Land Application of Treated Industrial Wastewater on a Chihuahuan Desert Shrubland: Impacts on the Natural Vegetation

Abstract

Impacts of wastewater land application on desert vegetation are not adequately known. In a 4-yr field study, we evaluated the effects of treated, salineÀsodic industrial effluent application on the aboveground vegetation biomass and mineral accumulation of a Chihuahuan Desert shrubland. The vegetation included two shrubs, Larrea tridentata (DC.) Coville and Prosopis glandulosa Torr. var. glandulosa, and seven herbaceous species in the intershrub spaces. Early summer fruit dry weights on terminal branches of the irrigated shrubs were 3 to 14 times higher than those on the non-irrigated shrubs. The combined irrigated vegetation produced 2 Mg of additional dried biomass per ha above that of the non-irrigated plot, and contained excesses of total Kjeldahl-N (TKN) and Ca 2þ equivalent to 18% of effluent N deposition and 12% of effluent Ca 2þ deposition. Under irrigated and highly sodic conditions (soil sodium adsorption ratio up to 35), the herbaceous Lepidium alyssoides A. Gray var. alyssoides produced the highest biomass of all plant species. However, there was a decline in plant species diversity as L. alyssoides became dominant in the irrigated intershrub spaces. While the findings demonstrate the natural attenuation of effluent minerals by native Chihuahuan Desert vegetation, highly sodic conditions may alter the composition of the vegetation community.