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Chinese Journal of Applied Ecology ›› 2026, Vol. 37 ›› Issue (5): 1353-1364.doi: 10.13287/j.1001-9332.202605.017

• Special Features of Stable Isotope Ecology • Previous Articles     Next Articles

Decline and mortality of poplar shelterbelt induced by hydraulic limitations, carbon starvation, and drying of mid-depth soil layers.

HE Chunxia1,2,3, HU Xiaochuang1,2,3, SUN Shoujia1,2,3*, GUAN Chongfan1,2,3, LI Zijing1,2,3, ZHANG Jinsong1,2,3, CAI Jinfeng2   

  1. 1Research Institute of Forestry, Chinese Academy of Forestry/Key Laboratory of Tree Breeding and Cultivation of the State Forestry and Grassland Administration, Beijing 100091, China;
    2Collaborative Innovation Center of Sustainable Forestry in Southern China, Nanjing Forest University, Nanjing 210037, China;
    3Henan Xiaolangdi Forest Ecosystem National Observation and Research Station, Jiyuan 454650, Henan, China
  • Received:2025-09-22 Accepted:2026-04-10 Online:2026-05-18 Published:2026-11-18

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Abstract: We assessed tree health scores, growth status, percent loss of conductivity(PLC), hydraulic safety margin (HSM), non-structural carbohydrates (NSC), and stable isotopes in healthy, declining, and dying trees of poplar shelterbelts in Zhangbei County, Hebei Province, China. We examined the internal and external drivers of poplar decline and quantified their relative importance, to elucidate the underlying causes and mechanisms. Health scores differed significantly among status classes, averaging 90.0, 62.0, and 37.7 for healthy, declining, and dying trees, respectively. Compared with healthy trees, water uptake from the 10-50 cm soil layer increased significantly by 12.1% in declining trees and by 26.4% in dying trees. Dying trees had significantly lower individual-leaf area (-29.6%) and leaf C:N (-23.2%), whereas specific leaf area increased significantly (+29.3%) relative to healthy trees. In terms of hydraulic function, dying trees exhibited lower leaf water potential (-80.5%), branch water potential (-68.0%), and HSM (-27.2%), while branch PLC and P50(the water potential at 50% loss of hydraulic conductivity) increased significantly by 71.7% and 19.2%, respectively. There was no difference between declining poplars and healthy poplars. NSC concentrations in dying trees decreased significantly in the trunk (-40.6%) and roots (-30.5%) compared with healthy trees. In declining trees, trunk NSC also declined (-19.2%), whereas no significant differences were detected in leaves and branches. Relative to healthy trees, dying trees had significantly lower leaf δ13C (-5.8%) and higher δ18O (+9.9%), while declining trees differed little from healthy trees. Principal component analysis and quantitative importance assessment identified PLC as the primary factor associated with poplar decline (21.0%), followed by mid-layer soil moisture and individual-leaf area, while NSC in roots and trunks also contributed substantially. Overall, hydraulic failure appeared to be the dominant internal driver of poplar decline, with carbon starvation further aggravating decline, and mid-soil drying representing the principal external stressor.

Key words: poplar tree, embolism of branch, carbon starvation, stable carbon and oxygen isotopes, leaf trait