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Huggett, Brett A.

Forestry Program

2006

M.S.

There is growing evidence that various anthropogenic factors (e.g., high acid loading, nitrogen saturation, forest harvesting, changing climatic conditions, soil aluminum (A1) mobilization, and declines in atmospheric base cation deposition) may be responsible for the depletion of calcium (Ca) from forest ecosystems. Because Ca is a biologically essential element, anthropogenic alterations of this cation may have serious forest health implications. In particular, because Ca plays an important role in plant growth and defense systems, Ca deficiency could result in compromised stress responses and predispose trees to decline following exposure to even "normal" stresses including drought, insects, pathogens, and wounding. My research examines whether or not perturbations in Ca nutrition could affect the growth and stress response of sugar maple (Acer saccharum Marsh.) trees. I surveyed and wounded forest-grown sugar maple trees in a long-term, replicated Ca manipulation study at the Hubbard Brook Experimental Forest in New Hampshire, USA, in which plots received applications of Ca (to boost Ca availability above depleted ambient levels) or A1 (to compete with Ca uptake and further reduce Ca availability). I found significantly greater total foliar Ca in plots fertilized with Ca when compared with A1 supplemented and control plots (P 0.0036). Coinciding with foliar Ca differences, trees exhibited a significant difference in crown vigor rating and in percent branch dieback between treatments (P < 0.05) with a trend towards improved canopy health as Ca levels increased. Annual basal area increment growth for the years following treatment initiation (1998-2004) was significantly greater in trees subjected to Ca treatment compared to control and A1 treatments. Treatment-related improvements in growth were particularly evident after overstory release following the 1998 ice storm. In addition, the amount of wound closure was greatest in trees in Ca addition plots relative to A1 addition and control plots (P 0.0414). There were no significant treatment differences (P > 0.05) in wound-initiated production of lignin or callose. These findings extend past evidence that Ca nutrition is important for sugar maple health, and uniquely highlights the influence of Ca on growth following release from competition and wounding.