Litter removal effects on dynamics of soil humic substances in subalpine forests of western Sichuan, China

doi:10.17521/cjpe.2021.0166

Abstract

Abstract:

Aims Forest litter are the main sources of soil humic substances, and different litter types can have differential effects on the formation and composition of soil humic substances. The aim of this study was to determine how variations in litter input would affect the dynamics of soil humic substances in subalpine forests of western Sichuan.
Methods A field in-situ litter manipulation experiment incorporating litter removal was established on sites of coniferous, broad-leaved, and mixed coniferous and broad-leaved forest stands. Measurements were made on the contents of soil extractable humic substances, humic acid, and fulvic acid; ratios of humic acid to fulvic acid and humic acid to humic substances were also computed.
Important findings The contents of extractable humic substances, humic acid and fulvic acid of soils varied significantly among forest types. The extractable humic substances content followed a descending order of coniferous forest > mixed coniferous and broad-leaved forest > broad-leaved forest, and the humic acid content of mixed coniferous and broad-leaved forest > coniferous forest > broad-leaved forest, and the fulvic acid content of coniferous forest > broad-leaved forest > mixed coniferous and broad-leaved forest. Fulvic acid was the predominant fraction of soil humic substances in all the three forest types. Time of measurements also significantly affected the contents of extractable humic substances, humic acid and fulvic acid, with an increasing trend for up to 1.5-year followed by decreases thereafter. With few exceptions, litter removal generally reduced the contents of extractable humic substances, humic acid and fulvic acid. The ratios of humic acid/fulvic acid and humic acid/extractable humic substances indicate low degree of humification for all the three forest types, which followed a descending order of mixed coniferous and broad-leaved forest > broad-leaved forest > coniferous forest. Litter removal improved the humic substances quality in the broad-leaved and mixed coniferous and broad-leaved forests to some extent. Correlation analysis showed significantly positive correlations of soil extractable humic substances with soil organic carbon, total nitrogen and soil water content, and a significantly negative correlation with temperature. In summary, short-term litter removal reduced the soil humic substances content, with differential effects by different litter types. We draw conclusion that the dynamics of soil humic substances are comprehensively regulated by litter type and environmental factors. Therefore, the impact of litter changes on soil humic substances needs further long-term research.

Key words: humic substances, humic acid, fulvic acid, litter, subalpine forest

LIU Yao, JIAO Ze-Bin, TAN Bo, LI Han, WANG Li-Xia, LIU Si-Ning, YOU Cheng-Ming, XU Zhen-Feng, ZHANG Li. Litter removal effects on dynamics of soil humic substances in subalpine forests of western Sichuan, China[J]. Chin J Plant Ecol, 2022, 46(3): 330-339.

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URL: https://www.plant-ecology.com/EN/10.17521/cjpe.2021.0166

https://www.plant-ecology.com/EN/Y2022/V46/I3/330

Figures/Tables 7

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森林类型 Forest type	海拔 Altitude (m)	优势乔木 Dominant tree	主要林下植物 Major understory species
针叶林 Coniferous forest	3 000	岷江冷杉 Abies fargesii var. faxoniana	茜草 Rubia cordifolia 高山冷蕨 Cystopteris montana 高山杜鹃 Rhododendron lapponicum
针阔混交林 Mixed coniferous and broad-leaved forest	2 985	岷江冷杉 Abies fargesii var. faxoniana 红桦 Betula albosinensis	高山杜鹃 Rhododendron lapponicum 箭竹 Fargesia spathacea 高山冷蕨 Cystopteris montana
阔叶林 Broad-leaved forest	3 010	红桦 Betula albosinensis	箭竹 Fargesia spathacea 蟹甲草 Parasenecio forrestii 高山冷蕨 Cystopteris montana

森林类型 Forest type	海拔 Altitude (m)	优势乔木 Dominant tree	主要林下植物 Major understory species
针叶林 Coniferous forest	3 000	岷江冷杉 Abies fargesii var. faxoniana	茜草 Rubia cordifolia 高山冷蕨 Cystopteris montana 高山杜鹃 Rhododendron lapponicum
针阔混交林 Mixed coniferous and broad-leaved forest	2 985	岷江冷杉 Abies fargesii var. faxoniana 红桦 Betula albosinensis	高山杜鹃 Rhododendron lapponicum 箭竹 Fargesia spathacea 高山冷蕨 Cystopteris montana
阔叶林 Broad-leaved forest	3 010	红桦 Betula albosinensis	箭竹 Fargesia spathacea 蟹甲草 Parasenecio forrestii 高山冷蕨 Cystopteris montana

