Study on Growth Adaptability of Agropyron Mongolicum Population in Desert Steppe of Ningxia
In this study,the Agropyron mongolicum populations,which distributed in desert steppe in Ningxia were selected as the research objects.Through the in door germination,pot culture control and wild seedling establishment experiments,combining with natural vegetation investigation,the germination characteristics of seeds under different temperature and water conditions,the root system characteristics and chlorophyll fluorescence characteristics under different sowing pattern and water control conditions,the settlement laws of seedlings under different micro-habitats in the field and the resource allocation characteristics of A.mongolicum under natural growth conditions were studied to explore the growth adaptability of A.mongolicum population.The main results are as follow:(1)The suitable germination temperature for A.mongolicum seeds was 25/15℃-30/20℃,and the highest germination rate was 68%under normal water supply at 30/20℃.The seeds germination were restricted with the increasing of water potential.A.mongolicum adapted to drought by delaying germination,shortening germination period and reducing germination rate.(2)Water stress significantly affected the root system configuration of A.mongolicum，resulting in the reduction of root volume and biomass.Sowing patterns mainly influenced the total root length of A.mongolicum.The root systems of A.mongolicum and A.desertorum showed symbiosis of favoritism under mild and severe drought stress and symbiosis of mutualism under moderate stress when they were sown together.(3)The relative chlorophyll contents in the leaves of A.mongolicum increased with the increase of water stress under single planting.The Fv/Fm and PIabs in the leaves of A.mongolicum increased with the increase of water stress under mixed planting.(4)The emergence rates of A.mongolicum under the conditions of vegetation removal and natural coverage in the field were less than 40%,and the survival rates were 35.93%～51.15%.The plants adapted to natural habitats by transferring biomass to underground.When mixed with A.desertorum,the seedlings of A.mongolicum mainly enhanced the interspecies competitiveness by increasing leaf area.(5)In natural habitats,the biomass distribution rates of the root and stem ofA.mongolicum were significantly higher than that of the leaves,and the component biomass of different communities were as follows:root biomass>stem biomass>leaf biomass>spike biomass.The biomass and nutrient distribution were mainly restricted by soil moisture,while the above-ground components were mainly affected by soil nutrients and particle composition.