VARIATION OF TREE POLLEN INFLUX VALUES IN SEVERAL FORESTED REGIONS OF POLAND

According to the Pollen Monitoring Programme guidelines, deposition of modern pollen was investigated in the years 1998-2002. Pollen traps were placed across vegetation transitions from closed forest to open situations in northern Poland. Some stands of monitoring are located in the Tuchola Forest District – the great complex of pine woodlands with the natural stands of yew (The Wierzchlas reserve). The next stands are located in the Las Piwnicki reserve (near Toruñ) and in the Brodnica Lake District with deciduous and mixed forests. And the last traps were placed in the forests of the southeastern Poland in the Roztocze National Park. This region with its beech and fir forests is considered to be a very important climatic boundary where the influences of the Atlantic climate vanish. Influx values of such tree taxa as Fagus sylvatica, Abies alba, Picea abies and Taxus baccata are of special interest because their ranges of distributions occur in the territory of Poland. Pollen deposition fluctuates widely from year to year. In 2000 pollination of many trees /beech, fir, spruce among them/ was extremely abundant. The influx values for Fagus sylvatica achieved 8000 grains/cm2/year in beech forests, while those of Abies alba – 2200 grains/cm2/year in fir woodland. Average pollen influx of beech do not exceed 500 grains/cm2/year and of fir 1100 grains/cm2/year. Weather parameters are taken into account to explain this phenomenon because factors such as cyclicity in abundant flowering of some trees are not satisfactory explanation. Correlation with mean air summer temperature of the previous year seems probable. The explanation of factors influencing abundant pollination needs further studies and longer series of monitoring.