Survival and growth of four floodplain forest species in an Upper Mississippi River underplanting

Forest restoration efforts commonly occur in degraded ecosystems. For the floodplain forests of the Upper Mississippi River, the combination of aging canopy trees and expansion of invasive species such as reed canary grass (Phalaris arundinacea L.) can shift forested ecosystems to open meadows. Before this shift occurs, there may be opportunities to proactively underplant. Our study reports 2-year survival and growth of four tree species (swamp white oak (Quercus bicolor Wild.), silver maple (Acer saccharinum L.), hackberry (Celtis occidentalis L.), and sycamore (Platanus occidentalis L.) planted under a moderate canopy of silver maple (approximately 60 percent overstory cover) across three elevational gradients. Swamp white oak had high survival across all three of the elevational zones and showed limited effects by herbivory or insects. Growth and survival of sycamore and hackberry depended on the elevational zone; sycamore performed better on lower elevational sites and hackberry did better on higher elevational sites. Our results highlight the potential for underplanting in floodplain forests as a proactive restoration strategy, with consideration given to local site conditions.