Sprouting in temperate trees: A morphological and ecological review

Sprouting in trees, which results in the production of secondary trunks, is an induced response to injury or to a dramatic change in surrounding environmental conditions. This article reviews the forestry and ecology literature to produce an integrated view of the role of sprouting in both disturbed habitats and closed-canopy forests. Sprouting is a universal attribute of temperate angiosperm trees through the sapling stage of development but is much less common among gymnosperms. Four basic types of sprout morphologies are described: collar sprouts from the base of the trunk, sprouts from specialized underground stems (lignotubers and rhizomes), sprouts from roots, and opportunistic sprouts from layered branches. In a survey of 68 species of trees native to northeastern North America, 41% were found to retain the ability to sprout from the collar into adulthood; 26% sprout from branch layers under natural conditions; and 25% have the capacity to form root suckers. Sprouting in seedlings promotes their survival under a variety of stressful conditions, including suppression by canopy trees, herbivory, site exposure, and desiccation. In contrast, sprouting in mature trees extends the life span of the individual following damage and, in the case of root-suckering species, promotes the colonization of new ground. Although the sprouting of mature trees is more conspicuous than the sprouting of seedlings, its ecological significance is not as great. As a broad generalization, species that grow in stressful sites or sites with frequent disturbances are likely to sprout more vigorously and to retain the sprouting ability longer than are species that grow in less stressful sites or sites with less frequent disturbance. Near the limits of a species’ altitudinal or latitudinal range, the production of basal sprouts, root suckers, rhizomes, and/or branch layers allows trees to spread into adjacent areas, thereby circumventing the difficulties associated with seedling establishment.