The characteristics of whole-tree fuel stocks from silvicultural cleanings and thinnings

Abstract

The fuel properties of small-sized whole-tree fuel stocks were studied in roadside and in-stand storages. The significance of pile cover, season and storage site on moisture content and heating value of Scots pine ( Pinus sylvestris ) and pubescent birch ( Betula pubescence ) fuel stocks were observed. When the fuel stocks are placed in a well-ventilated location moisture content may be lowered below the 40% mark during one summer period. Covering the piles will give up to 6% units lower moisture content in comparison with non-covered piles. The most benefit is gained from covering during snow melting in spring and the least in midwinter when the snow is dry. Multi-tree harvested stemwood with no limbs seasoned equally well as the whole trees both in roadside and in-stand trials. This is because the processing of multi-tree bunches caused some debarking to take place. As a result, the transpiration drying capability of whole trees was equalized by the evaporation of moisture via the open wood surface. Both assortments reached moisture contents below 30% in in-stand conditions during one summer's seasoning. The effective heating values of neither birch nor pine showed significant changes. However, heating value deviated with the composition of the fuel stock. The presence or absence of crown material was a factor. The microbial counts of mesophilic fungi in whole-tree fuel stocks were only 1% of that found in logging residues. The counts of thermo-tolerant fungi were still much smaller. Leaving the Scots pine piles uncovered will increase the number of mesophilic fungal spores and bacteria.