Hassel (Corylus avellana) som indikator på markanvändningshistorik
Hazel (Corylus avellana L.) is a common feature of meadows and pastures where it can grow in large populations and become very old. Is it possible to use the size of hazel stools for age determination and is it possible to use the size distribution of a population to provide information about how the land has been used? Hazel populations on ground where the lake-water level had been lowered, has been studied to validate an already developed growth model of hazel clones. Different hazel populations, on wooded meadows affected by mowing or grazing or overgrown meadows, were studied to evaluate the method utilizing hazel as land use indicator. The growth model was used to compare the size distributions of hazel populations with historical periods, which has been important for changes in agriculture or demography. The results show that the current growth model needs to be refined, but the method itself with a growth model based on the circumference of hazel bushes seems feasible. Additional studies about the influence of, for example, soils of different fertility are needed. The results also show that the size distribution in a population depends on how much meadows have been affected by mowing or grazing and that areas with similar land use have similar size distribution. Finally, some examples are reported about how a growth model can be used to compare historical periods of changes in agriculture, for example reduced livestock, with variations of the size distribution in a hazel population.