
==== Front
Sci Rep
Sci Rep
Scientific Reports
2045-2322
Nature Publishing Group UK London

39261650
71927
10.1038/s41598-024-71927-w
Article
Effects of mixed biocrusts on soil nutrients and bacterial community structure: a case study from Hilly Loess Plateau, China
Zhang Lei 2015127022@chd.edu.cn

12
1 https://ror.org/017zhmm22 grid.43169.39 0000 0001 0599 1243 Technology Lnnovation Center for Land Engineering and Human Seutlements, Xi’an Jiaotong University, Xi’an, 713599 China
2 https://ror.org/024e3wj88 Shaanxi Provincial Land Engineering Construction Group Co., Ltd., Xi’an, 710054 China
11 9 2024
11 9 2024
2024
14 212651 8 2023
2 9 2024
© The Author(s) 2024
2024
https://creativecommons.org/licenses/by-nc-nd/4.0/ Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/.
The ecological function of biological crusts in arid and semi-arid areas is of great importance. Bacteria, as a crucial microbial group in biological crusts, play a key role in the formation, nutrient cycling, and regulation of these crusts. However, the succession of biological crusts and the diversity of bacterial communities, along with key environmental factors in the Loess Plateau’s hilly and gully areas, remain unclear. This study investigated soil bacterial abundance and diversity in bare soil (BS), alga-lichen mixed crust (MC), and alga-lichen mixed crust subsoil (MCS) using high-throughput sequencing methods. It explored the relationship between the bacterial community in biological crusts and key environmental factors. The results indicated that the Chao1, Shannon index, and phylogenetic diversity of bacteria significantly increased with the succession of biological crusts. There were notable differences in the community composition and structure of bacteria at different stages of crust development, with Rubrobacteria and Cyanobacteriia dominating in MCS. Effective phosphorus, available potassium, nitrogen, pH, and total organic carbon were identified as key environmental factors affecting soil bacterial communities. In summary, the succession of biological crusts alters soil physicochemical characteristics and creates different ecological niches for bacterial communities. Soil nutrients and pH play a crucial role in the selection of bacterial species and the shaping of bacterial communities in the Loess Plateau’s hilly and gully areas.

Keywords

Mixed biocrusts
Bacteria
Soil nutrients
Biological crusts
Subject terms

Microbiology
Ecology
Environmental sciences
Technology Innovation Center for Land Engineering and Human Settlements, Shaanxi Land Engineering Construction Group Co..ltd and Xi' an Jiaotong University2024WHZ0240 Zhang Lei The Innovation Team of Shaanxi Province2021TD-52 Zhang Lei Shaanxi Key Research and Development Program2022ZDLSF06-04 Zhang Lei Inner scientific research project of Shaanxi Land Engineering Construction GroupDJTD 2022-1 DJNY2024-41 DJNY-YB-2023-40 DJNY-YB-2023-48 DJNY2024-33 DJNY2024-18 DJNY2024-16 Zhang Lei issue-copyright-statement© Springer Nature Limited 2024
==== Body
pmcIntroduction

Biocrusts can cover up to 70% of the soil surface in drylands1, significantly influencing ecosystem processes such as preventing soil erosion, fixing C and N from the atmosphere, altering soil albedo, regulating water relations, and supporting seed germination and optimal nutrient levels in vascular plants2. The biological crust on the Loess Plateau has a similar composition and cementation mode to the biological crusts in desert areas worldwide. Both are organic complexes composed of microbial groups, lichen and bryophyte spore types, and soil particles3–5. Their physicochemical and biological characteristics are significantly different from those of physical crusts. Drylands, which include dry sub-humid, semi-arid, arid, and hyper-arid areas, cover roughly 41% of the Earth’s terrestrial surface6. In addition to hosting 38% of the global human population, drylands also host approximately 20% of plant and 30% of bird biodiversity hotspots, making these terrestrial biomes particularly vulnerable to global environmental changes7. Indeed, with the global need to sequester more carbon (C), drylands may store up to 25% of the world’s soil organic C, further emphasizing the importance of soil conservation in these areas.

