MYCORRHIZAL COLONIZATION, HYPHAL LENGTHS, AND SOIL-MOISTURE ASSOCIATED WITH 2 ARTEMISIA-TRIDENTATA SUBSPECIES

Mycorrhizal fungi are thought to benefit associated plant species via enhanced nutrient uptake and/or improved water relations. However, det ailed descriptions of the components of mycorrhizal colonization and m ycorhizal hyphal growth are not available for Artemisia tridentata. Th is species occupies sites characterized by relatively low levels of bo th soil nutrients and moisture. We studied patterns of vesicular, arbu scular, and hyphal mycorrhizal colonization, mycorrhizal hyphal length s, and soil moisture associated with two subspecies of A. tridentata o ver a 2-year period. A. tridentata ssp. vaseyana (ATV) is generally as sociated with more mesic and slightly higher elevation sites compared to A. tridentata ssp. tridentata (ATT). Nearly twice as much precipita tion was received the first year compared to the second. In general, t here were higher levels of colonization and hyphal lengths associated with ATV than with ATT. The ATV site received slightly more precipitat ion and was lower in available nutrients than the ATT site. Hyphal len gths and arbuscular colonization appeared more responsive to precipita tion than were either vesicular or hyphal colonization. Hyphal coloniz ation did not necessarily follow the same temporal pattern as hyphal l engths. Thus, mycorrhizal activity was greater for the subspecies that received slightly more precipitation and occupied a site lower in ava ilable nutrients. Arbuscular colonization and hyphal lengths appeared to be most closely associated with soil moisture and thus plant activi ty.