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Abstract. Soils on the Qinghai–Tibetan Plateau (QTP) have distinct physical propertiesfrom agricultural soils due to weak weathering and strong erosion. Theseproperties might affect permafrost dynamics. However, few studies haveinvestigated both quantitatively. In this study, we selected a permafrostsite on the central region of the QTP and excavated soil samples down to200 cm. We measured soil porosity, thermal conductivity, saturated hydraulicconductivity, and matric potential in the laboratory. Finally, we ran asimulation model replacing default sand or loam parameters with differentcombinations of these measured parameters. Our results showed that the massof coarse fragments in the soil samples (diameter >2  mm) was ∼55  % on average, soil porosity was less than 0.3 m 3  m −3 ,saturated hydraulic conductivity ranged from 0.004 to 0.03 mm s −1 ,and saturated matric potential ranged from −14 to −604  mm. Whendefault sand or loam parameters in the model were substituted with thesemeasured values, the errors of soil temperature, soil liquid water content,active layer depth, and permafrost lower boundary depth were reduced (e.g.,the root mean square errors of active layer depths simulated using measuredparameters versus the default sand or loam parameters were about 0.28, 1.06,and 1.83 m). Among the measured parameters, porosity played adominant role in reducing model errors and was typically much smaller thanfor soil textures used in land surface models. We also demonstrated that soilwater dynamic processes should be considered, rather than using staticproperties under frozen and unfrozen soil states as in most permafrostmodels. We conclude that it is necessary to consider the distinct physicalproperties of coarse-fragment soils and water dynamics when simulatingpermafrost dynamics of the QTP. Thus it is important to develop methods forsystematic measurement of physical properties of coarse-fragment soils and todevelop a related spatial data set for porosity.

The physical properties of coarse-fragment soils and their effects on permafrost dynamics: a case study on the central Qinghai–Tibetan Plateau