Purpose

Biological soil crusts (biocrusts) are commonly found in semi-arid ecosystems and complete biological nitrogen (N) fixation, build soil carbon (C) stocks, and increase soil moisture. Biocrusts were recently identified in Florida agroecosystems, and based on traits of semi-arid biocrusts, could contribute to crop growth and soil health. This study determined the influence of biocrusts in a Florida citrus orchard on microbial diversity and composition of surface and crop root zone soil as related to soil C, N, and moisture.

Methods

Soil samples were collected from areas with biocrust and proximate bare soil (control) in a Florida, USA, citrus orchard. Cores were divided into three soil depths, and soil bacterial and fungal communities were characterized using the 16S rRNA gene and ITS region sequences, respectively.

Results

Biocrust presence and sampling depth significantly impacted microbial community composition. Cyanobacteria and heterotrophic diazotrophs had low relative abundances compared to copiotrophic bacteria in the biocrust soil. Soil below biocrusts had increased moisture, nutrient concentrations, and relative abundances of nitrifying bacteria compared to the root zone below bare soil. Copiotrophic bacteria were enriched under biocrusts, indicating potential for nutrient competition between roots and microorganisms. Biocrust subsoil had elevated relative abundances of Ascomycota and Basidiomycota which contributed to higher fungal community richness and evenness in the rooting zone.

Conclusions

Biocrust subsoil had increased relative abundances of microbiota compared to bare soil without biocrusts, potentially influencing nutrient cycling, crop nutrient uptake and growth, and soil health.

中文翻译：

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沙质农业生态系统中的生物土壤结壳构造了地下微生物组

目的

在半干旱的生态系统中通常会发现生物土壤结皮（生物结皮），并能完全固定生物氮（N），建立土壤碳（C）储量并增加土壤湿度。最近在佛罗里达州的农业生态系统中发现了生物结皮，该生物结皮基于半干旱生物结皮的特性，可以促进作物生长和土壤健康。这项研究确定了佛罗里达柑桔园中的生物结皮对微生物多样性以及与土壤碳，氮和水分有关的表层和作物根区土壤成分的影响。

方法

从美国佛罗里达州柑桔园中具有生物结皮和邻近裸露土壤（对照）的地区收集土壤样品。将核心分为三个土壤深度，分别使用16S rRNA基因和ITS区域序列表征土壤细菌和真菌群落。

结果

生物结皮的存在和取样深度显着影响了微生物群落组成。蓝细菌和异养重氮菌比生物壳土壤中的营养缺陷菌具有较低的相对丰度。与裸露土壤的根部区域相比，生物结皮之下的土壤具有增加的水分，养分浓度和硝化细菌的相对丰度。亲营养菌在生物结壳下富集，表明根与微生物之间存在营养竞争的潜力。地壳生物底土中的子囊菌和担子菌菌落的相对丰度较高，这有助于生根区真菌群落的丰富度和均匀度提高。

结论

与没有生物结皮的裸露土壤相比，生物结皮下层土壤的微生物群落相对丰度增加，可能影响养分循环，作物养分吸收和生长以及土壤健康。