Effects of Phragmites australis and Spartina alterniflora litter decomposition on soil organic carbon at different tidal flat elevations

doi:10.3969/j.issn.1000-5641.2026.03.006

Abstract

Abstract:

In this study, we examined the synergistic effects of tidal inundation and vegetation type on litter decomposition and soil carbon dynamics in coastal wetlands, quantifying their influence on organic carbon (OC) fractions and providing a scientific foundation for enhancing wetland carbon sequestration. Specifically, we assessed how the co-effects of hydrological conditions and plant, species contribute to promoting the cycling of carbon. The study was conducted in the Chongming Dongtan wetland area of the Yangtze Estuary, in which we performed a 1-year in situ litter decomposition experiment, using Phragmites australis and Spartina alterniflora, to compare two tidal flood environments, namely, high (HM) and low (LM) elevational marshland areas. The rates of plant decomposition were determined based on the litter bag method, and soil samples were analyzed for the contents of soil organic carbon (SOC), particulate organic carbon (POC), mineral-associated organic carbon (MAOC), microbial biomass carbon (MBC), and dissolved organic carbon (DOC), using density fractionation and fumigation extraction techniques. The results revealed higher rates of decomposition in HM than in LM, with S. alterniflora and P. australis being characterized by rates of 0.0032 d^–1 and 0.0021 d^–1 in HM, respectively, which were 16% and 15% higher than those in LM at 360 days. Whereas initially, the decomposition of P. australis was more rapid in LM (p<0.01), the rates in HM were more pronounced during the latter stages of measurement. In HM, we detected significant elevations in the stocks of soil POC, MAOC, and SOC, associated with the efficient conversion of POC and MBC to MAOC, whereas in LM, we observed a lower DOC-to-MBC conversion and limited accumulation of POC. In addition, the type of vegetation was found to have an influence on carbon dynamics, with the levels of P. australis SOC peaking earlier in HM due to efficient conversion, whereas during the latter stages of the experiment, the levels of S. alterniflora SOC surpassed those of P. australis. Comparatively, in LM, the type of plant had a minimal influence on the dynamics of carbon fractions. Collectively, our findings provide evidence that by shaping the soil environment, tidal inundation can have a pronounced regulatory effect on the rates of plant decomposition and soil carbon stocks, with the species of plant modulating the conversion of carbon fractions in response to differing hydrological conditions. Compared with the marshland at lower elevations, that at higher elevations was established to have a greater carbon sequestration potential. On the basis of these observations, we recommend that wetland management should integrate hydrological and vegetation factors to optimize carbon storage, and further research should focus on the microbial mechanisms underlying these processes.

Key words: wetland plants, tidal elevation gradients, litter decomposition, microbial biomass carbon, mineral-associated organic carbon, SOC partitioning

CLC Number:

Q948

Xinhan DONG, Zhongzheng YAN. Effects of Phragmites australis and Spartina alterniflora litter decomposition on soil organic carbon at different tidal flat elevations[J]. J* E* C* N* U* N* S*, 2026, 2026(3): 69-87.

Figures/Tables 11

Fig.1

Table 1

Table 2

Fig.2

Fig.3

Table 3

Temperature, moisture, salinity, pH, total nitrogen (TN), and the C/N ratio of soils adjacent to Spartina alterniflora (SA) and Phragmites australis (PA) litter and control soils in the high (HM) and low (LM) marshland sites during decomposition"

样本	温度/℃				水分/%
样本	90 d	180 d	270 d	360 d	90 d	180 d	270 d	360 d
HM-SA	29.1±1.0^Aa	7.9±0.5^Ab	12.4±0.6^Ac	20.7±0.3^Ad	48.9±2.6^Aa	57.6±6.5^Ab	56.4±5.9^Ab	51.5±2.1^Aa
LM-SA	27.9±0.3^Ba	9.4±0.4^Bb	11.8±0.5^Bc	21.9±0.1^Bd	49.7±3.3^Aa	65.3±9.2^Ab	61.8±6.5^Ab	52.1±4.1^Aa
HM-PA	28.6±0.8^Aa	8.4±0.3^Ab	11.8±0.6^Ac	20.8±0.5^Ad	48.3±1.6^Aa	48.7±9.3^Aa	55.8±8.2^Ab	44.8±6.9^Aa
LM-PA	27.7±0.4^Ba	9.3±0.6^Bb	11.9±1.6^Ac	22.2±0.3^Bd	49.9±4.9^Aa	60.8±9.1^Bb	55.1±6.4^Aab	52.0±2.3^Ba
HM-Control	30.5±0.7^Aa	8.5±0.1^Ab	11.4±1.1^Ac	20.6±0.3^Ad	44.8±6.1^Aa	55.8±2.1^Aa	47.3±12.1^Aa	44.2±6.6^Aa
LM-Control	28.5±0.2^Ba	9.8±0.3^Bb	11.1±0.7^Ac	22.3±0.1^Bd	37.5±2.5^Aa	52.2±20.5^Aab	61.0±1.5^Ab	49.4±1.3^Aab

