Wednesday, November 15, 2006

Saltcedar (Tamarix spp.) Leaf Litter Impacts on Surface Soil Chemistry: Electrical Conductivity and Sodium Adsorption Ratio.

April Ulery and Cheryl Rosel. New Mexico State Univ, Plant & Environmental Sciences Dept, P.O. Box 30003 MSC 3Q, Las Cruces, NM 88001

Deciduous Tamarix spp. have become naturalized in the US since their introduction in the early 1800’s.  High evapotranspiration rates and salt tolerance contribute to the species’ success.  According to anecdotal evidence and limited field studies, salt glands on leaves exude salts and may create saline soil environments.  However, a quantification of the rate and pattern of soil salinization has not been reported.  A greenhouse experiment was performed to quantify Tamarix leaf litter (duff) impact on surface soil salinity and sodicity.  Three duff treatments (0, 2, and 6 cm thick) and 0.5 in irrigations (simulated rainfall) were applied to soil at different frequencies in three consecutive experimental stages.  The stages represented three moisture patterns: very wet with little or no soil drying, wet with some soil drying, and complete soil drying.  Soil was sampled at 0-1 and 1-5 cm depths and soil-water (1:5) extracts were analyzed for electrical conductivity (EC) and sodium adsorption ratio (SAR).  In stage one, only one irrigation was needed to leach salts from the duff into the surface 1 cm of soil.  Two to three consecutive weekly irrigations showed a rapid decrease in EC and SAR in the 0-1 cm depth and a more gradual increase and leveling off in the 1-5 cm depth.  In stage two, EC and SAR increased and decreased in correlation with soil drying and wetting.  In stage three, as much as a nine-fold increase over baseline values in EC and a six-fold increase over baseline values in SAR were noted in the 0-1 cm soil depth.  This was higher than the EC and SAR found after the initial input of salts in stage one.  As little as one 0.5 in irrigation coupled with extensive soil drying caused the EC and SAR of the surface soil to exceed that of a non-invaded soil.