In terms of ecological functions, biological crusts can increase soil organic carbon and organic nitrogen through photosynthesis and nitrogen fixation, thus improving soil fertility. Additionally, biological crusts can maintain surface stability in different regions8–10. However, biological crusts on the Loess Plateau differ significantly from those in the desert regarding ecological functions. On the Loess Plateau, different types of biological crusts can effectively reduce rainfall kinetic energy and runoff scour, minimize soil loss, maintain soil moisture, and promote vegetation succession11,12. Soil bacteria are among the most diverse, abundant, and functional groups of soil microorganisms13. They are important drivers of biogeochemical cycles, participate in the transformation of soil nutrients14, and are key organisms in the material and energy cycles of ecosystems15. Microbial diversity plays an important role in promoting the local environment and ecological functions of biological crusts in the ecosystem16. Extensive research has been conducted on the characteristics of microbial communities in biological soil crusts. A study of soil crusts in the Taberas Basin, Spain, found that cyanobacteria had a high abundance in the crusts and a low abundance in the subcrusts17. The colonization and development of biological soil crust in dune zones benefit soil microbial characteristics and soil quality in vegetation restoration areas18. Currently, most research on biological crust focuses on changes in the bacterial community within the biological crust itself or comparisons between different types of crust. There is a lack of detailed comparison and analysis of the composition and diversity of microbial communities between biological crust and the bare surface of the same thickness, as well as between the soil beneath. In this study, soil from algal crust and subcutaneous layers, as well as the corresponding surface soil of bare land, was collected in the Loess Plateau area. The effects of biological crust on the soil bacterial community and its living environment were comprehensively analyzed. The results provide a theoretical basis for studying microbial diversity, ecological function, artificial culture, and ecological restoration of biological crusts in the Loess Plateau.

Materials and methods

Field experiment design

The study area is located in the Yangwangou land consolidation project area (36° 10′ 36″–37° 02′ 05″ N, 109° 14′ 10″ 110° 05′ 43″ E) of Nanniwan Town, Yan’an City, Shaanxi Province. This area belongs to the hilly and gully region of the Loess Plateau, characterized by loess bar hills formed by the erosion of a dendritic river system. The climate is a plateau continental warm temperate semi-arid type, with dry and windy springs and hot, rainy summers. The average annual temperature ranges from 7.710.6 °C, annual sunshine totals 2445 h, annual rainfall is 450–650 mm, and the frost-free period lasts 155–188 days. The predominant soil types are yellow soil and brown soil. Due to prolonged gully and slope erosion, slope gravity erosion is active, making the area prone to collapse and landslides, resulting in a very fragile ecological environment. Biological crusts are the most common surface micro-landscape in this region and are found in large quantities under various types of land use.

Field sampling and laboratory testing were conducted in 2021 based on a field survey. In this study area, the algae-moss mixed crust is predominant. Sampling sites were selected from three areas (S1–S3) at the front, middle, and back of the gully (Fig. 1). From each area, three samples of 0.5 m × 0.5 m were taken and mixed with a shovel three times along the diagonal as a composite sample. Sampling of bare soil samples followed the same procedure. Samples were collected from the cortex (0–1.5 cm) and soil below the cortex (1.5–11.5 cm). Adjacent bare soil (undisturbed soil) was taken as a control (within 10 m) (0–11.5 cm), resulting in a total of three treatments: bare soil (BS), algae-moss mixed crust (MC), and soil below the crust (MCS). The collected soil samples were kept at low temperatures during sampling. Samples for microbial diversity analysis were stored at − 80 °C, while samples for physicochemical properties were air-dried and sieved through 20 and 100 mesh sieves.Fig. 1 The distribution of sampling points and the phenotype of some biological crusts. Sampling sites (a: S1–S3) and the Different soil types (b: Mixed crust; c: Mixed crust subsoil; d: Bare soil on the surface).

Determination of basic physico-chemical properties and microbial diversity of soils

Soil pH was measured using a pH meter. Soil available phosphorus (AP) was determined by sodium bicarbonate leaching and molybdenum-antimony resistance spectrophotometry. Soil organic matter (SOM) was measured by the potassium dichromate volumetric method. Soil available potassium (AK) was determined by sodium nitrate leaching and turbidimetric method, while soil total nitrogen (TN) was measured by the persulfate digestion method. Soil microbial samples were collected and sent to Shanghai Meiji Biomedicine Technology Co., Ltd. for high-throughput sequencing of 16S rRNA gene amplicons. Primers 338F (5ʹ-ACTCCTACGGGAGGCAGCAG-3ʹ) and 806R (5ʹ-GGACTACHVGGGTWTCTAAT-3ʹ)11 were used for PCR amplification of the V3–V4 variable region.

