Research Brief: Surprises in Forest Succession

Dennis Riege on lunch break during research at Finnerud Forest

Dennis Riege on lunch break during research at Finnerud Forest

Studying how forests change is a long-term commitment. Forest succession is the natural replacement of trees that do not tolerate shade with those that do. It can take many decades for shade-tolerant species to dominate the canopy. This community, referred to as a climax community, will remain stable until an external disturbance sets the forest back to an earlier successional stage.

Ecologists monitor and track changes in forest composition and function over time. One method they use is sampling: systematically counting and measuring the size of trees in a designated area. This data can then be used to predict what the forest will be like in future decades. Often it is the next generation of scientists who check the predictions many years later.

Dr. Dennis Riege is an exception. In 1975, as part of his MS thesis, he sampled the Finnerud Forest, an old-growth red pine forest and the UW–Madison Arboretum’s northernmost outlying property. Based on this work, Dr. Riege predicted that the red pine forest would shift toward hardwoods such as red maple, of which there were many saplings waiting in the understory for an opening in the canopy. Dr. Riege returned to Finnerud Forest in 2007 to test his prediction himself.

Wisconsin’s northern pine forests typically change to include hardwoods. To his surprise, Dr. Riege found that white pine seedlings and saplings had become abundant, especially where old red pines were dying of natural causes. Riege plans to resample Finnerud at 5-year intervals to track this unusual forest dynamic, adding knowledge to the field of forest ecology and to reserve management. This site, and others like it, offer the opportunity to observe patterns of succession over time and investigate the factors responsible.

Located in Vilas County, Finnerud Forest is one of the few remaining stands of mature pine in Wisconsin. It is a designated National Natural Landmark and Wisconsin State Natural Area, and one of 11 outlying properties managed by the Arboretum.

Dr. Riege is an Associate Professor in the Department of Social, Behavioral, Natural and Mathematical Sciences at the University of Maryland University College in Rhode Island. He received his MS from the UW–Madison and his PhD from the University of Washington.

Research article
Riege, D. A., 2012. Surge in regeneration of Pinus strobus L. in three Wisconsin forests not projected by past demography. Journal of the Torrey Botanical Society 139(3):299–310.