The high water-holding capacity of petrocalcic horizons

Title	The high water-holding capacity of petrocalcic horizons
Publication Type	Conference Paper
Year of Publication	2004
Authors	Duni D, Herrick JE, Monger CH, Brinegar H.R.
Conference Name	Soil Science Society of America Annual Meeting
Date Published	October 31-Novem
Conference Location	Seattle, WA
ARIS Log Number	170976
Keywords	arid, ecosystems, horizons, Petrocalcic, soil, soil water, water-holding capacity
Abstract	Petrocalcic soil horizons develop extensively in arid ecosystems around the world, often within the rooting zone of many desert plant species. In coarse textured soils, this results in a dramatic change in moisture holding capacity through the conversion of a horizon dominated by large pores to a fine pore matrix. We conducted a replicated experiment to measure the characteristic moisture release curve for a range of petrocalcic horizon materials. Samples from both the plugged and laminar horizons from two stage V petrocalcic horizons in southern New Mexico were sampled. Tensions closer to zero were measured using a pressure plate; more negative tensions (down to –5Mpa) were measured using a chilled mirror water potential device (Decagon Devices WP4). Our method was repeatable and results were fitted using the vanGenuchten equation. Plant available volumetric water holding capacity for desert species (with permanent wilting point set at –4Mpa) ranged from 24% in plugged horizons to 3% in some laminar horizons in contrast to approximately 5.5% in a loamy sand. Cementation by calcium carbonate dramatically alters the water-holding characteristics of soils and understanding these horizons is crucial for understanding patterns of soil water in desert systems.