Forest certification as an instrument for improved forest management within small-scale forestry

Since early 1990 ties, Swedish forest land is increasingly becoming certified. Today all major forest owners have joined the Swedish FSC-standard (Forest Stewardship Council), while small-scale forest owners preferably are joining the PEFC scheme (Programme for the Endorsement of Forest Certification). With the overall aim of gaining a better insight into which small-scale forest owners that have decided to take up on forest certification, and how their forest management practices have been affected by this choice, two set of data has been analyzed; one consisting Data Base of Forest Owner Analysis (DBFOA) data relating to approximately 14,000 properties whereof 1955 were found to be certified, and the other one including data from a follow up questionnaire sent out only to owners with certified forest properties. Results show that certified and non-certified forest properties are managed differently and in particular that harvesting on certified properties has increased. Differences in management seem to be connected principally to the fact that forest owners from generally more active sub-groups embrace forest certification requirements. Moreover, our results shows that economic motives for joining a certification scheme are just as prevalent as environmental motives and a majority of forest owners regard certification as something that favors profitability rather than consider it to restrict economic yield

Assessment of bias due to random measurement errors in stem volume growth estimation by the Swedish National Forest Inventory

We evaluated the performance of two methods for estimating stem volume increment at individual tree level with respect to bias due to random measurement errors. Here, growth is either predicted as the difference between two consecutive volume estimates where single-tree volume functions are applied to data from repeated measurements or by a regression model that is applied to data from a single survey and includes radial increment. In national forest inventories (NFIs), the first method is typically used for permanent plots, the second for temporary plots. The Swedish NFI combines estimates from both plot types to assess growth at national and regional scales and it is, therefore, important that the two methods provide similar results. The accuracy of these estimates is affected by random measurement errors in the independent variables, which may lead to systematic errors in predicted variables due to model non-linearity. Using Taylor series expansion and empirical data from the Swedish NFI we compared the expected bias in stem volume growth estimates for different diameter classes of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.). Our results indicate that both methods are fairly insensitive to random measurement errors of the size that occur in the Swedish NFI. The empirical comparison between the two methods showed greater differences for large diameter trees of both pine and spruce. A likely explanation is that the regressions are uncertain because few large trees were available for developing the models