Stoichiometric responses in topsoil and leaf of dominant species to precipitation change and nitrogen addition in an alpine meadow

doi:10.17521/cjpe.2022.0105

Abstract

Abstract:

Aims Precipitation regime alteration and increasing nitrogen deposition have substantially altered the structure and function of grassland ecosystems. However, the responses of stoichiometry in soil and vegetation remain elusive, which limits the accuracy in predicting functional changes of alpine meadow.

Methods Based on a manipulation experiment platform of nitrogen addition (10 g·m^-2·a^-1) and precipitation change (precipitation reduction by 50% and increase by 50%) in an alpine meadow on the southern foot of Qilian Mountains, organic carbon (SOC), total nitrogen (SN), total phosphorus (SP) contents in topsoil (0-10 cm), and foliar carbon (LC), nitrogen (LN), phosphorus (LP) and potassium (LK) contents of dominant plant species, including Gentiana straminea, Elymus nutans, Oxytropis ochrocephalaand Kobresia humilis,were continuously surveyed from 2017 to 2020.

Important findings The soil stoichiometry varied significantly among different years, but was not affected by experimental treatments. The aboveground plant biomass showed inter-annual variations and was significantly affected by nitrogen addition. The responses of leaf stoichiometry were species-specific. Foliar stoichiometry of a resource-conservative species, E. nutans, showed limited variations, while that of the sensitive species, K. humilis, fluctuated significantly. To exclude the impacts of temporal variations, we conducted the analysis based on the relative changes (Δ) between treatment plots and the control plots from the same year and the results showed that nitrogen addition significantly increased ΔPB by 15.6%. Precipitation reduction significantly decreased ΔLC of O. ochrocephala by 6.8% while increased ΔLP of K. humilis by 19.8%. Our findings suggest that only nitrogen addition increased aboveground biomass and precipitation reduction altered LC and LP contents in some plant species. The temporal or species-specific effect, rather than experiment treatments effect, dominated the stoichiometric variations of soil and vegetation, highlighting the complex responses of alpine meadow to precipitation regime alteration and nitrogen addition.

Key words: alpine meadow, precipitation change, nitrogen addition, stoichiometry, dominant plant species

LI Hong-Qin, ZHANG Fa-Wei, YI Lü-Bei. Stoichiometric responses in topsoil and leaf of dominant species to precipitation change and nitrogen addition in an alpine meadow[J]. Chin J Plant Ecol, 2023, 47(7): 922-931.

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URL: https://www.plant-ecology.com/EN/10.17521/cjpe.2022.0105

https://www.plant-ecology.com/EN/Y2023/V47/I7/922

Figures/Tables 6

Fig. 1 Layout of experiment plots of the alpine meadow in Haibei Station. +50%, rainfall enrichment by 50%; -50%, rainfall reduction by 50%; CK, control check; E, microorganism addition; K, potassium addition; N, nitrogen addition; N+50%, N and rainfall enrichment by 50%; N-50%, N and rainfall reduction by 50%; NK, N and K; NP, N and phosphorus addition; NPK, N, P, and K; NPK+50%, N, P, and K and rainfall enrichment by 50%; NPK-50%, N, P, K and rainfall reduction by 50%; NPK+E, N, P, K and microorganism addition; PK, P and K.

Table 1 Linear mixed-effect models of soil stoichiometry and aboveground plant biomass (PB) to precipitation change (Rain) and nitrogen addition (N) in an alpine meadow of Haibei Station

处理 Treatment	SOC	SN	SP	SOC:SN	SOC:SP	SN:SP	PB
年份 Year	<0.001	<0.001	<0.001	<0.001	<0.001	<0.001	<0.001
降水改变 Rain	0.24	0.23	0.67	0.85	0.76	0.79	0.23
氮添加 N	0.59	0.69	0.50	0.40	0.76	0.88	0.01
年份×降水改变 Year × Rain	0.08	0.35	0.72	0.08	0.32	0.74	0.99
年份×氮添加 Year × N	0.85	0.62	0.74	0.78	0.86	0.90	0.02
降水改变×氮添加 Rain × N	0.04	0.19	0.18	0.42	0.97	0.98	0.54

Fig. 2 Interannual differences of topsoil organic carbon content (SOC, A), total nitrogen content (SN, B), total phosphorus content (SP, C), and aboveground plant biomass (PB, D) of the alpine meadow in Haibei Station (mean ± SD). Different lowercase letters represent significant difference (p < 0.05); solid squares and lines of boxes are mean and median values, respectively.

Fig. 3 Response of relative changes of aboveground plant biomass (ΔPB, A), leaf carbon content (ΔLC) of Oxytropis ochrocephala (B), leaf phosphorus content (ΔLP, C) and ΔLC (D) of Kobresia humilis to precipitation change (Rain) and nitrogen addition (N) of the alpine meadow in Haibei Station (mean ± SD). Different lowercase letters represent significant difference (p < 0.05); solid squares and lines of boxes are mean and median values, respectively. +50%, rainfall enrichment by 50%; -50%, rainfall reduction by 50%; CK, control check; N+50%, N addition and rainfall enrichment by 50%; N-50%, N addition and rainfall reduction by 50%.

Fig. 4 Differences of leaf carbon content (LC, A), nitrogen content (LN, B), phosphorus content (LP, C), and potassium content (LK, D) of Gentiana straminea, Elymus nutans, Oxytropis ochrocephala, and Kobresia humilis of the alpine meadow in Haibei Station (mean ± SD). Different lowercase letters represent significant difference (p < 0.05); solid squares and line of boxes are mean and median values, respectively.

Table 2 Linear mixed-effect models of leaf carbon (LC), nitrogen (LN), phosphor (LP), and potassium (LK) of dominant plant species to precipitation change (P) and nitrogen addition (N)

物种 Species	化学计量 Stoichiometry	年份 Year	Rain	N	年份×降水改变 Year × Rain	年份×氮添加 Year × N	Rain × N
麻花艽 Gentiana straminea	LC	0.18	0.52	0.79	0.43	0.47	0.94
	LN	0.02	0.59	0.97	0.77	0.08	0.87
	LP	0.02	0.79	0.33	0.41	0.40	0.18
	LK	0.44	0.27	0.69	0.29	0.92	0.95
垂穗披碱草 Elymus nutans	LC	0.68	0.42	0.71	0.23	0.49	0.27
	LN	0.31	0.06	0.26	0.59	0.42	0.26
	LP	0.65	0.69	0.56	0.90	0.83	0.89
	LK	0.45	0.67	0.19	0.79	0.64	0.68
黄花棘豆 Oxytropis ochrocephala	LC	0.03	0.03	0.97	0.03	0.82	0.70
	LN	0.36	0.78	0.21	0.79	0.44	0.73
	LP	0.13	0.99	0.29	0.71	0.62	0.96
	LK	0.06	0.51	0.54	0.73	0.68	0.40
矮生嵩草 Kobresia humilis	LC	0.02	0.05	0.61	0.01	0.23	0.38
	LN	0.03	0.64	0.23	0.48	0.38	0.16
	LP	<0.001	0.02	0.62	0.34	0.53	0.53
	LK	<0.001	0.16	0.21	0.53	0.72	0.47

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