关键词: 生态对策, CSR策略, 冠层高度, 季节变动

Abstract:

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.

Key words: ecological strategy, CSR strategy, canopy height, seasonal variation