Effects of simulated nitrogen deposition on growth and decomposition of two bryophytes in ombrotrophic peatland, southwestern Hubei, China

doi:10.17521/cjpe.2022.0160

Abstract

Abstract:

Aims Ombrotrophic peatlands, dominated by Sphagnum, are important carbon sinks in terrestrial ecosystems. The dynamics of growth and decomposition of dominant plants usually determine the carbon sink potential of ombrotrophic peatland. However, it is still controversial how nitrogen deposition impact on the growth and decomposition of mosses in ombrotrophic peatland. Moreover, the effects of nitrogen deposition on the growth and decomposition of dominant mosses are rarely reported in subtropical ombrotrophic peatlands.
Methods We selected an ombrotrophic peatland in southwestern Hubei Province as the study area. Different concentrations of NH₄Cl solution were sprayed in situ. Here biomass harvesting and decomposition bag methods were adopted to estimate growth and litter decomposition of S. palustre and Polytrichum commune.
Important findings (1) Nitrogen deposition had obvious effects on the height and biomass of the two mosses. Moreover, there was a threshold value of nitrogen deposition at the level of about 3 g·m^-2·a^-1. (2) The effects of nitrogen deposition on the growth of the two mosses were different, and the response sensitivity of S. palustre to nitrogen deposition was greater than that of P. commune. (3) High nitrogen deposition levels (i.e., 6 and 12 g·m^-2·a^-1) inhibited the decomposition of S. palustre, while the effect of low nitrogen deposition (i.e., 3 g·m^-2·a^-1) on the decomposition of S. palustre depends on time. All the concentrations of nitrogen deposition inhibited the decomposition of P. commune litter. (4) After one year of decomposition, the average final mass residual percentage of S. palustre was 105.99%, and 70.79% for P. commune. The decomposition rate of P. commune was much higher than that of S. palustre. (5) Nitrogen deposition significantly affected the chemical element content and stoichiometric ratio of the two moss litters, and was closely related to decomposition time.

Key words: Sphagnum bog, decomposition, moss, nitrogen input, production

LI Xiao-Ling, ZHU Dao-Ming, YU Yu-Rong, WU Hao, MOU Li, HONG Liu, LIU Xue- Fei, BU Gui-Jun, XUE Dan, WU Lin. Effects of simulated nitrogen deposition on growth and decomposition of two bryophytes in ombrotrophic peatland, southwestern Hubei, China[J]. Chin J Plant Ecol, 2023, 47(5): 644-659.

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URL: https://www.plant-ecology.com/EN/10.17521/cjpe.2022.0160

https://www.plant-ecology.com/EN/Y2023/V47/I5/644

Figures/Tables 12

Table 1 Important values of dominant plant species in Taishanmiao peatland

物种 Species	重要值 IV (%)	物种 Species	重要值 IV (%)
泥炭藓 Sphagnum palustre^*	90.23	耳叶杜鹃 Rhododendron auriculatum	24.94
大理薹草 Carex rubrobrunnea var. taliensis	62.31	芒 Miscanthus sinensis	23.45
齿缘吊钟花 Enkianthus serrulatus	61.83	茶荚蒾 Viburnum setigerum	13.26
多齿长尾槭 Acer caudatum var. multiserratum	48.00	紫萁 Osmunda japonica	11.64
金发藓 Polytrichum commune^*	40.35	华西华楸 Sorbus wilsoniana	9.18
西南凤尾蕨 Pteris wallichiana	36.25	湖北海棠 Malus hupehensis	8.43
灯心草 Juncus effusus	31.36	四川冬青 Ilex szechwanensis	6.19
小灯心草 Juncus bufonius	25.12	金丝桃 Hypericum monogynum	4.81

Fig. 1 Distribution pattern of Sphagnum palustre and Polytrichum commune in Taishanmiao peatland.

Table 2 Initial chemical composition of Sphagnum palustre and Polytrichum commune in Taishanmiao peatland (mean ± SE, n = 4)

物种 Species	初始总碳(C)含量 Initial total carbon (C) content (%)	初始总氮(N)含量 Initial total nitrogen (N) content (%)	初始总酚含量 Initial total phenolics content (%)	初始C:N Initial C:N	初始总酚:C Initial total phenolics:C	初始总酚:N Initial total phenolics:N	初始灰分含量 Initial ash content (%)
泥炭藓 Sphagnum palustre	37.39 ± 0.07^b	0.98 ± 0.03^b	1.26 ± 0.02^b	39.50 ± 0.09^a	3.34 ± 0.04^b	1.29 ± 0.02^b	0.96 ± 0.02^b
金发藓 Polytrichum commune	42.28 ± 0.09^a	1.35 ± 0.01^a	2.04 ± 0.03^a	31.40 ± 0.22^b	4.83 ± 0.06^a	1.52 ± 0.01^a	4.17 ± 0.04^a

