Comparisons of seasonal changes in photosynthetic capacity, pigments, and carbohydrates of healthy sapling and mature red spruce and of declining and healthy red spruce

Abstract

To determine whether healthy sapling and mature red spruce (Picearubens Sarg.) or healthy and declining mature red spruce were physiologically similar, photosynthetic capacity, pigments, and carbohydrates of the three or four most current age-classes of foliage were measured through one growing season. Foliar nutrients were measured once in September. The healthy trees were located at low pollution deposition sites near Howland (mature trees) or Millinocket (saplings), Maine, while the trees in decline were located at a high pollution deposition site at 1100 m on Whiteface Mountain, New York (mature trees). The seasonal time courses of all variables were similar regardless of tree age or vigor. For healthy trees, photosynthetic capacity and foliar nitrogen were positively correlated and declined with age of foliage. For trees in decline, photosynthetic capacity was not correlated with nitrogen and nitrogen did not decline in older foliage. Calcium and magnesium were low in current-year foliage from trees in decline, as were total soluble sugars and raffinose. The nutrient imbalances, lack of correlation between nitrogen and photosynthetic capacity, and low foliar carbohydrates indicate that the trees in decline are physiologically impaired. The low levels of total soluble sugars and raffinose also indicate that current-year foliage of trees in decline may have reduced cold tolerance and thus should predispose that foliage to winter damage.