Altitudinal distribution patterns of soil bacterial communities in the Huoditang coniferous forests of the Qinling Mountains

doi:10.17520/biods.2024180

Abstract

Abstract:

Aims: Soil bacteria play an important role in maintaining forest ecosystem function and soil nutrient cycling. The Huoditang forest area is a representative region in the southern slope of the Qinling Mountains, but the altitude distribution pattern of soil bacterial communities in its coniferous forests is still unclear. Our study aims to explore the distribution of soil bacterial communities in the Huoditang coniferous forests, as well as provide basic data and decision-making references for further research to protect the Qinling ecosystem.
Methods: Soil samples were collected from two typical coniferous forests (Tsuga chinensis forest and Larix principis-rupprechtii forest) from a range of altitudes. 16S rRNA amplicon sequencing was used to characterize the soil microbial communities. Canonical correspondence and correlation analyses were used to identify the driving factors that affect the soil microbial communities in these areas.
Results: (1) There was no significant difference in the α-diversity of soil microbial communities in coniferous forests at different altitudes, but the β-diversity changed significantly. (2) The dominant bacterial phyla were Proteobacteria, Acidobacteria and Actinobacteria, which accounted for 66.02%-73.78% of the total bacteria. At the genus level, the bacterial community composition varied greatly with altitude. (3) Our LEfSe (linear discriminant analysis effect size) and FAPROTAX (functional annotation of prokaryotic taxa) functional prediction also indicated that high-altitude coniferous forest soils were mainly enriched in Proteobacteria with nitrogen (N) cycle-related functions, while low- and mid-altitude coniferous forest soils were largely enriched in Acidobacteria and carbon (C) cycle-related functions. (4) Altitude, pH, TK and C/N were also correlated with bacterial community structure. Proteobacteria were positively correlated with altitude and C/N, while Acidobacteria were negatively correlated. However, Actinobacteria were negatively correlated with pH and positively correlated with TK.
Conclusion: In summary, the composition and structure of soil bacterial communities in the Huoditang coniferous forests changed significantly with the altitudinal gradient, which greatly influenced their function. Together, this study creates an in-depth understanding of the changes and driving mechanisms of soil bacterial community composition in the Huoditang coniferous forests and provides a theoretical basis for their conservation and ecological restoration in the Qinling Mountains.

Key words: coniferous forest, bacterial community structure, altitude, environmental factors, Qinling Mountains

Shiyu Wei, Tianjiao Song, Jiayi Luo, Yan Zhang, Zixuan Zhao, Jingwen Ru, Hua Yi, Yanbing Lin. Altitudinal distribution patterns of soil bacterial communities in the Huoditang coniferous forests of the Qinling Mountains[J]. Biodiv Sci, 2024, 32(9): 24180.

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URL: https://www.biodiversity-science.net/EN/10.17520/biods.2024180

https://www.biodiversity-science.net/EN/Y2024/V32/I9/24180

Figures/Tables 7

Table 1 Changes of soil physical and chemical properties in two types of coniferous forests along the altitude gradients (mean ± SD)

	海拔 Altitude (m)	pH	土壤有机质 SOM (g/kg)	全氮 TN (g/kg)	全磷 TP (g/kg)	全钾 TK (g/kg)	碱解氮 AN (mg/kg)	速效磷 AP (mg/kg)	速效钾 AK (mg/kg)	C/N
T	1582	5.95 ± 0.04^b	341.29 ± 13.57^a	14.1 ± 0.58^a	1.07 ± 0.03^a	12.61 ± 0.51^b	713.08 ± 24.31^a	35.76 ± 5.59^a	175 ± 7.81^a	24.21 ± 0.48^b
	1874	7.26 ± 0.1^a	62.96 ± 29.31^b	2.36 ± 1.01^b	0.65 ± 0.26^b	13.91 ± 0.77^b	159.67 ± 50.58^b	34.87 ± 25.31^a	203.33 ± 104.84^a	26.25 ± 2.49^b
	2400	5.8 ± 0.27^b	91.64 ± 9.18^b	3 ± 0.28^b	0.78 ± 0.02^ab	22.51 ± 2.33^a	239.01 ± 47.34^b	43.8 ± 8.68^a	210.33 ± 15.82^a	30.49 ± 0.48^a
L	1578	5.55 ± 0.26^b	70.36 ± 35.09^a	3.37 ± 1.84^a	0.67 ± 0.23^a	20.41 ± 1.03^a	228.16 ± 102.01^a	13.82 ± 5.89^a	239.33 ± 96.77^a	21.26 ± 1.21^c
	1809	6.94 ± 0.36^a	58.22 ± 1.99^a	2.7 ± 0.05^a	0.81 ± 0.08^a	17.5 ± 1.29^b	178.89 ± 5.17^a	36.32 ± 13.6^a	222.33 ± 23.71^a	21.56 ± 0.64^c
	1979	5.67 ± 0.32^b	61.09 ± 43.85^a	2.02 ± 1.48^a	0.76 ± 0.05^a	19.67 ± 0.93^ab	146.36 ± 71.48^a	41.78 ± 18.87^a	186 ± 48.45^a	30.47 ± 0.6^a

