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碳水化合物不足是高山林线树种生长限制假说之一,国内外以碳水化合物为基础的高山林线研究已有很多,而与高山林线相比,人们对碳水化合物在灌丛线形成中的作用知之甚少.除此之外,土壤养分亦被视为限制高山树种向上分布的重要因素之一.本研究将探究欧亚多种高山灌木不同器官中非结构性碳水化合物(NSCs)、氮(N)和磷(P)在不同季节及高低海拔上的含量变化规律.研究结果显示,除了与夏季相比冬季细根中具有较低的P含量以外,不同海拔与季节对灌木不同器官中的N和P含量均无显著影响.冬季灌木枝条中的NSCs和可溶性糖含量显著高于夏季.海拔与季节对细根中NSCs、淀粉、可溶性糖和糖与淀粉比值的影响均有显著的交互作用.在冬季,灌木细根中的可溶性糖与淀粉含量在海拔上限处要显著低于其在低海拔处;而在夏季,这些指标在高低海拔间均无显著差异.本研究结果表明,与高山林线树种相似,海拔分布上限的灌木冬季细根中较低的非结构性碳水化合物含量可能限制了灌木的向上分布.“,”Aims Carbon and nutrient physiology of trees at their upper limits have been extensively studied,but those of shrubs at their upper limits have received much less attention.The aim of this study is to examine the general patterns of nonstructural carbohydrates(NSCs),nitrogen(N)and phosphorous(P)in shrubs at the upper limits,and to assess whether such patterns are similar to those in trees at the upper limits.Methods Across Eurasia,we measured the concentrations of soluble sugars,starch,total NSCs,N and P in leaves,branches and fine roots(＜0.5 cm in diameter)of five shrub species growing at both the upper limits and lower elevations in both summer(peak growing season)and winter(dormancy season).Important Findings Neither elevation nor season had significant effects on tissue N and P concentrations,except for lower P concentrations in fine roots in winter than in summer.Total NSCs and soluble sugars in branches were significantly higher in winter than in summer.There were significant interactive effects between elevation and season for total NSCs,starch,soluble sugars and the ratio of soluble sugar to starch in fine roots,showing lower soluble sugars and starch in fine roots at the upper limits than at the lower elevations in winter but not in summer.These results suggest that the carbon physiology of roots in winter may play an important role in determining the upward distribution of shrubs,like that in the alpine tree-line trees.