胡杨枝叶功能性状对地下水位梯度的响应与适应

Response and Adaptation of Twig-leaf Functional Traits of Populus euphratica to Groundwater Gradients

以塔里木荒漠河岸林建群种胡杨为研究对象,测定胡杨叶厚度(LTS)、叶面积(LA)、比叶面积(SLA)、叶干物质含量(LDMC)、叶组织密度(LTD)与当年生小枝长(TSL)、小枝茎直径(TSD)、叶面积比率(LAR)、叶茎质量比(LSMR)、小枝茎密度(TSWD)、胡伯尔值(HV)等枝叶功能性状,研究地下水位梯度(GWD)上胡杨枝叶性状的变异特征,采用单因素方差分析、Pearson相关与主成分分析,研究胡杨枝叶功能性状间的协调与权衡关系及性状组合,以期从功能性状的角度揭示胡杨适应干旱荒漠环境的生态策略。结果表明:(1)胡杨枝叶性状种内变异较大,变异系数8.61%~59.31%,其中HV变异系数最大(59.31%),LDMC、LAR变异系数较低(8.61%、9.75%),且二者对GWD变化不敏感,保守性较高。(2)方差分析显示,胡杨枝叶功能性状在GWD 1.5 m与4.8 m间差异显著(P<0.05),而LTS、LTD、TSL、HV在GWD≤2.4 m和GWD≥3.5 m之间均差异显著(P<0.05)。(3)相关与主成分分析表明,LA、SLA、LDMC、LTS、LTD、LAR、TSWD、HV可作为反映胡杨枝叶性状特征的重要指标;28对枝叶性状显著相关(P<0.05),其中HV与TSL、TSD分别呈显著负相关、正相关关系(P<0.05),与展叶效率(LAR、LSMR)、LA、LM均呈显著负相关关系(P<0.05);展叶效率(LAR、LSMR)与LDMC呈极显著负相关关系(P<0.01),LA、SLA与TSWD均呈负相关关系,表明干旱区荒漠植物在维持水力-机械安全和碳收益之间存在潜在的权衡机制。研究发现,胡杨采取降低LA、SLA、展叶效率(LAR、LSMR),增大LTS、LDMC、TSWD、HV等一系列有利于减少水分散失、储存资源(养分、水分)和增强抗性的生态策略来适应干旱贫瘠的荒漠环境;植物经济谱同样存在于荒漠生态系统中,随全球变暖与区域水资源短缺,总体上向慢速投资收益的保守型一端转移。

We studied leaf and twig functional traits,namely,leaf thickness(LTS),leaf area(LA),specific leaf area(SLA),leaf dry weight of every leaf(LM),leaf dry matter content(LDMC),leaf tissue density(LTD)and twig length(TSL),twig diameter(TSD),leaf area ratio(LAR),leaf/stem mass ratio(LSMR),Twig stem wood density(TSWD)and Huber value(HV)of Populus euphratica Oliv.in Tarim extremely arid area.We analyzed the variation characteristics of these functional traits along the groundwater depth gradient(GWD),and the trade-off between leaf-twig traits and functional traits combination by One-way ANOVA,Pearson correlation and principal component analysis(PCA),in order to reveal the ecological strategy of P.euphratica to adapt the extremely arid desert environment.The results showed that:(1)the variation coefficient was from 8.61%to 59.31%,the HV was the largest(59.31%),LDMC and LAR were the smallest(8.61%,9.75%)and the most conservative traits.(2)Variance analysis showed that thirteen traits of P.euphratica had significant difference between GWD 1.5 m and 4.8 m,and there were significant difference of LTS,LTD,TSL and HV between GWD≤2.4 m and GWD≥3.5 m.(3)Correlation and principal component analysis(PCA)showed that LA,SLA,LDMC,LTS,LTD,LAR,TSWD and HV could be used as important indicators to reflect the characteristics of P.euphratica twig-leaf traits.There were significant correlation between 28 pairs of leaf-twig traits(P<0.05),especially HV was significantly negative correlation with TSL and positive correlation with TSD(P<0.05),and TSL was negative correlation with TSD,as well.HV was significantly negative correlation with LAR,LSMR,LA,LM(P<0.05).Also,leaf display efficiency(LAR and LSMR)were significantly negative correlation with LDMC(P<0.05),and TSWD was negative correlation with LA and SLA.It indicated that there was a potential trade-off mechanism between machine-water safety and carbon availability of P.euphratica in arid areas.P.euphratica adopted the ecological strategy,such as reducing LA,SLA and leaf display efficiency(LAR and LSMR),increasing LTS,LDMC,TSWD and HV,which were beneficial to reduce water loss,storing resources(nutrients and water)and enhancing resilience,to adapt the arid-barren desert environment.Plant economic spectrum also existed in desert ecosystems.With global warming and regional water shortage,it generally shifted towards the conservative strategy of slow investment-return.