Increased dark respiration and calcium deficiency of red spruce in relation to acidic deposition at high-elevation southern Appalachian Mountain sites

For Picea rubens a consistent and highly significant reduction in the ratio of net photosynthesis to dark respiration was found at the highest sites on each mountain compared with lower sites. This response was produced by significant increases in dark respiratioan that were associated with low foliar Ca levels and high foliar Al levels found at the higher elevation sites. A consistently inverse relationship between dark respiration and foliar Ca was found across highest and lowest elevation sites, while the midelevation sites, where Ca:Al ratios were highest, showed less evidence of respiratory response to Ca. Calcium in shoots was significantly reduced in association with increasing levels of soil Al in the rooting zone across all sites. Reduced Ca supply, occurring in association with competitive inhibition of Ca uptake by high concentrations of Al found in soil, may have reduced the availability of carbon for red spruce growth at higher elevation sites. -from Authors