Effects Of Grazing On Tiller Characteristics Of Stipa Breviflora

Stipa breviflora is one of the most representative types of dominant species in desert steppe.The main reproduction mode of Stipci breviflora is asexual reproduction,while the manifestation of asexual reproduction is tiller.The number of tillers can vividly reflect grazing pressure,and it is also the best indicator of grazing.In this study,a complete random block design experiment with CK,LG,MG and HG four stocking rate.The response of tiller characteristics of Stipa breviflora to stocking rate was analyzed in combination with local hydrothermal conditions,by measuring the plant height(PH),basal cluster diameter(DS),tiller number(TIL),aboveground biomass(BIO),endogenous hormone content(IAA,CTK,GA3,ABA),leaf calorific value(CV),and leaf water content(LW)of Stipa breviflora.The main results are as follows:(1)The effect of grazing on had a significant effect on the tiller characteristics of Stipa breviflora,the basal plexus diameter was significantly increased with the increase of the stocking rate;the number of tillers,plant height,and biomass increased with the increase of stocking rate.Grazing had a significant effect on the endogenous hormone content and caloric value of Stipa breviflora,as IAA,GA3,ABA content increased significantly with the increase of stocking rate,however caloric value decreased with the increase of stocking rate.(2)The monthly dynamic change of tiller characteristics was as follows:the base cluster diameter gradually increased from four to five months,peaked in June,and decreased from July to September.The number of tillers reached a peak in April,then gradually decreased from May to July,then gradually decreased after the increasing in August.Plant height and biomass increased from April to August,then decreased in September.The contents of IAA,CTK,GA3 and ABA were the lowest in April,and increased after April.(3)The increase of hormone concentration and the decrease of diameter of stem will lead to the decrease of tiller number of Stipa breviflora,and the water content and calorific value of leaves can promote the hormone content of Stipa breviflora.CTK,calorific value and leaf water content promoted plant height.Biomass is regulated by many factors.Four endogenous hormones,calorific value and leaf water content have significant positive correlation with biomass.(4)The regression model of the relationship between tiller nulber and endogenous hormone concentration,basal cluster diameter,leaf water content and calorific value was as follows:TIL=-0.3574 CTK-0.2301 ABA+6.2224 DS.