岷江源区两种优势针叶树当年生小枝性状与生物量分配随海拔的分异规律

Differentiation patterns of current⁃year twig traits and biomass allocation of two dominant coniferous trees along an altitudinal gradient on the eastern edge of the Tibetan Plateau

当年生小枝具有较少的次生组织,同时是植物分支系统中最具活力的部分,木本植物当年生小枝性状与生物量分配的海拔变化是理解物种对不同生境适应策略的重要内容。通过分析青藏高原东缘岷江源区两种优势亚高山针叶乔木(紫果云杉和岷江冷杉)当年生小枝性状(茎长、茎粗、比茎长)与不同部位器官(茎、叶)的生物量随天然生境的海拔(3500—3550 m、3650—3700 m和3800—3850 m)变化,尝试揭示两物种当年生小枝在不同海拔下的生物量权衡及其生长策略。结果表明:(1)不同海拔下茎生物量种间差异大于种内差异,3650—3700 m处的茎生物量变异最大(128.4%)。(2)云杉的茎生物量、总叶生物量与海拔间存在显著的负相关关系(P<0.05),比茎长与海拔呈显著正相关(P<0.05);冷杉的总叶生物量与海拔间为显著负相关关系(P<0.05)。(3)随着海拔的升高,云杉茎生物量分配比逐渐从33.0%降低到27.0%;而冷杉的茎生物量分配比则从23.0%渐增至28.0%。(4)3500—3550 m和3650—3700 m两处的云杉茎生物量与总叶生物量、茎长与茎粗呈异速生长关系;3500—3550 m、3650—3700 m和3800—3850 m三处的冷杉茎生物量与总叶生物量、茎长与茎粗一直呈现异速生长关系。两种针叶树的茎生物量分配比及相关性状随海拔的变化差异表明冷杉更适应高海拔的胁迫环境。

The current year twigs have less secondary tissue and are the most active part of the plant branching system.The variation along elevation gradients of current year twig traits and biomass allocation in woody plants are critical to understand the adaptation strategies of plant species to different habitats.This study was conducted in the headwater region of Minjiang River on the eastern edge of the Qinghai-Tibet Plateau,aimed to deal with the functional traits changes of twigs(stem length,stem diameter and specific stem length)and the biomass allocation in different organs(stem and leaf)of two dominant subalpine coniferous trees species(i.e.,Picea purpura and Abies faxoniana).Plant traits and biomass allocation were compared at different altitude(3500—3550 m,3650—3700 m,3800—3850 m),figuring out their biomass trade-off and growth strategies at different altitudes.The findings revealed that(1)the altitudinal interspecific difference of stem biomass was greater than their intraspecific difference,and the stem biomass at 3650—3700 m showed the greatest variation(128.4%).(2)Specific stem length of P.Purpurea existed a significantly positive correlation with altitude(P<0.05).Furthermore,there was a significantly negative correlation between stem biomass,leaf biomass,and altitude(P<0.05).A.faxoniana presented a significantly negative correlation between leaf biomass and altitude(P<0.05).(3)With the increase of altitude,the biomass allocation ratio of P.Purpurea stem decreased from 33.0%to 27.0%.The stem biomass allocation ratio of A.faxoniana increased from 23.0%to 28.0%(4)At 3500—3550 m and 3650—3700 m,there were allometric relationships of P.purpura between stem biomass and leaf biomass,stem length and stem diameter;There were allometric relationships of A.faxoniana between stem biomass and leaf biomass,stem length and stem diameter at 3500—3550 m,3650—3700 m,and 3800—3850 m.The differences of two species in the biomass allocation ratio of their stem and related traits with altitude revealed that A.faxoniana was better adapted to high-altitude stress.