Sequence analysis of 16S rRNA amplicons

Data from the Miseq PE300 platform were processed using the QIIME2 platform. The QIIME2 (Quantitative Insights into Microbial Ecology 2) Linux analysis platform was used for raw next-generation high-throughput sequencing data from the Illumina Miseq platform19. Raw data were imported using q2-demux, and sequence primers and linkers were removed using the cutadapt plugin. Double-ended sequenced sequences were merged using vsearch20,21. Sequences with a q-score > 25 quality were retained for further analysis. Sequences were denoised using the deblur plugin22, correcting sequencing errors and ensuring that more than 99.50% of the sequences met the requirements23,24. Microbial data mining was performed using the feature table generated after denoising, and OTUs were annotated at 97% similarity using the SILVA database. Microbial community structural diversity was calculated using the diversity plugin of QIIME2. Alpha diversity was generated, and non-parametric tests were performed using the Kruskal–Wallis test. Distance matrices for beta diversity were generated and plotted in R (version 4.0.3) using the vegan and ggplot2 packages. ANOSIM analysis was performed on each distance matrix using the vegan package. Species stacked histograms were generated using the taxa plugin for QIIME2 to count microbial species at different taxonomic levels and plotted using ggplot2 in R. Differential microbial analyses were performed using the online LEfSe (Linear discriminant analysis Effect Size) program (http://huttenhower.sph.harvard.edu/galaxy/) on biomarkers from different treatments25.

Results

Analysing soil physical and chemical properties at different sampling sites in the hilly and gulleyed Loess Plateau

The analysis of BS data in Table 1 shows that the initial soil fertility in the hilly and gully region of the Loess Plateau was low. After the formation of the algae-moss mixed crust, the soil chemical indices of the MC samples were significantly higher than those of the other two soil samples, except for pH (Table 1). Notably, although the content of total nitrogen, available phosphorus, available potassium, and organic matter in the MC and MCS samples was higher than in the BS samples, these differences did not reach a significant level. This still suggests that the algae-moss mixed crust formed on both sides of the gully in the Loess Plateau can effectively activate soil nutrients and transfer them to adjacent soil layers.Table 1 Analysis of soil physical and chemical properties of different samples.

Sample type	SOM/(g·kg−1)	TN/(g·kg−1)	AP/(mg·kg−1)	AK/(mg·kg−1)	pH	
MC	5.79 ± 0.41 a	0.51 ± 0.05 a	12.65 ± 0.41 a	70.00 ± 0.81 a	8.07 ± 0.04 b	
MCS	4.22 ± 0.47 b	0.40 ± 0.04 b	11.15 ± 0.85 ab	68.33 ± 7.85 a	8.26 ± 0.08 a	
BS	3.25 ± 0.41 b	0.31 ± 0.01 b	9.51 ± 0.98 b	64.00 ± 7.48 a	8.05 ± 0.09 b	
(1) Means ± standard error, different letters in the same row mean the significant difference between treatments (Duncan method, P < 0.05). (2) MC, Mixed crust; MCS, Mixed crust subsoil; BS, Bare soil on the surface; AP, available phosphorus, AK, available potassium, TN, total nitrogen, OM, organic matter. The same below.

Impact of crust on soil bacterial diversity

The analysis of soil microbial diversity, including the Shannon–Wiener index and the Chao richness estimator in Fig. 2, showed that the microbial diversity index of the soil in the Jiexiao area (MC) was significantly lower than that of the Jiexiao area (MCS) and the surface bare soil (BS). According to Fig. 2C, regarding the variation of microbial community structure in different soil types, the first principal component (PC1) explained 83.23% of the variation, and the second principal component (PC2) explained 6.07% of the variation. This effectively reflects the characteristics of microbial community structure in different soil types. PC1 can distinguish the microbial community structure of soil in the subcutaneous layer (MC) from that in the subcutaneous layer (MCS). There were significant differences in the bacterial community composition between the nodules (MC) and the other two soil samples. Interestingly, the subcutaneous soil (MCS) and the surface bare soil (BS) differed in the dimensions of PC1 and PC2 but could not be effectively distinguished.Fig. 2 Principal component analysis of Alpha and Beta diversity of different samples.

Effect of crust on soil bacterial community composition

The Circos diagram of bacterial community composition at the class level (Fig. 3) shows bacteria with a relative abundance of less than 0.01% classified as "others". The top 17 bacterial classes in relative abundance are depicted in the figure.Fig. 3 Ternary phase diagram of the relationship between samples and species.

The top seven bacteria in relative abundance were Actinobacteria, Alphaproteobacteria, Rubrobacteria, Thermoleophilia, Chloroflexia, Bacteroidia, and Cyanobacteria. Interestingly, compared to the other two soil sample groups, Cyanobacteria in the substrate layer (MC) accounted for 77.37%, which was significantly higher than in the surface bare soil (BS) (15.02%) and the substrate layer (MCS) (7.61%). Another ternary diagram at the class level (Fig. 4) shows that Rubrobacteria and Cyanobacteria are enriched in the soil samples in the nodal cortex (MC).Fig. 4 Circos diagram of the relationship between samples and species.

