Mineral nutrition and leaf longevity in Ledum palustre: the role of individual nutrients and the timing of leaf mortality.

The effects of fertilization on leaf longevity and leaf mortality in the Alaskan evergreen shrub, Ledum palustre (Ait.) Hult., were investigated in a field experiment. The fertilization treatments included N alone, P alone, N plus P, and N plus P plus K. After 5 years all treatments had the same effect on leaf longevity, decreasing life expectancy from about 2 years in controls to 1-1.5 years in the fertilized plants. In the NPK-fertilized plants, most of the decrease in leaf longevity was due to increased winter leaf mortality; fertilization actually decreased leaf losses during the growing season. The results are consistent with previous research suggesting that one function of overwintering evergreen leaves is to serve as nutrient storage organs, a function that is superfluous when nutrient supplies for new growth can be obtained from current uptake.