Plant succession may be initiated by patch formation by the pioneer plants. This research will consist of a series of experiments to determine whether the formation of these patches is related to mycorrhizal colonization on recently deglaciated till. Initial colonization by individual plants may be controlled by abiotic factors such as microsites for seed deposition and water catchment, while later patch formation may be regulated by both abiotic and biotic factors. These biotic factors are the focus of this study. The initial colonizing plant may act as a "nurse " plant both by ameliorating the microenvironment and by providing a source of mycorrhizal inoculum for later colonists. The investigators hypothesize that the initial colonizers in boreal Alaska are facultatively mycorrhizal, and that they can survive in glacial till without mycorrhizae until inoculum is naturally dispersed. The next wave of plant colonists may be facultatively or obligately mycorrhizal, and they may establish more rapidly if their seeds are deposited near a nurse plant. Thus patch formation in the initial stages of glacial succession in Alaska may depend on mycorrhizal fungi. Experiments will consist of planting both vesicular- arbuscular (VA) and ectomycorrhizal inoculated and uninoculated nurse plants on glacial till, planting uninoculated seedlings around the nurse plant, and observing natural plant and mycorrhizal colonization. The effects of microenvironmental amelioration by the nurse plants versus mycorrhizal inoculation can be separated by comparing plant growth near and at a distance from inoculated versus uninoculated nurse plants. The physiological response of the individual plants to mycorrhizae will be measured under controlled conditions. Many early to mid- seral plants have been reported to be both VA and ectomycorrhizal during succession on glacial till, and both types of fungi will be manipulated and observed.
