M nniokaste morfomeetriast Edela-Eesti luitemaastikku ilmestavas Tolkuse rabas

Although in Estonia bog forests are ancient biotopes relatively little affected by human activity so far, the ever-intensifying anthropogenic impacts are beginning to threaten also the existence of bogs. In the Baltic States Tolkuse bog is the only bog with a peripherally oligotrophic development path whose central part has better nutrition conditions than its peripheral parts. In the course of the project changes in the length, dry mass and area of the needles of bog pines were studied moving from the margin of the bog towards its centre. Comparison of the concentrations of N, P, K, Ca and Mg in the upper peat layers in Tolkuse bog with the respective average concentrations in raised bogs, transitional bogs and moorlands revealed that Tolkuse bog was poorer in Ca and also N and P. Site V had significantly higher N, P and Ca concentrations than the other sampling sites. The height growth of 60-90-year-old bog pines was 5,6 ± 1,1 m and diameter 14,2 ± 4,1 cm. The pines of site I had the longest needles (in the crown at a height of 1.5 m from ground on average 3.7 cm and at 3 m 4.1 cm). This shows that marginal areas of the bog have the best conditions for pine growth. The shortest needles were observed in pines growing on site VII (on average 2.7-3.0 cm). This area is located in the centre of the bog and is surrounded by hollows. The average dry mass of a pine needle at a height of 1.5 m from ground was 0.006-002 g and at a height of 3 m, 0.008-0.01 g. Similarly to needle mass, the needle area was largest in site V, located at a somewhat higher position on a bog islet and having higher concentrations of nutrients in peat than other sites. It is important is to preserve the diverse and peculiar bog pine forests in Estonian scenery. In other European countries such forests have preserved only fragmentarily due to intensive human activity. Therefore it is absolutely necessary to continue the monitoring of the status of Estonian bogs and ecological investigations to get information on future trends.