Effects of Caragana microphylla shrubs on the soil nitrogen-fixing microbial communities in steppe land

doi:10.11686/cyxb2021403

Abstract

Abstract:

Encroachment of woody species has become a common phenomenon in arid and semi-arid grassland worldwide. However， the effects of shrubs on soil nitrogen-fixing microbial （NFM） communities and the mechanisms underlying them are poorly known. Caragana microphylla （Fabaceae） is widely distributed in the Inner Mongolian Steppe. It is important to explore the effects on NFM communities. In this paper， we compared the differences of soil NFM communities outside and within the canopy areas of shrubs in different soil horizons of desert steppe （arid zone） and typical steppe （semi-arid zone） by traditional culture methods and molecular biology techniques. Furthermore， our study explored the mechanisms underlying the shrub effects in terms of the species selectivity， fertile-island effect， and the interaction of the shrub and aridity effects. It was found that C. microphylla significantly increased the abundance and richness of NFM communities， and also affected their community composition. The change in community composition was manifested as significant variation in abundance of 37.50%-58.33% of genera， as change in the dominant genera and their dominance position， as a large Jaccard dissimilarity index （0.40-0.76） for samples from outside and samples from within shrub canopies， and differences in the ordination of NMDS （non-metric multidimensional scaling） results inside and outside shrub canopies. Based on these data an ‘analysis of similarity’ test showed significant differences in NFM community composition outside and within shrubs. The effect of shrubs on NFM communities decreased with increasing soil depth， and increased with increasing aridity. Shrubs exerted a greater effect on NFM communities than aridity. The mechanisms underlying the C. microphylla effects on NFM communities were： 1） Shrubs had a selective effect on NFM species presence； 2） Shrubs affected NFM communities through soil physical and chemical characteristics； 3） Climate aridity enhanced the impact of shrubs on NFM communities； 4） Shrubs affected NFM communities through mitigating climatic impacts.

Key words: climatic aridity, nitrogen-fixing microbe, microbial community composition, fertile-island effect, woody species encroachment

Chun-wen WANG, Fang ZHAO, Chen ZHANG, Li-na XIE, Cheng-cang MA. Effects of Caragana microphylla shrubs on the soil nitrogen-fixing microbial communities in steppe land[J]. Acta Prataculturae Sinica, 2022, 31(10): 28-40.

Figures/Tables 10

References 48

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项目 Item	土层 Soil depth	荒漠草原Desert steppe			典型草原Typical steppe
项目 Item	土层 Soil depth	正选择 Positive-selective	负选择 Negative-selective	总选择 Total selective	正选择 Positive-selective	负选择 Negative-selective	总选择 Total selective
共生Symbiotic	0~10 cm	52.94	17.65	70.59	25.00	12.50	37.50
	10~20 cm	27.78	16.67	44.45	6.67	20.00	26.67
	30~40 cm	20.00	20.00	40.00	14.29	28.57	42.86
自生Free-living	0~10 cm	54.55	0.00	54.55	55.56	0.00	55.56
	10~20 cm	44.44	0.00	44.44	37.50	12.50	50.00
	30~40 cm	33.33	16.67	50.00	60.00	20.00	80.00

项目 Item	土层 Soil depth	荒漠草原Desert steppe			典型草原Typical steppe
项目 Item	土层 Soil depth	正选择 Positive-selective	负选择 Negative-selective	总选择 Total selective	正选择 Positive-selective	负选择 Negative-selective	总选择 Total selective
共生Symbiotic	0~10 cm	52.94	17.65	70.59	25.00	12.50	37.50
	10~20 cm	27.78	16.67	44.45	6.67	20.00	26.67
	30~40 cm	20.00	20.00	40.00	14.29	28.57	42.86
自生Free-living	0~10 cm	54.55	0.00	54.55	55.56	0.00	55.56
	10~20 cm	44.44	0.00	44.44	37.50	12.50	50.00
	30~40 cm	33.33	16.67	50.00	60.00	20.00	80.00

项目 Item	土层 Soil depth	灌丛 Shrub canopies	气候干旱 Climate aridity
共生 Symbiotic	0~10 cm	45.27	16.67
	10~20 cm	53.61	26.47
	30~40 cm	69.03	0.00
自生 Free-living	0~10 cm	74.47	28.69
	10~20 cm	33.61	7.00
	30~40 cm	49.39	0.00

项目 Item	土层 Soil depth	灌丛 Shrub canopies	气候干旱 Climate aridity
共生 Symbiotic	0~10 cm	45.27	16.67
	10~20 cm	53.61	26.47
	30~40 cm	69.03	0.00
自生 Free-living	0~10 cm	74.47	28.69
	10~20 cm	33.61	7.00
	30~40 cm	49.39	0.00