Effects of Willows (Salix brachycarpa) on Populations of Salicylate-Mineralizing Microorganisms in Alpine Soils

We used the substrate-induced growth-response (SIGR) method to quantify salicylate-mineralizing microbes and total microbial biomass in soils from under willows (Salix brachycarpa) and in surrounding meadows dominated by the sedge Kobresia myosuroides. Willows had a strong effect on the biomass of salicylate-mineralizing microbes in both years of this study. There were always higher biomass levels of salicylate mineralizers in soils from under Salix (4.6–10.1 g C/g) than under Kobresia (0.23–0.76 g/g). In contrast, total microbial biomass was not significantly different under these plant species in 1996 and was only higher under Salix on one date in 1997. These results show that the standing biomass and activity of salicylate-mineralizing microbes can be greatly enhanced by salicylate-producing plants in the field. Given this finding, it is unlikely that simple phenolic compounds like salicylate would persist for very long in soil beneath the plants that produce them.