Winter and early spring microclimate within a mid-elevation conifer forest canopy

Although micrometeorological data are available for numerous low-elevation locations, data from mid- and upper-elevational sites on mountains are sparse. As part of a study on winter water relations in conifers, we instrumented forested sites at two elevations (640 and 715 m) on Mt. Ascutney, Vermont, USA to gain information on the within-canopy micrometeorology of the forest and possibly support or refute hypotheses about factors controlling trees growing at the edges of their elevational range. Here, we report on micrometeorological data collected within the canopy at two middle elevation sites in 1997, 1998 and 1999. Mean air temperatures were generally colder at the higher elevation site than the lower site in any given month of the study. Smaller standard deviations in soil temperatures compared to air temperatures suggest that soil temperatures were significantly damped relative to air temperatures. The adiabatic lapse rate between a nearby low-elevation monitoring station and each study site was roughly half of published annual values for the region. Relatively moderate wind speeds suggest strong damping effects by the forest canopy. Solar radiation maxima suggest that even in a closed-canopy, strong solar radiation can penetrate small areas.