Effects of precipitation change on biomass and nutrient allocations in different organs of two plants in an alpine meadow
Plant biomass and nutrient allocation reflect growth strategies that maximize the utilization of external resources.Understanding the effects of precipitation on biomass and nutrient allocation in different plant organs can help predict future plant responses to climate change.Five simulated precipitation treatments were set up in an alpine meadow:decreasing water by 90％(0.1 P),50％(0.5P),and 30％(0.7P);natural water(CK);and increasing water by 50％(1.5P).Moreover,we compared the biomass and nutrient content in the flowers,stems,and leaves of Anaphalis lactea and Saussurea nigrescens and the factors influencing the biomass and nutrient allocation of these two plants were explored.The results showed that:(1)Compared to the CK,0.1P and 0.7P increased the biomass in each organ of the two plants.The biomasses of stems,leaves,and flowers of A.lactea were the lowest in the 1.5P treatment,whereas those of stems,leaves,and flowers of S.nigrescens was the lowest in the 0.5P treatment.(2)The biomass allocation of A.lactea was in the order:stems(42.95％±7.66％)＞flowers(35.05％±7.42％)＞leaves(22.01％±6.57％).Meanwhile,the biomass allocation of S.nigrescens was in the order:leaves(37.44％±9.29％)＞stems(31.75％±6.83％)＞flowers(30.75％±7.58％).(3)Although the growth rates of the reproductive organ biomasses of A.lactea in the 0.5P and 0.7P treatments were marginally higher than those in the CK,the vegetative and reproductive biomasses of A.lactea grew at the same speed.Conversely,the vegetative biomass of S.nigrescens grew significantly faster than the reproductive biomass in the 0.1 P and 1.5P treatments,indicating an allometric growth relationship.(4)The flower carbon and leaf carbon contents of the two plants varied insignificantly between the five precipitation treatments;however,1.5P significantly enhanced the flower nitrogen and flower phosphorus contents of the two plants.(5)The structural equation model showed that precipitation mainly influenced biomass allocation in different organs of A.lactea through soil total nitrogen and precipitation also influenced nutrient allocation through soil water content(SWC).SWC and soil available phosphorus were the key factors affecting the biomass and nutrient allocation of S.nigrescens,respectively.Concludingly,precipitation did not significantly change the structural matter content in the different organs of the two plants;however,it affected plant biomass and nutrient allocation by changing soil factors.In this study area,an appropriate reduction in precipitation favors the reproductive growth of A.lactea,whereas the vegetative growth of S.nigrescens is more advantageous under increased precipitation.
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