红砂和珍珠在不同干旱强度下的死亡风险评估和反应策略
Mortality risk assessment and response strategies of Reaumuria soongorica and Salsola passerina under varied drought intensities
[目的]干旱引起树木水力失效或碳饥饿而导致死亡,可能与干旱强度相关。然而,有关荒漠树木在遭遇不同干旱胁迫时死亡的风险及其抗旱策略的报道仍然很少。[方法]本试验在遮雨棚中移植了红砂和珍珠进行盆栽试验,并在经过 3种水分处理(即,充分供水,慢速干旱和快速干旱)后测定了与水和碳相关的生理性状。[结果](1)与充分供水处理相比,慢速干旱处理下红砂的边材(KS)和叶比导率(KL)无显著变化,而在快速干旱处理下显著降低,珍珠的KL有一致的变化。红砂和珍珠的导水率损失 50%的水势值(P50)在慢速和快速干旱处理下均显著大于充分供水,但慢速和快速干旱处理间无显著差异。(2)在 3种水分处理下,红砂和珍珠的水力安全阈值(HSM50)之间均存在显著差异,且充分供水处理下的值最大,快速干旱处理下的值最小。(3)在慢速或快速干旱胁迫下,红砂的P50显著大于珍珠,HSM50显著小于珍珠。(4)净光合速率、边材比导率和P50、正午水势、叶片和茎可溶性糖是红砂性状变异的主轴,充分供水处理下的树木有最大的净光合速率和水分运输效率,快速干旱处理下的树木有最大的抗栓塞能力和渗透调节能力,慢速干旱处理下的树木介于两者之间。正午水势、叶片和茎可溶性糖是珍珠性状变异的主轴,3 种水分处理下的个体分布均与耐旱性状相关。[结论]水力失效可能是红砂和珍珠死亡的原因。它们在快速干旱胁迫下更容易发生水力失效,其中红砂比珍珠更容易因过度栓塞而死亡。在抵抗干旱胁迫时,红砂和珍珠的抗旱策略不同,红砂采取出一种避旱策略,珍珠采取出一种耐旱策略。这一研究证明结合水力性状、非结构性碳、光合特性可以很好的预测荒漠树木的死亡。
[Objective]Drought-induced tree mortality,resulting from hydraulic failure or carbon starvation,is hypothesized to be modulated by specific drought intensities.However,there is a paucity of studies investigating the risk of mortality in desert trees under various drought stresses and the corresponding strategies employed for drought resilience.[Method]We conducted an experiment involving the transplantation of Reaumuria soongorica and Salsola passerina into pots within a rain shelter.Subsequently,these trees were subjected to three water treatments(i.e.,control,slow drought,and rapid drought).Following these treatments,we assessed various physiological traits associated with water and carbon.[Result](1)In response to drought,R.soongorica and S.passerina exhibited distinct changes in hydraulic traits.Under slow drought treatment,R.soongorica showed no significant alterations in marginal conductance(KS)and leaf-specific conductance(KL),while both KS and KL decreased significantly under rapid drought treatment.In contrast,S.passerina displayed consistent changes in KL.The water potential at which the hydraulic conductivity decreased by 50%(P50)was significantly higher in R.soongorica and S.passerina under both slow and rapid drought treatments compared to the sufficient water supply treatment,with no significant difference observed between the two drought treatments.(2)Notably,there were significant differences in the hydraulic safety margin(HSM50)between R.soongorica and S.passerina under all three moisture treatments.The highest HSM50 was recorded in the sufficient water supply treatment,while the lowest value was observed in the rapid drought treatment.(3)Under both slow and rapid drought stress,R.soongorica exhibited a significantly higher P50 compared to S.passerina,indicating a higher resistance to embolism.In contrast,the HSM50 of R.soongorica was significantly lower than that of S.passerina,suggesting a lower hydraulic safety margin.(4)The main axes of variation in R.soongorica traits include net photosynthesis rate,KS,P50,midday water potential,and soluble sugars in leaves and stems.Trees under the sufficient water supply treatment demonstrated the highest net photosynthesis rate and KS.Conversely,trees under the rapid drought treatment exhibited the highest P50,and soluble sugars in leaves and stems.Trees under the slow drought treatment fell between these two extremes.Midday water potential,leaf-specific conductance,and soluble sugars in leaves and stems are the primary factors influencing the variation in S.passerina traits,and the distribution of individuals under the three moisture treatments correlates with drought tolerance traits.[Conclusion]This study reveals that hydraulic failure could potentially lead to mortality in both R.soongorica and S.passerina.Under rapid drought stress,these trees exhibited increased vulnerability to hydraulic failure,with R.soongorica displaying a higher susceptibility to excessive embolism compared to S.passerina.Notably,R.soongorica and S.passerina demonstrated distinct strategies in combating drought stress.R.soongorica adopted a drought avoidance strategy,while S.passerina adopted a drought tolerance strategy,allowing them to effectively cope with drought.These findings highlight the significance of considering hydraulic traits,non-structural carbon,and photosynthetic properties when assessing the risk of mortality in desert trees.
王红永;解婷婷;牛富荣;何彩;师亚婷;单立山;
甘肃农业大学林学院,兰州,730070;甘肃农业大学林学院,兰州,730070;甘肃农业大学林学院,兰州,730070;甘肃省武威市林业科学研究院,武威,733000;甘肃农业大学林学院,兰州,730070;甘肃农业大学林学院,兰州,730070;
hydraulic failure carbon starvation drought response strategies
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