Current issue: 55(5)
Under compilation: 56(1)
The regeneration of forests in Hämeenkangas area in Southern Finland has been difficult due to various damages from the middle of the 1800s. Few seed trees were left in the area, and artificial regeneration has been used since 1880s. The area became an experimental area of the Forest Research Institute in 1924. The aim of the study was to survey the area before it was transferred to the Finnish Defense Forces.
The original Scots pine (Pinus sylvestris L.) forest of the esker area suffered from many forest fires. The total area is 13,000-14,000 ha, of which the experimental forests of Forest Research Institute cover 6,000 ha. The area is dry upland forest, and drought affects the survival of germlings. Soil frost is a major cause of loss of young seedlings. Sowing method affects the early development of the seedlings. Band sowing proved to be the best method regarding the soil frost. A total of 39 different harmful insect species, 8 pathogen species and 7 other causes of damages have been detected in the area.
The development of seedling stands follow a certain pattern, reported also in other studies. Many of the pine seedling stands develop well until they reach a certain height. After that seedlings begin to suffer from damages, but after reaching another stage develop normally. The damages affect the height growth of the seedlings. Some common damages are caused by Pissoides weevils, needle damages caused by certain beetles, shoot damages by Evetria resinella, and pine blister rust (Peridermium pini and Cronartium flaccidum).The PDF includes a summary in German
This review discusses whether forests are affected by biotic damages due to present or future environmental disturbances, and do environmental threats, such as air pollution and climatic change, weaken the condition of forest in a way that makes them vulnerable to damages by fungi and insect. The defence mechanisms of trees and factors affecting the development of an outbreak are described. Finally, the ways that air pollution and climatic change may affect biotic damages are discussed.