Effects of stand spatial structure on above-ground biomass of Eucalyptus grandis×urophylla plantations

doi:10.13466/j.cnki.lczyyj.2025.06.009

Abstract

Abstract:

This study elucidates the mechanisms through which stand spatial structure influences above-ground biomass(AGB)in Eucalyptus grandis×urophylla plantations,providing a theoretical basis for optimizing stand spatial structure and enhancing carbon sequestration capacity.Using Eucalyptus grandis×urophylla plantations aged from 2 to 7 years in Guangxi’s Huangmian State-owned Forest Farm.Stand spatial structure was characterized using the uniform angle index,size ratio,opening degree,and competition index.Backward stepwise regression and grey relational analysis were employed to identify key spatial structure factors influencing AGB accumulation across distinct growth stages.The regression model exhibited high explanatory power(R²=0.928).Size ratio,opening degree,and competition index showed significant negative correlations with AGB(P<0.05).Opening degree demonstrated the strongest inhibitory effect on AGB,evidenced by the largest absolute regression coefficient(-1480.402).Grey relational analysis further revealed dynamic age-dependent relationships between spatial structure factors and AGB changes.Early growth stages(2 to 3 years),uniform angle and size ratio exerted dominant influences on AGB.Pre-maturation stages,competition index emerged as the primary limiting factor.Opening degree maintained consistently high relevance across all stages,though its association with AGB exhibited non-monotonic fluctuations with stand age.To optimize resource utilization and AGB accumulation,optimize tree size hierarchy(size ratio)and spatial distribution(uniform angle)at early growth stages(2 to 3 years),implement thinning to alleviate competition pressure(competition index)at near-maturity stages(4 to 7 years),and sustain appropriate canopy openness(opening degree)throughout the rotation cycle.These stratified interventions provide a scientific basis for precision forestry aimed at carbon sequestration enhancement.

Key words: stand spatial structure, above-ground biomass(AGB), Eucalyptus grandis×urophylla plantations

CLC Number:

S792.39

ZHAO Xingkui, HUANG Jinjun, HE Wen, YAO Yuefeng. Effects of stand spatial structure on above-ground biomass of Eucalyptus grandis×urophylla plantations[J]. Forest and Grassland Resources Research, 2025, (6): 91-99.

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龄组	林龄/ a	样地数/个	树高/m	胸径/cm	地上生物量/kg
幼龄林	2	3	9.32±0.08a	7.48±0.06a	813.00a
中龄林	3	3	10.89±0.08a	8.35±0.11a	1 162.20a
近熟林	4	3	16.00±0.10b	12.77±0.12b	3 070.20b
成熟林	5~6	3	18.05±0.19c	13.54±0.19c	4 299.50c
过熟林	7	3	19.09±0.24c	14.52±0.21c	5 208.40c

龄组	大小比数	角尺度	开敞度	竞争指数
幼龄林	0.518±0.006a	0.411±0.051a	0.296±0.019a	1.552±0.059a
中龄林	0.496±0.017a	0.487±0.031a	0.218±0.023b	4.765±0.759b
近熟林	0.509±0.013a	0.423±0.028a	0.187±0.003bc	1.432±0.023a
成熟林	0.494±0.011a	0.452±0.018a	0.161±0.006bc	2.197±0.224a
过熟林	0.501±0.005a	0.437±0.025a	0.150±0.004c	1.784±0.272a

变量	系数	标准误差	t	P	VIF	R²	F
大小比数	-345.200	130.673	-2.642	<0.05	1.057
开敞度	-1 480.402	130.674	-11.329	<0.01	1.057	0.928	60.532
竞争指数	-718.190	127.338	-5.640	<0.01	1.004