Forest management is not obligatory in Finland for the forest owner. In principle, there is only one obligation: after a regeneration felling a new forest stand must be established within a certain time.

This must be done by a method that is most probably successful in the conditions at the forest site. If the method appears unfavourable on the basis of existing forestry know-how, the authorities must demand better methods.

The success of the regeneration effort is also monitored. So, if a new stand does not start to grow within the defined time frame, the authorities must demand that the forest owner remedies the situation.

This obligation also extends to continuous-cover forestry. If a forest under the continuous-cover system is logged and the procedure can be considered regeneration felling – another name for which is clearcutting – a new stand must be established.

Apart from this statutory obligation, forest owners are free to use any management methods they like.

Tahvonen’s paper contains many reservations
Even the environmental organizations have traditionally been of the opinion that continuous-cover silviculture is not as profitable as the periodic cover system. Now they are starting to change their minds.

The new claims are usually based on a working paper by Mr. Olli Tahvonen, Professor at the Finnish Forest Research Institute. The paper – ‘Optimal choice between even- and uneven-aged forest management systems’ – is taken to claim that continuous cover system brings 30 percent more profit than the periodic cover system.

In fact, such a conclusion is not warranted by Tahvonen’s paper. This is easy to see if one just reads through the whole paper. There are many reservations and caveats, and the paper expressly states that it is not meant to serve as a practical model for forest management.

The very starting point of the paper is revealing: it does not even aim at comparing different forestry systems. Instead it aims at developing an open model, and only with the help of this model would it be possible to compare systems – and even then, only as far as forest regeneration and the relation between forest density and growth are concerned.

The paper also says that general forestry guidelines based on it may be misleading. There are many reasons for this.

For the first, the paper is completely theoretical and only based on desktop calculations. A growth model has been developed for one tree species only, the Nordic Spruce. It is assumed that the model functions on all types of sites and that the new forest stand is regenerated naturally on all sites in an ideal manner, and the cost of harvesting and establishing a new forest after it are excluded from the model. The effect of interests is included, but only one of the interest rates used is realistic.

In addition to this the model assumes that the use of continuous-cover silviculture starts when the site is covered with forest, while the periodic cover system is assumed to have its starting moment on a clear-cut site.

“Intermediate” system considered to be best
Even after these reservations the paper does not claim that the system known as continuous-cover silviculture brings the highest earnings. Instead, it says that the best one is an “intermediate” system somewhere between the continuous-cover and rotational systems.

The paper defines this system as a forest grown in “cohorts”, but in such a way that the forest cover is continuous. This system is called by at least two different names: uneven–even-aged and unrestricted forestry.

We are not told whether the tree cohorts are defined according to age or size of the trees, what the boundary values and areas of the cohorts are, or what the size of open areas allowed in the forest cover is.

What we are told is that this theoretical system of growing a theoretical forest brings 30 percent more profit than the periodic cover system, which is continuously being tested in practice. Using this conclusion as an argument in practical discussion has to be based on dishonesty or simple ignorance.

By Hannes Mäntyranta



Professor Tahvonen's working paper