TY - JOUR
T1 - Crown pruning and understory removal did not change the tree growth rate in a Chinese fir (Cunninghamia lanceolata) plantation
AU - Li, Renshan
AU - Han, Jianming
AU - Guan, Xin
AU - Chi, Yonggang
AU - Zhang, Weidong
AU - Chen, Longchi
AU - Wang, Qingkui
AU - Xu, Ming
AU - Yang, Qingpeng
AU - Wang, Silong
N1 - Funding Information:
This work was supported by the National Key Research and Development Program of China (Grant no. 2016YFD0600204 ), the National Natural Science Foundation of China (Grant Nos. 41630755 and 41977092 ). We also thank Xiuyong Zhang, Zhenqi Shen, Xiaojun Yu, Ke Huang, and Munan Zhu for their invaluable assistance in the laboratory and the field experiments.
PY - 2020/5/15
Y1 - 2020/5/15
N2 - How tree growth and the underlying photosynthesis of leaves, especially those multi-aged leaves, change after the application of both pruning and understory removal remains unclear. In this study, the tree growth and photosynthetic responses of various-aged needles to pruning, understory removal and their interactions were investigated in a Chinese fir (Cunninghamia lanceolata) plantation. The biochemical and stomatal limitations to photosynthesis was separated by the combined measurements of stable carbon (δ 13C) and oxygen (δ 18O) isotopes in needles. Our results showed that the tree growth rates did not respond to pruning, understory removal, and their interactions. Pruning significantly stimulated the net photosynthetic rates (PA) and stomatal conductance (gs) of remaining foliage (especially the current- and one-year-needles). Although pruning had no effect on needle total nitrogen (N) concentration, the concentrations of water-soluble N (NS), the ratio of water-soluble N to sodium dodecyl sulfate (SDS)-insoluble N (NS/ND), and the photosynthetic N use efficiency (PNUE) were higher in needles of pruned trees compared with the unpruned trees. A significant and positive correlation between PNUE and NS/ND was also detected. The constant δ 13C and declined δ 18O in the current-year-needles from pruned trees suggested that both the photosynthetic capacity and the gs were responsible for the enhancement in PA of the youngest needles. Conversely, in the previous year needles, δ 13C and δ 18O were not significantly different between the control and pruned trees. Consistent with the response of tree growth rate, the foliar photosynthesis also did not exhibit changes following understory removal in both pruned and unpruned stands. We highlighted that pruning caused an up-regulation in PA of remaining foliage, thereby mitigating the negative effects of canopy loss on carbon assimilation.
AB - How tree growth and the underlying photosynthesis of leaves, especially those multi-aged leaves, change after the application of both pruning and understory removal remains unclear. In this study, the tree growth and photosynthetic responses of various-aged needles to pruning, understory removal and their interactions were investigated in a Chinese fir (Cunninghamia lanceolata) plantation. The biochemical and stomatal limitations to photosynthesis was separated by the combined measurements of stable carbon (δ 13C) and oxygen (δ 18O) isotopes in needles. Our results showed that the tree growth rates did not respond to pruning, understory removal, and their interactions. Pruning significantly stimulated the net photosynthetic rates (PA) and stomatal conductance (gs) of remaining foliage (especially the current- and one-year-needles). Although pruning had no effect on needle total nitrogen (N) concentration, the concentrations of water-soluble N (NS), the ratio of water-soluble N to sodium dodecyl sulfate (SDS)-insoluble N (NS/ND), and the photosynthetic N use efficiency (PNUE) were higher in needles of pruned trees compared with the unpruned trees. A significant and positive correlation between PNUE and NS/ND was also detected. The constant δ 13C and declined δ 18O in the current-year-needles from pruned trees suggested that both the photosynthetic capacity and the gs were responsible for the enhancement in PA of the youngest needles. Conversely, in the previous year needles, δ 13C and δ 18O were not significantly different between the control and pruned trees. Consistent with the response of tree growth rate, the foliar photosynthesis also did not exhibit changes following understory removal in both pruned and unpruned stands. We highlighted that pruning caused an up-regulation in PA of remaining foliage, thereby mitigating the negative effects of canopy loss on carbon assimilation.
KW - Carbon sequestration
KW - Foliar nitrogen
KW - Needle age
KW - Nitrogen trade-off
KW - Stable isotopic signature
KW - Timber yield
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U2 - 10.1016/j.foreco.2020.118056
DO - 10.1016/j.foreco.2020.118056
M3 - Article
AN - SCOPUS:85080985672
SN - 0378-1127
VL - 464
JO - Forest Ecology and Management
JF - Forest Ecology and Management
M1 - 118056
ER -