Table 3 Two-way ANOVA on the effects of nitrogen deposition, species and interaction on height increment, net primary productivity of two bryophytes

因素 Factor	df	高度增长量 Height increment (cm)		净初级生产力 Net primary productivity (g·m^-2)
因素 Factor	df	F	p	F	p
氮沉降 Nitrogen deposition	3	5.210	0.007	30.851	<0.001
物种 Species	1	129.062	<0.001	41.170	0.021
氮沉降×物种 Nitrogen deposition × species	3	1.231	0.320	4.502	0.102

Fig. 2 Effects of simulated nitrogen deposition on increment of height growth (A) and net primary productivity (B) of Sphagnum palustre and Polytrichum commune in the growing season (mean ± SE, n = 4). Different lowercase letters indicate significant differences at different nitrogen levels in Sphagnum palustre (p < 0.05), and different uppercase letters indicate significant differences at different nitrogen levels in Polytrichum commune (p < 0.05). * refers a significant difference between the two species (p < 0.05).

Table 4 Multivariate analysis of variance on the differences in the decomposing indicators of two bryophytes litters among nitrogen deposition, species and decomposition time

因素 Factor	df	质量残留率 Mass remaining rate (%)		总碳含量 Total carbon (C) content (%)		总氮含量 Total nitrogen (N) content (%)		总酚含量 Total polyphenol content (%)		碳氮比 C:N		总酚:氮 Total phenolics:N		灰分含量 Ash content (%)
因素 Factor	df	F	p	F	p	F	p	F	p	F	p	F	p	F	p
氮沉降 Nitrogen deposition	3	7.617	0.001	10.63	<0.001	2.769	0.045	6.607	<0.001	2.747	0.046	2.939	0.036	1.085	0.358
分解时间 Decomposition time	4	52.281	0.001	140.99	<0.001	40.725	<0.001	79.714	<0.001	14.593	<0.001	218.590	<0.001	2.541	0.043
物种 Species	1	222.556	<0.001	257.46	<0.001	53.950	<0.001	14.674	<0.001	97.856	<0.001	213.010	<0.001	0.563	0.048
氮沉降×物种 Nitrogen deposition × species	3	4.154	0.008	9.32	<0.001	4.811	0.003	1.684	0.174	4.507	0.005	0.576	0.632	0.871	0.458
氮沉降×分解时间 Nitrogen deposition × decomposition time	12	4.073	<0.001	1.43	0.163	3.137	0.001	2.238	0.014	3.017	0.001	2.752	0.002	0.949	0.502
物种×分解时间 Species × decomposition time	4	27.864	<0.001	15.49	<0.001	55.146	<0.001	12.199	<0.001	20.915	<0.001	199.327	<0.001	0.635	0.639
氮沉降×物种×分解时间 Nitrogen deposition × species × decomposition time	12	2.175	0.017	4.127	<0.001	1.336	0.207	2.429	0.007	1.743	0.066	2.535	0.005	0.899	0.550

Fig. 3 Effects of simulated nitrogen deposition on remaining rate of Sphagnum palustre (A) and Polytrichum commune (B) litters (mean ± SE, n = 4). N0, N3, N6 and N12 represent nitrogen addition concentrations of 0, 3, 6 and 12 g·m-2·a-1, respectively. Different lowercase letters indicate significant differences at different nitrogen level at the same time periods (p < 0.05).

Fig. 4 Effects of simulated nitrogen deposition on element contents of the Sphagnum palustre (A, C, E) and Polytrichum commune (B, D, F) (mean ± SE, n = 4). N0, N3, N6 and N12 represent nitrogen addition concentrations of 0, 3, 6 and 12 g·m-2·a-1, respectively. Different lowercase letters indicate significant differences at different nitrogen level at the same time periods (p < 0.05).

Fig. 5 Effects of simulated nitrogen deposition on element ratios of the Sphagnum palustre (A, C) and Polytrichum commune (B, D) litters (mean ± SE, n = 4). N0, N3, N6 and N12 represent nitrogen addition concentrations of 0, 3, 6 and 12 g·m-2·a-1, respectively. Different lowercase letters indicate significant differences at different nitrogen level at the same time periods (p < 0.05).

Fig. 6 Effects of simulated nitrogen deposition on ash content of Sphagnum palustre (A) and Polytrichum commune (B) litters (mean ± SE, n = 4). N0, N3, N6 and N12 represent nitrogen addition concentrations of 0, 3, 6 and 12 g·m-2·a-1, respectively. Different lowercase letters indicate significant differences at different nitrogen level at the same time periods (p < 0.05).

Fig. 7 Effects of simulated nitrogen deposition on the total nitrogen content of Sphagnum palustre (mean ± SE, n = 4). Different lowercase letters indicate significant differences at different nitrogen levels (p < 0.05).

Fig. 8 Correlation between the initial chemical traits and the decomposition indicators of two bryophytes litters. *, p < 0.05; **, p < 0.01; ***, p < 0.001。

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