Phone/Fax:  717.399.0195
Mobile: 717.538.0393
Lancaster, PA 17603
Email:   gonative@voicenet.com

Tree.jpg
Nursery  Address: 678 S Chiques Rd Manheim, PA 17545
Office Address: 2310 Chestnut View Drive Lancaster, PA 17603
Dedicated to the understanding, preservation, and recovery of the Eastern American forest
 

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Reforestation Options for American Chestnuts

Copyright© 2016 by Go Native Tree Farm

 

Introduction

Before 1900, American Chestnut (Castenea dentata) was a dominant eastern North American forest species. Then an ecological disaster occurred on par with an asteroid extinction event, and four billion American Chestnuts died. The fungus Cryphonectria parasitica appeared suddenly on the trees, which almost certainly was brought by humans on chestnuts imported from Eurasia. Within a few decades, an estimated four billion chestnut trees died in the forest. A few dozen survivors are still present in scattered stands, mostly in Michigan, Wisconsin, and Georgia. On the west coast, specimen trees still survive because the blight is not present there. Root shoots can be found in the historic range today, because the basal tissue and root stock are not always killed by the fungus. Recovery of the forest species in the native range is the topic of this essay.

 

There are things that you can do about it. There are three primary tactics that have been identified to help solve the problem. All are valid scientific approaches, and may best be used in tandem to ultimately restore the species. The following is a summary of the avenues that are being pursued.

 

Recovery Tactics

1)      Back-crossing with Asian Species. The American Chestnut Foundation (TACF) has been active for many years, following the technical approach of back-crossing American Chestnuts and Asian chestnuts. As of this writing, they have produced up to 15/16 Castenea dentata genome. Although this process requires many years of successional effort, it should ultimately result in a nearly pure native genome. Each generation of halving the Asian genome requires a minimum of ten to fifteen years, so the process is slow by human standards. Meanwhile, the drawbacks include the new introduction of Asian genome into the forest, plus the difficulty of obtaining a significant enough number of plants to effect a substantial effort.(See figure 1)

backcross mice

2)      Extreme Natural Selection. The American Chestnut Cooperator’s Foundation (ACCF) is following the approach of extreme natural selection by manually cross-pollinating the few disparate old survivors, which can be described as extreme natural selection. ACCF geneticists calculated that perhaps 10% (estimates range from 5% to 20%) of the plants produced in this manner will exhibit blight resistance at least as favorable as the parent trees. Furthermore, they believe that the progeny of these plants should all exhibit natural blight resistance. The advantage of this approach is to immediately produce potentially resistant 100% C. dentata seedlings. A drawback is the difficulty of obtaining a significant enough number of plants to effect a substantial recovery effort.(See figure 2)

 Charles Darwin

3)      Genetic Weakening of the Fungus. Another approach which may eventually prove to be essential is the development of hypo-virulent chestnut blight inoculants. This weakened form of the fungus spores has been introduced into wild populations, which has the effect of making the trees less susceptible to the blight. The weakened blight should also be helpful in protecting the Allegheny Chinkapin (Castenea pumila) from Chestnut Blight.(See figure 3)

needle

It is likely that a combination of these approaches will ultimately result in recovery of the species as a forest tree.

 

Our Experience

We have concluded that we prefer the ACCF approach in the near term, since it is unclear how to remove the Asian genome from the forest once it is introduced. The weakened blight genome is likely already out in the environment, and already it may be becoming helpful. The outlook has definitely improved in recent years, due to a combination of the above research work. It is now possible to plant this species with reasonable hope for survival.

 

Over fifteen years ago, we obtained fifty manually cross-pollinated seedlings from old survivors (Tactic 2) and planted them as a recovery grove. Voles took one-third of them the first winter, after which we surrounded each plant with 1/4 “- mesh steel screen tubes. After seven to ten years, the remaining plants had grown to nearly thirty feet in height and began to produce nuts. Now, fifteen years later, about eight trees still survive, and are forty to fifty feet tall and 8- to 12”-caliper. Two of them exhibit the best resistance features, i.e. no sprouts at the trunk base, a nicely formed crown, and no branch or crown die-off. They all have swollen burls on their trunks, but seem to be growing through it. In other words, the blight is present but the trees still survive and produce nuts each year. So if the geneticist calculations are correct, then we are most of the way through the winnowing process. Last fall we collected about 600 seeds from the grove.  We now collect seed from the two best plants (pictured below), so we have effectively concentrated the blight resistance factor to about one part in 2.5 billion [(40/4 billion) X (2/50)]. (see Figure 4 and 5).

alfa chestnutbeta chestnut

We offer our seedlings to recovery projects, and we can offer advice to planters to prevent animal damage and related infant mortality issues. Based on the above information, we can estimate that at least two out of three seedlings should exhibit favorable blight resistance, at least sufficient to allow plants to live for fifteen years or greater. The plants are 100% American genome. Starting three to get two survivors is a big improvement from a few decades ago, when it was nearly impossible to do so. Please contact us if you have questions or wish to obtain seedlings for a recovery project.

 

 Go Native Tree Farm™                  

2310 Chestnut View Drive                                                     Phone/Fax:      717-399-0195

Lancaster, PA 17603                                                              Mobile phone:  717-538-0393

www.gonativetrees.com                                                    Email:gonative@voicenet.com

 

Latin

Name

Common

Name

Plant and Container Size

#

On hand

Castenea
 dentata

American
Chestnut

10-12”, D60 cells

24-36", 5 gal.

745

58

Castenea
 pumila

Allegheny Chinkapin

12-24”, 1 gal tall.

24-36”, 2 gal.

81

18