Purpose

Thaw slumps are widely distributed in the Qinghai-Tibet Plateau (QTP) due to global warming and engineering constructions. However, an understanding of the effect of thaw slumps on the 3-D soil macropore networks is lacking. In this study, we aimed to quantify the responses of soil macropore structure to thaw slumps in QTP.

Materials and methods

Three stages were selected according to the intensities of thaw slumping, including the original grassland, collapsing areas, and collapsed areas. Nine undisturbed soil cores (0–30-cm deep) were collected in total with 3 replicates sampled at each stage, and they were scanned by X-ray computed tomography (CT).

Results and discussion

The results showed that collapsing areas had higher macroporosity, branch density, and node density than the original grassland and collapsed areas. The macropore networks in the collapsing areas had the highest connectivity among the three thaw slump stages. Macropores with volume > 10 mm³ accounted for more than 50% of the total macropore volume in the original grassland, collapsing areas, and collapsed areas. We speculate that compared with the other two stages, the soil macropore structure in the collapsing areas is more conducive to water infiltration and lateral migration. The connectivity of macropore networks in the collapsed areas was the lowest among the three stages, which may result in water infiltration difficulties after thaw slumps.

Conclusions

Thaw slumps affected the soil macropore structure remarkably. The effects of thaw slumps on soil macropore network characteristics were more significantly than on the macropore size distribution.