By Bill Adamsen - Wilton, CT
Director of The American Chestnut Foundation, President, CT Chapter
Several months ago a friend sent a link to an article which provides evidence that chestnut really was a dependable source of food for wildlife - something frequently mentioned - but without documentation. After reading the article Hard Mast Production Before and After the Chestnut Blight I thought more CT Chapter members might appreciate the opportunity to read it. It provides a comparison of estimated hard nut production in a Southern Appalachian forest that happened to be assessed carefully at the time of the blight, for hardwood composition.
The immediate impression the article had on me - was realization of the impact the loss of a high volume producer (chestnut) must have had on wildlife. Looking at the graph below (or reading the referenced article) one is struck by how dissimilar the large year-to-year variability in mast production among oaks is to chestnuts (the bright green section on histogram bars to left). The loss of American chestnut must have greatly increased mortality for many mammals and birds which would have depended on the stable and consistent food supply chestnut provided.
The below graph uses the data provided in Hard Mast Production Before and After the Chestnut Blight to display calculated total hard mast production for a 10 yr interval in a Coweeta Basin forest before and approximataly 35 years after the chestnut blight epidemic.
All data by Diamond, Giles, Kirkpatrick and Griffin
Graph formatting by Bill Adamsen
The publication is available on-line. The authors are Seth J. Diamond, Robert H. Giles, Jr., and Roy L. Kirkpatrick, Department of Fisheries and Wildlife Sciences, and Gary J. Griffin, Department of Plant Pathology, Physiology, and Weed Science, Virginia Polytechnic Institute.
Thanks to Leila Pinchot for forwarding the article.
It is interesting to see that the large year-to-year variability in mast production among oaks, which is well-known and occurs among many tree species, does not seem to be the same for chestnuts in this study. Is the relatively consistent production confirmed in other chestnut studies?
There is another interesting revelation in the bar graph of nut production--a confirmation of the hypothesis that oak trees have a periodic cycle of 4-5 years of negligible to abundant production. The lean years reduce the number of mice, squirrels etc. that feed on the nuts so that in the super production year, most of the nuts remain for propagation.
@Robert - that's a keen observation. It also makes one wonder just how important mast is for survival and how long it typically serves as a food crop. Ultimately it would be interesting to know - perhaps on a calorie basis - what percentage of a forest animal's food supply is typically served by mast.@David - this was the first actual study I'd seen where there was an attempt to estimate mast production. With the tree functionally extinct for most of the past century here in the Northeast there are few opportunities to test that theory. Perhaps as we get to reforestation and the attempt to keep trees surviving (no selection pressure) we can get some metrics on production consistency.
Regarding David's question, I believe there have not been any quantitative studies of chestnut mast, which is why I found this article so useful. This is probably because foresters were not interested in tree mast production before blight. I just looked through a handful of old forestry books, all published before 1913, and only one mentioned chestnut nut production:“Seed years are not infrequent, but the nuts are eaten so extensively by men and rodents, and are so injured by insects, that reproduction depends largely upon sprouts.” Hawley and Hawes, Forestry in New England, 1912.
This suggests that chestnut does in fact have seed years, which is also implied in Brook's 1937 publication in the journal Castanea.
http://ctacf.org/enclosures/Brooks1937.pdf
However neither article mentions experiments to prove their theory. This is a common theme in chestnut literature.
The only other paper I've found that looks quantitatively at chestnut mast is Paillet and Rutter's 1989 publication.
http://ctacf.org/enclosures/PailletRutter1989.pdf
Quantitative samples of nut production made only in 1987 (so one year only) found that nut production by naturalized chestnut trees (in Wisconsin) growing in competition with other forest trees was much less than that of open-grown trees, and some large chestnut trees did not produce fruit in that given year. (pg. 3464)
Again this suggests that chestnuts may not necessarily produce large crops each year. But the tree may produce decent crops every year, whereas oak in some years has scant to no production.
Here is a paper by Paillet that discusses the importance of chestnut to wildlife:
http://chestnut.cas.psu.edu/Meetings/NPS/proceedin...
He theorizes that because chestnut produces flowers late, its flowers and developing embryos avoid spring frosts, and this is one reason the mast years are more regular than those of oak.
Also, here is an article in the TACF journal that discusses the effect that chestnut blight had on turkey populations:
http://chestnut.cas.psu.edu/PDFs/Journals/journ_vo...
Fred Hebard may have better insight to this question, as he has first hand experience with his orchards. They undoubtedly will produce larger crops than forest trees, from the additional available light, but he may have noticed a pattern in seed crop years.
I hope this is helpful. Leila
