GROWTH AND ELEMENTAL CONTENT OF SEVERAL SAGEBRUSH-STEPPE SPECIES IN UNBURNED AND POST-WILDFIRE SOIL AND PLANT EFFECTS ON SOIL ATTRIBUTES

Fire is the principal means of stand renewal in big sagebrush-steppe c ommunities of western North America. Plant growth following fire may b e influenced by heat-induced changes in the nutrient status of the soi l. Moreover, post-wildfire pioneer plant species may alter soil proper ties, and thereby, impact subsequent plant recruitment. Our study comp ared the growth and elemental content of big sagebrush (Artemisia trid entata), squirreltail (Elymus elymoides), cheatgrass (Bromus tectorum) , and Indian ricegrass (Achnatherum hymenoides), grown under greenhous e conditions in post-wildfire and similar unburned soil. We also exami ned soil attributes following plant growth. Cheatgrass and squirreltai l, grown in post-wildfire soil, had significantly (p less than or equa l to 0.05) greater aboveground mass than plants grown in unburned soil . As compared with unburned soil, post-wildfire soil engendered the fo llowing significant (p less than or equal to 0.05) differences in leaf elemental content: 1) big sagebrush had higher levels of P and lower levels of Mn; 2) squirreltail accumulated more P and N; and 3) all gra ss species had higher SiO2 content. Following harvest of plants, post- wildfire soil generally contained significantly (p less than or equal to 0.05) more KCl-extractable ortho-P, NH4+, and SO42-, than unburned soil. Plant growth in both burned and unburned soils fostered a signif icant (p less than or equal to 0.05) increase in the bicarbonate-extra ctable pool of P as compared with unplanted controls. Soil Kjeldahl-N was significantly (p less than or equal to 0.05) greater after plant g rowth in burned treatments as compared with the control. This study de monstrates that post-wildfire soil can have a stimulatory effect on pl ant growth for some species. Squirreltail deserves consideration as a post-wildfire revegetation species. Furthermore, pioneer plant growth following wildfires can attenuate soil properties and therefore influe nce plant succession.