Soil cracking is an important process and feature of degradation in terrestrial ecosystems. However, the patterns and causes of cracks related to alpine rangeland overgrazing have not been reported. In this study, we used a multiscale approach to investigate the distribution of soil-cracking areas at a landscape scale (217 survey sites), selected the grazing-induced parameter that was closely related to the cracks at a small scale (2013)(2014)(2015)(2016)(2017), and evaluated the water infiltration due to mosaic cracking at a microscale. The results showed that cracks only formed in the alpine meadow after overstocking. Soil compaction and water content explained 89.0% of the total variance in the crack characteristics, and soil compaction was closely related to cracking. The initial infiltration rate and steady infiltration rate of the healed cracks were significantly higher than those in the raised areas in the centre of the mosaic crack patches (p < .001). We propose a new model of alpine meadow degradation considering the cracking phenomenon due to overgrazing and provide key and easy-to-measure indicators to prevent overgrazing and cracking: a residual biomass greater than 65 g m −2 and a height greater than 6 cm, and the soil compaction should be lower than 1,044.26 ± 188.88 kPa. These safeguard thresholds warn rangeland managers to reduce the stocking rate or improve grazing management.We suggest that the cracking stage of alpine rangelands is the most critical turning point in the process of rangeland degradation and that rangeland managers should pay more attention to crack phenomena to prevent severe degradation.

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Background Plateau zokor (Myospalax baileyi) is a subterranean rodent endemic to the Tibetan Plateau. This species has been generally viewed as a pest in China due to the competition for food with livestock and also causing soil erosion. As a result, plateau zokor has been the target of widespread poisoning or trapping campaigns designed to control or eliminate it since 1970s. But there is little research on the effect of plateau zokor on plant diversity in alpine rangelands. Therefore, objectively evaluating the positive effects of the plateau zokors disturbance on their living environment and plant communities is of great significance to understand the function of plateau zokor in alpine ecosystem. Methods Here, we selected three rangelands (alpine meadow, alpine steppe and alpine shrub meadow) in which plateau zokors are typically distributed on the Tibetan Plateau, and five zokor mound density gradients were selected in each rangeland type to study the effects of the mounds on soil moisture and temperature related to plant species diversity. Results The results showed that, with the mound density increasing, the soil temperature decreased significantly in all three rangeland types, and the soil moisture significantly increased in all three rangeland types. In the alpine meadow, both the plant diversity and cumulative species richness increased significantly with increasing mound density. The increase in broad-leaved forbs is the main reason for the increase of plant diversity in the alpine meadow disturbed by zokor mounds. In the alpine steppe, the plant diversity decreased significantly with increasing mound density, while the cumulative species richness initially decreased and then increased. In the alpine shrub meadow, the plant diversity first increased and then decreased with increasing mound density as did the cumulative species richness. In conclusion, plateau zokor mounds dominated the distribution of soil moisture and temperature and significantly affected plant diversity in these three rangelands on Tibetan Plateau; the results further deepen our understanding toward a co-evolved process.

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