Study On The Seasonal Dynamics Of Non-structured Carbohydrates For Phragmites Australis In Inland River Wetlands

Non-structured carbohydrate(NSC)plays an important role in the adaptation of plants to the environment.Clonal plants have good ecological adaptation strategies for heterogeneous habitats due to their unique physiological characteristics.The inland river wetland distributed in the arid region of northwest China is not only the sensitive area of ecological environment,but also the important base of biodiversity protection and the important support of oasis development,which is extremely important for the growth and life of plants.Therefore,it is necessary to systematically the non-structural carbohydrate seasonal variation of Phragmites australis population about clonal plant in inland river wetland.Phragmites australis is a kind of typical clonal plants roots type,with the advantage of physiological uniqueness,morphological plasticity,breed diversity,and stronger ability to adapt the environment,occupy the important position in the wetland ecosystem,the Phragmites australis non-structural carbohydrates seasonal dynamic research helps understand the impacts of environmental changes on plant growth and physiological response and adaptation mechanism of ecological processes.In view of this,the paper takes the inland river wetland of Dunhuang yangguan nature reserve as the research area,takes the typical clonal plant Phragmites australis as the research object,and sets up three different sampling gradients according to the distance from the reservoir and the community density and coverage characteristics,namely,the wetland area(500 m),the salt marsh area(1500 m)and the desert area(2500 m).The variation characteristics and factors affecting of non-structural carbohydrate and component contents of the whole Phragmites australis and its clonal modules growing in three different habitats(wetland,salt marsh and desert)in May(early growth stage),July(mid-growth stage)and September(late growth stage)were compared and analyzed.The aim is to elucidate the stress adaptability of Phragmites australis to growing season and environment from the perspective of the distribution of non-structural carbohydrate content in the whole plant and clonal modules,so as to provide a theoretical basis for further understanding the response mechanism of clonal plants to heterogeneous environment.The main research results are as follows:(1)Under the conditions of wetland,salt marsh and desert habitats,with the change of growing season,the average soil water content showed an overall trend of decline,reached the maximum value at the beginning of the growing season,and the surface,middle and deep water content showed an overall trend of rise.The average value of soil salinity and pH showed an overall trend of rising and reached the maximum value at the end of the growth period,but the salinity of each layer of soil showed a trend of decreasing from the surface layer to the deep layer in each growing season.However,the pH value of soil in each layer showed different trends from the surface to the deep layer,and the pH value of soil in each layer was >8,showing weak alkalinity.(2)The species composition of plant communities in the three habitats was relatively simple,the plant community and Phragmites australis population structure is simple,the diversity is low.Margalef index,Shannon-wiener index,Pielou index and Simpson index of plant communities increased with the change of seasons,and coverage,density,frequency and biomass of Phragmites australis showed an increasing trend in each growing season.However,with the enhancement of environmental stress,the Margalef index and Shannon-wiener index of plant community decreased,while the Pielou index and Simpson index increased,while the coverage,density,frequency and biomass of Phragmites australis population continued to decrease.(3)The contents of NSC,soluble sugar and starch in the whole plant and clonal modules of Phragmites australis showed seasonal variations with gradually increasing trends in wet,salt marsh and desert habitats,but the soluble sugar contents of leaves showed seasonal variations with decreasing trends;The investment of NSC and their compositions contents were differences in the clonal modules among the three habitats,showing that the NSC and soluble sugar were mainly invested in rhizomes and were transferred from leaves to stems,while starch were mainly invested in stems and were transferred from rhizomes to roots during the transition from wetland to desert habitat.(4)In wetland,salt marshes,desert habitat conditions,the average soil water content,pH value and salinity is the main influence factors of plant growth,especially the layers of water,the surface salinity and middle pH value.Specifically,the average and surface,middle and deep water content,average salt content and pH value were significantly correlated with the contents of non-structural carbohydrates,soluble sugars and starches in the whole plant and the clonal modules(P < 0.05).