样本	盐度/ppt				pH
样本	90 d	180 d	270 d	360 d	90 d	180 d	270 d	360 d
HM-SA	0.67±0.11^Aa	2.20±0.66^Ab	1.60±0.29^Ab	0.46±0.08^Ac	8.57±0.15^Aa	8.80±0.10^Ab	9.25±0.05^Ac	8.99±0.10^Ab
LM-SA	0.90±0.20^Ba	2.67±0.58^Ab	2.28±0.35^Bb	0.85±0.32^Ba	8.90±0.00^Ba	9.03±0.06^Ba	9.03±0.21^Aa	8.93±0.15^Aa
HM-PA	0.72±0.14^Aa	1.63±0.47^Ab	1.72±0.47^Ab	0.50±0.15^Ac	8.63±0.15^Aa	9.01±0.10^Ab	9.17±0.15^Ab	9.09±0.10^Ab
LM-PA	0.89±0.32^Aa	2.40±0.57^Bb	1.91±0.31^Ab	1.03±0.20^Ba	8.90±0.10^Aa	8.95±0.05^Aa	8.95±0.15^Aa	8.93±0.15^Aa
HM-Control	0.66±0.07^Aa	1.88±0.23^Ab	1.40±0.64^Ab	0.53±0.05^Aa	8.93±0.15^Aa	9.03±0.15^Aa	9.03±0.15^Aa	9.02±0.25^Aa
LM-Control	0.47±0.06^Ba	2.10±1.23^Ab	2.35±0.24^Ab	0.53±0.08^Aa	9.15±0.05^Aa	9.15±0.05^Aa	9.20±0.10^Aa	9.30±0.20^Aa

样本	TN/(g·kg^–1)				C/N
样本	90 d	180 d	270 d	360 d	90 d	180 d	270 d	360 d
HM-SA	0.42±0.11^Aa	0.30±0.05^Ab	0.47±0.12^Aa	0.29±0.05^Ab	5.77±0.98^Aa	11.68±3.09^Ab	8.30±0.87^Ac	9.94±1.01^Ac
LM-SA	0.49±0.18^Aa	0.39±0.06^Bab	0.32±0.16^Bbc	0.23±0.05^Bc	5.92±1.29^Aa	10.21±3.52^Ab	6.18±2.25^Ba	6.66±0.64^Ba
HM-PA	0.39±0.09^Aab	0.42±0.08^Aa	0.34±0.07^Ab	0.25±0.05^Ac	6.06±1.18^Aa	9.24±1.57^Ab	9.03±0.88^Ab	9.21±1.70^Ab
LM-PA	0.69±0.31^Ba	0.38±0.14^Ab	0.32±0.09^Ab	0.25±0.07^Ab	5.26±0.93^Aa	8.51±1.57^Ab	5.23±1.51^Ba	7.34±1.63^Bb
HM-Control	0.41±0.07^Aa	0.32±0.04^Aab	0.25±0.11^Ab	0.26±0.05^Ab	4.03±0.22^Aa	8.58±0.55^Ab	6.87±1.18^Abc	6.10±1.48^Ac
LM-Control	0.37±0.06^Aa	0.26±0.14^Aa	0.24±0.04^Aa	0.22±0.07^Aa	3.71±0.41^Aa	6.35±0.31^Bb	4.39±0.31^Bc	4.88±0.18^Ac

Table 3

Fig.4

Fig.5

Table 4

Table 5

Fig.6

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样地	温度/℃	水分/%	盐度/ppt	氧化还原电位/mV	黏土/%	粉砂/%	砂土/%
HM	22.4±1.0^A	44.5±8.6^A	1.7±0.6^A	72.7±171.2^A	4.1	70.5	25.4
LM	25.2±0.6^B	44.6±6.0^A	1.7±0.4^A	205.1±154.5^B	3.1	59.9	37.1

凋落物	TN/(g·kg^–1)	TC/(g·kg^–1)	C/N	半纤维素/%	纤维素/%	可溶性化合物/%	木质素/%
SA	6.1±0.8^A	419.3±1.2^A	69.2±9.4^A	13.7±0.1^A	35.7±0.1^A	43.7±0.1^A	6.9±0.1^A
PA	9.5±0.3^B	394.4±3.0^B	41.5±1.6^B	12.7±0.6^A	36.9±1.3^A	41.9±2.0^A	8.5±0.1^B

变量	效应	F	p-value
SOC	时间	9.388	0.0008
	高程	7.691	0.0136
	时间×高程	7.650	0.0022
DOC	时间	142.800	<0.0001
	高程	39.690	<0.0001
	时间×高程	22.850	<0.0001
	时间×植物类型	3.490	0.0404
MBC	时间	46.680	<0.0001
	高程	55.910	<0.0001
	植物类型	6.756	0.0194
	时间×高程	6.127	0.0056
	时间×植物类型	5.373	0.0094
	高程×植物类型	8.958	0.0086
	时间×高程×植物类型	5.330	0.0097
POC	时间	22.850	<0.0001
POC	时间×高程	3.978	0.0271
MAOC	时间	12.410	0.0002
	高程	54.120	<0.0001
	时间×高程	13.370	0.0001
	时间×高程×植物类型	4.660	0.0159
k	时间	31.58	<0.0001
k	植物类型	80.36	<0.0001
LR	时间	87.100	<0.0001
	高程	9.307	0.0076
	植物类型	145.500	<0.0001
	时间×高程	10.250	0.0005

凋落物k	温度	水分	盐度	pH	TN	C/N	SOC	DOC	MBC	POC	MAOC
SA-k	0.29*	−0.11	−0.05	−0.48*	0.48**	−0.17	0.19	−0.47*	0.60**	0.51**	−0.15
PA-k	0.32**	0.03	−0.05	−0.28	0.52**	−0.27*	0.36**	−0.57**	0.16	0.41**	−0.11

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