Articles by Esko Kangas

A forest damage was detected in spring 1931 near electro-chemical factory in Imatra in Eastern Finland. It was deduced that it was caused by a gas discharge from the factory. A survey was made to describe the damages. Forests in the damaged area of five hectares were Scots pine (Pinus sylvestris L.) dominated and 60-80 years old. According to the factory, the exhaust gases contained 0.4 mg chlorine per liter. In addition, chlorate containing liquids evaporated thorough the chimney, which seemed to have been the main cause of the damage. The chlorates may have concentrated in the snow covering the trees during the winter. The Scots pine trees had lost all the needles in spring, but grew new needles in the summer. In some trees the new needles were few or undeveloped. Some mild damages were noticed in pine and Betula sp. during the growing season. Forest edges and trees higher that the other trees were worst damaged. Pine was most sensitive to the emission. Pine weakened by the gas damages were attacked by insects, the most important being Pissodes sp. The secondary insect damage is likely to kill the surviving trees. The dying pines should be removed only if it is necessary to prevent the spreading of insect damage. The trees may hinder the spreading of further gas emissions. In future, other tree species should be preferred over pine.

The PDF includes a summary in German.

• Kangas, E-mail: ek@mm.unknown

Regeneration of large open areas in dry mineral soil forest sites that usually grow Scots pine (Pinus sylvestris L.) have several problems. For instance, soil frost, snow, ground vegetation and dryness can prevent germination and growth of seedlings. The damages caused by insects and fungi in seedlings of a large burned area in Siikakangas in Southern Finland was studied. A forest fire burned the area nearly completely in 1909, and 310 hectares have been sowed or planted with mostly Scots pine during the following years. Minor areas have been regenerated with Pinus montana Noll, Pinus excelsa Lamb., Pinus murrayana Balf. and Larix sibirica Ledeb.

No completely healthy pine seedling stands could be found in the area. About 41% of the seedlings in the sample plots were damaged. The most common causes for damage were Evetria resinella (now Retinia resinella L.), Luperus pinicola (now Calomicrus pinicola (Duft.)), Pissodes notatus (now Pissodes castaneus Degeer), Evetria turionana Hb. and Hylobious abietis L. The most usual fungal disease was Lophodermium sp. Evetria resinella caused damages in all the area. Evetria turionana, Pissodes notatus and Hylobius abietina were found in the older seedling stands. Other damages were more localized. The slacks in the terrain seemed to have most damages, the original cause being probably soil frost. Some damages, as Lophodermium, were related to the density of the seedlings, especially in the sown areas. Cleaning of seedling stands could decrease these damages. Planting seems to have succeeded better than patch sowing.

The PDF includes a summary in German.

• Kangas, E-mail: ek@mm.unknown

This paper is a review on the silvicultural research in Finland, researchers and the main subject of the research within the previous 50 years. The task of silvicultural research is to serve forest management work and create a foundation for the practical operations, on one hand, and to answer to the constantly arising questions in the practice of forest management, on the other.

It can be said that the forestry as an independent branch of science began in 1909. At first the research was primarily biological, dealing with both the foundations and practices of silviculture. The main subjects are divided to forest sites and vegetation, biology of trees and stand, and methods of forest management.

The article is published in Finnish in separate PDF Acta Forestalia Fennica vol 70 no 3.

• Mikola, E-mail: pm@mm.unknown
• Kangas, E-mail: ek@mm.unknown
• Heikurainen, E-mail: lh@mm.unknown

This paper is a review on the silvicultural research in Finland, researchers and the main subject of the research within the previous 50 years. The task of silvicultural research is to serve forest management work and create a foundation for the practical operations, on one hand, and to answer to the constantly arising questions in the practice of forest management, on the other.  

Forestry as an independent branch of science began in 1909. At first the research was primarily biological, dealing with both the foundations and practices of silviculture. The main subjects are divided to forest sites and vegetation, biology of trees and stand, and methods of forest management. 

The article is published in English in separate PDF Acta Forestalia Fennica vol 70 no 4. 

