Vegetation-environment analysis of areas with peat accumulation and hummock formation in the context of NiN (Natur i Norge). A study from Laggu, Gamvik municipality, Troms and Finnmark county.

Abstract

A conspicuous type of heath and forest with peat accumulation and hummock formation in terrestrial systems has been investigated in Laggu, Gamvik municipality in northern Norway. The aim was to describe vegetational composition, soil depth and hummock distribution, and identify environmental factors that cause terrestrial peat accumulation.

Vascular plants, bryophytes and lichens were registered in 58 plots of 1×1 meter, located within seven transects that covered terrestrial peat accumulating areas and a gradual transition into their surrounding nature types. 26 explanatory variables were registered in each plot. To identify compositional turnover along the main gradients and relate the explanatory variables to the observed pattern, parallel ordination with DCA and GNMDS was applied. Land cover–mapping of the transects and their surrounding nature types was also conducted. Additionally, peat depth and maximum hummock height in areas surrounding each transect was recorded.

The results discovered three distinct gradients along the investigated transects. The main gradient was related to a well-known gradient from forest to exposed ridges. The second gradient was related to peat accumulation. The third gradient was related to the presence and cover of the allelopathic evergreen shrub Empetrum nigrum.

The results from this study indicate that peat accumulation rates is likely a result of a cold climate, the low decomposition rate of the soil and in a positive feedback–loop with the allelopathic properties of Empetrum nigrum and the intrinsic slow decomposition rates of Polytrichum juniperinum, in addition to effects caused by frost processes. Regarding the NiN-system, this study concludes that there exists a peat accumulation gradient in terrestrial systems, similar to the LEC Peat accumulating ability (TE) in wetland systems. Further research is needed to describe the details of the hummock and evaluate the snow cover and frost processes that is connected to terrestrial peat accumulation.