plant height and basal plexus diameter of A.mongolicum.The plant height and basal plexus diameter of A.mongolicum in Site4 were 32.22cm and 3.58cm respectively,which were significantly lower than those in other habitats(P<0.05).A.mongolicum adapted to the changes of habitat conditions by slowing down the growth rate to reduce water and nutrient consumption.(2)In order to adapt to the change of habitat,the functional traits of A.mongolicum showed synergy and tradeoff.In Site4,the A.mongolicum mainly adapts to the environment with limited resources by increasing leaf thickness,leaf tissue density,reducing leaf shape index and specific leaf area.Soil total carbon,total phosphorus and pH value were the main factors affecting leaf functional traits of A.mongolicum.(3)The response of root morphology for A.mongolicum to habitat change was related to its overall adaptation strategy.The root surface area,root volume,root bifurcation number,root tip number,total root length and root dry weight of A.mongolicum in Site1 habitat were the highest,and the root volume,root surface area and total root length of A.mongolicum in Site4 habitat were the second highest.Among the habitat factors,soil texture significantly affected the root architecture of A.mongolicum.(4)The total biomass of A.mongolicum in Site4 habitat was the lowest,which was 5.44g/plant,and the ratio of root to shoot was relatively large.In the habitat with limited resources,A.mongolicum could obtain more resources by increasing the root biomass allocation to increase the contact area between root and soil.Under different habitats,the contents of carbon,nitrogen,phosphorus and potassium in the parts for aboveground of A.mongolicum were significantly higher than those in the roots.As an important organ for plants to absorb nutrients,transported nutrients to the aboveground parts for the growth and reproduction of A.mongolicum,which reflected the trade-off of resources among various components of A.mongolicum.(5)The A.mongolicum in desert steppe could form a set of defense strategies through its own metabolic regulation to protect the plant from environmental stress.The physiological characteristics such as proline,soluble sugar and peroxidase were significantly responsive to habitat changes.(6)Soil total phosphorus,soil pH value,soil conductivity and soil total carbon were the main environmental factors affecting the phenotypic and eco-physiological characteristics of A.mongolicum in heterogeneous habitats.In conclusion,changes of habitat conditions lead to the plasticity changes in individual growth,morphological characteristics and physiological characteristics of A.mongolicum.In habitats with arid climates and poor soil nutrients,A.mongolicum can adapt to harsh environment by slowing down the growth process,increasing leaf thickness and tissue density,reducing specific leaf area,increasing root length,root tip number,root shoot ratio and cytoplasmic concentration.