The Niche Of Annual Artificial Grassland Of Avena Sativa L. And Vicia Villosa Roth In Response To Density In The Upper Reaches Of Heihe River, Western China

Niche is significant means to appraise the intra-and inter-specific interactions andstatus of species in community. Plant height and tiller (branch) number are an importantindicator of intensity of plant photosynthesis, root system morphology reflected theecological strategy. The change of relative densities of mixed species influence the resourceuse efficiency of plant, the rate of plant height and root length gain and contribution tobiomass have changed form different spatial niche. Many researchers studied the impacts ofgraze and soil salt of alpine region on growth characteristics and interspecific competition ofgrass, but the impacts of density dependant on niche breadth and overlap and its response tothe intraspecific and interspecific competition isn’t clear. Given this, this article uses thereplacement series experiments to build mixed-seeding meadow in upper reaches ShiYangRiver, depend on the density ratio of Avena sativa L. and Vicia vilosa Roth set up sevengrass-legume seeding ratios: KY(1:0), A (8:2), B (6:4), C (5:5), D (4:6), E (2:8), KM(0:1).Under density dependant and time series, studying the biological characteristic, interspecificcompetition of grass, niche of plant height and root system of Avena sativa L. and Viciavilosa Roth. Makes utilization resources with maximum efficiency and competition andcooperation mechanisms of plant populations clear.The results showed that:(1) From A to E plant height of Avena sativa L. and Vicia vilosa Roth showed agradually decreasing tendency, but tiller (branch) number showed a gradually increasingtendency. tiller (branch) number of grass in clean culture less than mixed-seeding meadow.Stolon stem of Vicia vilosa Roth underpinned by upright stem of Avena sativa L inmixed-seeding meadow, and it been change under density dependant.(2) Relative crowding coefficient, relative yield of Avena sativa L. less than1in allmix-sowing treatments except A at seeding stage and tillering of Avena sativa L. and it lessthan1of all mix-sowing treatments in the later growth stage. Relative crowding coefficientand relative yield of Vicia vilosa Roth less than1in the whole growth stage.Competitiveness of Avena sativa L. bigger than Vicia vilosa Roth, interspecific bigger thanintraspecific in mixed-seeding meadow.(3) Relative yield total of mixed-seeding meadow less than1at seeding stage andtillering of Avena sativa L. and it more than1at the later growth stage in all mix-sowingtreatments except A. Aggressivity of mix-sowing treatments E more than1at seeding stageand tillering of Avena sativa L. and it less than1in the later growth stage; Aggressivity of other mix-sowing treatments less than1in the whole growth stage. The mix-sowing isconducive to growth of Avena sativa L., Avena sativa L. and Vicia vilosa Roth have asymbiosis in mixed-seeding meadow.(4) Biomass contribution value of Vicia vilosa Roth of all mix-sowing treatments lessthan expected value in the whole growth stage. Contribution value of Avena sativa L. lessthan expected value and total biomass more than expected value in all mix-sowingtreatments except A at seeding stage and tillering of Avena sativa L. Contribution value andtotal biomass of Avena sativa L. more than expected value in all mix-sowing treatmentsexcept E at jointing stage. Contribution value and total biomass of Avena sativa L. more thanexpected value in all mix-sowing treatments at efflorescence and mature stage.(5) With the growth of forage, the niche breadth of Avena sativa L decreases graduallyand Vicia vilosa Roth. showed a gradually increasing tendency in all group of mixedgrassland, niche overlap of Vicia vilosa Roth and Avena sativa L. showed a reducingtendency. In mixed grassland with Avena sativa L relative density decreases and the relativedensity increase of Vicia vilosa Roth., niche breadth of Avena sativa L decreases graduallyand Vicia vilosa Roth showed a gradually increasing tendency, the niche overlap of Avenasativa L and Vicia vilosa Roth increases gradually.(6) Under density dependant, root length density of top root of Avena sativa L. increasesignificant (P<0.05), and Vicia vilosa Roth. decrease significant (P<0.05). As soil wasdeepened, root length density of lateral root of Avena sativa L. from0-5cm soil layer to0-10cm soil layer, and Vicia vilosa Roth. showed a increases first and then decreasestendency.(7) Niche breadth of top root of Avena sativa L. gradually increasing and Vicia vilosaRoth. showed a gradually decreasing tendency. Niche overlap of top root of Avena sativa Land Vicia vilosa Roth increases gradually. As soil was deepened, Niche breadth of lateralroot of Vicia vilosa Roth and Niche overlap of lateral root of Avena sativa L and Vicia vilosaRoth showed a increases first and then decreases tendency.Different grow conditions has changed the species use intensity of resources, plantsadapted to climatic conditions and density dependant changes by plasticity of plant height,tiller (branch) number and root length, influences the intensity of the interspecificcompetition. The niche of plant height changing trend opposed to root, there is a trade-offelationship between the overground parts of plant and underground use of resources. Plant-plant relationships of mutually beneficial make the plant of alpine region best use of natural and soil resources, get a higher dry above ground biomass based on the good planting model,inform a interaction stable and effect ecosystems.