Individual Size Differences With Root Biomass And Architecture Traits Of Reaumuria Soongorica In Desert Grassland

As the important bridge between plants and soil and organ of uptake soil resources,plant root has functions to captured and making use of water and nutrients and so on.The change of root biomass allocation ratio will affect the whole eological system,Plant root uptake and utilization efficiency and potential of soil resources is affected by the topology pattern of root system,and especially the root branch plays a key role to absorpting nutrient.Root architecture reflects the three-dimensional arrangement of plant roots in the living space,which influences the root absorption efficiency and maintenance cost of the root system.The root fork numbers and root length of attachment,and branch root number and root branch angle of the relationship can reflected the root distribution spatial and extension vividly,which reflects the environment adaptation mechanism of plants under the environment stress,and it is an one of the important way to understand the regeneration strategy of plant population.The adjustable of the biomass allocation pattern determines the plant's ability to assess resources in heterogeneous environment,thus affecting the competitiveness in the community,runing through the whole life cycle of plants,having important ecological and evolutionary significance for understanding the phenotypic plasticity of plants under different habitat conditions.R.soongorica is super xerophytic shrub in desert regions of Central Asia,which has low plant height,thick roots,wide ecological amplitude,strong adaptability,and it is the good windbreak and sand fixation plant species to improve the ecological environment of the desert.In view of this,the north slope of qilian mountains was grassland desert in the northwest and different plant size R.soongorica selected for study.Total of 90 plants were divided into different size classes based on the volume: d(the cube root of plant volume)? 20 cm,20 cm < d ?40 cm,and d > 40 cm.Standardized major axis estimation method(SMA)was used,analyzed the relationship of biomass allocation model between aboveground and underground,the different biomass allocation patterns among different branch orders,weighing relationship between root fork numbers and root link length,between root fork numbers and root branch angle,reflected the mode of resource allocation of plan root architecture and environmental response mechanism of root traits,and enhance the plant resources absorption efficiency.The results show that:(1)With the increasing of the plant size,the height,the aboveground and belowground biomass of R.soongorica was gradually increased,the ratio of aboveground and underground biomass of R.soongorica was decreased,and the soil moisture is also significantly reduced.(2)The proportion of the first-order branch and the second-order branch biomass of R.soongorica gradually decreased(p<0.05),while proportion of third-order branch biomass increased(p<0.05).(3)Three size classes R.soongorica first-order branch biomass and second-order branch biomass,first-order branch biomass and third-order branch biomass showed a significant positive correlation(p<0.05),with increasing of first-order branch biomass,second-order branch biomass and third-order branch biomass were increased.An isometric relationship was found between second-order branch biomass and third-order branch biomass in plots within each slope(p<0.05),but the growth speed of first-order branch biomass was greater than that of second-order and third-order branch biomass.(4)Different plant size of R.soongorica Root-shoot ratio,root depth,and specific root length exist significant differences(p<0.05).Specific root was size I > size II> size III,root-shoot ratio and root depth were size I < size II < size III.(5)Different plant size of R.soongorica root fork numbers,root length and root branch angle exist significant differences(p<0.01).There was significant positive correlation connection between root fork numbers and root length,root fork numbers and root branch angle(p<0.05).the regression slope of root length and leaf area was size I > size II > size III,whereas,the regression slope of root fork numbers and root branch angle.was size I < size II < size III.Changes of plant branching pattern restricted by plant size,and plants in different individual size limited by resource acquisition ability,the coordinated allocation the limited resourrces of functional traits by R.soongorica,such as aboveground biomass,underground biomass,root link length,the number of root fork numbers and root branch angle and so on,to optimize the spatial pattern of root ordinal structure.Not only ensure full expansion in the soil,but also promoted the plant adaptability and root absorbing water efficiency.Different sizes of plant because the ecological niche is not same,leading to its choice of different growth modelws,but also the plant ecological niche differentiation and compensation requirement and inevitable result.