Effects of different stages of growing season and twig ages on twig traits in evergreen conifers

doi:10.17521/cjpe.2025.0022

Abstract

Abstract:

Aims Previous studies have shown that different stages of growing season and twig ages are the key factors influencing variation in plant twig traits. However, few studies have simultaneously investigated how twig traits and their relationship shift in response to changes in growing season stages and twig ages.

Methods In this study, Pinus koraiensis, Picea koraiensis, and Abies nephrolepis, typical evergreen conifers in northeast China, were studied. We measured seven twig traits in 135 trees across three growing season stages (early: July; middle: September; late: November): specific twig length (STL), twig dry matter content (TDMC), twig wood density (TWD), pith proportion cross-sectional area ratio, xylem proportion cross-sectional area ratio, phloem proportion cross-sectional area ratio and resin channel proportion cross-sectional area ratio. Both annual and perennial twigs from these trees were analyzed to explore how twig traits and their correlations change throughout seasonal progression and with twig aging.

Important findings In the early growing season, twig dry matter content and twig wood density were significantly lower than those in the middle and late stages. Xylem proportion cross-sectional area ratio and phloem proportion cross-sectional area ratio increased significantly with twig age. The negative correlation between specific twig length and twig dry matter content was only observed in the early growing season. Notably, annual twigs displayed a “quick investment-return” survival strategy characterized by high specific twig length and low twig dry matter content in the early season, contrasting with the “slow investment-return” survival strategy in the late growing season and perennial twigs. Our findings provide insight into how plants adapt to habitat changes by regulating twig traits.

Key words: growing season stage, twig age, twig wood density, xylem proportion cross-sectional area ratio, phloem proportion cross-sectional area ratio

HAO Ya-Xin, JIN Guang-Ze, LIU Zhi-Li. Effects of different stages of growing season and twig ages on twig traits in evergreen conifers[J]. Chin J Plant Ecol, 2026, 50(2): 279-292.

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URL: https://www.plant-ecology.com/EN/10.17521/cjpe.2025.0022

https://www.plant-ecology.com/EN/Y2026/V50/I2/279

Figures/Tables 7

Table 1 Statistical information of twig traits of three evergreen conifers

性状 Trait	最大值 Maximum	最小值 Minimum	平均值(标偏差) Mean (SD)	变异系数 ^KCV (%)
比枝长 Specific twig length (cm·g^-1)	588.235	5.692	82.52 (74.45)	66.99
枝干物质含量 Twig dry matter content (g·g^-1)	0.815	0.044	0.44 (0.19)	39.57
木质密度 Twig wood density (g·cm^-3)	0.671	0.039	0.32 (0.12)	35.73
髓面积占比 Pith proportion cross-sectional area ratio	0.144	0.004	0.04 (0.02)	52.79
木质部面积占比 Xylem proportion cross-sectional area ratio	0.557	0.021	0.15 (0.09)	33.98
韧皮部面积占比 Phloem proportion cross-sectional area ratio	0.202	0.020	0.09 (0.03)	47.39
树脂道面积占比 Resin channel proportion cross-sectional area ratio	0.171	0.007	0.05 (0.02)	49.40

Table 2 Linear Mixed-effect Models (LMM) of twig traits, growing season stages and twig ages of three evergreen conifers

性状 Trait	生长季阶段 Growing season stages		枝龄 Twig ages		生长季阶段×枝龄 Growing season stages × twig ages		截距 Intercept
性状 Trait	估计标准差 Estimate SD	p	估计标准差 Estimate SD	p	估计标准差 Estimate SD	p	估计标准差 Estimate SD	p
STL (cm·g^-1)	-0.049 7	0.092 6	-0.143 9	<0.001^***	0.025 1	0.178 1	0.433 4	<0.001^***
TDMC (g·g^-1)	0.224 9	<0.001^***	0.261 4	<0.001^***	-0.101 9	<0.001^***	-0.046 1	0.385 0
TWD (g·cm^-3)	0.098 8	<0.001^***	0.138 9	<0.001^***	-0.040 2	<0.001^***	0.089 4	0.063 6
R_PA	0.037 8	0.180 3	-0.048 2	0.272 4	-0.024 2	0.177 4	0.369 8	0.006 4^**
R_XA	0.036 6	0.077 7	0.229 7	0.019 2^*	0.004 3	0.744 3	-0.166 2	0.028 4^*
R_PHA	0.043 1	0.027 9^*	0.212 2	<0.001^***	-0.005 0	0.687 9	-0.020 6	0.579 9
R_RC	-0.008 1	0.158 4	-0.008 1	0.756 6	-0.034 1	0.013 6^*	0.264 8	<0.001^***

Fig. 1 Difference of twig traits of three evergreen conifer species in different stages of growing season and different twig ages. Different uppercase letters indicate significant differences between twig traits in different stages of growing season (p < 0.05), and different lowercase letters indicated significant difference in twig traits at different ages (p < 0.05).

Fig. 2 Spearman correlation heat map for twig traits of three evergreen conifers. RPA, pith proportion cross-sectional area ratio; RPHA, phloem proportion cross-sectional area ratio; RRC, resin channel proportion cross-sectional area ratio; RXA, xylem proportion cross-sectional area ratio; STL, specific twig length; TDMC, twig dry matter content; TWD, twig wood density. *, p < 0.05; **, p < 0.01.

Fig. 3 Correlation of twig traits in different stages of growing season among three evergreen conifer species. RPA, pith proportion cross-sectional area ratio; RPHA, phloem proportion cross-sectional area ratio; RRC, resin channel proportion cross-sectional area ratio; RXA, xylem proportion cross-sectional area ratio; STL, specific twig length; TDMC, twig dry matter content; TWD, twig wood density. *, p < 0.05; **, p < 0.01; ***, p < 0.001. Different color marks represent the correlation slopes between traits in different stages of growing season, the black marks in N represent the same correlation slope among the twig traits in the three growing season stages. If there is no significant correlation between traits (p < 0.05), no lines are displayed.

Fig. 4 Correlation of twig traits of three evergreen conifer species at different ages. RPA, pith proportion cross-sectional area ratio; RPHA, phloem proportion cross-sectional area ratio; RRC, resin channel proportion cross-sectional area ratio; RXA, xylem proportion cross-sectional area ratio; STL, specific twig length; TDMC, twig dry matter content; TWD, twig wood density. *, p < 0.05; **, p < 0.01; ***, p < 0.001. Different color marks represent the correlation slopes between traits at different twig ages, the black marks indicate the same correlation slope between the two ages traits. If there is no significant correlation between traits (p < 0.05), no lines are displayed.

Fig. 5 Principal component (PC) analysis of twig traits. A, Principal component analysis of annual twigs in different stages of growing season. B, Principal component analysis of different twig ages. RPA, pith proportion cross-sectional area ratio; RPHA, phloem proportion cross-sectional area ratio; RRC, resin channel proportion cross-sectional area ratio; RXA, xylem proportion cross-sectional area ratio; STL, specific twig length; TDMC, twig dry matter content; TWD, twig wood density.

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