Pollen Phenology of the Most Important Trees in Finland

The pollen frequency of Alnus correlated negatively at the 10% level with the daily mean temperature and at the 5% level with the temperatures of the previous day, and of the same week in 1975; and with the same levels of chance with humidity in 1974. The pollen frequency of Betula correlated positively with the mean temperature both of the same and previous day. Because of the rainy year 1974, birch pollen amount correlated very significantly negatively with humidity. The correlations showed the same tendencies in the other two years. The Pinus pollen frequency correlated positively with the mean daily temperature either at the 0.1% or 1% level, and in the same way with the mean temperature of the previous day. The correlation ofPinus to humidity was negative. Pine pollen showed fairly significant negative correlation with the snow cover thickness in 1974 and 1976. In 1975, there was less snow in S. Finland than normally, and Pinus had no significant correlations to this factor.