Species differences between groups

The top 50 species in relative abundance at the class level were selected to analyze the differences between groups. Figure 5A shows the analysis of species differences between the MC and MCS soil sample groups. In MC and MCS, Cyanobacteria, Chloroflexi, Rubrobacteria, Bacilli, Acidimicrobiia, and Thermoleophilia exhibited significant differences between the treatments. Acidimicrobacteria and Pyrophilic Oleobacteria are two of the earlier evolved branches of the phylum Actinomycetes. Their abundance in the soil (MCS) below the nodule cortex is much higher than in the nodule cortex. Notably, the relative abundance of Cyanobacteria is much higher in MC than in MCS. Furthermore, analysis of the differences between MC and BS soil samples showed that Rubrobacteria and Cyanobacteria were specifically enriched in MC (Fig. 5B).Fig. 5 Analysis of species differences between MC and BS (A) and MCS (B) at the class level.

Relationship between environmental factors and soil bacterial community composition

Figure 6 illustrates the relationship between soil chemical properties and bacterial community composition using RDA (Redundancy Analysis). The interpretative values of the RDA1 and RDA2 axes are 74.0% and 3.79%, respectively. The effects of environmental factors on the composition of the bacterial community were total organic matter (SOM), total nitrogen (TN), available phosphorus (AP), pH, and available potassium. In Fig. 6, the sampling points are distributed across two regions. Region I, the positive semi-axial part of RDA1, includes the sample points of MCS and BS. Region II, the negative axis of RDA1, includes the MC sample points. The bacterial community composition of BS and MCS in Region I was negatively correlated with pH and positively correlated with other factors. The bacterial community composition of the MC sample group in Region II was positively correlated with all factors except pH. Detailed analysis showed that Rubrobacter tended to be enriched in the biological cortex, and correlation analysis indicated that Rubrobacter was significantly positively correlated with organic matter content.Fig. 6 RDA analysis of bacterial community composition and soil chemical properties. Points of different colors or shapes in the figure represent sample groups under different environments or conditions; species in the RDA figure are represented by green arrows by default; species in the figure are represented by green inverted triangles; the red arrow represents the quantitative environmental factor, and the length of the environmental factor arrow represents the degree of influence (interpretation) of the environmental factor on the species data; the angle between the arrows of environmental factors represents positive and negative correlation (acute angle: positive correlation; obtuse angle: negative correlation; right angle: no correlation); projection from the sample point to the arrow of the quantitative environmental factor, the distance between the projection point and the origin represents the relative influence of the environmental factor on the distribution of the sample community.

Discussion

The presence of biological crust has a substantial impact on the α diversity of bacteria

The microbial alpha diversity index is a crucial indicator for evaluating the diversity of soil microbial communities. This study found that the Chao 1 index, Shannon index, and PD index of biological crust bacteria were highest in bare land, lowest in algal crust, and then showed an upward trend. In bare land, the organic matter content and bacterial abundance were both the lowest, indicating a very low number of bacteria. The weak competition between different bacterial species allowed them to coexist, leading to higher alpha diversity in bare land26. During the algal crust stage, the reproduction and increase of filamentous cyanobacteria gradually became dominant 26, causing other species to be at a disadvantage and possibly exit the bacterial community. This resulted in the lowest alpha diversity in the algal crust stage. As the biological crust develops into lichen crust and moss crust, lichens provide more abundant organic matter27, which benefits the growth and reproduction of bacterial communities. Consequently, the alpha diversity of bacteria in lichen and moss crusts is significantly higher than in algal crust. However, as the number of bacteria increases in the lichen and moss crust stages, competition between different species intensifies, potentially eliminating less competitive species and reaching a stable equilibrium state. This may explain why the alpha diversity of bacteria in lichen and moss crusts is lower than in bare land28. This study found Rubrobacter significantly enriched in the biocrust layer. RDA (redundancy analysis) revealed a significant positive correlation between Rubrobacter and soil effective phosphorus, nitrogen, and organic matter content (Fig. 6). The higher relative abundance of Rubrobacter may be due to increased organic matter and fast-acting phosphorus in the biocrusts, and possibly the increased density of bacteria in the biocrusts. Although bacterial biomass was not measured in this study, other studies have confirmed higher bacterial biomass in biocrusts compared to bulk soils29. The dominant species of the biological crust play a key role in the formation and development of the biological crust. This study demonstrates that Rubrobacteria and Cyanobacteriia are significantly enriched in the crust layer. Their enrichment is significantly positively correlated with available soil phosphorus, organic matter, and total nitrogen. These research conclusions are less reported in previous studies.

