Soil nutrient loss by gully erosion on sloping alpine steppe in the northern Qinghai-Tibetan Plateau

Global warming and grazing activities have exacerbated soil erosion in alpine steppe. Gully erosion is a great threat to land degradation in alpine steppe ecosystem. Yet, little is known about the in-situ effects of gully erosion on soil properties at cross section and lengthwise position in alpine steppe ecosystem on the Qinghai-Tibetan Plateau. Here, we used a paired sampling method to compare the soil properties of two erosion gullies (shallow gully and deep gully) at cross section and lengthwise position. The results showed that gully erosion generally induced serious soil nutrient loss and differed between shallow gully and deep gully. However, available phosphorus variation (Delta AP) showed an increase both in shallow gully (from -0.86% to 17.17%) and deep gully (from 8.00% to 45.60%), and pH variation (Delta pH) showed an increase (from -3.40% to 9.01%) in the deep gully. Soil sand content and soil nutrient properties were more sensitive to gully erosion in different cross sections than that in different lengthwise positions, which indicated that the depth of erosion gullies largely determining soil nutrients loss in erosion gullies. Therefore, it is necessary to pay more attention to the ecological restoration of deep erosion gullies to control soil loss and reduce the loss of soil nutrients. These results may conducive to offer a theoretical guidance to achieve the combined goal of gully erosion regulation of alpine steppe ecosystem on the Qinghai-Tibetan Plateau.

Automated summary

The study found that gully erosion generally leads to serious soil nutrient loss and varies between shallow gully and deep gully. However, both shallow gully and deep gully showed an increase in available phosphorus variation, while deep gully also demonstrated an increase in pH variation. Soil sand content and soil nutrient properties were more sensitive to gully erosion in different cross sections, indicating that the depth of erosion gullies largely determines soil nutrient loss.