Research Report from the Yale School Forests
Oak Regeneration: the Real Story
vol. 1, issue 2: May 2013
Research Highlights
• Large cohorts of red oak seedlings establish infrequently (once
every 10+ years)
• Seedling recruitment and survival are higher in upper slope positions than in valleys
• Environmental conditions of drought and shade mediate competition between establishment and growth of oak and non-oak species
• Shade from residual overstory in shelterwood treatments and slow
recruitment favor development of competing species (e.g. birch)
R
esearch on oak seedlings at Yale-Myers Forest is helping scientists and practitioners understand the conditions needed for regeneration. In his doctoral work at Yale
School of Forestry & Environmental Studies, former School
Forests research coordinator Brent Frey used a combination of site measurements, controlled tests and field experiments to study regeneration success of red oak seedlings
across a number of important environmental gradients.
Red oaks (Quercus, section Erythrobalanus) are a dominant
component of southern New England’s mixed-hardwood forests. They serve important ecological roles, particularly as the
primary source of food resources for wildlife, and as one of
the most commercially valuable timber species in the region.
Long-term data suggests a decline in the dominance of oak in
the region, primarily because oaks of these forests are being
harvested as they reach economic and biological maturity. Red
oak regeneration ecology is complicated by the irregular production of seed (masting), dependence on establishment in the
understory prior to canopy disturbance, relative shade intolerance, slower initial growth than competitors, and deer browse.
Frey used a series of studies detailing long-term development of oak regeneration and associated species across different topographic positions representing varying shade environments and soil conditions typical of this region. First,
he examined the cohort dynamics and development of seedlings in the forest understories to understand natural recruitment and survival of seedlings. Second, in a garden study of
Photo by Geoff Giller
Photo by Brent Frey
five planted red oak species he evaluated growth and survival in the same sites. Third, he used a series of experimental
gaps to assess patterns of regeneration, particularly the release
of advance growth in relation to shade and soil types. Finally, he assessed the potential of several alternative silvicultural
approaches for regenerating mixed-oak stands in this region.
Frey’s work helped shed light on the dynamics of oak regeneration, highlighting the steep competition red oak seedlings
face on optimal sites. Frey’s findings suggest that some kinds
of shelterwood treatments, the oak regeneration approach
used by most silviculturalists, may in fact favor competing
vegetation. His research underscores the importance of understanding site conditions when planning regeneration harvests.
Management Implications
• To encourage oak, regeneration treatments must capitalize on oak
masting events, especially on moist sites
• Regeneration treatments can maintain higher residual cover on drier
sites (e.g. uniform and irregular shelterwoods), but canopy cover
must be removed on moist sites when regeneration is adequate (e.g.
one-cut shelterwood)
• Erratic seed production may limit effectiveness of the establishment
cut of a shelterwood; the shade of residual trees favors development
of competitors (e.g. black birch)
• Where advance regeneration of oak is lacking, treatments should (a)
be delayed and timed to mast-seedling establishment events, and (b)
include follow-up treatments to reduce competition from black birch
• Group shelterwoods (groups of 1/­2 acre in size) may be better than
uniform systems on midslopes with patchy regeneration, particularly where structural diversity is desired; small group removals limit
establishment of competing species while maintaining adequate
numbers of oaks for several years
For more information:
Visit the Yale Forests page: environment.yale.edu/forests and click on Research.
Full article citation: Frey B.R., Ashton, M.S., McKenna J.J., Ellum D.S., and Finkral A.
2007. Topographic and temporal patterns in tree seedling establishment, growth, and
survival among masting species of southern New England mixed-deciduous forest.
Forest Ecology and Management 245: 54-63.
Frey, B.R. 2012. Spatial and temporal regeneration ecology of oak-dominated forests
of southern New England. Ph.D. Dissertation, Yale University, New Haven, CT, USA.