Chinese zokor (Myospalax fontanierii) excavating activities lessen runoff but facilitate soil erosion - A simulation experiment

The Chinese zokor (Myospalax fontanierii) affects the physical and chemical properties of soil and the evolution of vegetation. However, few studies have evaluated the effects of zokors on soil erosion. In this study, alfalfa (Medicago sativa L.) was planted in tanks to quantify the effects of zokor excavation activities on runoff and soil erosion rate. Three slope gradients of 5 degrees, 10 degrees, and 15 degrees were set, two soil tanks (with and without a zokor) were used for each gradient, and six soil tanks were prepared in total. Laboratory simulated rainfall was applied using a side-spray simulation system, and the rainfall intensity was set to 80 mm h(-1) with the rainfall duration of 60 min after runoff generation. Results showed that the soil bulk density of fresh zokor mounds was 0.82 +/- 0.02 g cm(-3), which was 39% lower than that of the soil matrix (1.35 g cm(-3)). The vegetation coverage decreased to 32%, 45%, and 43% respectively, after 3 days of disturbance by zokor, compared with 87%, 90%, and 92% in the tanks without zokor. The presence of zokor reduced the runoff rate by 88% on the lowest gradient to 21% on the steepest gradient, and increased the water infiltration and soil water storage within 90 cm depth. The soil mounds and herbivorous tunnel changed the microtopography and consequently the runoff pathway, increased the sediment yield, and intensified soil erosion, especially at a steep slope gradient. Although the activity of zokors does not directly increase soil erosion, and the tunnel system can facilitate water infiltration and lessen runoff, the mounds they create provide loose and erodible materials. The destruction of vegetation by zokors would facilitate soil erosion and reduce the benefit of vegetation restoration. This study provides insights into the effects of subterranean rodents on soil erosion in the Loess Plateau.