Response characteristics of phenolic compounds in plant leaves and roots along an alpine shrub encroachment gradient

doi:10.17521/cjpe.2025.0182

Abstract

Abstract:

Aims With the intensification of climate change, shrub expansion or encroachment in high-altitudes and high-latitude has become increasingly significant. However, the patterns and driving mechanisms of changes in plant defensive chemicals such as total phenols and condensed tannins during such shrub expansion processes in alpine regions remain poorly understood.

Methods Taking the alpine shrub-meadow transition zone or ecotone in western Sichuan on the eastern Qingzang Plateau as the study area, sample plots were established along a shrub expansion gradient including control (0% coverage), light expansion (<30% coverage), light-moderate expansion (30%-45% coverage), moderate-heavy expansion (45%-60% coverage), and heavy expansion (>60% coverage). The impact of shrub expansion on the content of plant defensive chemical compounds and their relationships with environmental factors such as altitude, soil pH, and moisture content was analyzed by a space-for-time substitution approach.

Important findings The results showed that: (1) Shrub expansion significantly increased the density, height, volume, and weighted density of shrubs in the alpine shrub-meadow transition zone of western Sichuan; (2) Compared to herbaceous plants and Sorbus rufopilosa, Rhododendron lapponicum exhibited higher levels of phenolic compounds during the shrub expansion process; (3) Changes in species composition at the community level had a significantly greater impact on the variation in plant phenolic compounds than intraspecific variation resulting from phenotypic plasticity among individuals; (4) Concentrations of phenolic compounds in both plant leaves and roots showed significant correlations with their carbon to nitrogen ratios, while soil factors had a relatively minimal effect, supporting the Carbon-nutrient Balance Hypothesis. This study sheds light on the positive impact of shrub expansion on plant defense compounds and provides critically theoretical underpinnings for ecosystem management and plant conservation in the context of global change.

Key words: shrub encroachment, phenolic compounds, intraspecific trait variation, carbon to nitrogen ratio, Carbon-nutrient Balance Hypothesis

SONG Si-Yu, DU Piao, LIN Qin, QI Xiang, DU Ke-Yu, LI Cong, CHEN Ya-Mei, HUANG You-You, LIU Yang. Response characteristics of phenolic compounds in plant leaves and roots along an alpine shrub encroachment gradient[J]. Chin J Plant Ecol, 2025, 49(12): 2119-2136.

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Figures/Tables 9

References 87

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灌木扩张水平 Shrub encroachment level	冠幅 Crown width (m²)	盖度 Coverage (%)	高度 Height (m)	灌丛数量 Number of shrubs	灌丛体积 Shrub volume (m³)	灌丛加权密度 Weighted shrub density	海拔 Altitude (m)
对照(高山草甸) CK (alpine meadow)	0.00 (0.00)^e	0.00 (0.00)^e	0.00 (0.00)^c	0.00 (0.00)^c	0.00 (0.00)^e	0.00 (0.00)^c	4 200.00 (0.00)^a
轻度扩张 SE-I	106.31 (6.85)^d	26.58 (1.71)^d	1.44 (0.15)^b	49.80 (6.59)^b	77.14 (10.29)^d	653.33 (79.74)^b	4 110.00 (18.71)^b
轻中度扩张 SE-II	153.35 (7.45)^c	38.34 (1.86)^c	1.88 (0.19)^ab	59.80 (5.64)^b	130.51 (12.35)^c	815.21 (67.40)^b	4 090.00 (18.71)^b
中重度扩张 SE-III	212.50 (10.93)^b	53.12 (2.73)^b	1.68 (0.13)^ab	72.00 (12.02)^ab	175.71 (16.99)^b	978.73 (158.74)^ab	4 080.00 (33.91)^b
重度扩张 SE-IV	280.47 (17.70)^a	70.12 (4.43)^a	1.97 (0.19)^a	92.40 (14.92)^a	281.87 (20.22)^a	1 288.15 (197.77)^a	4 020.00 (12.25)^c
F	105.88	105.87	29.18	13.46	58.58	15.26	10.63
p	<0.001	<0.001	<0.001	<0.001	<0.001	<0.001	<0.001

灌木扩张水平 Shrub encroachment level	冠幅 Crown width (m²)	盖度 Coverage (%)	高度 Height (m)	灌丛数量 Number of shrubs	灌丛体积 Shrub volume (m³)	灌丛加权密度 Weighted shrub density	海拔 Altitude (m)
对照(高山草甸) CK (alpine meadow)	0.00 (0.00)^e	0.00 (0.00)^e	0.00 (0.00)^c	0.00 (0.00)^c	0.00 (0.00)^e	0.00 (0.00)^c	4 200.00 (0.00)^a
轻度扩张 SE-I	106.31 (6.85)^d	26.58 (1.71)^d	1.44 (0.15)^b	49.80 (6.59)^b	77.14 (10.29)^d	653.33 (79.74)^b	4 110.00 (18.71)^b
轻中度扩张 SE-II	153.35 (7.45)^c	38.34 (1.86)^c	1.88 (0.19)^ab	59.80 (5.64)^b	130.51 (12.35)^c	815.21 (67.40)^b	4 090.00 (18.71)^b
中重度扩张 SE-III	212.50 (10.93)^b	53.12 (2.73)^b	1.68 (0.13)^ab	72.00 (12.02)^ab	175.71 (16.99)^b	978.73 (158.74)^ab	4 080.00 (33.91)^b
重度扩张 SE-IV	280.47 (17.70)^a	70.12 (4.43)^a	1.97 (0.19)^a	92.40 (14.92)^a	281.87 (20.22)^a	1 288.15 (197.77)^a	4 020.00 (12.25)^c
F	105.88	105.87	29.18	13.46	58.58	15.26	10.63
p	<0.001	<0.001	<0.001	<0.001	<0.001	<0.001	<0.001

