Red Maple Seedling Soil Warming Experiment in Harvard Forest Lath House 2015

Microhabitat environmental conditions are an important filter for seedling
establishment, controlling the availability of optimal recruitment sites.
Understanding how tree seedlings respond to warming soil temperature is critical
for predicting population recruitment in the future hardwood forests of
northeastern North America, particularly as environmental conditions and thus
optimal microhabitat availabilities change. We examined the effect of 5˚C soil
warming during the first growing season on germination, survival, phenology,
growth, and stem and root biomass allocation in Acer rubrum (red maple)
seedlings. While there was no effect of soil warming on germination or survival,
seedlings growing in warmer soils demonstrated significantly accelerated leaf
expansion, delayed autumn leaf senescence, and an extended leaf production
period. Further, seedlings growing in warmer soils showed larger leaf area, stem
and root structures at the end of the first growing season, with no evidence of
biomass allocation tradeoffs. Results suggest A. rubrum seedlings can capitalize
on soil warming by adjusting leaf phenology and leaf production, resulting in a
longer period of carbon uptake and leading to higher overall biomass. The
absence of growth allocation tradeoffs suggests A. rubrum will respond
positively to increasing soil temperatures in northeastern forests, at least in
the early life stages.