Plant functional traits and carbon-nitrogen stoichiometry of plantations at different forest ages in North China

doi:10.17521/cjpe.2025.0183

Abstract

Abstract:

Aims Clarify the variation patterns and corresponding response mechanisms of plant functional traits and carbon-nitrogen stoichiometry in artificial plantations of different tree species under the age gradient.

Methods In this study, Populus tomentosa, Platycladus orientalis and Styphnolobium japonicum at different ages were selected as the research objects to determine and explore the changes and relationships of different organ functional traits, carbon-nitrogen stoichiometry and soil physicochemical properties.

Important findings (1) With the increase of forest age, the content of soil nutrients, clay and silt of different tree plantations increased significantly. While soil total phosphorus content of Populus tomentosa plantations, and soil pH value of Platycladus orientalis plantations decreased. (2) The specific leaf area of different tree species increased significantly with the increase of forest age, while the specific leaf mass decreased significantly. The root carbon content (average 36.25%) was lower than that of branches (45.52%) and leaves (44.83%), and the leaf nitrogen content (1.98%) was higher than that of roots (1.30%) and branches (0.64%). With the increase of forest age, the nutrient content and carbon-nitrogen ratio of different organs varied with tree species. (3) The functional traits of Populus tomentosa plantations of different organs were coordinated, while the functional traits of leaves and roots of Platycladus orientalisplantations evolved independently, forming a decoupling strategy. (4) The increase of soil water content and the improvement of soil texture are important reasons for the changes in plant traits. (5) The soil total nitrogen content was significantly negatively correlated with the carbon content in leaves and roots. Redundancy analysis showed that soil electrical conductivity significantly affected plant functional traits. (6) Random forest analysis showed that the significant factors affecting the carbon-nitrogen ratio of leaves, branches and roots included soil total phosphorus and clay contents, specific leaf area, leaf dry matter mass and plant nutrient content. The research results reveal the differences in plant functional traits and organ carbon and nitrogen distribution among different tree species under the forest age gradient, enriching the theoretical framework of the plant economic spectrum.

Key words: forest age, functional trait, plant economic spectrum, carbon to nitrogen ratio

CHEN Ya-Xuan, HAN Yu-Yin, CHEN Yan-Mei, LIU Qian-Yuan. Plant functional traits and carbon-nitrogen stoichiometry of plantations at different forest ages in North China[J]. Chin J Plant Ecol, 2026, 50(2): 318-333.

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URL: https://www.plant-ecology.com/EN/10.17521/cjpe.2025.0183

https://www.plant-ecology.com/EN/Y2026/V50/I2/318

Figures/Tables 9

Table 1 Basic information of the artificial plantations sample plots of each tree species

树种 Species	林龄 Forest age (a)	简称 Abbreviation	经纬度 Longitude and latitude	海拔 Altitude (m)	郁闭度 Canopy density (%)	平均胸径 Average diameter at breast height (cm)	平均树高 Average height (m)
毛白杨 Populus tomentosa	10	XY	37.49° N, 114.38° E	169	15	6.5	4.6
	16	ZY	37.48° N, 114.38° E	174	20	10.5	7.2
	30	LY	37.50° N, 114.39° E	157	25	22.3	13.4
侧柏 Platycladus orientalis	12	XB	37.49° N, 114.39° E	165	10	2.4	2.5
	19	ZB	37.50° N, 114.39° E	185	60	6.8	5.5
	36	LB	37.52° N, 114.39° E	246	80	18.1	7.2
国槐 Styphnolobium japonicum	9	XH	37.45° N, 114.41° E	99	10	4.0	3.7
	13	ZH	37.45° N, 114.41° E	47	40	10.1	9.5
	16	LH	37.51° N, 114.39° E	199	65	12.5	7.1

