Soil exploitation strategies of fine roots in different tree species of the southern boreal forest of eastern Canada

This study compared the ability of conifers (Abies balsamea (L.) Mill., Pic ea glauca (Moench) Voss) and deciduous trees (Populus tremuloides Michx., B etula papyrifera Marsh.) and shrubs and herbs to exploit soils in a souther n boreal forest. Root samples were collected from undisturbed soil and ingr owth cores (disturbed soil) of aspen-and conifer-dominated plots. Total fin e-root biomass was similar in aspen and conifer plots but length density wa s higher under aspen. The low root length density (0.7 cm.cm(-3)) of conife rs suggests a dependency on mycorrhizal associations for effective nutrient uptake. Coniferous fine roots were thicker than in the ether species. Root tip and internode lengths in deciduous trees showed little differences bet ween undisturbed and disturbed soil, whereas these parameters increased sub stantially in conifers in disturbed soil. Root growth and architecture in d isturbed soil indicated that conifers follow a conservative strategy of opt imizing soil exploitation efficiency through the relatively slow developmen t of coarse fine-root systems. In contrast, deciduous trees and understorey shrubs and herbs colonized favourable soil environments to a larger extent maintaining highly ramified thin fine rests to optimize the exploited soil volume. The different soil exploitation strategies may be as important as those differences reported for aboveground growth to explain the coexistenc e of these species.