Riparian forests : a comparison of tree diversity, deadwood and canopy cover between primary and production riparian forests along headwaters

Abstract: Headwaters and their adjacent riparian forests (RF) have been recognized for years for their tight interlinkage and essential ecological and biogeochemical services. Notwithstanding, headwaters in Sweden have historically been overlooked in forest management, which has led to conifer-dominated RFs with simplified even-age structure. This simplified structure may not provide the same ecosystem functioning as a primary RF ecosystem, thus forest management that aims to mimic natural disturbances has been promoted as a more sustainable alternative. However, little is known about the stand characteristics of primary RFs and how they differ compared to mature production RFs along headwaters. In this thesis, I investigated the stand characteristics (i.e. tree species, tree sizes, deadwood and stream canopy cover) in five primary RFs and five mature production RFs along headwaters in Västerbotten and Västernorrland county. Measurements were conducted in six 10x10 m plots along a 110 m stream transect. The primary RF had more tree species, higher tree density, lower mean DBH, more riparian deadwood and lower mean canopy cover compared to the production RF. The primary RF followed an inverse J-shape diameter distribution, while the production RF followed a uniform bell-shaped diameter distribution. Norway spruce was the dominant tree species in both RF types. No significant difference was found on in-stream deadwood between the primary and the production RF. The presented results could aid to improve forest management to increase RFs functionality. However more research over climatic gradients and different forest types is needed before active and adaptive forest management can be applied.