Health and mycorrhizal colonization response of sugar maple (Acer saccharum) seedlings to calcium addition in Watershed 1 at the Hubbard Brook Experimental Forest

We examined the health and mycorrhizal colonization rates of sugar maple germinants on a Calcium (Ca)- treated watershed at Hubbard Brook Experimental Forest and compared their status to the health of seedlings growing on reference sites. We quantified general sugar maple germinant health by height, leaf area, biomass, and chlorophyll content. To determine vesicular-arbuscular mycorrhizal colonization rates, we first cleared and stained germinant roots and then examined their structures microscopically. We found that sugar maple seedlings on the Ca-addition site were taller, had larger leaves, more root, leaf, and stem biomass, and more chlorophyll per unit leaf area. These seedlings also had a significantly larger percentage of their roots colonized by mycorrhizal fungi. Our results indicate a correlation between soil Ca availability, mycorrhizal colonization rates, and overall seedling health. These data were gathered as part of the Hubbard Brook Ecosystem Study (HBES). The HBES is a collaborative effort at the Hubbard Brook Experimental Forest, which is operated and maintained by the USDA Forest Service, Northern Research Station.