Contrasting effects of microbiotic crusts on runoff in desert surfaces

• Published in: Geomorphology (Amsterdam, Netherlands) Vol. 139; pp. 484 - 494
• Main Authors: Kidron, Giora J., Monger, H. Curtis, Vonshak, Ahuva, Conrod, William
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15.02.2012; Elsevier
• Subjects: alluvium; Animal and plant ecology; Animal, plant and microbial ecology; arid lands; Biological and medical sciences; Biological soil crusts; Chihuahuan Desert; chlorophyll; conservation areas; Earth sciences; Earth, ocean, space; Exact sciences and technology; Exopolysaccharides; Fundamental and applied biological sciences. Psychology; Geomorphology, landform evolution; gypsum; Infiltration; infiltration rate; Marine and continental quaternary; Microrelief; New Mexico; Physical crust; quartz; rain; runoff; sand; species diversity; surface roughness; Surficial geology; Synecology; Terrestrial ecosystems; New Mexico; Chihuahuan Desert; United States; Microrelief; Infiltration; Chihuahuan Desert; Physical crust; Exopolysaccharides; Biological soil crusts; fine-grained materials; sulfates; North America; roughness; silicates; alluvium; framework silicates; encrustations; soils; rainfall; chlorophyll; runoff; quartz; gypsum; infiltration; sand; deserts; biogenic origin; biogenic effects; landform evolution
• DOI: 10.1016/j.geomorph.2011.11.013
• ISSN: 0169-555X

Microbiotic crusts (MCs) play an important role in surface hydrology by altering runoff yield. In order to study the crust's role on water redistribution, rainfall and runoff were measured during 1998–2000 at three sites within the northern Chihuahuan Desert, New Mexico, USA: the Sevilleta National Wildlife Refuge (SEV), the White Sands National Monument (WS), and the Jornada Experimental Range (JER). Whereas quartz and gypsum sand characterize the SEV and WS sites, respectively, both of which have high infiltration rates, silty alluvial deposits characterize the JER site. Runoff was measured in four pairs of 1.8–6.4 m 2 plots having MCs, one of which was scalped in each pair. No runoff was generated at WS, whether on the crusted or the scalped plots. Runoff was however generated at SEV and JER, being higher on the crusted plots at SEV and lower on the JER plots. The results were explained by the combined effect of (a) parent material and (b) the crust properties, such as species composition, microrelief (surface roughness) and exopolysaccharide (EPS) content (reflected in the ratio of carbohydrates to chlorophyll). Whereas the effective rainfall, the fines and the EPS content were found to explain runoff initiation, the effective rainfall and the crust microrelief were found to explain the amount of runoff at SEV and JER where runoff generation took place. The findings attest to the fundamental role of the parent material and the crust's species composition and properties on runoff and hence to the complex interactions and the variable effects that MCs have on dryland hydrology. ► Contrasting runoff results were obtained from three sites in the Chihuahuan Desert. ► The properties of the microbiotic crusts explain the contradicting results. ► Effective rainfall, parent material and exopolysaccharides explain runoff initiation. ► Runoff amount (but not runoff initiation) is also controlled by microrelief. ► Low exopolysaccharides explain lake of runoff in the White Sands.