青藏高原三种优势植物生物量分配的变化规律

该研究利用4个由高到低不同海拔的同质园实验,以青藏高原高寒草地优势植物垂穗披碱草(Elymus nutans)、矮嵩草(Kobresia humilis)和珠芽蓼(Polygonum viviparum)为对象,分析了植物个体根、茎、叶生物量分配及根冠比的变化规律及影响因素。结果表明:(1)植物个体根、茎、叶质量比和根冠比具有显著的种间差异;与垂穗披碱草和珠芽蓼相比,矮嵩草具有显著较高的根质量比而叶、茎质量比较低,所以其根冠比较高。(2)在向低海拔移栽的过程中,珠芽蓼叶质量比保持不变,茎质量比显著降低而根质量比显著升高,根冠比表现出显著上升的趋势;垂穗披碱草则相反,即叶、茎质量比显著升高而根质量比显著降低,根冠比表现出显著下降的趋势;矮嵩草根、茎、叶质量比和根冠比则无显著变化。(3)随着海拔降低,年均气温明显升高而年均降雨量明显降低,且在植物个体种源地和土壤基质保持一致的条件下,向低海拔移栽过程中温度是导致珠芽蓼根、茎、叶生物量分配及根冠比变化的重要因素,而水分是垂穗披碱草根、茎、叶生物量分配及根冠比变化的重要驱动因素;矮嵩草根、茎、叶生物量分配及根冠比受其遗传因素影响较大。因此,在将来暖干化的背景下,青藏高原高寒草地植物生物量的分配将会发生改变,导致它们对资源(光照、水分和土壤养分)获取和利用的变化而改变它们的种间关系,从而影响群落的物种多样性与组成,最终可能导致生态系统功能的变化。

Changes in biomass allocation to leaves,stems and roots of three dominant alpine species from the Tibetan Plateau

In this study,using four common gardens from high to low elevations,we examined the shifts in the biomass allocation to leaves,stems and roots of three dominant species Elymus nutans,Kobresia humilis and Polygonum viviparum in alpine grasslands on the Tibetan Plateau,and explored whether this changes were controlled by the environmental factors,or by the genetic factors.In 2012,using three dominant species in alpine grasslands from the same provenance,we established four common garden experiments in Dawu,Guoluo;the Haibei Station,Haibei;Xining and Yuzhong,Lanzhou from high to low altitudes.We used the mass fraction of leaves (LMF),stems (SMF),roots (RMF) and shoot to root ratios (R/S ratio) individually as the variables to describe plant allocation.Our results were as follows: (1) There were significant differences in the biomass allocation to leaves,stems,roots and R/S ratios among three species examined;compared to Elymus nutans and Polygonum viviparum,Kobresia humilis had a higher RMF but lower LMF and SMF,and thus a higher R/S ratio.(2) During the transplantation from high to low altitudes,for Polygonum viviparum,SMF apparently decreased while RMF significantly increased,but LMF had no changes,leading R/S ratios to have an increasing trend;by contrast,for Elymus nutans,LMF and SMF markedly increased while RMF significantly declined,which led R/S ratio to having a decreasing trend.(3) since mean annual temperature increases and mean annual precipitation decreased from high to low elevations,and there were the same plant origin and soil matrix among four common gardens,temperature was the main factor driving the shifts of biomass allocation to leaves,stems,roots of Polygonum viviparum,by contrast,water availability was the primary factor driving the shifts of biomass allocation to leaves,stems,roots of Elymus nutans,whereas the changes in biomass allocation to leaves,stems,roots of Kobresia humilis was controlled by its genetic effects.Therefore,under the future warmer and drier conditions,the biomass allocation to leaves,stems,roots of plant species in alpine grasslands would shift,and this shift would change the acquisition and utilization of resources (such as light,water and soil nutrients) and further change interspecific interactions,and would lead to changes in community diversity and species composition,and even ecosystem functioning.