Seedling microenvironment in full-tree and tree-length logging slash

Abstract

In response to concerns about the effects of slash removal on natural regeneration, a microenvironment study was conducted in logging slash using weighed full-tree (FT) and tree-length (TL) slash loads, and no slash (control), in the first summer after harvesting a mixed stand in New Brunswick. Significantly higher temperatures at the litter surface occurred in control and FT plots than in TL plots. Potentially lethal temperatures for new conifer germinants were recorded 18 times in FT and control plots combined, and once in TL plots. Differences among treatments in temperature peaks diminished in prolonged droughty weather. There were no differences in soil moisture tension at 10 cm depth, apparently because of restricted drainage. An average of 95% of full solar radiation (W/m2, response range of measuring device 0.35–2.5 μm) was measured in FT slash and 66% in TL slash. No significant differences in mortality or height growth of established coniferous advance growth (Picea spp. and Abiesbalsamea (L.) Mill., mean height = 28.5 cm) occurred, but significantly less mortality and significantly greater height growth of small AcerrubrumL. seedlings (mean height = 7 cm) occurred in the FT and control treatments than in the TL treatment. Results suggest that harvesting methods that involve slash removal could result in increased mortality of small conifer seedlings from direct heat damage and in increased competition from pioneering hardwoods.