Consequences of alternative forest management in riparian buffer zones : a GIS analysis

Sammanfattning: With increasing pressure from policymakers and the general public to conduct alternative forest management throughout the European Union (EU), Sweden needs to find ways to best prioritize the implementation of this alternative management. Alternative management is a term used to describe alternative management methods to clear-cut rotation forestry and can include silvicultural methods such as continuous cover forestry, management increasing proportion tree diversity and presence of broadleaves, and extended rotation lengths. Riparian buffers are one possible location for this management that may provide a win-win solution for meeting EU goals of increasing conservation of productive forests and use of alternative management, as well as benefiting water quality and biodiversity. Riparian buffers can protect the ecological functioning of a stream, typically by leaving a strip of unharvested trees in place around the stream, but in Sweden these buffers are often narrow (5-7m) and are dominated by a single tree species. Implementation of alternative forest management that would promote a diversity of tree species in wide riparian buffers could benefit streams, as well as assist Sweden in meeting EU goals. To determine the amount of forest land contained within buffers under 5 m, 15 m, 30 m, and 60 m buffer width scenarios I conducted a GIS analysis of 11 study areas throughout Sweden. I also examined the current tree species composition in these potential buffer zones and analysed the area around both natural channels, and forest ditches. I found that there is a significant latitudinal gradient in species composition within the buffer zones from north to south, with total tree volume, deciduous tree volume, and spruce tree volume increasing from north to south, whereas the proportion of pine is highest in northern study regions. This latitudinal trend was not seen in terms of the proportion of forest land contained within the buffers that was productive forest land; however, there was a significant difference between the amount of productive forest land found around ditches versus streams. If ditches were to be buffered with wide 60 m buffers, it would require converting 5-6% of productive forestland. Buffering both ditches and natural channels, with 30 m buffers, would require about 20% of productive forestland. On a spatial scale, converting riparian buffers to alternative forest management appears to offer potential for maximizing protection of sensitive riparian zones, while minimizing economic losses in a way that meets EU goals for alternative management and conservation, although future studies are needed to examine the practical implementation of conducting alternative forest management within riparian buffer zones and the form that this management would take.