• Mikola, E-mail: pm@mm.unknown
• Kangas, E-mail: ek@mm.unknown
• Heikurainen, E-mail: lh@mm.unknown

Many countries have enacted plant protection laws or statutes that consist timber imported into a country, both raw wood and processed timber. This has caused some inconvenience to the international timber trade. Necessary protection against the spread of pests via export is fully acceptable, but the protection should be based on actual need.
When considering processed or barked raw timber, the problem concerns only species that pass their development in the wood. The four most important biological requirements affecting the risk are 1) the tree species of the importing country and affinity of the pest, 2) climatic conditions of the importing country and the pest’s range and adaptability to the climate, 3) biological factors regulating the population, and 4) suitability of the individual development of the pest for transmission. These risks are discussed in the article.

It is concluded that it is possible largely to eliminate the species that might be conveyed via export timber. It is often possible to decide in advance what danger threatens the importing country from species that might be conveyed via export timber. This would make it possible to adapt plant protection regulations to suit the relation between the exporting and importing countries.

The Acta Forestalia Fennica issue 61 was published in honour of professor Eino Saari’s 60th birthday.

• Kangas, E-mail: ek@mm.unknown

Observatons of drying of Norway spruce (Picea abies (L.) Karst.) stands increased in 1930s in Southern Finland. The aim of the study was to analyse the advance and causes of drying. The work was begun in 1930s before the Second World War, and the damages caused to the forests by the war was used as supplemental observations in the study. A special method, drying analysis, was developed to study the process. It was used both in cases of insect and fungal diseases in the four research areas in Raivola and Ruotsinkylä. In addition, 7 observation areas were studied.

Several causes for drying of the trees were observed in the Norway spruce stands. These included European spruce bark beetle (Dendroctonus micans), root rot (Heterobasidion annosum), pine weevils (Pissodes sp.), bark beetles and honey fungus (Armillaria mellea).

The role of primary and secondary causes for drying, resistance of the trees and the drying process are discussed. Finally, the influence of forest management in drying process is analysed. Forests in natural state can be considered to be in an ideal balance. On the other hand, forest management can be used to maintain the vitality and resistance of the forests. Drying of Norway spruce stands can be taken into consideration when the stands are managed.

The PDF includes a summary in German.

• Kangas, E-mail: ek@mm.unknown

Temperatures needed in extracting Scots pine (Pinus sylvestris L.) seeds is relatively high, however, there is little information on its effect on germination of the seeds. This survey aimed at studying how different temperatures affect both extraction result and germination of Scots pine seeds. Comparisons between different temperatures (20, 30, 40, 50, 60 and 70 ºC) were made from cones collected from same sample trees, three trees in total.

Temperatures 20 and 30 ºC resulted in incomplete opening of the cones, and gave thus smaller amount of seeds. Complete extraction requires at the least the temperature of 40 ºC. The result is slightly better in 50 ºC, but germination of the seeds is little lower. Temperatures 60 and 70 ºC improve the results, but in the cost of germination. The main reason for lower germination percentage was that the higher temperatures release more empty and defective seeds from the cones. Results of different sample trees were different due to, for instance, quality and size of cones. Higher temperatures accelerated the extraction. According to the study, perfect extraction in 40 ºC requires longer extraction time than when the temperature of 50 ºC is used. In practice, 50 ºC temperature or even little higher temperatures can be used when the extraction time is shorter. Decessive factors in choosing the temperature would be the humidity of cones and length of extraction time.

The PDF includes a summary in German.

• Kangas, E-mail: ek@mm.unknown

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).

• Kangas, E-mail: ek@mm.unknown

The article discusses entomological analyses and their applications. Recent improvements in the methodology are presented and examples of application in the field of pines drying up standing are discussed. Further improvements to the method are proposed. The results of the studies so far indicate that there is need for further studies on duration of the generation of pine weevils (Pissodes sp.)

The PDF contains a summary in Finnish.  

• Kangas, E-mail: ek@mm.unknown