Effects of cyanobacterial soil crusts on surface roughness and splash erosion

Soil surface roughness (SSR) modifies interactions and feedback processes between terrestrial 20 and atmospheric systems driven by both the abiotic and biotic components of soils. This paper 21 compares SSR response to a low intensity multi-day rainfall event for soils with and without 22 early successional stage cyanobacteria-dominated biological soil crusts (CBCs). A rainfall 23 simulator was used to apply 2 mm, 5 mm and 2 mm of rain separated by a 24-hour period over 3 days at an intensity of 60 mm hr-124 . Changes in SSR were quantified using geostatistically25 derived indicators calculated from semivariogram analysis of high resolution laser scans. The 26 CBCs were stronger and splash erosion substantially less than from the physical soil crusts. 27 Prior to rainfall treatment soils with CBCs had greater SSR than those without. The rainfall 28 treatments caused the physical crusted soils to increase SSR and spatial patterning due to the 29 translocation of particles, soil loss and the development of raindrop impact craters. Rainfall 30 caused swelling of cyanobacterial filaments but only a slight increase in SSR, and raindrop 31 impact cratering and splash loss were low on the soils with CBCs.There is no relationship 32 between random roughness and splash erosion, but an increase in splash loss was associated with 33 an increase in topographic roughness and small-scale spatial patterning. A comparison of this 34 study with other research indicates that for rainfall events up to 100 mm the effectiveness of 35 CBCs in reducing soil loss is >80% regardless of the rainfall amount and intensity which 36 highlights their importance for landscape stabilization.