The document "Hough, A. F. and Forbes, R. D. 1943. The Ecology and Silvics of Forest in the High Plateaus of Pennsylvania, Ecological Monographs, Vol. 13, No. 3, July 1943" describes a 536 year old hemlock apparently located near the creek bottom of East Tionesta Creek. It does not mention any older hemlocks being located. I can email you a copy of the report if you are interested. (2.16 MB).
I have the 1977 report: "Bjorkbom, John C., and Larson, Rodney G. 1977. The Tionesta Scenic and Research Natural Areas, Forest Service General technical Report NE-031, Upper Darby, PA: U. S. Department of Agriculture, Forest Service, Northeastern Forest Experimental Station. 24 p." http://www.treesearch.fs.fed.us/pubs/4015
It likewise does not mention the older tree from the report you mention.
Charlie Cogsbill mentions a number of older hemlock trees in this discussion from our website: http://www.nativetreesociety.org/specie ... ck_age.htm
The Hough reference is this article: "Hough, A. F. 1960. Silvical characteristics of eastern hemlock (Tsuga canadensis). Res. Pap. NE-132. U.S. Department of Agriculture, Forest Service, Northeastern Forest Experiment Station. 23 p. http://www.treesearch.fs.fed.us/pubs/13718
At maturity, hemlock may reach large size and great age. The record for age is 988 years; for d.b.h., 84 inches; and for total height, 160 feet ( 23 , 53 ).3 ,7 These trees were in original old-growth stands.
The first reference cited by Hough 1960 is Frothingham, E. H. 1915. The eastern hemlock. U.S. Dept. Agr. Bul. 152. 43 pp., illus http://www.archive.org/stream/bulletino ... t_djvu.txt
but it does not give really old tree ages in the text. The second reference is Morey, H. F. 1936. Age-size relationship of Hearts Content, a virgin forest in northwestern Pennsylvania. Ecology 17: 251-257. I don't have a copy of that article.
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