VARIABILITY IN SOIL REDISTRIBUTION IN THE NORTHERN CHIHUAHUAN DESERT BASED ON CESIUM-137 MEASUREMENTS

Authors: Ritchie, Jerry; Herrick, Jeffrey - Jeff; RITCHIE, CAROLE - BOTANICAL CONSULTANT

Submitted to: Journal of Arid Environments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/28/2002
Publication Date: 9/17/2003
Citation: Ritchie, J.C., Herrick, J.E., Ritchie, C.A. 2003. Variability in soil redistribution in the Northern Chihuahuan desert based on Cesium-137 measurements. Journal of Arid Environment. 55(4):737-746.

Interpretive Summary: Measuring the redistribution of soil resources is a key factor for understanding the stability of Northern Chihuahuan Desert landscapes. In this study we used radioactive fallout to measure soil movement in different vegetation communities (black grama grass, tobosa grass, tarbush, mesquite) at the USDA-ARS Jornada Experimental Range in New Mexico. The Cesium-137 data showed significant soil redistribution has occurred at the shrub sites. The data confirms that significant plant-interspace scale soil redistribution occurs at mesquite dune vegetation with little Cs-137 found in the between dunes while in the arid grassland-shrub sites with black grama grass and tobosa grass the Cs-137 data show a homogeneous distribution of soil resources with little evidence of soil movement. Our data clearly show that Cs-137 can be effectively used to quantify soil redistribution at both plant-interspace and Jornada basin scales.

Technical Abstract: A hypothesis for understanding the stability of Northern Chihuahuan Desert landscapes is that the distribution of soil resources changes from spatially homogeneous in arid grasslands to spatially heterogeneous in invading shrublands. Since radioactive fallout Cesium-137 was deposited uniformly across the landscape during the 1950s and 1960s and was quickly adsorbed to soil particles, any redistribution of Cs-137 across the landscape would be due to soil redistribution or instability at either plant-interspaces or on a landscape scale. The concentration of Cs-137 in soils collected from different vegetation communities (black grama grass, tarbush, tobosa grass, mesquite) at the USDA-ARS Jornada Experimental Range in the Northern Chihuahuan Desert in New Mexico was determined. At the black grama grass, and tobosa grass sites, Cs-137 was uniformly distributed at the plant interspace scale. At the mesquite sites, Cs-137 was concentrated in the dune area under mesquite shrubs with little to no Cs-137 in the interdune areas. Cesium-137 data support the hypothesis that significant soil redistribution has occurred at dune sites created by invading mesquite. In the arid grassland-shrub sites with black grama grass, tobosa grass, and tarbush the Cs-137 data support the hypothesis of spatially homogeneous distribution of soil resources. High concentrations of Cs-137 in the biological soil crusts (0-5mm) at the tarbush sites indicate that biological soil crusts can contribute to the stability of these sites.