Can tree functional traits drive ecosystem properties and processes across environmental and community gradients?

Recent studies have highlighted specific traits of forest trees as regulators of ecosystem processes; many have implicated mycorrhizal association of dominant trees as a specific driver of forest biogeochemical cycling. This perspective replaces long-held views related to environmental gradients and abiotic factors as master variables. Studies that examine the relative influence of mycorrhizal tree types and environmental controls across natural gradients are clearly needed. The Adirondack Park (AP) of upstate NY is an ideal system for studying such relationships due to a small number of tree species, distinct climatic gradients, and uniform geology. We established study plots in 3 distinct regions of AP that vary with respect to climate and relative species dominance, but have similar land-use history and geology. At each site, 24 15-m radius plots are centered on a dominant focal tree with the goal of varying mycorrhizal tree dominance and relative influence of abiotic factors (n=72). % ectomycorrhizal (ECM) basal area ranged from 98% to 22% across all sites with an even split in ECM vs arbuscular mycorrhizal (AM) focal trees. Plots established in the driest region of AP revealed relatively even distributions of ECM vs AM tree types on both south and north aspects, but that AM and ECM dominance varied with aspect and expected differences in soil temperature/moisture. Forest floor mass and soil inorganic nitrogen content at 10 cm depth followed hypothesized trends of decreasing inorganic nutrients and increased dependence on organic nutrient cycling with greater ECM dominance. However, this relationship was not apparent at the 20 cm depth. We will present data for belowground pools of nutrients and microbial processes across all three of our sites. Thus far, we conclude that specific mycorrhizal distribution patterns are apparent across short distances and provide some support for hypothesized patterns of biogeochemical cycling related to tree functional traits.