Algae influence the hydrophysical parameters of a sandy soil

Abstract

abstract Article history:Received 2 August 2011Received in revised form 31 January 2012Accepted 3 February 2012Available online xxxxKeywords:AlgaeBiological soil crustSoil water repellencySand duneSorptivityHydraulic conductivity Biological soil crusts have a major effect on water flow in soils. Two study sites, located at a pine-forest gladecovered with a biologicalsoil crust, formed the basis of our study. The sand soil atthe surface (Glade soil) wascompared to a control soil (Pure sand) with limited impact of vegetation or organic matter, occurring at50 cm depth beneath a glade area. To assess the influence ofalgae in the biological soil crust on the propertiesof pure sand, a coccal green alga (Choricystis minor), filamentous green alga (Klebsormidium subtile) and stra-menopile alga (Tribonema minus) were isolated from the top layer of glade soil and grown in the lab in Petridishes on sterile pure sand as monoalgal and bialgal (C. minor and K. subtile) crusts for 3, 5, 7, 9, 11, 13, 15, 17,19, and 21 days. Atthe end ofeach growth stage, the hydrophysicalparametersof crusted sand were estimat-ed after drying at 50 °C for 15 h (equivalent to a 3-day hot spell) and compared to the parameters of puresand. The hydrophysical parameters were substantially different between the two surfaces. The glade soilhad an index of water repellency about 18-times that of pure sand and the persistence of water repellencyalmost 54-times that of pure sand. Both sorptivity and hydraulic conductivity in the glade soil were about7% those of the pure sand, respectively. The growth of artificial algal crusts, characterized by an increase inorganic carbon content from 0.16% to 0.33%, resulted in an increase in water drop penetration time of thedried crusts up to 14-times that of the pure sand and a decrease in the water sorptivity of the dried crustsup to 10% that of the pure sand. Whereas K. subtile crusts (both monoalgal and bialgal with C. minor) hadup to a 9% decrease in hydraulic conductivity compared to pure sand, there was no impact of monoalgalC. minor and T. minus crusts on hydraulic conductivity. K. subtile was possibly limited to surface growth,whereas C. minor and T. minus penetrated to depth. Consequently, K. subtile may have clogged the toppores more effectively than the other two strains. The water repellency cessation time increased with anincrease in water drop penetration time for all the dried monoalgal and bialgal crusts used in this study. Agreater impact of K. subtile on the shifts in hydraulic behaviour could influence water capture and storage,potentially decreasing evaporation during dry periods, but enhancing overland flow diminishing leachingduring wet periods.© 2012 Elsevier B.V. All rights reserved.