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 sal icylate-mineralizing microbes and total microbial biomass in soils from und er willows (Salix brachycarpa) and in surrounding meadows dominated by the sedge Kobresia myosuroides. Willows had a strong effect on the biomass of s alicylate-mineralizing microbes in both years of this study. There were alw ays higher biomass levels of salicylate mineralizers in soils from under Sa lix (4.6-10.1 mug C/g) than under Kobresia (0.23-0.76 mug/g). In contrast, total microbial biomass was not significantly different under these plant s pecies in 1996 and was only higher under Salix on one date in 1997. These r esults show that the standing biomass and activity of salicylate-mineralizi ng microbes can be greatly enhanced by salicylate-producing plants in the f ield. Given this finding, it is unlikely that simple phenolic compounds lik e salicylate would persist for very long in soil beneath the plants that pr oduce them.