Articles by Erik Lönnroth

The article describes the method of improving the leveling line of the volume of sample trees so that the volume figures themselves indicate the best leveling. The original method of leveling line originates from Kopezky. Here the method is illustrated with a data from Finnish pine forest.

The PDF contains a summary in Finnish.  

• Lönnroth, E-mail: el@mm.unknown

In a natural state growing closed forest the amount of timber grows yearly. However, in the same time the timber volume also decreases when part of the trees die in the competition for light and other growth factors.

There are many interactive functions and characteristic that influence the growth and drain in a stand. These can be illustrated as mathematical models. The article discusses a set of models.

The volume 34 of Acta Forestalia Fennica is a jubileum publication of professor Aimo Kaarlo Cajander.

• Lönnroth, E-mail: el@mm.unknown

To achieve a continuous and constant timber flow over a longer time period, the forest holding structure should be close to normal forest or regulated forest. Concept of normal forest is presented as the model of achieving the highest possible sustainable yield and hence also the best economic return. The article discusses the regulations on the management of a forest holding with the view on regulating the forest yield.   

Felling need to be planned according to the forest site and tree species. The main tree species for silvicultural purposes are pine, spruce and birch. After the widely used controlled burning of forests the state of Finnish forests is mostly weak and far from the “normal forest”. Majority of forests are of young and there are lots of broadleaved forests.  Because of the great variation of the forest sites and their productivity as well as the small size of holdings in Finland, the selection of forest management regime, mainly the felling style (clear cut or light selection) is also important. The idea of management plans is represented.  

• Lönnroth, E-mail: el@mm.unknown

Volume formulas have been developed already for long time but there are still some questions to be solved. The volume of a stem can be calculated based on measurements of diameter on various heights or based on mathematic formula. The article presents the formula development for that. The study is based on measurements of 24 pine stands.   

The results of the new formula can be seen satisfactory with the relatively small data of this study. Coincidentally the formally best mean solution of the here compared volume calculation formulas was the one based on Denzin’s formula. There the deviation from total mean is almost zero.   

• Lönnroth, E-mail: el@mm.unknown

The article presents the principle of working if a dendrometer and the mathematical theory behind it. Dendrometer is a new measuring instruments used to determine the height and diameter of a standing tree. The usability of the instruments is proofed to be very good thought there are some limitations to its use. 

• Lönnroth, E-mail: el@mm.unknown

The mean has a great importance in statistics in general and also in forest statistical calculations. The meaning of the average tree and its characteristics is important also for the practical forest mensuration work. However, the question is how are the statistical numbers of a mean tree related to the statistical numbers of the stand.   

Study is based on the strip-wise survey of forests in southern Finland. From that information the 30 sample plots were chosen, 10 of each of most typical forest site types, MT, VT and CT. The stands are of different ages and development classes, varying from 14 to 159 years.

For the determination of the average tree are the statistical numbers of five characteristics needed: volume, basal area, diameter, height and form factor. The stereometric mean tree of the stand can be calculated with only one statistical method and that solution is absolute.

Theoretically and statistically absolute solution for the problem is the continuous solution by the mean that is weighted with the number of stems. This solution however is not very useful in practical sense.

A simple, practical and adequately exact solution for determining the average tree by approximation procedure of a certain arithmetic mean. 

• Lönnroth, E-mail: el@mm.unknown

Study is based on the strip-wise survey of forests in southern Finland. From that information the 30 sample plots were chosen, 10 of each of most typical forest site types, MT, VT and CT. The stands are of different ages and development classes, varying from 14 to 159 years.

The article discusses the earlier literature on the factors effecting forest stands and presents the data in detail. The results section is divided into paragraphs on number of stems of the stand, height, crown, breast height diameter, basal area and volume. The statistical numbers are calculated and presented.    

• Lönnroth, E-mail: el@mm.unknown