THE ADVANTAGE OF MAST YEARS FOR WIND POLLINATION

A model which demonstrates how mast years increase the effectiveness of wind pollination is based on 7 assumptions relating to the timing and distribution of reproductive effort. Field data from reproduction in lodgepole pine Pinus contorta demonstrate how relaxing some of the assumptions influences the effectiveness of wind pollination. Relaxing 5 of the assumptions raises or lowers, but does not eliminate, the advantage of increased fecundity resulting from having the extreme variation in annual reproduction characteristic of species with mast years. If 2 of the assumptions are relaxed, the model quickly loses relevance. These assumptions are that 1) both male and female reproductive efforts vary synchronously and 2) the cost of producing a female is nearly the same whether she is fertilized or not. These 2 assumptions tend to be true for both the gymnosperms and angiosperms of boreal forests and false for the wind-pollinated angiosperms and one gymnosperm of temperate deciduous forests. The difference in the application of the model and two of its assumptions to these 2 major forest biomes is indicative of a fundamental difference in their strategies of pollination. -Authors