You are here:
FACTORS INFLUENCING FALL FOLIAGE COLOR EXPRESSION IN SUGAR MAPLE TREES.
Citation:
Impact/Purpose:
Scientific study intended improve understanding of the mechanisms by which acid deposition impacts forest ecosystems; for use by academic science community, policy analysts in NGOs and all levels government organizations, and the interested public.
Description:
Abstract: We evaluated factors influencing red autumn coloration in leaves of sugar maple (Acer saccharum Marsh.) by measuring mineral nutrition and carbohydrate concentrations, moisture content, and phenology of color development of leaves from 16 mature open-grown trees on 12 dates from June through October 1999. Mean foliar nutrient and carbohydrate concentrations and water content were generally within the range published for healthy sugar maple trees. However, foliar nitrogen (N) concentrations were near deficiency values for some trees. The timing and extent of red leaf coloration was consistently correlated with both foliar N concentrations and starch or sugar concentrations, which also varied with N status. Trees with low foliar N turned red earlier and more completely than high-N trees. Low-N trees also had higher foliar starch concentrations than high-N trees. During the autumn transition to red, foliar starch and then glucose and fructose concentrations were positively correlated with red. At peak red expression, the concentrations of glucose, fructose, sucrose, and stachyose were all positively correlated with the percentage of red expressed. There is evidence that a primary function of red anthocyanin pigments in senescing leaves of woody plants is to protect them from photooxidative damage and thereby enhance nutrient (especially N) recovery. Nitrogen deficiency results in elevated foliar starch accumulation, and N deficiency and high sugar concentrations are recognized triggers of anthocyanin biosynthesis. We hypothesize that N limitations in our trees could have provided the biochemical stimulus (low N and high sugar signals), energy, and carbohydrate building blocks needed for the facultative production of anthocyanins, which were preferentially expressed when N was limited, photosynthetic capacity low, and N recovery most beneficial to the tree. Although experimental manipulation is needed to test this hypothesis, an ability for trees to alter anthocyanin production to meet spatial or temporal N limitations could help account for noted tree-to-tree, and year-to-year differences in red color expression.