Print PageAcidic deposition and reduced atmospheric inputs of calcium (Ca) have depleted Ca and increased the availability of phytotoxic aluminum (Al) in soils in 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 a species that is particularly sensitive to Ca deficiency and potential Al toxicity. We investigated the influence of long-term Ca and Al treatments on belowground and aboveground tissues of sugar maple trees at the Nutrient Perturbation (NuPert) study at HBEF to provide a comprehensive assessment of the influence of altered soil nutrition on tree function. We sampled radial growth from increment cores, fine roots, stems, and foliage from five dominant sugar maple trees in each of four plots for the three treatments at NuPert: Ca-addition, Al-addition, and control. For the same five trees we also assessed the amount of foliar damage from a late spring 2010 frost and the ability of trees in each treatment plot to produce a second flush of leaves.
Results/Conclusions
Maple in treated plots had greater root concentrations of Ca and Al, consistent with treatment application. Membrane leakage of fine roots (an indicator of stress) was significantly reduced for trees in Ca-addition plots, and greatest in Al-addition plots, suggesting that Ca:Al balance is critical to maintaining root health. Radial growth tended to be greatest in Ca-addition plots, and stored sugars were generally highest in Al-addition plots, though neither trend was significant. When these measures were integrated to account for the diversion of carbon (C) into structural use versus sugar storage, Ca-addition plots had significantly higher growth:storage ratios than control and Al-addition plots. A late spring frost injured foliage from trees on all treatments equally. However, a second flush of leaves was greatest on Ca and control plots compared with Al-addition plots. Insufficient C stores were not the cause of this delay because no differences in sugar storage were found among the treatments. We propose that elevated antioxidant activity in Al-treated trees may have reduced the oxidative triggers that induce break bud and initiate leaf expansion. Considering impacts on stem growth:storage and crown dynamics following stress, reduced Ca and elevated Al may be particularly harmful to maple C relations.
