Response of ammonia oxidizing bacteria to nitrogen fertilization and plant litter input on desert steppe

doi:10.17521/cjpe.2022.0220

Abstract

Abstract:

Aims This study aimed to explore the response of ammonia oxidizing bacteria (AOB) to litter decomposition and nitrogen application in the topsoil of desert steppe, and the main environmental factors influencing the AOB were also analyzed. Thus, this study will contribute to better understanding of the mechanism of nitrogen cycle function gene abundance in response to nitrogen deposition in arid and semi-arid desert steppe regions.
Methods We conducted the nitrogen fertilization experiment in the desert steppe in Yanchi, Ningxia. The four plant litters, including Sophora alopecuroides, Artemisia scoparia, Stipa breviflora and Agropyron mongolicum were selected as plant litter input treatments. The nitrogen fertilization treatments, including control (0 g·m^-2·a^-1) and nitrogen application (9.2 g·m^-2·a^-1), were applied to explore the response of AOB to nitrogen deposition and different litter inputs in top soil (0-5 cm) of desert steppe by fluorescent quantitative PCR and high-throughput sequencing.
Important findings Our results showed that there were 3 phyla, 4 classes, 6 orders, 7 families, 8 genera and 17 species of AOB in the topsoil of desert steppe under nitrogen application and litter decomposition. The AOB communities were mainly derived from Nitrosomonas and Nitrosospira, which were from beta-Proteobacteria, and Nitrosospira was the dominant species. Compared with the control, the gene copy number of AOB was significantly decreased under nitrogen application, indicating that nitrogen application inhibited nitrification in the topsoil of the desert steppe. Whereas, the response of AOB-ammonia monooxy genase subsuit A (amoA) gene abundance varied under different plant litter decomposition. Litter input could alleviate the inhibition of nitrogen enrichment on soil AOB-amoA gene abundance to a certain extent, but did not change the trend of soil AOB-amoA gene abundance. A redundancy analysis confirmed that soil organic carbon, total phosphorus, ammonium nitrogen and nitrate nitrogen contents were the key environmental factors affecting niche separation of AOB-amoA gene abundance in desert steppe soil. The results showed that nitrogen addition could significantly reduce the gene abundance of AOB-amoA, thereby affecting the nitrification and the direction of soil nitrogen transformation in the topsoil of desert steppe.

Key words: ammonia oxidizing bacteria, desert steppe, diversity, nitrogen deposition, litter addition, microbial ecology

ZHANG Ya-Qi, PANG Dan-Bo, CHEN Lin, CAO Meng-Hao, HE Wen-Qiang, LI Xue-Bin. Response of ammonia oxidizing bacteria to nitrogen fertilization and plant litter input on desert steppe[J]. Chin J Plant Ecol, 2023, 47(5): 699-712.

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URL: https://www.plant-ecology.com/EN/10.17521/cjpe.2022.0220

https://www.plant-ecology.com/EN/Y2023/V47/I5/699

Figures/Tables 9

Table 1 Chemical properties of soil under effects of nitrogen application and different litter addition in a desert steppe (mean ± SD)

土壤因子 Soil factor	氮处理 Nitrogen treatment	枯落物处理 Litter input treatment				N	L	L × N
土壤因子 Soil factor	氮处理 Nitrogen treatment	短花针茅 ZM	沙芦草 BC	猪毛蒿 H	苦豆子 K	N	L	L × N
pH	CK	8.96 ± 0.08^Aa	8.95 ± 0.06^Aa	8.83 ± 0.05^Aa	8.43 ± 0.11^Ab	0.091	0.127	0.607
pH	N	8.91 ± 0.08^Aa	8.46 ± 0.80^Ac	8.72 ± 0.05^Ab	8.43 ± 0.11^Ac	0.091	0.127	0.607
SOC (mg·kg^-1)	CK	36.12 ± 3.04^Aa	33.00 ± 4.44^Ab	28.99 ± 0.50^Ac	23.79 ± 0.41^Bd	0.000^**	0.000^**	0.000^**
SOC (mg·kg^-1)	N	34.78 ± 3.76^Ab	35.00 ± 5.93^Ab	28.00 ± 4.32^Ac	66.08 ± 0.49^Aa	0.000^**	0.000^**	0.000^**
TN (mg·kg^-1)	CK	4.03 ± 1.12^Ad	3.86 ± 0.10^Bc	5.52 ± 2.88^Aa	4.32 ± 0.02^Ab	0.004^**	0.191	0.077
TN (mg·kg^-1)	N	4.71 ± 0.24^Ac	6.76 ± 0.83^Aa	5.47 ± 1.24^Ab	4.60 ± 0.29^Ac	0.004^**	0.191	0.077
TP (mg·kg^-1)	CK	3.32 ± 0.47^Ac	3.84 ± 0.37^Ab	3.95 ± 0.64^Ab	4.48 ± 0.03^Aa	0.000^**	0.617	0.095
TP (mg·kg^-1)	N	4.33 ± 0.19^Bb	4.39 ± 0.48^Ab	3.97 ± 0.15^Ac	4.48 ± 0.03^Aa	0.000^**	0.617	0.095
NO₃^--N (mg·kg^-1)	CK	28.47 ± 2.36^Bb	23.86 ± 3.84^Bc	18.73 ± 0.52^Bc	80.29 ± 13.29^Ba	0.001^**	0.011^*	0.000^**
NO₃^--N (mg·kg^-1)	N	42.56 ± 6.51^Ac	30.18 ± 2.61^Ac	56.18 ± 6.09^Ab	107.76 ± 20.23^Aa	0.001^**	0.011^*	0.000^**
NH⁺₄-N (mg·kg^-1)	CK	20.73 ± 2.55^Bd	26.86 ± 4.63^Ac	26.86 ± 4.63^Ac	30.20 ± 0.63^Bb	0.001^**	0.016^*	0.005^**
NH⁺₄-N (mg·kg^-1)	N	42.56 ± 6.51^Ab	32.18 ± 9.33^Ac	33.19 ± 6.70^Ac	54.84 ± 0.98^Aa	0.001^**	0.016^*	0.005^**
TS (mg·kg^-1)	CK	0.29 ± 0.05^Ab	0.25 ± 0.04^Ab	0.27 ± 0.06^Bb	0.37 ± 0.03^Aa	0.020^*	0.312	0.321
TS (mg·kg^-1)	N	0.30 ± 0.04^Ad	0.33 ± 0.06^Ab	0.37 ± 0.01^Aa	0.37 ± 0.03^Aa