时间 Time (a)	指标 Index	土壤含水量 Soil water content (%)	温度 Temperature (°C)	pH	有机碳含量 Organic carbon content (g·kg^-1)	全氮含量 Total nitrogen content (g·kg^-1)	全磷含量 Total phosphorus content (g·kg^-1)
1	BFI	54.94 ± 3.41^a	10.56 ± 0.05^a	5.82 ± 0.14^a	161.70 ± 25.4^a	0.25 ± 0.08^a	0.89 ± 0.07^a
	MFI	41.75 ± 9.09^a	10.41 ± 0.30^a	5.08 ± 0.11^b	121.83 ± 21.55^a	0.17 ± 0.07^a	0.87 ± 0.05^a
	CFI	55.61 ± 2.35^a	10.15 ± 0.06^a	4.76 ± 0.07^b	171.80 ± 20.08^a	0.28 ± 0.03^a	0.83 ± 0.05^a
	BFR	45.86 ± 7.70^a	10.45 ± 0.04^a	5.48 ± 0.06^a	96.46 ± 43.51^a	0.21 ± 0.06^a	0.86 ± 0.10^a
	MFR	53.82 ± 7.35^a	10.14 ± 0.15^a	5.50 ± 0.09^a	192.46 ± 44.59^a	0.30 ± 0.13^a	0.76 ± 0.06^a
	CFR	54.96 ± 1.50^a	9.75 ± 0.06^a	5.10 ± 0.25^a	166.63 ± 12.94^a	0.27 ± 0.06^a	0.78 ± 0.04^a
1.5	BFI	57.57 ± 2.10^a	5.00 ± 0.14^a	6.22 ± 0.14^a	186.73 ± 12.12^b	13.10 ± 1.59^a	0.76 ± 0.14^a
	MFI	57.59 ± 7.96^a	4.75 ± 0.11^a	5.37 ± 0.25^a	240.58 ± 18.48^a	11.36 ± 3.33^a	0.79 ± 0.05^a
	CFI	50.79 ± 1.88^a	4.65 ± 0.07^a	5.68 ± 0.45^a	211.02 ± 6.00^ab	11.10 ± 2.62^a	0.63 ± 0.13^a
	BFR	50.32 ± 3.02^a	4.70 ± 0.06^a	5.97 ± 0.35^a	116.24 ± 20.35^a	10.36 ± 0.84^a	0.74 ± 0.10^a
	MFR	53.32 ± 5.71^a	4.65 ± 0.07^a	5.54 ± 0.27^a	177.99 ± 51.16^a	10.37 ± 3.13^a	0.83 ± 0.08^a
	CFR	52.90 ± 4.42^a	4.56 ± 0.25^a	5.69 ± 0.24^a	228.29 ± 16.32^a	14.07 ± 1.11^a	0.71 ± 0.08^a
2	BFI	53.40 ± 8.82^a	10.24 ± 0.21^a	5.86 ± 0.21^a	121.61 ± 41.60^a	8.18 ± 2.54^a	0.47 ± 0.11^a
	MFI	58.46 ± 5.45^a	9.13 ± 0.05^a	5.81 ± 0.05^a	156.81 ± 31.94^a	7.75 ± 1.55^a	0.41 ± 0.06^a
	CFI	46.65 ± 3.35^a	9.09 ± 0.05^a	5.79 ± 0.05^a	99.19 ± 5.10^a	2.60 ± 1.19^a	0.22 ± 0.04^a
	BFR	46.29 ± 3.96^a	9.86 ± 0.05^a	5.74 ± 0.05^a	84.60 ± 18.86^a	3.29 ± 1.09^ab	0.44 ± 0.05^a
	MFR	48.75 ± 6.25^a	8.90 ± 0.12^a	5.91 ± 0.12^a	102.31 ± 21.54^a	5.25 ± 0.71^a	0.36 ± 0.04^ab
	CFR	43.88 ± 0.75^a	9.10 ± 0.14^a	5.62 ± 0.14^a	106.16 ± 10.74^a	0.82 ± 0.13^b	0.26 ± 0.02^b

