%0 Articles
%T Modelling bilberry and cowberry yields in Finland: different approaches to develop models for forest planning calculations
%A Turtiainen, Marjut
%D 2015
%J Dissertationes Forestales
%V 2015
%N 185
%R doi:10.14214/df.185
%U http://dissertationesforestales.fi/article/1974
%X The aim of this research was to create yield models for the two most significant wild berry species in Finland, namely, the bilberry and the cowberry. In particular, the aim was to develop models applicable to multi-objective forest planning calculations. The models were developed using approaches based on both expertise and empirical measurements. In expert-knowledge-based studies, different methods of data collection were used: experts evaluated berry production of different forest stands (i) from slides, (ii) visually in the field and (iii) using a questionnaire. Data for empirical studies were also collected using different methods: measurements (i) of systematically placed sample plots and (ii) of forest stands found to be advantageous with respect to berry production. Statistical analyses of data and modelling techniques varied from study to study. Thus, another aim was to test different methods of data collection and different modelling techniques and also assess their usability.

According to the results, the best bilberry yield can be found in a mature stand which is not too dense and is located on a mineral soil site of medium or rather poor fertility. It is also obvious that pine-dominated heath forests of rather poor or poorer fertility have the highest cowberry yields. A stand suitable for cowberry picking should not be dense. These results are very much in line with previous studies on the effects of site and stand characteristics on berry production. However, it is concluded that there is still a need to for further research to explore the dependence of cowberry crops on stand characteristics on poor mineral soil sites.

Comparisons of the results of this thesis with empirical berry yield studies and also with earlier berry models indicate that modelling expertise is a reasonable way to create production functions for different wild berry species. This finding encourages the utilization of expertise in other applications for the development of models for different non-wood forest products. In particular, the method based on visual assessments conducted in the field was found to be a promising one.