Out of sight, but not out of mind: Soil microorganisms in moisture-limitedforests

Microorganisms play a critical role in the maintenance and productivity of forest ecosystems by their regulation of soil nutrient availability and org anic matter decomposition. Regardless, it is uncommon for managers to consi der the microbial community and its processes when assessing forest managem ent options. The reasons for this incongruity are of little surprise. Micro organisms lack the charisma attributed to key plant and wildlife species, a nd thus are "out of sight, out of mind." More detrimental, however, is our incomplete understanding of how microorganisms respond to natural and manag ement-induced disturbances. Whether changes in microbial processes followin g disturbance are sufficient to alter the sustainability of forest ecosyste ms is unclear, thus providing limited input for decision making by forest m anagers. Information from studies of moisture-limited forests on the easter n slopes of the Cascade Mountains indicates that (1) microbial communities are well adapted to the conditions of water stress, (2) long-term decline i n microbial biomass can result from continuous silvicultural treatment, and (3) microbial activity is limited by available soil carbon content. Manage ment options which maintain or enhance site organic matter are recommended as the best practice to sustain microbial processes.