The objective of the study was to investigate the factors affecting the deterioration of urban forests based on literature. Regression analysis is applied to the material obtained from unpublished material of the latter author. The size of forest stand, and its fertility proved to exercise the greater effect on the deterioration of urban forests. A model based on these factors has been developed and its area of applying is discussed.
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The paper describes the systematics, distribution, abundance and nest sites of Formica rufa -group in different Finnish forest types. In addition, it has been estimated the availability of Finnish ants in the biological competition.
F. polyctena, F. aquilonia and F. lugubris are distributed over whole Finland. F. rufa and F. nigricans to Southern Finland only. The relative abundace of ant nests diminish to Northern Finland. F. rufa -group prefer most forest on moist land (Myrtillus and Oxalis-Myrtillus types), mixed forests of Norway spruce (Picea abies (L.) H. Karsts), Scots pine (Pinus sylvestris L.) and birch (Betula sp.), and the silvicultural density 0.6–0.7 (good or satisfactory density), but they avoid broadleaved and pure one-tree species forests. For the biological competition the most competitive ant species seem to be F. polyctena and F. aquilonia.
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