Biocrusts impact soil properties and ecological stoichiometry characteristics in frozen ground regions on the Qinghai-Tibet Plateau

Biocrusts are one of the most important components of the land cover in frozen ground regions on the Qinghai–Tibet Plateau, which increased the silt particle content, enhanced field moisture capacity, and reduced soil bulk density. Biocrusts significantly increased levels of SOC (22.6–30.8 g kg −1 ) and TN (2.1–2.8 g kg −1 ) within the 0–40 cm soil layer, while they had no significant influence on the TP contents. Biocrusts also had influence on the stoichiometry characteristics, and the C/N, C/P and N/P ratios of the biocrusts were all higher than that of the bare land, which revealed that biocrusts enhanced the contents of SOC and TN in presuccessional period of biocrusts and reduced the availability of P in their post-successional period. Biocrusts (BSCs) are widely distributed in frozen ground regions on the Qinghai-Tibet Plateau, and they are considered an important component of cold ecosystems. However, the specific impacts of BSCs on frozen soil remains relatively unclear. The aim of our study was to clarify the influence of BSCs (light BSCs and dark BSCs in two different succession stages) on the physical properties and ecological stoichiometry characteristics of frozen soil. Our results showed that BSCs increased the silt particle content in 20–40 cm soil layer, leading to a decrease in soil bulk density. And the field water capacity increased about 10%–40% compared to bare land. Additionally, BSCs significantly increased the contents of soil organic carbon (SOC, 22.6–30.8 g kg −1 ) and total nitrogen (TN, 2.1–2.8 g kg −1 ) in the upper 40 cm soil layer, both of them were approximately 1.3–2.0 and 1.3–4.0 times higher than those observed in bare land. However, BSCs did not have significant influence on soil total phosphorus (TP). BSCs had a significant impact on the stoichiometric ratios within 40 cm. The C/N ratios of the two types of BSCs ranged from 8.8 to 13.5, the C/P ratios ranged from 6.6 to 13.8, and the N/P ratios ranged from 0.6 to 1.2, which were all higher than those of the bare land. There were no significant differences among the C/N, C/P, and N/P ratios between two types of BSCs. However, the increment of C/P and N/P ratios of dark BSCs were significantly higher than those of light BSCs within 0–30 cm, which indicated that a reduction in the availability of phosphorus during the later stages of BSCs succession. These findings provided a theoretical basis for further research on the ecological functions of BSCs in frozen ground regions.