Plant size, branch age and environment factors co-drive variations of branch traits of Pinus koraiensis

doi:10.17521/cjpe.2020.0173

Abstract

Abstract:

Aims Variations of many branch traits are affected by plant size, branch age and environment factors, but the relative importance of these factors to intraspecies variations of branch traits has rarely been evaluated simultaneously.
Methods In this study, we took Pinus koraiensis as the research object, to explore the effects of plant size (diameter at breast height (DBH) or tree height), branch age and environmental factors (light intensity, soil nutrient content and water availability) on branch traits, by measuring morphological traits, chemical traits and anatomical traits in different branch ages of 69 individuals with DBH in the range of 0.3-100.0 cm.
Important findings Our results showed that: (1) DBH and tree height had different effects on branch traits: wood density (WD), the xylem area-to-total cross-sectional area ratio (R_XA), the phloem area-to-total cross-sectional area ratio (R_PHA) and the pith area-to-total cross-sectional area ratio (R_PA) were more sensitive to DBH, while the total resin canal area-to-total cross-sectional area ratio (R_RC) and wood nitrogen content (WN) were more affected by the tree height; (2) branch age was the most important factor in driving intra-specific variations of branch traits of P. koraiensis, followed by plant size, while the impact of environment factors was minimal; (3) WD and R_PHA were significantly positively correlated with DBH, while R_PA was significantly negatively correlated with DBH; and R_RC and WN were significantly positively correlated with tree height. Except for WN, the relationships between branch traits and branch age were significant, and as tree growth, the rate of R_RC decreasing with branch age was enhanced, but the rate of R_PA decreasing with branch age was weakened. The results of our study are helpful to understand the driving factors of intraspecific variation of branch traits at the local scale and the adaptation mechanism of branches to cope with environmental changes.

Key words: branch age, diameter at breast height, tree height, environment, wood density, anatomical trait, wood nitrogen content

YU Qing-Han, JIN Guang-Ze, LIU Zhi-Li. Plant size, branch age and environment factors co-drive variations of branch traits of Pinus koraiensis[J]. Chin J Plant Ecol, 2020, 44(9): 939-950.

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https://www.plant-ecology.com/EN/Y2020/V44/I9/939

Figures/Tables 7

Fig. 1 Schematic diagram of anatomical structure of branches of different ages under an optical microscope for Pinus koraiensis. A, Current-year branch. B, Two-years-old branch. C, Three-years-old branch. D, Four-years-old branch.

Table 1 Akaike information criterion (AIC) values in the regressions of diameter at breast height (DBH) or tree height against each branch traits of Pinus koraiensis

性状 Trait	DBH (cm)	树高 Tree height (m)
木质密度 WD (g·cm^-3)	-1 025	-1 022
枝氮含量 WN (mg·g^-1)	1 282	1 272
木质部面积占比 R_XA	-327	-325
韧皮部面积占比 R_PHA	-1 090	-1 086
髓面积占比 R_PA	-1 364	-1 362
树脂道总面积占比 R_RC	-1 129	-1 142

Table 2 Statistical information of wood density (WD), wood nitrogen content (WN), the xylem area-to-total cross-sectional area ratio (RXA), the phloem area-to-total cross-sectional area ratio (RPHA), the pith area-to-total cross-sectional area ratio (RPA) and the total resin canal area-to-total cross-sectional area ratio (RRC)

性状 Trait	最大值 Maximum	最小值 Minimum	平均值 Mean (标准偏差 SD)	变异系数 Coefficient of variation (%)
WD (g·cm^-3)	0.548	0.272	0.39 (0.03)	8
WN (mg·g^-1)	19.080	1.067	8.99 (3.72)	41
R_XA	0.634	0.092	0.31 (0.12)	39
R_PHA	0.146	0.026	0.09 (0.02)	22
R_PA	0.098	0.005	0.03 (0.01)	33
R_RC	0.136	0.000	0.07 (0.02)	29

Fig. 2 Variations of branch traits in current-year and old branches with plant size (DBH or tree height) for Pinus koraiensis. DBH, diameter at breast height; RPA, pith area-to-total cross-sectional area ratio; RPHA, phloem area-to-total cross-sectional area ratio; RRC, total resin canal area-to-total cross-sectional area ratio; RXA, xylem area-to-total cross-sectional area ratio; WD, wood density; WN, wood nitrogen content. *, p > 0.05; **, p > 0.01; ***, p > 0.001.

Table 3 Generalized linear models (GLM) among branch traits, tree size, branch age and environment factors (light availability, soil water content, soil nitrogen content, soil phosphorus content) for Pinus koraiensis

性状 Trait	胸径 DBH (cm)	树高 Tree height (m)	枝龄 Branch age (year)	光照强度 Light intensity (mol·m^-2·d^-1)	土壤含水量 Soil water content (g·g^-1)	土壤氮含量 Soil nitrogen content (mg·g^-1)	土壤磷含量 Soil phosphorus content (mg·g^-1)	截距 Intercept
木质密度 WD (g·cm^-3)	0.007^**		0.009^***	0.003	0.003	-0.001	-0.001	0.393^***
枝氮含量 WN (mg·g^-1)		1.732^***	-0.373	0.121	-0.062	0.302	-0.224	8.881^***
木质部面积占比 R_XA	-0.006		0.090^***	-0.009	0.005	0.020^**	-0.019^*	0.310^***
韧皮部面积占比 R_PHA	0.006^***		0.007^***	-0.005^**	0.005^*	-0.001	-0.003	0.087^***
髓面积占比 R_PA	-0.003^***		-0.008^***	>0.001	>0.001	-0.001	>0.001	0.033^***
树脂道总面积占比 R_RC		0.011^***	-0.008^***	0.002	>0.003	-0.003	-0.001	0.067^***

Fig. 3 Variations of branch traits of different plant sizes (DBH or tree height) with branch age for Pinus koraiensis. DBH, diameter at breast height; RPA, pith area-to-total cross-sectional area ratio; RPHA, phloem area-to-total cross-sectional area ratio; RRC, total resin canal area-to-total cross-sectional area ratio; RXA, xylem area-to-total cross-sectional area ratio; WD, wood density; WN, wood nitrogen content. *, p > 0.05; **, p > 0.01; ***, p > 0.001.

Fig. 4 Variation trend of the slope of branch traits against branch age with different plant sizes (DBH or tree height) for Pinus koraiensis. DBH, diameter at breast height; RPA, pith area-to-total cross-sectional area ratio; RPHA, phloem area-to-total cross-sectional area ratio; RRC, total resin canal area-to-total cross-sectional area ratio; RXA, xylem area-to-total cross-sectional area ratio; WD, wood density. *, p > 0.05; **, p > 0.01.

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