Effect of crust type on biocrust and underlying soil chemistry

The positive effects of biocrusts on surface C and N accumulation have been demonstrated in various ecosystems30–33. In this study, our objective is to delve deeper into the microbial processes that facilitate the enrichment of soil nutrients and the alteration of soil physicochemical properties through the succession of biological crusts. We have refined our research methodologies to focus more intently on the intricate dynamics of the bacterial communities within and beneath the crust layer, as well as the distinct phases of biological crust succession. Notably, we have observed significant shifts in the dominant species throughout these stages, which are crucial for the formation and maturation of the biological crusts. We found that the C and N content of biological crusts was significantly higher than that of the top bare soil and the soil below the crust. The microbial diversity index of the soil in the crust layer was significantly lower than that of the soil below the crust and the top bare soil. Additionally, the positive impacts of biocrusts on underlying soil nutrients have been documented. For example, in a sandy dune system, Xu et al. 34 detected higher organic matter, total N, and available N in soils underneath biocrusts compared to non-crusted soil. Although leaching of available N from biocrusts has been clearly demonstrated35,36, this phenomenon has not been uniformly observed, making the fate of available biocrust N a controversial topic34,36,37. Lichen-type crusts were not considered in the present results, although they also function to increase soil nutrients. In the Loess Plateau area, lichen crust cover is less than 10% 38. Therefore, the contribution of lichen-type crusts to soil nutrients in this zone is usually ignored. Using biocrust as a model ecosystem, this study confirmed the relationship between biocrust bacterial community structure and soil nutrients. Specifically, the organic carbon and effective nitrogen contents of mixed biocrust soils were closely associated with significant enrichment of specific bacterial communities. These results have important implications for predicting the accumulation of soil nutrients by mixed biocrust on a larger scale.

Conclusions

The Loess Plateau faces severe soil erosion and a fragile ecological environment, which limits the development of the local economy and society. Biological crusts, widely distributed in arid and semi-arid regions, possess various key attributes and ecological functions. Algae-moss crusts can significantly increase the content of available phosphorus, total nitrogen, and organic matter in soils in the hilly and gully region of the Loess Plateau. This study revealed the effects of biological crust on soil physical and chemical properties and bacterial community structure in the loess hilly region. A significant increase in the relative abundance of many potentially beneficial microorganisms, such as Rubrobacteria and Cyanobacteria, was observed in the bionode cortex. Redundancy analysis showed a significant correlation between the bacterial community in the biological crusts of the hilly and gully regions of the Loess Plateau and changes in the soil content of available phosphorus, total nitrogen, and organic matter. The enrichment of certain bacteria, such as Rubrobacter, may be involved in photosynthesis and nitrogen fixation processes, contributing to an increase in soil organic matter and organic nitrogen. In summary, the succession of biological crusts changes soil physicochemical characteristics and provides different ecological niches for bacterial communities. Soil nutrients and pH play an important role in the selection of bacterial species and the shaping of bacterial communities in the hilly and gully areas of the Loess Plateau.

Acknowledgements

This research was funded by Technology Innovation Center for Land Engineering and Human Settlements, Shaanxi Land Engineering Construction Group Co. Ltd. and Xi’an Jiaotong University (2024WHZ0240), The Innovation Team of Shaanxi Province (2021TD-52), Shaanxi Key Research and Development Program (2022ZDLSF06-04), and Inner scientific research project of Shaanxi Land Engineering Construction Group (DJTD 2022-1, DJNY2024-41, DJNY-YB-2023-40, DJNY-YB-2023-48, DJNY2024-33, DJNY2024-18, DJNY2024-16).

Author contributions

Conceptualization, L.Z.; methodology, L.Z.; software, L.Z.; validation, L.Z.; formal analysis, L.Z.; investigation, L.Z.; resources, L.Z.; data curation, L.Z.; writing—original draft preparation, L.Z.; writing—review and editing, L.Z.; visualization, L.Z.; supervision, L.Z.; project administration, L.Z.; funding acquisition, L.Z. All authors have read and agreed to the published version of the manuscript.

Data availability

The datasets generated and analysed during the current study are not publicly available due [The data are sourced from government classified projects] but are available from the corresponding author on reasonable request. Sequencing raw data was deposited in the NCBI database under the accession number PRJNA926510. This article does not contain any studies with human or animal subjects performed by any of the authors.

Competing interests

The author declares no competing interests.

