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Chinese Journal of Applied Ecology ›› 2020, Vol. 31 ›› Issue (10): 3340-3348.doi: 10.13287/j.1001-9332.202010.008

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Stem hydraulic architecture of Malus sieversii in degraded wild fruit forest in Ili valley, China

SUN Yi-xiang1,2, ZHANG Jing1, ZHOU Xiao-bing1, TAO Ye1, ZHANG Yuan-ming1*   

  1. 1State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China;
    2University of Chinese Academy of Sciences, Beijing 100094, China
  • Received:2020-04-01 Accepted:2020-07-24 Online:2020-10-15 Published:2021-04-15
  • Contact: * E-mail: zhangym@ms.xjb.ac.cn
  • Supported by:
    National Key R&D Program of China (2016YFC0501502), the Tianshan Innovation Team Project (2018D14009), and the Regional Collaborative Innovation Project of Xinjiang Uygur Autonomous Region (2019E01016).

Abstract: To reveal mechanisms underlying the dieback of Malus sieversii in degraded wild fruit forest in Ili valley of China, we compared the differences in stem hydraulic architecture, water transport effectiveness and safety, as well as their influencing factors among three growth classes of dead branches ratios, including Class Ⅰ (<20%), Class Ⅱ (40%-60%) and Class Ⅲ (>80%), respectively. With the increases in degradation degree of Xinjiang wild fruit forest, sapwood-specific hydraulic conductivity and leaf-specific hydraulic conductivity decreased, without significant differences among the three growth classes. Branch embolism at dusk and hydraulic safety significantly increased. The xylem water potential at 50% loss of hydraulic conductivity was -1.87, -1.35 and -0.53 MPa for Class Ⅰ, Ⅱ and Ⅲ, respectively. Predawn and midday leaf water potential and the hydraulic safety margin exhibited an order of Ⅰ>Ⅱ>Ⅲ. Xylem anatomical cha-racteristics and branch and leaf traits related to hydraulics were significantly different among the three growth classes. Results from correlation analysis revealed a weak tradeoff between xylem-specific hydraulic efficiency and xylem safety of M. sieversii. Stem hydraulic architecture of M. sieversii altered with the decline of Xinjiang wild apple forest. With increasing degrees of degradation, the severity of xylem embolisms aggravated, resistance to cavitation embolisms reduced, and the risk of water imbalance increased.

Key words: declining wild fruit forest, Malus sieversii, hydraulic architecture, xylem, embolism vulnerability