Changes in water use with growth in Ulmus pumila in semiarid sandy land of northern China
Changes in water use with growth in Ulmus pumila in semiarid sandy land of northern China
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DOI：
10.1007/s00468-013-0928-3
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发表时间：
2014-02
期刊：
影响因子：
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通讯作者：
H. Su;Yonggeng Li;Wei Liu;Hong Xu;O. Sun
中科院分区：
文献类型：
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作者：
H. Su;Yonggeng Li;Wei Liu;Hong Xu;O. Sun
摘要榆树种群更新失灵已成为中国北部沙地植被保护和环境变化预测的一个重要问题。为了更好地理解FU的生活史策略。在半干旱环境中，我们研究了与水分利用有关的生态生理和形态特征。树龄分为四个年龄段：当年苗(UC)、2-5年生幼树(US)、幼树(Uj)和成熟树(Um)。通过对木质部汁液、不同层次土壤水分和地下水中氢同位素数据的比较，发现UC主要依赖于表土(0~40 cm)的土壤水分，Us和Uj主要从深层土壤(>；40 cm)吸收土壤水分，而Um主要利用直根很深的稳定地下水。与Uj和Um相比，UC的黎明前叶水势显著降低，表明UC经历了更严重的水分胁迫，恢复能力较弱。日最大净同化率、日最大蒸腾速率和日最大气孔导度均以UC最高，中午显著下降。UC可能正在实施一种“全力以赴”的战略，试图提供他们建立所需的增长，但有很大的死亡风险。UM采用了更保守的策略，有效地调节了瞬时水分利用效率，并保持了稳定的气体交换水平和显著更高的长期水分利用效率。与不同年龄的植株相比，UJ通过形成更陡峭的叶角、更密集的叶片短柔毛和更多的气孔来耐受和适应干旱条件。我们的研究结果表明，耶鲁大学制定了显著不同的用水策略。根据不同的水源，从苗期到成熟期，这些植物的生长情况都不同。
Key messageUlmus pumilavary its water use strategy from seedling to maturity in a water-limited sandy land by adopting different photosynthetical capacities, water use efficiencies and morphological traits.AbstractRegeneration failure of naturalUlmus pumilapopulations has become a growing concern related to vegetation conservation and prediction of environmental change in the sandy lands of northern China. To better understand the life-history strategies ofU. pumilaand its adaptation to drought in semiarid environments, we studied ecophysiological and morphological traits related to water use in an age sequence ofU. pumilarepresenting four age classes: current-year seedlings (Uc), age 2- to 5-year-old saplings (Us), juveniles (Uj), and mature trees (Um). A comparison of hydrogen isotope data in xylem sap, soil water in different layers and groundwater showed that Uc relied on the soil water in the topsoil (0–40 cm), Us and Uj absorbed soil water from deeper soil (>40 cm), while Um mainly used stable groundwater with very deep (>2 m) taproots. Significantly lower predawn leaf water potentials were observed in Uc than in Uj or Um, suggesting that Uc experienced more severe water stress and had a weaker capacity to recovery. Moreover, Uc had the highest daily maximum net assimilation rate, daily maximum transpiration rate and daily maximum stomatal conductance, all of which decreased remarkably at midday. A “go for broke” strategy is probably practiced by Uc which try to provide the growth they need to become established, but with a great risk of mortality. Um used a more conservative strategy by effectively regulating the instantaneous water-use efficiency, and maintaining both stable gas exchange levels and significantly higher long-term water-use efficiency. Uj endured and adapted to drought conditions by developing steeper leaf angles, denser leaf pubescence and more stomata than differently aged plants. Our findings illustrate that significantly different water-use strategies were developed byU. pumilatrees as they grew from seedlings to maturity, which were based on different water sources.