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<i>Key message</i> <p>Low-altitude trees allocate a greater proportion of assimilated carbon to growth, whereas treeline trees preferentially allocate carbon to storage to cope with environmental constraints.</p> Abstract <p>Photosynthetic rates and growth rates regulate tree source–sink dynamics, yet their effects on nonstructural carbohydrates (NSCs) in trees remain unclear. We monitored mature <i>Picea meyeri</i> in situ for two years in both treeline and low-altitude habitats. We compared the seasonal dynamics of NSCs in the needles, branches, stems, and roots and evaluated the effects of the net photosynthetic rates (P<sub>n</sub>) and growth rate on NSCs in different tree organs. The results revealed that (1) needle and branch growth at the treeline was significantly lower than that at low altitudes; however, the mean concentrations of soluble sugars, starch, and NSCs in all organs were greater at the treeline. Moreover, the mean P<sub>n</sub> in the trees did not differ significantly between the two habitats; (2) the soluble sugar concentrations in the trees were generally negatively correlated with the growth rate, whereas the starch concentrations tended to be positively correlated with the growth rate; (3) the relationships between the NSCs and the growth rate were stronger in the low-altitude trees than in those at the treeline; and (4) the NSC concentrations were negatively correlated with the P<sub>n</sub> at low altitudes but positively correlated at the treeline. Overall, our findings suggest that low-altitude trees allocate a greater proportion of assimilated carbon to growth, whereas treeline trees preferentially allocate carbon to storage to cope with environmental constraints. This work provides new insights into the habitat-dependent carbon allocation strategies of mature trees and offers a scientific basis for predicting forest responses to future climate change.</p>

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Photosynthates in mature Picea meyeri are preferentially allocated to nonstructural carbohydrate storage at the treeline and to growth at low altitudes on Luya Mountain, Northern China

  • 期刊论文

  • 发表日期：

    2026年2月21日

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  • Xianji Yang,
  • Yuan Jiang,
  • Xinyuan Ding,
  • Minghao Cui,
  • Jingling Liu

摘要

Key message

Low-altitude trees allocate a greater proportion of assimilated carbon to growth, whereas treeline trees preferentially allocate carbon to storage to cope with environmental constraints.

Abstract

Photosynthetic rates and growth rates regulate tree source–sink dynamics, yet their effects on nonstructural carbohydrates (NSCs) in trees remain unclear. We monitored mature Picea meyeri in situ for two years in both treeline and low-altitude habitats. We compared the seasonal dynamics of NSCs in the needles, branches, stems, and roots and evaluated the effects of the net photosynthetic rates (Pn) and growth rate on NSCs in different tree organs. The results revealed that (1) needle and branch growth at the treeline was significantly lower than that at low altitudes; however, the mean concentrations of soluble sugars, starch, and NSCs in all organs were greater at the treeline. Moreover, the mean Pn in the trees did not differ significantly between the two habitats; (2) the soluble sugar concentrations in the trees were generally negatively correlated with the growth rate, whereas the starch concentrations tended to be positively correlated with the growth rate; (3) the relationships between the NSCs and the growth rate were stronger in the low-altitude trees than in those at the treeline; and (4) the NSC concentrations were negatively correlated with the Pn at low altitudes but positively correlated at the treeline. Overall, our findings suggest that low-altitude trees allocate a greater proportion of assimilated carbon to growth, whereas treeline trees preferentially allocate carbon to storage to cope with environmental constraints. This work provides new insights into the habitat-dependent carbon allocation strategies of mature trees and offers a scientific basis for predicting forest responses to future climate change.