Fig. 1 Structure and diversity of soil microbial communities in two types of coniferous forests. (a-c), PcoA (principal co-ordinates analysis) based on Bray-Curtis; (d-f), α-diversity values. T, Tsuga chinensis forest; L, Larix principis-rupprechtii forest; TL, Low-altitude T. chinensis forest; TM, Mid-altitude T. chinensis forest; TH, High-altitude T. chinensis forest; LL, Low-altitude L. principis-rupprechtii forest; LM, Mid-altitude L. principis-rupprechtii forest; LH, High-altitude L. principis-rupprechtii forest.

Fig. 2 Relative abundance of soil microbial communities at the phylum level (a) and genus level (b) in two types of coniferous forests. T, Tsuga chinensis forest; L, Larix principis-rupprechtii forest; TL, Low-altitude T. chinensis forest; TM, Mid-altitude T. chinensis forest; TH, High-altitude T. chinensis forest; LL, Low-altitude L. principis-rupprechtii forest; LM, Mid-altitude L. principis-rupprechtii forest; LH, High-altitude L. principis-rupprechtii forest. The colour shades in the scale bar on the right side of figure (b) indicate the degree of difference between the genus abundance and the mean value. Based on the mean value of genus abundance in the same sample, values above the mean are positive and marked in red; on the contrary, values below the mean are negative and marked in blue.

Fig. 3 LEfSe (linear discriminant analysis effect size ) showing soil community differences at different altitudes in Tsuga chinensis forest (a) and Larix principis-rupprechtii forest (b). Each circular ring deposits all taxa within a taxonomic level, and the circular ring from inside to outside represents supergroup, phylum, class, order, and family, respectively. The node on the circular ring represents taxon, affiliating within the taxonomic level. The diameter of each node is proportional to the abundance of the group. Taxa that have significantly higher relative abundance in a certain treatment within each altitude gradient are color-coded within the cladogram. TM, Mid-altitude T. chinensis forest; TH, High-altitude T. chinensis forest; LL, Low-altitude L. principis-rupprechtii forest; LM, Mid-altitude L. principis-rupprechtii forest; LH, High-altitude L. principis-rupprechtii forest.

Fig. 4 FAPROTAX functional prediction of soil bacterial communities across different altitudinal gradients of Tsuga chinensis forest (a) and Larix principis-rupprechtii forest (b). The color shades indicate the degree of difference between the expression of metabolic function and the mean. The average value of gene expression in the same sample is used as the benchmark, and the expression above the average is positive, and the mark is red; conversely, the expression below the average is a negative value and marked as blue. TL, Low-altitude T. chinensis forest; TM, Mid-altitude T. chinensis forest; TH, High-altitude T. chinensis forest; LL, Low-altitude L. principis-rupprechti forest; LM, Mid-altitude L. principis-rupprechtii forest; LH, High-altitude L. principis-rupprechtii forest.

Fig. 5 Correlation analysis of environmental factors. Altitude, Altitude; pH, Soil pH; SOM, Soil organic matter; TN, Total nitrogen; TP, Total phosphorus; TK, Total potassium; AN, Available nitrogen; AP, Available phosphorus; AK, Available potassium; C/N, Carbon to nitrogen ratio. The values in the right scale bar indicate the Pearson correlation coefficients. The color of the square indicates the direction of the correlation, where red indicates positive correlation and blue indicates negative correlation, and the darker color indicates the stronger correlation. * P < 0.05; ** P < 0.01; *** P < 0.001.

Fig. 6 Correlation analysis between environmental factors and soil microbial communities. (a) Canonical correspondence analysis; (b) Spearman correlation analysis. Altitude, Altitude; SOM, Soil organic matter; TN, Total nitrogen; TP, Total phosphorus; TK, Total potassium; AN, Available nitrogen; AP, Available phosphorus; AK, Available potassium; C/N, Carbon to nitrogen ratio. The color of the bar indicates the Spearman’s correlation coefficients, where red indicates positive correlation and blue indicates negative correlation, and the darker color indicates the stronger correlation. TL, Low-altitude Tsuga chinensis forest; TM, Mid-altitude T. chinensis forest; TH, High-altitude T. chinensis forest; LL, Low-altitude Larix principis-rupprechtii forest; LM, Mid-altitude L. principis-rupprechtii forest; LH, High-altitude L. principis-rupprechtii forest. * P < 0.05; ** P < 0.01; *** P < 0.001.

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