- Oak forests were once dominant across eastern US but have declined significantly since pre-settlement times due to factors like fire suppression and land use changes. - Today, oaks are limited to areas that experienced heavy cutting or pasture use in the past. Conditions that allowed oaks to regenerate then, like lack of deer, no longer exist. - Multiple threats further endanger oaks, including pests/pathogens, climate change, overabundant deer, and current forestry practices. Without active management, most oak species in the region will continue to decline.

1. The Future of Oak Forests
The Deep Roots of the Oak Regeneration Problem
Charles Canham
Senior Scientist
Cary Institute of Ecosystem Studies
Millbrook, NY

2. Marc Abrams, Bioscience, 1998
Greg Nowacki and Marc Abrams, BioScience 2008
Marc Abrams, BioScience 2003
The roots of the problem…

3. The issue locally…
Changes in oak abundance since pre-settlement times
 Is fire suppression responsible for a reduction in the regional
dominance of oak species in many parts of the eastern US?
 Has the reduction in the abundance of oaks over the past 200 years
fundamentally altered the flammability of these forests?
 Is there a future for oak in our forests?
http://oaksavannas.org/fire-fuel.html
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10
20
30
40
50
60
70
80
Oaks Hickories Hemlock Pine Maples
Presettlement Forests
Current Forests
Percent
Tree Species
composition of the Cary Institute forests

4. ? Have the forests “recovered”?
(and, to
what?)
Land clearing, cultivation, and abandonment:
Conversion of oak forests to forests dominated by maples, birches, and pines
The loss of oak from the best soils

5. Where are our oaks today?
(on hilltops and in old pastures)
 Essentially none of the pre-settlement oak forest regenerated by fire is
present today
 Oaks today are largely limited to lands with two very different land-use
histories:
Highlands and hilltops that were heavily and repeatedly cut for timber
and firewood
Pastures, in which scattered oaks were left for shade and acorns
 Conditions under which they
regenerated 50 - 150 years ago:
Heavy cutting followed by sprouting
Absence of deer

6. Quercus - The Oak genus worldwide
 Distributed in north temperate regions worldwide (North America,
Europe, Asia)
 Evolved in dry, savanna-like conditions, 40-60 million years ago
Center of evolution was in what is now the Southwest US and Mexico
 ~ 350 species of true “oaks” (subgenus Euquercus) worldwide
 North America has the highest diversity of true oaks
Quercus is the largest genus of trees native to the US
 Oak species make up 9 of the 50 most common tree species in eastern
U.S. (more than any other genus)

7. Our most important oaks locally…
Scarlet oak
Quercus coccinea
Northern red oak
Quercus rubra
Black oak
Quercus velutina
White oak
Quercus alba
Chestnut oak
Quercus prinus
THE “RED OAK” GROUP
(Erythrobalanus)
THE “WHITE OAK” GROUP
(Lepidobalanus)
Photos by Jerry Jenkins,
Northern Forest Atlas Project

8. Relative abundance of northern red
oak and white oak in US Forest
Service Forest Inventory plots
To give you a sense of
their importance…

9. Salient features of the ecology of our oaks
 The species vary, but all are generally not very shade tolerant
Red oak is the most shade tolerant, but even those seedlings have high
mortality when they receive < 10% of full sunlight
 Canopy oaks are fierce competitors when dominant, but highly sensitive to
suppression when overtopped
 They sprout vigorously from cut stumps, but sprout vigor is reported to
decline if the trees are very large when cut
 A good online source:
Silvics of North America (USDA Agriculture Handbook 654)
http://www.na.fs.fed.us/spfo/pubs/silvics_manual/table_of_contents.htm

10. Reproduction in oaks
White Oak Group
 Flowers every few years in
spring
 Acorns mature and drop that
fall
 Germinate almost immediately
after seedfall
Red Oak Group
 Flowers every few years in
spring
 Acorns mature and drop in fall
of following year
 Stay dormant overwinter then
germinate in spring

11. Current threats to oak abundance in the region
 Air pollution
 Pests and Pathogens
 Climate change
 Current harvest practices
 Deer

12. Air Pollution...
 Ozone exposure
 CO2 fertilization
 Acid deposition and soil
calcium depletion
 Nitrogen deposition
Thomas, R. Q., C. D. Canham, K. C. Weathers, and C. L. Goodale. 2010. Increased tree carbon
storage in response to nitrogen deposition in the US. Nature Geoscience 3:13-17.
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Nitrogen deposition generally increases
forest productivity region wide,
But species other than oaks tend to
benefit the most…

13. Pests and Pathogens
 Arguably the most pervasive human impacts* on eastern US forests
over the past century have been from the introduction of new pests and
pathogens…
Chestnut blight
Dutch elm disease
Gypsy moth
Beech bark disease
Hemlock wooly adelgid
Emerald ash borer
Asian longhorned beetle
…? (including changes in
outbreaks of native pests
and pathogens)
Heavily diseased and resistant beech trees
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*on distribution and abundance of
specific tree species

14. Climate change…
 Since oaks are even more abundant in warmer climates, will they
benefit from climate change?
 Over time, will new oak species migrate northward?
 Well, not much, and not anytime soon…
The Cary Computer Cluster
(used to analyze the data from thousands of USFS
forest inventory plots, and simulate future forests)

15. Predicted changes in distribution and abundance:
Northern red oak
(under current logging regimes, with and without climate
change)

16. Predicted changes in distribution and abundance:
White oak
(under current logging regimes, with and without climate
change)
Similar or even more precipitous declines predicted for black oak and chestnut oak

17. Current harvest practices in northeastern forests
 Clearcutting has been
replaced by selective
logging as the dominant
harvest regime in
northeastern forests
(except in a few forest types)
Percent of biomass harvested
Percentofarealogged

18. Impacts of over-abundant white-tailed deer
• It seems clear that hunting can solve this
problem, at least on larger landholdings
• it has worked remarkably well for us in the
Cary Institute forests
• But the hunting population is getting smaller
and older – can we reverse this?

19. The future for oaks in the northeast…
 The conditions that created the pre-settlement oak forests and existing
post-settlement oak forests no longer exist
 Four factors currently work against oaks
The absence of fire
The increase in more shade tolerant tree species, particularly maples
The abundance of deer,
Light selective harvests
 In the absence of deliberate management, it seems inevitable that most
of the region’s species of oak will continue to gradually decline in
abundance.