Recovery of grasslands after woody invasions is a persistent problem for land managers in many arid and semi-arid ecosystems Although it is widely accepted that the potential for grassland recovery varies greatly across the landscape, there is relatively little guidance in the scientific literature to help land managers decide where to concentrate their restoration efforts. Soil profile characteristics can control plant community composition and production through their effects on spatial and temporal patterns of plant available water. In addition to affecting current plant communities, these relatively static properties contribute to degradation resistance and recovery potential. Petrocalcic soil horizons develop extensively in arid ecosystems around the world, often within the rooting zone of many desert plant species. We report temporal variability in plant available water by depth across a chronosequence of calcareous soils in a mixed shrub and grass community in southern New Mexico, USA: a deep sandy soil with little carbonate accumulation, a soil with moderate carbonate accumulation, and a soil with an extensive, indurated petrocalcic horizon. Sites selected had relatively little clay accumulation above a 50-60cm deep high carbonate horizon. Soil profiles were instrumented with TDR soil moisture probes, both above and within the high carbonate horizons. All soil profiles, including calcic and petrocalcic horizons, received substantial increases in soil water from above average winter precipitation in 2004-2005. Both the calcic and petrocalcic horizons retained significantly more winter precipitation into the spring than the non-carbonate sandy soil. However, all profile water contents were reduced to pre-winter levels by the late spring. Petrocalcic and partially indurated calcic horizons are often overlooked when assessing soil profile available water. This study indicates that petrocalcic and calcic horizons contain significant amounts of plant available water and can be recharged by winter rains.
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