Fig. 1 Effects of nitrogen application (A) and litter addition (B) on gene abundance of ammonia oxidizing bacteria ammonia monooxy genase subsuit A (AOB-amoA) in a desert steppe (mean ± SD). CK, control group; N, nitrogen addition treatment. BC, Agropyron mongolicum; H, Artemisia scoparia; K, Sophora alopecuroides; ZM, Stipa breviflora. different uppercase letters indicate significant differences between different nitrogen additions in the same litter treatment (p < 0.05); Different lowercase letters indicate statistically significant difference between different litter treatments in the same nitrogen application treatment (p < 0.05).

Fig. 2 Difference of soil ammonia oxidizing bacteria (AOB) diversity under control and nitrogen application treatment in a desert steppe. CK, control group; N, nitrogen addition treatment.

Fig. 3 Difference of soil ammonia oxidizing bacteria (AOB) diversity under nitrogen application and litter input in a desert steppe. CKBC, control group + Agropyron mongolicum; CKH, control group + Artemisia scoparia; CKK, control group + Sophora alopecuroides; CKZM, control group + Stipa breviflora; NBC, nitrogen addition treatment + Agropyron mongolicum; NH, nitrogen addition treatment + Artemisia scoparia; NK, nitrogen addition treatment + Sophora alopecuroides; NZM, nitrogen addition treatment + Stipa breviflora. Different lowercase letters indicate significant differences between different nitrogen addition treatments of the same species (p < 0.05)

Table 2 Two-way variance analysis of soil ammonia oxidizing bacteria (AOB) community diversity by nitrogen addition and litter type in a desert steppe

指标 Index	氮添加 Nitrogen addition (N)		枯落物种类 Litter type (L)		L × N
指标 Index	F	p	F	p	F	p
Shannon-Wiener	7.243	0.016^*	3.208	0.049^*	6.217	0.005^*
Simpson	0.887	0.360	3.371	0.045^*	6.957	0.003^*
Ace	0.641	0.435	4.880	0.013^*	2.630	0.086
Chao1	0.658	0.429	4.852	0.014^*	2.115	0.139
Sobs	1.720	0.208	0.476	0.009^**	2.896	0.067

Fig. 4 Principal component analysis (PCA) of soil ammonia oxidizing bacterial operational taxonomic unit (OTU) level under nitrogen application (A) and litter input (B) in a desert steppe. CK, control group; N, nitrogen addition treatment. CKBC, control group + Agropyron mongolicum; CKH, control group + Artemisia scoparia; CKK, control group + Sophora alopecuroides; CKZM, control group + Stipa breviflora; NBC, nitrogen addition treatment + Agropyron mongolicum; NH, nitrogen addition treatment + Artemisia scoparia; NK, nitrogen addition treatment + Sophora alopecuroides; NZM, nitrogen addition treatment + Stipa breviflora.

Fig. 5 Community composition of soil ammonia oxidizing bacteria (AOB) under nitrogen application (A) and litter input (B) in a desert steppe. OTU, operational taxonomic unit. CK, control group; N, nitrogen addition treatment. CKBC, control group + Agropyron mongolicum; CKH, control group + Artemisia scoparia; CKK, control group + Sophora alopecuroides; CKZM, control group + Stipa breviflora; NBC, nitrogen addition treatment + Agropyron mongolicum; NH, nitrogen addition treatment + Artemisia scoparia; NK, nitrogen addition treatment + Sophora alopecuroides; NZM, nitrogen addition treatment + Stipa breviflora; Different lowercase letters in Figure B indicate significant differences in the percentage relative abundance of OTU in soil AOB under different N application treatments for the same species (p < 0.05).

Fig. 6 Phylogenetic tree of soil ammonia oxidizing bacteria (AOB) gene under nitrogen application and litter addition in a desert steppe. Values indicate the percentage of 1 000 replicate trees supporting the branching order; values below 50 are omitted. AY627780-KY474829 are the Genbank accession numbers. OTU, operational taxonomic units under 97% similarity.

Fig. 7 Redundancy analysis (RDA) between ammonia monooxy genase subsuit A gene abundance of soil ammonia oxidizing bacteria and soil physical and chemical properties under nitrogen application and litter addition in a desert steppe. NH+4-N, ammonium nitrogen content; NO3--N, nitrate nitrogen content; SOC, soil organic carbon content; TN, total nitrogen content; TP, total phosphorus content; TS, total salt content. CKBC, control group + Agropyron mongolicum; CKH, control group + Artemisia scoparia; CKK, control group + Sophora alopecuroides; CKZM, control group + Stipa breviflora; NBC, nitrogen addition treatment + Agropyron mongolicum; NH, nitrogen addition treatment + Artemisia scoparia; NK, nitrogen addition treatment + Sophora alopecuroides; NZM, nitrogen addition treatment + Stipa breviflora.

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