Table 2 Attributes of plant functional traits

功能性状 Functional trait	缩写 Abbreviation	单位 Unit	计算公式 Calculation formula
叶片含水量 Leaf water content	LWC	%	LWC = (LFM-LDM)/LFM
比叶面积 Specific leaf area	SLA	cm²∙g^-1	SLA = LA/LDM
比叶质量 Leaf mass per area	LMA	g∙cm^-2	LMA = LDM/LA
叶干物质含量 Leaf dry matter content	LDMC	g∙g^-1	LDMC = LDM/LFM
叶片氮含量 Leaf nitrogen content	LNC	%
叶片碳含量 Leaf carbon content	LCC	%
叶片碳氮比 Leaf carbon to nitrogen ratio	L_C:N		L_C:N =LCC/LNC
枝条氮含量 Branch nitrogen content	BNC	%
枝条碳含量 Branch carbon content	BCC	%
枝条碳氮比 Branch carbon to nitrogen ratio	B_C:N		B_C:N =BCC/BNC
根系生物量 Root biomass	RB	kg∙m^-3	RB = RDM/SV
根平均直径 Root average diameter	RD	mm
根长密度 Root length density	RLD	km∙m^-3	RLD = RL/SV
根表面积密度 Root surface area density	RAD	m²∙m^-3	RAD = RA/SV
比根长 Specific root length	SRL	m∙g^-1	SRL = RL/RDM
根比表面积 Specific root area	SRA	m²∙g^-1	SRA = RA/RDM
根组织密度 Root tissue density	RTD	g∙cm^-3	RTD = RDM/RV
根氮含量 Root nitrogen content	RNC	%
根碳含量 Root carbon content	RCC	%
根碳氮比 Root carbon to nitrogen content	R_C:N		R_C:N = RCC/RNC

Table 4 Changes in soil physicochemical properties at different forest ages in north China

Fig. 1 Changes in functional traits of plantations at different forest ages in north China. Different lowercase letters indicate the significant differences of the same species at different forest ages (p < 0.05).

Fig. 2 Changes in carbon (C), nitrogen (N) content and stoichiometry of plantations at different ages. Different lowercase letters indicate the significant differences of the same species at different forest ages (p < 0.05).

Fig. 3 Principal component (PC) analysis of leaf traits (A) and root traits (B). PO, Platycladus orientalis plantations; PT, Populus tomentosa plantations; SJ, Styphnolobium japonicum plantations. Abbreviations of plant functional traits are shown in Table 2. ***, p < 0.001.

Fig. 4 Correlations among soil physicochemical properties, plant functional traits, and stoichiometry. C:N, soil carbon to nitrogen ratio; C:P, soil carbon to phosphorus ratio; Clay, soil clay content; EC, soil electrical conductivity; N:P, soil nitrogen to phosphorus ratio; pH, soil pH; Sand, soil sand content; Silt, soil silt content; TN, soil total nitrogen content; TOC, soil total organic carbon content; TP, soil total phosphorus content; WC, soil water content. Abbreviations of plant functional traits are shown in Table 2. *, p < 0.05; **, p < 0.01; ***, p < 0.001.

Fig. 5 Redundancy analysis (A) and explanation rate (B) of leaf and root functional traits, and soil physical and chemical properties. C:N, soil carbon to nitrogen ratio; C:P, soil carbon to phosphorus ratio; Clay, soil clay content; EC, soil electrical conductivity; N:P, soil nitrogen to phosphorus ratio; pH, soil pH; Sand, soil sand content; Silt, soil silt content; TN, soil total nitrogen content; TOC, soil total organic carbon content; TP, soil total phosphorus content; WC, soil water content. Abbreviations of plant functional traits are shown in Table 2. ***, p < 0.001.

Fig. 6 Relative importance of indicators affecting carbon to nitrogen ratio of leaves (A), branches (B), and roots (C). C:N, soil carbon to nitrogen ratio; C:P, soil carbon to phosphorus ratio; Clay, soil clay content; EC, soil electrical conductivity; N:P, soil nitrogen to phosphorus ratio; pH, soil pH; Sand, soil sand content; Silt, soil silt content; TN, soil total nitrogen content; TOC, soil total organic carbon content; TP, soil total phosphorus content; WC, soil water content. Abbreviations of plant functional traits are shown in Table 2. Var, variance; X.IncMSE, Variable x’s increase in mean squared error. *, p < 0.05; **, p < 0.01.

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