Effects of simulated nitrogen deposition on physiological and morphological characteristics of Sphagnum in wetland, southwestern Hubei Province, China

doi:10.17521/cjpe.2022.0426

Abstract

Abstract:

Aims Sphagnum, as the dominant species in Sphagnum wetland, is the most important carbon (C) sequestration plant. The physiological and morphological characteristics of Sphagnum determine the carbon sink potential of Sphagnum wetland. Nitrogen (N) deposition has a significant effect on the physiological and morphological characteristics of Sphagnum,but the effects of N deposition on such characteristics of Sphagnum in the wetland environment remain controversial. Moreover, there are few reports on the physiological and morphological characteristics of Sphagnum in subtropical wetlands.

Methods We selected a Sphagnum wetland in southwestern Hubei Province as the study area. Different concentrations of NH₄Cl solution were sprayed in situto investigate the effects of simulated N deposition on physiological and morphological characteristics of Sphagnum. Four N concentrations were applied, namely 0 (N0), 3 (N3), 6 (N6) and 12 g·m^-2·a^-1 (N12), with N0 representing the control (CK).

Important findings (1) Nitrogen deposition had significant effects on the contents of total C and total N in Sphagnum. Among the treatments, the contents of total C and total N in Sphagnumunder the N3 treatment were the highest, and compared with those of the CK, increased by 3.78% and 88.52%, respectively. (2) Nitrogen deposition had no obvious effect on chlorophyll content and fluorescence activities of Sphagnum. However, N deposition significantly promoted the antioxidant enzyme activities and the contents of osmotic substances in Sphagnum,especially the contents of soluble sugars and peroxidase activity. (3) With the increase in N deposition, the height, branch number, mass per plant, and leaf cell area of Sphagnum tended to initially increase and thereafter decrease. The maximum values were observed in response to N deposition of 3 g·m^-2·a^-1. (4) Sphagnum was sensitive to N deposition, and there was a certain load value of the effect of N deposition on physiological and morphological characteristics of Sphagnumafter 2 years treatment, which was approximately 3 g·m^-2·a^-1. When the amount of N deposition is greater than 3 g·m^-2·a^-1, the effects on morphological indicators of Sphagnum are detrimental and the stress to Sphagnumwill increase significantly. The results of this study indicated that the current natural atmospheric N deposition is beneficial to the growth of Sphagnum in the wetland in southwestern Hubei Province. However, continual or doubled N deposition might be harmful to the growth of Sphagnum.

Key words: Sphagnum, nitrogen input, chlorophyll, antioxidant enzymes, morphology

YU Yu-Rong, WU Hao, GAO Ya-Fei, ZHAO Yuan-Bo, LI Xiao-Ling, BU Gui-Jun, XUE Dan, LIU Zheng-Xiang, WU Hai-Wen, WU Lin. Effects of simulated nitrogen deposition on physiological and morphological characteristics of Sphagnum in wetland, southwestern Hubei Province, China[J]. Chin J Plant Ecol, 2023, 47(11): 1493-1506.

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URL: https://www.plant-ecology.com/EN/10.17521/cjpe.2022.0426

https://www.plant-ecology.com/EN/Y2023/V47/I11/1493

Figures/Tables 11

Fig. 1 Schematic diagram of the simulated nitrogen deposition plot in Sphagnum wetland in southwestern Hubei Province. N0, N3, N6, and N12 indicate the nitrogen concentrations of 0, 3, 6, and 12 g·m-2·a-1, respectively.

Table 1 Effects of simulated nitrogen (N) deposition on soil physicochemical characteristics in Sphagnum wetland in southwestern Hubei Province (mean ± SE, n = 5)

N浓度 N concentration (g·m^-2·a^-1)	pH	总酚含量 Total polyphenol content (%)	总碳(C)含量 Total carbon (C) content (%)	总N含量 Total N content (%)	C:N
0 (N0)	4.1 ± 0.1^a	4.80 ± 0.94^a	29.62 ± 3.26^a	1.29 ± 0.07^a	22.86 ± 1.31^a
3 (N3)	4.0 ± 0.1^a	5.00 ± 0.94^a	33.21 ± 2.69^ab	1.44 ± 0.09^ab	23.07 ± 1.29^a
6 (N6)	4.1 ± 0.1^a	5.95 ± 1.24^a	40.21 ± 0.24^c	1.63 ± 0.04^bc	24.75 ± 0.60^a
12 (N12)	3.9 ± 0^a	6.66 ± 0.69^a	38.16 ± 0.51^bc	1.74 ± 0.06^c	21.94 ± 0.73^a

Fig. 2 Effects of simulated nitrogen (N) deposition on the total carbon (C) and total N contents of Sphagnum palustre (mean ± SE, n = 5). 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 difference between treatments in total C content; different uppercase letters indicate significant difference between treatments in total N content (p < 0.05).

Fig. 3 Effects of simulated nitrogen deposition on chlorophyll content of Sphagnum palustre (mean ± SE, n = 5). 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 difference among the treatments (p < 0.05).

Fig. 4 Effects of simulated nitrogen deposition on the measurement of maximum quantum yield (Fv/Fm) (A) and electron transport rate (ETR) (B) of Sphagnum palustre (mean ± SE, n = 5). 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 difference among the treatments (p < 0.05).

Fig. 5 Effects of simulated nitrogen deposition on contents of soluble sugar (A), soluble protein (B), and malondialdehyde (MDA) (C) of Sphagnum palustre (mean ± SE, n = 5). 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 difference among the treatments (p < 0.05).

Fig. 6 Effects of simulated nitrogen deposition on activities of superoxide dismutase (SOD) and peroxidase (POD) of Sphagnum palustre (mean ± SE, n = 5). 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 difference among the treatments (p < 0.05).

Fig. 7 Effects of simulated nitrogen deposition on the plant height of Sphagnum palustre (mean ± SE, n = 10). 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 difference among the treatments (p < 0.05).

Fig. 8 Effects of simulated nitrogen deposition on the branch number (A) and dry mass (B) of Sphagnum palustre (mean ± SE, n = 10). 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 difference among the treatments (p < 0.05).

Fig. 9 Effects of simulated nitrogen deposition on the cell area of Sphagnum palustre leaves (mean ± SE, n = 5). 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 difference among the treatments (p < 0.05).

Fig. 10 Electron micrographs of cells of Sphagnum palustre leaves under different nitrogen deposition treatments. N0, N3, N6, and N12 indicate the nitrogen concentrations of 0, 3, 6, and 12 g·m-2·a-1, respectively.

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