Print PageInputs of acidic deposition have depleted calcium (Ca) and increased the availability of phytotoxic aluminum (Al) in soils within the Northeastern U.S. – a phenomenon particularly well documented for the Hubbard Brook Experimental Forest (HBEF) in New Hampshire. Sugar maple (Acer saccharum Marsh.) is one species that is particularly sensitive to Ca deficiency and potential Al toxicity, both of which have been shown to reduce basal growth in the species. In fall of 2008, we collected xylem increment cores from dominant sugar maple, and intermediate sugar maple and American beech (Fagus grandifolia Ehrh.) - a potentially Al-tolerant species - growing in the replicated NuPert Ca- or Al-addition study at HBEF to assess the influence of soil treatment on woody growth of the two species. Increment cores were taken from 5 trees of each of 3 species/canopy categories per plot, for each of the 4 plots per soil treatment (Ca-addition, Al-addition, and control), for a total sample size of 180 trees. Cores were measured to the nearest 0.01 mm, visually crossdated and aged per standard dendrochronological methods. Basal area increment was calculated to evaluate growth on an area basis and was expressed as percent of total basal area per tree.
Results/Conclusions
Dominant maples decreased in growth for at least two years after a 1998 ice storm, whereas intermediate maples and American beech experienced growth increases after 1998 - presumably from release following injury to the overstory. Ca-treated dominant maples tended to have greater growth than similar trees in Al-treated and control plots but treatment differences were not significant, presumably as a result of increased variability in growth following the ice-storm. Ca-treated intermediate maples experienced greater radial growth than trees on control and Al-addition plots through 2007. American beech growth was unaffected by treatment until 2007 and 2008, when trees on Al-treated plots increased in growth relative to those on control and Ca-treated plots. We developed two theories for the positive influence of Al on beech growth: 1) Al-treatment resulted in physiological disruption to sugar maple, but was less disruptive to beech physiology, or 2) Al-addition, known to induce oxidative stress and trigger increases in constitutive antioxidant production, increased antioxidant activity in American beech which improved tree defenses and growth. Differential responses of maple and beech to soil amendment highlight potential changes in the species composition of northern hardwood forests exposed to anthropogenic alterations in soil Ca and Al availability.
