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Impact of selection harvesting on the foliar chemistry of sugar maple seedlings established on base-poor soils in central Ontario, Canada

Treasure, Theresa, Watmough, Shaun A., Eimers, M. Catherine, Murray, Hayley
Forest ecology and management 2019 v.435 pp. 1-7
Acer saccharum subsp. saccharum, Carex, acid deposition, botanical composition, calcium, canopy gaps, forest regeneration, hardwood forests, harvesting, logging, magnesium, man-made trails, nitrogen, nutrient availability, nutrient deficiencies, nutrients, phosphorus, physicochemical properties, potassium, seedlings, skidders, soil, trees, understory, Ontario
Sugar maple (Acer saccharum Marsh.) is a commercially important species throughout much of eastern North America and concerns have been raised regarding its successful regeneration owing to nutrient limitation, especially calcium (Ca) caused by acidic deposition. Timber harvesting can alter nutrient availability in soil, but the short-term effects of selection harvesting on sugar maple seedling chemistry have not been studied. In this study, sugar maple seedlings were collected for elemental analysis from unharvested areas, canopy gaps and skid trails one and two years post selection harvest in a mixed hardwood forest in central Ontario, Canada. Plant community composition and sugar maple seedling morphology were measured along with soil physical and chemical properties. While there were few measurable differences in soil physical or chemical characteristics amongst sites, understory vegetation was markedly different and Carex spp. were dominant in skid trails. In addition, sugar maple seedlings in the disturbed sites (gaps and skid trails) were morphologically different (decreased height:diameter ratio) and had lower foliar concentrations of essential plant nutrients including nitrogen (N), magnesium (Mg), potassium (K), and phosphorus (P) compared with unharvested sites. Calcium concentrations in seedlings were unaffected by harvesting, perhaps due to low soil Ca levels across all sites. In contrast to Ca, foliar concentrations of K and P in seedlings growing in gaps and skid trails were below or approached reported nutrient deficiency thresholds for mature trees, which may have potential consequences for forest regeneration that have not been previously considered.