Soil surface roughness exerts profound influence on runoff and sediments yield from
slopes． Biological soil crusts ( BSCs) are ubiquitous living cover in the open spaces between plants
in arid and semiarid ecosystems，which considerably impact the surface roughness． Aimed to determine
the effect of biological crusts on the surface roughness and its influence factors，this study investigated
the surface roughness of soil with BSCs at their different successional stages by using the
chain method． Besides，the impacts of slope aspects，soil water content and freezing and thawing on
surface roughness were also investigated． Then，the correlations between roughness and soil chemical
and physical properties were evaluated． The results showed that soil surface roughness decreased
at the initial successional stage of BSCs but increased along with BSCs’development in the region．
Soil roughness tended to be stabile since BSCs developed ten years later． The roughness was reduced
by 47． 0% by the light cyanobacteria-dominated crust and 20． 4% by the dark cyanobacteriadominated
crust ( moss coverage ＜ 20%) ，compared with the bare soil． Soil moisture significantly
impacted surface roughness． The surface roughness of BSCs changed obviously with soil moisture in
the early development，but only slightly in their later succession． Freezing-thawing also affected
surface roughness with BSCs． Ｒoughness was more susceptible to freezing-thawing in the early de-velopment of BSCs，with an increase of 29． 7% compared with the bare soil． The surface roughness
of late successional BSCs exhibited a slight change only after repeated freezing-thawing． The surface
roughness of BSCs showed a statistically significant relationship with the coverage of moss ( P ＜
0． 1) ．
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