Publisher's note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
==== Refs
References

1. Ferrenberg S Reed SC Belnap J Climate change and physical disturbance cause similar community shifts in biological soil crusts Proc. Natl. Acad. Sci. 2015 112 39 12116 12121 10.1073/pnas.1509150112 26371310
Ferrenberg, S., Reed, S. C. & Belnap, J. Climate change and physical disturbance cause similar community shifts in biological soil crusts. Proc. Natl. Acad. Sci. 112(39), 12116–12121 (2015).26371310 10.1073/pnas.1509150112
2. Concostrina-Zubiri, L., Molla, I., Velizarova, E., Branquinho, C. Grazing or not grazing: Implications for ecosystem services provided by biocrusts in mediterranean cork oak woodlands. Land Degradation Develop. (2017).
3. Bo, M., Zheng, Y., Faqi, W., Zhanbin, L. Effects of soil crust on slope runoff and sediment yield under soybean cover. Sci. Soil Water Conserv. (2015).
4. Zhao, Y., Gillen, J.R., Harris, D.A., Kron, I.L., Murphy, M.P., Lau, C.L. Treatment with placenta-derived mesenchymal stem cells mitigates development of bronchiolitis obliterans in a murine model. J. Thoracic Cardiovasc. Surg. 147(5) (2014).
5. Valentin C Biological soil crusts: Structure, function and management Geoderma. 2002 107 s3–4 299 301 10.1016/S0016-7061(02)00085-X
Valentin, C. Biological soil crusts: Structure, function and management. Geoderma. 107(s3–4), 299–301 (2002).10.1016/S0016-7061(02)00085-X
6. Balaguer, L., Valladares, F., Chico, J.M., Manrique, E. Energy dissipation in drought-avoiding and drought-tolerant tree species at midday during the Mediterranean summer. Tree Physiol. (2), 131–138.
7. Xinrong, L.I., Yuanming, Z., Yunge, Z. A study of biological soil crusts: Recent development, trend and prospect. Adv. Earth Sci. (2009).
8. Li, M., Liu, Q., Zhang, H., Wells, R.R., Wang, L., Geng, J. Effects of antecedent soil moisture on rill erodibility and critical shear stress. Catena Interdiscip. J. Soil Sci. Hydrol.-Geomorphol. Focusing Geoecol. Landsc. Evolut. (2022).
9. Zhao Y Xu M Potential nitrogen fixation activity of different aged biological soil crusts from rehabilitated grasslands of the hilly Loess Plateau, China J. Arid Environ. 2010 74 10 1186 1191 10.1016/j.jaridenv.2010.04.006
Zhao, Y. et al. Potential nitrogen fixation activity of different aged biological soil crusts from rehabilitated grasslands of the hilly Loess Plateau, China. J. Arid Environ. 74(10), 1186–1191 (2010).10.1016/j.jaridenv.2010.04.006
10. Zhang YM Wang HL Wang XQ Yang WK Zhang DY The microstructure of microbiotic crust and its influence on wind erosion for a sandy soil surface in the Gurbantunggut Desert of Northwestern China Geoderma 2006 132 3–4 441 449 10.1016/j.geoderma.2005.06.008
Zhang, Y. M., Wang, H. L., Wang, X. Q., Yang, W. K. & Zhang, D. Y. The microstructure of microbiotic crust and its influence on wind erosion for a sandy soil surface in the Gurbantunggut Desert of Northwestern China. Geoderma 132(3–4), 441–449 (2006).10.1016/j.geoderma.2005.06.008
11. Shen-Qi, X., Li-Qian, G., Yun-Ge, Z., Yue-Wei, G. Responses of runoff and soil loss from biological soil crustal slope to rainfall intensity under simulated rainfall. Chin. J. Appl. Ecol. (2019).
12. Guixiang, L., Keming, M. PICRUSt-based predicted metagenomic analysis of treeline soil bacteria on Mount Dongling, Beijing. Acta Ecologica Sinica. 38(6) (2018).
13. Liu C Jin Y Hu Y Tang J Xiong Q Xu M Drivers of soil bacterial community structure and diversity in tropical agroforestry systems Agric. Ecosyst. Environ. 2019 278 24 34 10.1016/j.agee.2019.03.015
Liu, C. et al. Drivers of soil bacterial community structure and diversity in tropical agroforestry systems. Agric. Ecosyst. Environ. 278, 24–34 (2019).10.1016/j.agee.2019.03.015
14. Ting, L., Wei, Z., Guangxiu, L., Tuo, C. Advances in the study of microbial ecology in desert soil. J. Desert Res. (2018).
15. Zhang XC Li JY Liu JL Cun-XiaYuan YXF Temporal shifts in cyanobacterial diversity and their relationships to different types of biological soil crust in the southeastern Tengger Desert Rhizosphere. 2021 17 100322 10.1016/j.rhisph.2021.100322
