The Effects of Select Herbicides on Biological Soil Crust in Shrub Steppe Areas of the Columbia Basin, Washington

Abstract

The effects of herbicides used on arid lands in the Columbia Basin, Washington State on components of biological soil crusts (BSCs) were investigated. Active ingredients in the herbicides investigated were two synthetic auxins, picloram and aminopyralid, and two enzyme inhibitors, glyphosate and imazapic. Moss and lichens of the BSC were the focus of the study; soil algae and cyanobacteria were also examined. In a retrospective field study, evidence indicated statistically significant association between glyphosate and low levels of BSC. The same study found no evidence for association between either picloram or imazapic and diminished BSC. In a controlled experiment, collected lichen and moss specimens were sprayed with herbicide (aminopyralid, glyphosate, or imazapic) in the lab and monitored for 31 to 37 days. Periodically sections were examined at 100X with a fluorescent microscope and levels of red fluorescence were measured for lichen green algae photobionts or moss chloroplasts. After weeks of observation, the chloroplasts of the herbicide exposed organisms were intact. Experiments involving herbicides diquat or pelargonic acid indicated that these herbicides are very toxic to BSC organisms.