First commercial thinnings in peatland pine stands: effect of timing on fellings and removals.

摘要

The aim of this study was to examine the fellings and removals and their dimension distributions in first commercial thinnings in Scots pine (Pinus sylvestris L.) stands growing on drained peatlands, when the cuttings are carried out at different stages of thinning maturity. The reference for standard thinning maturity was defined as in the present guidelines for silviculture on upland sites in non-industrial, privately owned pine forests in Finland. Experimental and/or simulated thinnings were applied in altogether fifteen stands representing a wide range in site productivity, climate, and time elapsed since first ditching, and premature (7 cases), mature (11), and over-mature (15) stages for thinning. The average stemwood volumes of fellings were 51, 69, and 92 m3ha-1 and those of harvest removals 36, 59, and 84 m3ha-1 for premature, mature, and over-mature cases, respectively. The removals from stands mature and over-mature for thinning were large enough to enable a commercially profitable harvesting operation in most cases, unlike those from the premature stands where the fellings were barely harvestable and consisted of clearly smaller stems. Considering the obvious trends of increasing supply and simultaneously decreasing price competitiveness of pine pulpwood, our results do not support early thinning unless absolutely necessary from the silvicultural point-of-view. Retarding the thinning until the stage when thinning maturity criteria are actually met, i.e. till stand dominant height of ca. 15 m or even further, would result in markedly better harvesting profitability and hence enhance the implementation of thinnings as a part of the best management practices of peatland stands..