Zhang, X. C., Li, J. Y., Liu, J. L. & Cun-XiaYuan, Y. X. F. Temporal shifts in cyanobacterial diversity and their relationships to different types of biological soil crust in the southeastern Tengger Desert. Rhizosphere. 17, 100322 (2021).10.1016/j.rhisph.2021.100322
16. Gholamhosseinian, M.E., Iraj. Assessing the role of lichens in the prevention of dust emission in dryland: Case study at north-eastern Iran. Aeolian Res. 50(1) (2021).
17. Liu Y Li X Xing Z Zhao X Pan Y Responses of soil microbial biomass and community composition to biological soil crusts in the revegetated areas of the Tengger Desert Appl. Soil. Ecol. 2013 65 52 59 10.1016/j.apsoil.2013.01.005
Liu, Y., Li, X., Xing, Z., Zhao, X. & Pan, Y. Responses of soil microbial biomass and community composition to biological soil crusts in the revegetated areas of the Tengger Desert. Appl. Soil. Ecol. 65, 52–59 (2013).10.1016/j.apsoil.2013.01.005
18. Zhao, P., Liu, J., Jia, T., Wang, Y., Chai, B. Environmental filtering drives bacterial community structure and function in a subalpine area of northern China. J. Basic Microbiol. (2019).
19. Martin, M. Cutadapt removes adapter sequences from high-throughput sequencing reads. Embnet J. 17(1) (2011).
20. Rognes, T., Flouri, T., Nichols, B., Quince, C., Mahé, F. VSEARCH: A versatile open source tool for metagenomics. PeerJ. 4(10) (2016).
21. Halushka M Fan J Bentley K Hsie L Shen N Weder A Patterns of single-nucleotide polymorphisms in candidate genes for blood-pressure homeostasis Nat. Genet. 1999 22 3 239 247 10.1038/10297 10391210
Halushka, M. et al. Patterns of single-nucleotide polymorphisms in candidate genes for blood-pressure homeostasis. Nat. Genet. 22(3), 239–247 (1999).10391210 10.1038/10297
22. Siqueira ELS Silva RR Taxonomic and morphological diversity of the ground-dwelling ant fauna in Eastern Amazonian grasslands Acta Oecologica 2021 110 103693 10.1016/j.actao.2020.103693
Siqueira, E. L. S. & Silva, R. R. Taxonomic and morphological diversity of the ground-dwelling ant fauna in Eastern Amazonian grasslands. Acta Oecologica 110, 103693 (2021).10.1016/j.actao.2020.103693
23. Salazar-Ramrez MT Senz-Mata J Preciado-Rangel P Fortis-Hernndez M Orozco-Vidal JA Plant growth-promoting rhizobacteria associated to candelilla rhizosphere (Euphorbia antisyphilitica) and its effects on Arabidopsis thaliana seedlings Notulae Botanicae Horti Agrobotanici Cluj-Napoca 2021 49 2 12294 10.15835/nbha49212294
Salazar-Ramrez, M. T., Senz-Mata, J., Preciado-Rangel, P., Fortis-Hernndez, M. & Orozco-Vidal, J. A. Plant growth-promoting rhizobacteria associated to candelilla rhizosphere (Euphorbia antisyphilitica) and its effects on Arabidopsis thaliana seedlings. Notulae Botanicae Horti Agrobotanici Cluj-Napoca 49(2), 12294 (2021).10.15835/nbha49212294
24. Parfrey, W.L., L. Stilianos, D. Michael. Decoupling function and taxonomy in the global ocean microbiome. Science. (2016).
25. Kaiser K Wemheuer B Korolkow V Wemheuer F Nacke H SchNing I Driving forces of soil bacterial community structure, diversity, and function in temperate grasslands and forests Sci. Rep. 2016 6 33696 10.1038/srep33696 27650273
Kaiser, K. et al. Driving forces of soil bacterial community structure, diversity, and function in temperate grasslands and forests. Sci. Rep. 6, 33696 (2016).27650273 10.1038/srep33696
26. Bai J Xu DM Xie DM Wang MS Li ZQ Guo XS Effects of antibacterial peptide-producing Bacillus subtilis and Lactobacillus buchneri on fermentation, aerobic stability, and microbial community of alfalfa silage Biores. Technol. 2020 315 123881 10.1016/j.biortech.2020.123881
Bai, J. et al. Effects of antibacterial peptide-producing Bacillus subtilis and Lactobacillus buchneri on fermentation, aerobic stability, and microbial community of alfalfa silage. Biores. Technol. 315, 123881 (2020).10.1016/j.biortech.2020.123881
27. Krucon T Dziewit L Drewniak L Insight into ecology, metabolic potential, and the taxonomic composition of bacterial communities in the periodic water pond on King George Island (Antarctica) Front. Microbiol. 2021 12 708607 10.3389/fmicb.2021.708607 34690951
Krucon, T., Dziewit, L. & Drewniak, L. Insight into ecology, metabolic potential, and the taxonomic composition of bacterial communities in the periodic water pond on King George Island (Antarctica). Front. Microbiol. 12, 708607 (2021).34690951 10.3389/fmicb.2021.708607
