Pit-mound microrelief in forest soils: Review of implications for water retention and hydrologic modelling

Martin Valtera and Randall J. Schaetzl

Forest ecosystems are known for their capacity to retain and redistribute water. Nevertheless, even in some forested watersheds, prolonged or intense rainfall events often exceed the retention threshold of the system, generating accelerated runoff. Surface microrelief is an important attribute of forest ecosystems that often act to mediate potential runoff. In most natural forests, the soil surface is typically unevenly broken with pit and mound microrelief, formed by both historical and recent tree uprooting events. In managed forests, however, tree uprooting is traditionally seen as undesirable. The systematic repression of this process may lead to gradual loss of microrelief. To date, little attention has been paid to the impacts of the pit-mound microrelief, or its absence, on forest hydrology. Restoration of naturally undulating microrelief in managed forests can help to accentuate water retention and mitigate runoff, while reducing drought stress and reinforcing forest productivity and resilience.

This paper summarizes the literature and presents insights on the effects of tree uprooting on the microrelief of forest soils and forest hydrology, focusing on its consequences to water retention, tree water supply, and forest health. Furthermore, we explore the mechanisms and possible consequences of the long-term repression of these processes in intensively managed forests, with implications for forest management and further research.