灌木 Shrub	对照 CK	轻度扩张 SE-I	轻中度扩张 SE-II	中重度扩张 SE-III	重度扩张 SE-IV
高山杜鹃 Rhododendron lapponicum	-	11.16 ± 2.53^Aa	11.66 ± 4.04^Aa	21.04 ± 7.86^Aa	6.00 ± 1.88^BCa
红毛花楸 Sorbus rufopilosa	-	7.70 ± 1.78^Ab	13.01 ± 3.83^Ab	22.30 ± 8.21^Ab	41.19 ± 3.41^Aa
金露梅 Dasiphora fruticosa	-	2.95 ± 0.62^Bab	3.76 ± 1.41^Bab	0.79 ± 0.37^Bb	5.73 ± 1.55^BCa
软条七蔷薇 Rosa henryi	-	2.32 ± 0.84^Bb	4.45 ± 1.22^Bb	2.55 ± 0.94^Bb	8.51 ± 2.06^Ba
绣线菊 Spiraea salicifolia	-	0.23 ± 0.21^Ba	0.18 ± 0.18^Ba	0.40 ± 0.37^Ba	1.37 ± 1.00^Ca
高山柳 Salix takasagoalpina	-	0.97 ± 0.36^Ba	2.65 ± 1.48^Ba	3.52 ± 1.68^Ba	2.94 ± 1.30^BCa
华西小檗 Berberis silva-taroucana	-	0.03 ± 0.03^Ba	0.51 ± 0.19^Ba	0.58 ± 0.28^Ba	0.11 ± 0.08^Ca
F	-	11.56	5.05	5.13	58.56
p	-	<0.001	<0.01	<0.01	<0.001

灌木 Shrub	对照 CK	轻度扩张 SE-I	轻中度扩张 SE-II	中重度扩张 SE-III	重度扩张 SE-IV
高山杜鹃 Rhododendron lapponicum	-	11.16 ± 2.53^Aa	11.66 ± 4.04^Aa	21.04 ± 7.86^Aa	6.00 ± 1.88^BCa
红毛花楸 Sorbus rufopilosa	-	7.70 ± 1.78^Ab	13.01 ± 3.83^Ab	22.30 ± 8.21^Ab	41.19 ± 3.41^Aa
金露梅 Dasiphora fruticosa	-	2.95 ± 0.62^Bab	3.76 ± 1.41^Bab	0.79 ± 0.37^Bb	5.73 ± 1.55^BCa
软条七蔷薇 Rosa henryi	-	2.32 ± 0.84^Bb	4.45 ± 1.22^Bb	2.55 ± 0.94^Bb	8.51 ± 2.06^Ba
绣线菊 Spiraea salicifolia	-	0.23 ± 0.21^Ba	0.18 ± 0.18^Ba	0.40 ± 0.37^Ba	1.37 ± 1.00^Ca
高山柳 Salix takasagoalpina	-	0.97 ± 0.36^Ba	2.65 ± 1.48^Ba	3.52 ± 1.68^Ba	2.94 ± 1.30^BCa
华西小檗 Berberis silva-taroucana	-	0.03 ± 0.03^Ba	0.51 ± 0.19^Ba	0.58 ± 0.28^Ba	0.11 ± 0.08^Ca
F	-	11.56	5.05	5.13	58.56
p	-	<0.001	<0.01	<0.01	<0.001

变异来源 Source of variation	总酚 Total phenolic	缩合单宁 Condensed tannin	碳 Carbon	氮 Nitrogen	碳氮比 Carbon:nitrogen	总酚RII Total phenolic RII	缩合单宁RII Condensed tannin RII
灌木扩张水平 SE	1.98^ns	2.18^ns	0.94^ns	1.24^ns	1.16^ns	0.30^ns	2.03^ns
植物类群 Plant group	136.32^***	117.79^***	2.99^ns	29.10^***	72.88^***	1.66^ns	2.87^ns
器官类型 Organ	404.94^***	112.01^***	69.67^***	127.36^***	83.50^***	-	-
灌木扩张水平×植物类群 SE × Plant group	1.17^ns	2.25^*	1.10^ns	1.02^ns	1.03^ns	-	-
灌木扩张水平×器官类型 SE × Organ	1.39^ns	0.84^ns	0.33^ns	1.66^ns	0.22^ns	0.42^ns	0.14^ns
植物类群×器官类型 Plant group × Organ	76.90^***	63.33^***	0.21^ns	9.36^***	4.04^*	-	-
灌木扩张水平×植物类群×器官类型 SE × Plant group × Organ	0.72^ns	1.73^ns	0.77^ns	1.24^ns	1.29^ns	-	-