Effects of microbiotic crusts under cropland in temperate environments on soil erodibility during concentrated flow

Abstract

Several studies illustrate the wind and water erosion‐reducing potential of semi‐permanent microbiotic soil crusts in arid and semi‐arid desert environments. In contrast, little is hitherto known on these biological crusts on cropland soils in temperate environments where they are annually destroyed by tillage and quickly regenerate thereafter. This study attempts to fill the research gap through (a) a field survey assessing the occurrence of biological soil crusts on loess‐derived soils in central Belgium in space and time and (b) laboratory flume (2 m long) experiments simulating concentrated runoff on undisturbed topsoil samples (0.4 × 0.1 m2) quantifying the microbiotic crust effect on soil erosion rates. Three stages of microbiotic crust development on cropland soils are distinguished: (1) development of a non‐biological surface seal by raindrop impact, (2) colonization of the soil by algae and gradual development of a continuous algal mat and (3) establishment of a well‐developed microbiotic crust with moss plants as the dominant life‐form. As the silt loam soils in the study area seal quickly after tillage, microbiotic soil crusts are more or less present during a large part of the year under maize, sugar beet and wheat, representing the main cropland area. On average, the early‐successional algae‐dominated crusts of stage 2 reduce soil detachment rates by 37%, whereas the well‐developed moss mat of stage 3 causes an average reduction of 79%. Relative soil detachment rates of soil surfaces with microbiotic crusts compared with bare sealed soil surfaces are shown to decrease exponentially with increasing microbiotic cover (b = 0·024 for moss‐dominated and b = 0·006 for algae‐dominated crusts). In addition to ground surface cover by vegetation and crop residues, microbiotic crust occurrence can therefore not be neglected when modelling small‐scale spatial and temporal variations in soil loss by concentrated flow erosion on cropland soils in temperate environments. Copyright © 2007 John Wiley & Sons, Ltd.

Soil erosion resistance effects on rill and gully initiation points and dimensions

“…Subsequent rain events have only a minor effect on Kc (Knapen et al, 2008b). Later in the growing season, when a dense root network has developed and microbiotic crusts appear on many sealed soil surfaces in the Belgian loess belt, Kc will further decrease (Knapen et al, 2007c). However, soil water content changes have a large impact on Kc and may mask the decreasing trend in Kc.…”

“…89, ME = 0 . 78, n = 171), when data of several studies (Knapen, 2007;Knapen et al, 2007bKnapen et al, , 2007cKnapen et al, , 2008aKnapen et al, , 2008b) are combined, is shown in Figure 1. ME is the model effi ciency as defi ned by Nash and Sutcliffe (1970).…”

“…Yet, a literature review (Knapen et al, 2007a) revealed that the number of factors affecting SER is large. Therefore, several experiments, simulating concentrated runoff (τ = 0-50 Pa) on undisturbed soil samples in a laboratory fl ume, were conducted to determine the main factors that control the spatial and temporal variations in SER for loessderived topsoils in central Belgium (Knapen et al, 2007b(Knapen et al, , 2007c(Knapen et al, , 2008a(Knapen et al, , 2008b. These studies focused on topsoils and did not include subsoils since both winter and summer gullies in the Belgian loess belt are usually restricted to the plough horizon (Nachtergaele and Poesen, 2002).…”

Contrasting effects of microbiotic crusts on runoff in desert surfaces

“…Nevertheless, although runoff was measured in tropical (Valentin and d'Herbès, 1999;van de Giesen et al, 2000), humid (Rutin, 1983;Jungerius and ten Harkel, 1994), temperate (Bergkamp et al, 1999;Knapen et al, 2007), and arid and semi-arid zones (Booth, 1941;Bergkamp et al, 1996;Li et al, 2008), the role of MCs as impacting surface hydrology is not yet clear (Eldridge, 2001;Warren, 2001a). Whereas some researchers observed that MCs promote runoff (Loope and Gifford, 1972;Brotherson and Rushforth, 1983;Graetz and Tongway, 1986;Kidron and Yair, 1997;Kidron et al, 2003), others maintained that MCs impede runoff (Finlayson et al, 1987;Harper and Marble, 1988;Greene and Tongway, 1989;Alexander and Calvo, 1990;Williams et al, 1995Williams et al, , 1999.…”

“…Runoff generation on sandy soils may, however, take place following the establishment of a MC (Eldridge, 2001;Warren, 2001b;Kidron, 2007). While a PC may precede the establishment of a MC (Bowker, 2007;Knapen et al, 2007), the presence of a MC has been seen as essential for runoff generation on sand (Kidron, 1999).…”