The American chestnut was a really
important tree species historically.
It existed in eastern North America
for about 10 million years.
It had a range from southern Canada
south into Mississippi,
east from the Piedmont,
west to the Ohio River Valley.
So it had about a 200 million acre
range, and it was thought to occupy
about 3 to 4 billion trees.
It was extremely versatile, extremely widespread.
It was thought to be a keystone species,
and it was here for ten million years,
and it was virtually wiped out in
less than 60 from the blight that
came in.
Breeding for resistance
to the chestnut blight started
almost immediately after
the blight was discovered.
Scientists realized that they could cross
Asian chestnut species,
like Chinese and Japanese chestnut,
with the American chestnut
to get blight resistance.
But the trick was to get a tree
that not only had blight resistance,
but also had good timber form
and grew fast like the American chestnut.
In the mid 1980's an approach
was developed called back-cross breeding.
With backcross breeding, a hybrid tree
is produced that theoretically has
94 percent of its genome
from the American chestnut
and 6 percent from an Asian chestnut species,
like the Chinese chestnut.
We refer to these trees as BC3F3's
or the third backcross generation.
This breeding work has taken
many decades to carry out
and it is still ongoing.
From a regional standpoint,
though we manage vast landscapes
of southern pine and upland hardwoods,
we never want to lose sight
of the conservation of forest tree species
that are threatened, or in the case
of the American chestnut, were lost.
We want to support and be an active
part of the chestnut reintroduction as
we continue working with our partners,
such as the Southern Research Station
of the U.S. Forest Service,
University of Tennessee,
and The American Chestnut Foundation
and provide test sites for chestnut plantings
on the Southern Region national forests.
We established our very first research
test planting of American chestnut in 2009,
and actually where I am standing
is the very first research test planting
of American chestnuts that have ever
been established on the national forest system
using the most advanced breeding material
available at the time.
These test plantings represent
a culmination of over 100 years
of research and breeding efforts
that have been underway to get
a blight resistant American chestnut
established back into its native range.
We knew that we had to grow the best
seedlings possible for planting
so that the trees would be competitive
in the woods and would escape
deer browsing more quickly.
So we grew the trees from nuts
in a commercial nursery for one year
to maximize their growth
and size prior to planting.
For every tree we were going to plant
we counted the seedlings roots
and measured its height
and its stem diameter.
We sorted the trees into an experimental
design for planting so we can empirically
test the effects of breeding, genetics,
and seedling size on overall field
performance over time.
We established thirteen plantings,
starting in 2009 and we also established
plantings in 2010, 2011, and 2015.
In all, we’ve planted about 4500 trees
in three states on three national
forests, the Cherokee, the Nantahala,
and the George-Washington-Jefferson.
We established this planting in 2009
with nuts that were collected in 2007
from the American Chestnut Foundation’s
orchard in Meadowview, Virginia.
In this particular planting,
where I’m standing, we planted around
400 trees total and about half of those are
the BC3F3 trees, or the 3rd generation
backcross trees, which are the most
advanced breeding generation available
for us to test, and those trees are
predicted to be highly blight resistant
but also look and behave like
an American chestnut.
So we want to see if the trees we planted
out here are going to have those desirable
characteristics of the American chestnut,
but have the desirable blight resistance
of the Asian species,
like the Chinese chestnut.
So one of the important things that
we’re looking at in these plantings
is not just whether or not the tree is
going to be resistant, but whether
the tree is going to be able to compete
with all of these native species around it.
We have poplars, and here is a small poplar.
There’s birches and striped maples
and trees like that that this tree has
to be able to get its head above
and get the sunlight in order
to stay competitive and then eventually,
hopefully produce fruit and reproduce.
As of the 12th growing season
after planting about 60 percent
of the trees that we planted are alive,
so 40 percent of them have died.
The majority of them died early on
right after planting,
and that’s kind of common
for hardwood plantings.
Trees go through what you call
planting shock, where they
have been growing in a nursery.
And you take them out of that
nice environment and put them out
into the real world and they kind of
go into a shock period.
So it can sometimes actually kill them,
but also trees die for other
unknown reasons that we don’t
totally understand.
They could have gotten browsed
too much by deer.
They could have gotten defoliated by insects.
They could have gotten cicada damage.
So there’s lots of reasons that trees
die other than just getting the chestnut
blight, and that’s really important
for us to document over time to give
managers that baseline information
for how these trees are going to survive
and perform over the long term.
This tree where I’m standing has really
good form. It’s tall. It’s straight.
It’s going straight up into the canopy.
Most of its leaves are up in the canopy,
and they are getting direct sunlight,
which is going to be really good
for nut production and flower production,
long term.
Whereas a Chinese chestnut is going
to grow a little bit more shrubby
in appearance, and be shorter,
and have more forking, and it’s just not
going to be as competitive as
a pure American chestnut.
And what we found is that
the BC3F3 trees look identical
to the American chestnut,
and they’re growing pretty similarly
to the pure American chestnut,
although slightly less fast
than the American chestnut,
but that could change over time.
The tallest trees on this site
reached 40 feet in 10 years
and that’s pretty remarkable.
They’re averaging around
25 feet in height growth right now
on average across the entire stand
after 12 years.
The BC3F3 trees are
doing significantly better in terms
of blight resistance compared
to the pure American chestnuts
that we planted.
About half of the BC3F3 trees are
still blight free compared to only
about 20 percent of the American chestnuts.
Two of the biggest problems we face
with restoration of American chestnut
other than blight resistance,
is deer browse on newly planted seedlings
and Phytophthora root rot.
We can mitigate for the deer browse
by planting larger size seedlings
and using tree shelters.
We mitigate for root rot by being very
careful about site selection to plant
on well-drained sites.
We’ve documented other non-native pests
that have had some negative impacts
to our plantings.
The Asiatic oak weevil defoliates trees
but doesn’t seem to kill them.
The Asian gall wasp lays eggs
inside of newly developing buds
and inhibits growth and flowering.
The Ambrosia beetle attacks weakened
or dying trees.
Restoration really has to be
about more than planting
a blight resistant tree.
We have to also consider
the impacts of other non-native pests
that are here now and those that are
likely to come.
Working with Dr. Clark is an important
part of the National Forest System
restoration goals and objectives because
she is focusing on the restoration
of the American chestnut.
The silvicultural toolbox is relatively unknown
for restoring American chestnut.
As Dr. Clark’s research develops further
we begin to understand more information
about how American chestnut
competes within the local communities
that it’s growing in and based
on that information we can design
treatments that are beneficial to creating
conditions for American chestnut
to survive and thrive as we look
at restoration opportunities.
These research test plantings represent
over 100 years of research and breeding efforts.
We’re only in the 2nd decade of
research in these test plantings and
American chestnuts can live over 300
years old.
So we are really in the early
phases of understanding how this tree
is going to perform out in the real world
forest conditions like you see here today.
So we think if you can get a tree that is
going to maintain blight resistance over time,
you will be able to restore these trees
back into their native range.