Effects Of Increased Precipitation And Nitrogen Deposition On Stoichiometric Characteristics Of Desert Ephemeral Plants

With the climate and global change,precipitation and nitrogen deposition in temperate desert ecosystem are changing dramatically.Water and nitrogen are the main limiting factors in desert ecosystem.The change of precipitation and the continuous increase of nitrogen deposition have a significant impact on plant growth.The quantitative characteristics of chemical elements in plants are closely related to their growth and development.With the growth of plants,the distribution and utilization of nutrients among organs will change.Ephemeral plants are important components of desert herbaceous plants,which can complete their life cycle in a short time.Therefore,the stoichiometric characteristics of different growth stages must change rapidly.However,the response characteristics and mechanism of this change to the increase of precipitation and nitrogen deposition are still unclear,which is of great significance for understanding the nutrient cycle of herbaceous plants in desert ecosystem.Therefore,a multi factor experiment of water,nitrogen and water nitrogen coupling was established in Gurbantonggut desert.Different water,nitrogen and water nitrogen coupling combinations were set up,and water,nitrogen and water nitrogen coupling treatments were carried out from 2018 to 2020.By measuring and analyzing the stoichiometric characteristics(C,N,P)of different organs in different growth stages of two life styles ephemeral plants in 2019 and the content of C,N,P in leaves of ephemeral plants during the vigorous growth period from 2018 to 2020,the following main conclusions were obtained.(1)The increase of precipitation had no significant effect on C content of two life style plants;The water increased the N and P content of the early growth stage of the E.distans,but had no significant effect on the N and P content of the E.inderiensis.Increasing 30% water significantly reduced C: N and C: P of annual ephemeral plants at the early growth stage,but the response of E.inderiensis was not significant.The increase of water 50% increased N:P significantly and was higher than 16,which may lead to P-restriction of E.distans.The increased precipitation had no significant effect on the C content of four ephemeral plant leaves in vigorous growth period of four short-lived plants,but significantly affected the N and P contents of E.distans plants in higher precipitation year(2018 and 2019);while the effect of stoichiometry on short-lived plants leaves in 2020 is not significant.(2)The effects of increased nitrogen deposition on C content in different organs of E.distans and E.inderiensis were closely related to the plant growth stage,and the response was sensitive at the early growth stage,but not significant at the reproductive growth stage;The content of N and P in different organs of E.distans was sensitive to the increase of N deposition,but the content of N in underground organs was more sensitive than that in aboveground organs.Nitrogen addition significantly reduced C: N,C: P of E.distans,but stoichiometry of E.inderiensis had no significant response to nitrogen.The increase of nitrogen deposition had no significant effect on leaf C content,but had significant effect on N and P content;the response of leaf stoichiometry of ephemeral plants to nitrogen was not significant in 2020.(3)Under water and nitrogen treatment,the C content of E.distans and E.inderiensis was relatively stable;The water and nitrogen treatment could increase the contents of N and P in different growth stages of Elymus tomentosa,but had no significant effect on the aboveground and underground organs;The coupling of water and nitrogen reduced C: N and C: P in the leaves of E.distans and E.inderiensis,but N: P of E.inderiensis was not sensitive to the coupling of water and nitrogen.Water and nitrogen coupling treatment significantly affected only annual ephemeral plants,but not perennial ephemeral plants.In conclusion,the stoichiometric characteristics of two life style ephemeral plants are closely related to plant growth stages,organs,precipitation and nitrogen deposition.Precipitation,increased nitrogen deposition and water nitrogen coupling had significant effects on stoichiometry of the two life style.E.distans to water and nitrogen was more sensitive than E.inderiensis.In the future,the increase of precipitation and nitrogen deposition may increase the N and P uptake of ephemeral plants,and then change the nutrient allocation strategy among their organs,while the stoichiometric characteristics of ephemeral plants are stable.