28. Ngosong C Buse T Ewald M Richter A Ruess L Influence of management intensity and environmental conditions on microbiota in biological soil crust and crust-free soil habitats of temperate forests Soil Biol. Biochem. 2020 144 107761 10.1016/j.soilbio.2020.107761
Ngosong, C., Buse, T., Ewald, M., Richter, A. & Ruess, L. Influence of management intensity and environmental conditions on microbiota in biological soil crust and crust-free soil habitats of temperate forests. Soil Biol. Biochem. 144, 107761 (2020).10.1016/j.soilbio.2020.107761
29. Beraldi-Campesi H Hartnett HE Anbar A Gordon GW Garcia-Pichel F Effect of biological soil crusts on soil elemental concentrations: Implications for biogeochemistry and as traceable biosignatures of ancient life on land Geobiology 2010 7 3 348 359 10.1111/j.1472-4669.2009.00204.x
Beraldi-Campesi, H., Hartnett, H. E., Anbar, A., Gordon, G. W. & Garcia-Pichel, F. Effect of biological soil crusts on soil elemental concentrations: Implications for biogeochemistry and as traceable biosignatures of ancient life on land. Geobiology 7(3), 348–359 (2010).10.1111/j.1472-4669.2009.00204.x
30. Heindel RC Governali FC Spickard AM Virginia RA The role of biological soil crusts in nitrogen cycling and soil stabilization in Kangerlussuaq, West Greenland Ecosystems 2019 22 2 243 256 10.1007/s10021-018-0267-8
Heindel, R. C., Governali, F. C., Spickard, A. M. & Virginia, R. A. The role of biological soil crusts in nitrogen cycling and soil stabilization in Kangerlussuaq, West Greenland. Ecosystems 22(2), 243–256 (2019).10.1007/s10021-018-0267-8
31. Maier, S., Tamm, A., Dianming, C., et al. Photoautotrophic organisms control microbial abundance, diversity, and physiology in different types of biological soil crusts. ISME J. Emultidiscip. J. Microbial Ecol. (2018).
32. Brankatschk, R., Fischer, T., Veste, M., Zeyer, J. Succession of N cycling processes in biological soil crusts on a Central European inland dune. Wiley/Blackwell (101111) 2013(1).
33. Guo, Y., Zhao, H., Zuo, X., Drake, S., Zhao, X. Biological soil crust development and its topsoil properties in the process of dune stabilization, Inner Mongolia, China. Environ. Geol. (2008).
34. Xu H Zhang Y Shao X Liu N Soil nitrogen and climate drive the positive effect of biological soil crusts on soil organic carbon sequestration in drylands: A Meta-analysis Sci. Total Environ. 2022 803 150030 10.1016/j.scitotenv.2021.150030 34525688
Xu, H., Zhang, Y., Shao, X. & Liu, N. Soil nitrogen and climate drive the positive effect of biological soil crusts on soil organic carbon sequestration in drylands: A Meta-analysis. Sci. Total Environ. 803, 150030 (2022).34525688 10.1016/j.scitotenv.2021.150030
35. Wang J Xiao J Zhang Z Yang L Liu Z Cheng Y Changes of bacterial community structure, monosaccharide composition and CO2 exchange along the successional stages of biological soil crusts Environ. Geochem. Health 2023 45 7 5387 5400 10.1007/s10653-023-01572-1 37147551
Wang, J. et al. Changes of bacterial community structure, monosaccharide composition and CO2 exchange along the successional stages of biological soil crusts. Environ. Geochem. Health 45(7), 5387–5400 (2023).37147551 10.1007/s10653-023-01572-1
36. Johnson SL Neuer S Garcia-Pichel F Export of nitrogenous compounds due to incomplete cycling within biological soil crusts of arid lands Environ. Microbiol. 2010 9 3 680 689 10.1111/j.1462-2920.2006.01187.x
Johnson, S. L., Neuer, S. & Garcia-Pichel, F. Export of nitrogenous compounds due to incomplete cycling within biological soil crusts of arid lands. Environ. Microbiol. 9(3), 680–689 (2010).10.1111/j.1462-2920.2006.01187.x
37. Wang, B., Huang, Y., Li, N., Yao, H., Yang, E., Soromotin, A.V. et al. Initial soil formation by biocrusts: Nitrogen demand and clay protection control microbial necromass accrual and recycling. Soil Biol. Biochem. (167), 167 (2022).
38. Wang, Q.L. Soil erosion resistance of "Grain for Green" vegetation types under extreme rainfall conditions on the Loess Plateau, China. Catena Interdiscip. J. Soil Sci. Hydrol.-Geomorphol. Focusing Geoecol. Landsc. Evolut. 141(Null) (2016).
