Rooting of peatland black spruce and tamarack in relation to depth of water table

Abstract

Rooting of Picea mariana Mill. BSP. and Larix laricina (Du Roi) K. Koch trees was examined in four peatlands with different depth of water table. Peat blocks, 60 cm deep, 1.0 m from the base of each tree, were excavated and sectioned into 10-cm horizontal strata and the roots extracted. The presence of and depth to frost and the depth of water table were determined on each peat block. The periodic annual increment in basal area of each tree was determined. Rooting depth was strongly correlated with depth to water table. On wet sites, roots of both black spruce and tamarack were confined to hummocks, while on dry sites, roots penetrated to 60 cm. The deep roots were generally <2 mm in diameter and held in frozen peat layers until late June. There was a strong positive correlation between fine root biomass and depth of water table; however, total root biomass was not correlated with depth to water table. In general, growth rates of both black spruce and tamarack were positively correlated with water table.