为阐明高海拔城市绿化树种金叶榆的多维适应机制,在西藏林芝测定其冠层垂直分层(上部、中部、基部)叶片在生长季(5—10月)的8个功能性状[叶绿素相对含量(RCC)、比叶面积(SLA)、叶干物质含量(LDMC)、叶体积(LV)、叶组织密度(LTD)、叶片相对含水量(LRWC)、叶厚度(LT)、叶面积(LA)],并结合植物生态策略模型从空间和时间尺度对其进行解析。结果表明:1)8个功能性状均表现为中等变异,变异系数(C_v)为20%~50%,并呈现“稳态—弹性”双模变异格局,其中叶片相对含水量(C_v=7.68%)稳定性最高,而叶绿素相对含量(C_v=44.24%)表现出最高的可塑性;2)性状之间存在显著权衡关系,光合性状(SLA)与结构性状(LTD、LDMC)呈极显著负相关(P<0.01),与水分保持能力(LRWC)呈显著正相关(P<0.05),表明光合能力与水分维持功能之间存在协同关系;3)沿冠层垂直分层,性状组合由树冠基部以高SLA为特征的资源获取型策略,向冠层上部以较高LT为特征的保守型策略转变,反映了光资源获取与环境胁迫之间的空间权衡;4)季节动态表明,资源分配持续向胁迫耐受倾斜(S值从39%增至66%),抗干扰值(R)下降,而竞争值(C)保持相对稳定(19%~27%),体现出以胁迫耐受为主导的资源分配规律,并推动生态策略由耐胁迫-抗干扰型/竞争-耐胁迫-抗干扰型策略(SR/CSR)经耐胁迫型/竞争-耐胁迫-抗干扰型策略(S/CSR)逐渐演变为生长季末期的耐胁迫型/竞争-耐胁迫型策略(S/CS)。金叶榆通过冠层垂直分层与季节动态中的性状权衡和策略转换,形成了时空互补的多维适应机制,以应对高海拔环境胁迫。

To elucidate the multidimensional adaptation mechanisms of Ulmus pumila ‘Jinye’,an urban greening colored-leaf tree species in high-altitude regions,this study quantified eight leaf functional traits[relative chlorophyll content(RCC),specific leaf area(SLA),leaf dry matter content(LDMC),leaf volume(LV),leaf tissue density(LTD),leaf relative water content(LRWC),leaf thickness(LT),and leaf area(LA)]across a vertical canopy gradient(upper,middle,and basal layers)during the growing season(May-October)in Linzhi,Xizang.The analysis integrated vertical canopy stratification with the CSR plant ecological strategy model to examine adaptations across spatial and temporal scales.The results showed that:1)The eight functional traits exhibited moderate variation(C_v range:20%-50%)with a "stability-plasticity" dual pattern:leaf relative water content(C_v=7.68%)maintained the highest stability,while relative chlorophyll content(C_v=44.24%)manifested the maximum plasticity.2)Significant trade-offs existed among traits:the photosynthetic trait(SLA)was exhibited a highly significant negative correlation with structural traits(LTD,LDMC)(P<0.01),but positively correlated with water retention capacity(LRWC)(P<0.05),indicating a synergy between photosynthesis and water maintenance.3)Along the vertical canopy gradient,trait combinations shifted from a resource-acquisitive type(higher SLA at the base)to a conservative type(higher LT at the top),reflecting a spatial trade-off between light resource capture and environmental stress.4)Seasonal dynamics revealed a continuous shift in resource allocation toward stress tolerance(S value:increasing from 39% to 66%),accompanied by a decline in reproductive investment(R)and relative stability in competitiveness(C)(19%-27%).This substantiates a resource allocation pattern dominated by stress tolerance,which drove the ecological strategy transition from the stress-tolerant/ruderal/competitive-stress-tolerant-ruderal(SR/CSR)strategy,through the stress-tolerant/competitive-stress-tolerant-ruderal(S/CSR)strategy,to ultimately evolve into the stress-tolerant/competitive-stress-tolerant(S/CS)strategy by the end of the growing season.In conclusion,Ulmus pumila ‘Jinye’ has developed a spatiotemporally complementary multidimensional adaptation mechanism to mitigate high-altitude environmental stress through trait trade-offs and strategic shifts along the vertical canopy gradient and across seasonal dynamics.