Ecological Factors Affecting White Pine, Red Oak, Bitternut Hickory and Black Walnut Underplanting Success in a Northern Temperate Post-Agricultural Forest
Truax, B., Gagnon, D., Fortier, J., Lambert, F., & Pétrin, M.-A. . 2018.
Abstract
This study took place in southern Québec (Canada) where young stands of white ash and
grey birch have been underplanted with white pine, red oak, bitternut hickory and black walnut.
The establishment success of white pine and red oak was measured with and without tree shelters
(to protect from deer). Ecological factors affecting the height growth of the four species were also
measured for protected trees. After 6 years, the survival and total height of unprotected oak was
29% and 44.3 cm vs. 80.5% and 138.5 cm for protected oak. White pine was less affected by browsing
(survival of 79.5 and 93.5%; height of 138.5 and 217.9 cm for unprotected vs. protected pine). Height
of white pine was higher in the grey birch stands, while height of all hardwoods was higher in the
white ash stands, which had better soil drainage, higher fertility, and an understory dominated by
Rubus species. Total height of all hardwoods was significantly (p < 0.05) correlated with Rubus cover
and with soil fertility. Pine and walnut height were strongly correlated (p < 0.001) to shelterwood
structure (canopy openness or total basal area). Pine was less sensitive to variations in shelterwood
characteristics, while black walnut showed high sensitivity. This study provides evidence that
underplanting is suitable for black walnut assisted migration northward and for bitternut hickory
restoration, despite soil conditions that were less favorable than in bottomland habitats mainly
supporting these species in eastern Canada. Tree shelters offering protection from deer browsing
and species-specific site selection are recommended for underplanting in the southern Québec
region.
Key Words
tree shelter; deer browsing; hardwood restoration; assisted migration; enrichment planting; shelterwood; Pinus strobus L.; Quercus rubra L.; Carya cordiformis (Wangenh.) K. Koch; Juglans nigra L.