时间 Time (a)	指标 Index	土壤含水量 Soil water content (%)	温度 Temperature (°C)	pH	有机碳含量 Organic carbon content (g·kg^-1)	全氮含量 Total nitrogen content (g·kg^-1)	全磷含量 Total phosphorus content (g·kg^-1)
1	BFI	54.94 ± 3.41^a	10.56 ± 0.05^a	5.82 ± 0.14^a	161.70 ± 25.4^a	0.25 ± 0.08^a	0.89 ± 0.07^a
	MFI	41.75 ± 9.09^a	10.41 ± 0.30^a	5.08 ± 0.11^b	121.83 ± 21.55^a	0.17 ± 0.07^a	0.87 ± 0.05^a
	CFI	55.61 ± 2.35^a	10.15 ± 0.06^a	4.76 ± 0.07^b	171.80 ± 20.08^a	0.28 ± 0.03^a	0.83 ± 0.05^a
	BFR	45.86 ± 7.70^a	10.45 ± 0.04^a	5.48 ± 0.06^a	96.46 ± 43.51^a	0.21 ± 0.06^a	0.86 ± 0.10^a
	MFR	53.82 ± 7.35^a	10.14 ± 0.15^a	5.50 ± 0.09^a	192.46 ± 44.59^a	0.30 ± 0.13^a	0.76 ± 0.06^a
	CFR	54.96 ± 1.50^a	9.75 ± 0.06^a	5.10 ± 0.25^a	166.63 ± 12.94^a	0.27 ± 0.06^a	0.78 ± 0.04^a
1.5	BFI	57.57 ± 2.10^a	5.00 ± 0.14^a	6.22 ± 0.14^a	186.73 ± 12.12^b	13.10 ± 1.59^a	0.76 ± 0.14^a
	MFI	57.59 ± 7.96^a	4.75 ± 0.11^a	5.37 ± 0.25^a	240.58 ± 18.48^a	11.36 ± 3.33^a	0.79 ± 0.05^a
	CFI	50.79 ± 1.88^a	4.65 ± 0.07^a	5.68 ± 0.45^a	211.02 ± 6.00^ab	11.10 ± 2.62^a	0.63 ± 0.13^a
	BFR	50.32 ± 3.02^a	4.70 ± 0.06^a	5.97 ± 0.35^a	116.24 ± 20.35^a	10.36 ± 0.84^a	0.74 ± 0.10^a
	MFR	53.32 ± 5.71^a	4.65 ± 0.07^a	5.54 ± 0.27^a	177.99 ± 51.16^a	10.37 ± 3.13^a	0.83 ± 0.08^a
	CFR	52.90 ± 4.42^a	4.56 ± 0.25^a	5.69 ± 0.24^a	228.29 ± 16.32^a	14.07 ± 1.11^a	0.71 ± 0.08^a
2	BFI	53.40 ± 8.82^a	10.24 ± 0.21^a	5.86 ± 0.21^a	121.61 ± 41.60^a	8.18 ± 2.54^a	0.47 ± 0.11^a
	MFI	58.46 ± 5.45^a	9.13 ± 0.05^a	5.81 ± 0.05^a	156.81 ± 31.94^a	7.75 ± 1.55^a	0.41 ± 0.06^a
	CFI	46.65 ± 3.35^a	9.09 ± 0.05^a	5.79 ± 0.05^a	99.19 ± 5.10^a	2.60 ± 1.19^a	0.22 ± 0.04^a
	BFR	46.29 ± 3.96^a	9.86 ± 0.05^a	5.74 ± 0.05^a	84.60 ± 18.86^a	3.29 ± 1.09^ab	0.44 ± 0.05^a
	MFR	48.75 ± 6.25^a	8.90 ± 0.12^a	5.91 ± 0.12^a	102.31 ± 21.54^a	5.25 ± 0.71^a	0.36 ± 0.04^ab
	CFR	43.88 ± 0.75^a	9.10 ± 0.14^a	5.62 ± 0.14^a	106.16 ± 10.74^a	0.82 ± 0.13^b	0.26 ± 0.02^b

因子 Factor	可提取腐殖质 EHS	胡敏酸 HA	富里酸 FA	胡敏酸/富里酸 HA/FA	胡敏酸/可提取腐殖质 PQ
凋落物 Litter	11.571^**	0.827	5.659^*	2.745	0.098
培养时间 Time	73.835^**	28.137^**	38.713^**	10.653^**	4.263^*
林型 Type	10.808^**	31.479^**	15.783^**	5.963^**	19.403^**
凋落物×时间 Litter × Time	15.654^**	19.443^**	8.544^**	2.142	2.054
凋落物×林型 Litter × Type	3.328	9.650^**	3.853^*	5.657^*	10.340^**
时间×林型 Time × Type	8.584^**	8.011^**	12.489^**	5.838^**	7.266^**
凋落物×时间×林型 Litter × Time × Type	1.111	5.777^**	4.080^**	4.936^**	8.496^**