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COSEWIC assessment and status report on the American Chestnut in Canada

Population Sizes and Trends

The extent of the distribution does not seem to have changed significantly since the earliest records of 1817 (Moss & Hosking, 1983), even though numbers have been drastically reduced (likely greatly exceeding 50%) from when this species was a dominant species in some areas of southern Ontario (e.g., Duncan, 1993; Morley, 2001). It is and was widespread throughout the Carolinian Zone but more predominant in some townships, such as in portions of Norfolk County and around Hamilton where the species was noted to be most abundant in the 1817 survey (Moss & Hosking, 1983). Duncan (1993) indicates that in the Dundas Valley, in the Hamilton area, American chestnut made up 25 or 30% of the forest. Potential habitat does exist in southern Ontario, but it is limited due to the high level of forest clearing.

Three surveys were conducted between the 1980s and 2001-02. In the most recent survey, selected populations were intensively documented, following a strategy of the American chestnut recovery plan (Boland et al., 2000). The occurrence of reproductive trees and blighted trees is compared in the appendix from the data of the original status report (Ambrose & Aboud, 1986), a survey in the 1990s (Boland et al., 1997) and the recent inventory (Tindall et al., 2004). Data were compiled and analyzed by Brian Husband. Although there are statistically significant differences in reproductive status and the occurrence of blight symptoms among the three surveys in some of the age classes, the different approaches to the three surveys may in part explain the differences, viz., the first survey’s focus was on reproductive trees, the second, chestnut blight and its level of occurrence and virulence, and the third, a general assessment of the status of American chestnut (but dead trees were not recorded). Thus it is inconclusive whether the status of this species has significantly changed since the early 1980s although several large trees have been lost. It should also be noted that the devastation of this species is still within the time frame of a single generation of healthy trees.

In the most recent survey of 2001-2002, 682 individuals of all sizes were inventoried in detail, 85 of them were observed to be reproductive (individuals may have multiple trunks; counts are of individuals not trunks). An additional 13 trees of potential reproductive size and 7 smaller individuals were observed by the author in 2003. Some of these were in previously known sites, but four new sites were found while inventorying 24 county forests (total 1306 acres) in an unrelated project in Norfolk County (Ambrose & Waldron, 2004). Another survey was recently conducted in 16 Long Point Region Conservation Authority forests (Draper, 2002). Of these, chestnut was recorded in 10 forests, 7 being new sites, but with only three trees over 8.5 cm diameter at breast height. This gives an idea of the number of undocumented populations in a core area such as Norfolk County. Nevertheless, we may be losing important individuals as large trees die and do not re-sprout, and many of the small sprouts that eventually die out; there is a continuing concern over the loss of genetic diversity until the blight can be brought under control. In summary, 101 trees of potentially reproductive size are known in 120 sites; it is estimated that there are 120-150 reproductive trees plus 1000 or more smaller, non-reproductive individuals in Ontario. A comparison of sites with information from the first and last inventories is shown in Table 1. This table only includes those sites where a direct comparison can be made over this time period. For an additional estimation of trends, the appendix should be consulted.

Table 1: Ontario populations of Castanea dentata with comparative data
Comparisons between surveys in 1979-1989 (1980s) and 2001-2003 (2000s)
no., name
# by size class (cm dbh)flowersseedsseedlgs.Blightchange, 1980s to 2000s
1980s1. Scotland  1     no 
2000sJul 03  dead      lost: tree cut down
1980s1a. Burford Nurs.1   1yesyes no 
2000sCinv: 2    dead    decline: large tree died
1980s2. S. Glen Morris2  1   yes  
2000sJul 03  1  yes?nonodecline: different tree
1980s5. Vienna1   1yes  no 
2000sCinv: 1          
1980s6. Riverbend farm122  yes 6no 
2000sCinv: 3          
1980s8. Springwater  1  yes  no 
2000sCinv: 13          
1980s11. Arner  1 1yesyes3yes 
2000sCinv: 2         decline: large tree with healing canker died; sprouting
1980s15. Walsh 1   yes  yes 
2000sCinv: 9          
1980s16. Smith Tract31   yes  no, yes 
2000sCinv: 1-2          
1980s18. NW of Delhi 1        
2000sJul 03         lost: roadside fencerow removed
1980s21. Wycombe  1?1 yes  no 
2000sJul 03   1 yes  nosame: original trees died and cut down, new tree to NW
1980s22. Backus Woods1172 1yesyes3yes 
2000sCinv: 75          
1980s23. Spring Arbour  2  yesyes no 
2000sJul 03 22   yesyesnogain? original 2 trees died
1980s24. Armstrong Tract  1  yes  no 
2000sCinv: 10          
1980s26. Sassafras Wds.31   yes    
2000sCinv: 1          
1980s27. Mineral Springs   2 yesyes3no 
2000sCinv: 5-7          
1980s28. Copetown 1   yesyes no 
2000sCinv: 2-3          
1980s30. Gartshore  2  yesyes no, yes 
2000sCinv: 3+          
1980s32. Cristie  1  yes  no 
2000sCinv: 1          
1980s33a. Highgatefew 3       
2000sOct 03 [W. Jay]         loss: original 3 trees and sprouts all dead
1980s34. Sunny Glades1 1  no  yes 
2000sCinv: 9          
1980s35. Smit's farm2  11yes 1no 
2000sCinv: 2          
1980s36. Warbler Wds.    1yes  no 
2000sMay 03 [B. Bergsma] 1  cut    decline; tree lost in housing devel.; sprout from cut tree?
1980s37. Mosa Tp.  1  yesyes no 
2000sCinv: 2          
1980s38. Skunks' Misery3003      yes 
2000sCinv: 24         [only part of site re-surveyed]
1980s40. Woodland Sch.    1yes  no 
2000sJul 03    dead    lost: stump where tree had been
1980s42. Clare Cycle  1     no 
2000sCinv: 1          
1980s43. Hillcrest Park1  1 yes  yes 
2000sJul 03 + Cinv: 1   dead     decline: large tree dead, stump remains.
1980s44. Moore Rd.~201   yesyes yes 
2000sCinv: 10          
1980s45. St. Davids Gorge 12  yesyes yes, no 
2000sJul 03         lost: one stump, others not found
1980s46. Short Hills    1yes 2no 
2000sCinv: 2          
1980s47. N. Glen Morris   1 yes  0 
2000sJul 03   dead     lost: tree dead, trunk 34cm dbh

Second line notes (2000s): Cinv: 2001-02 chestnut inventory, numbers only, size and other data not available at this time. Month 03: observations by author or others as noted.

The loss of several large trees documented in Table 1 that were reproductive and healthy in the early 1980s is a concern; whether they are being replaced by recruitment is inconclusive. For an analysis of all the data from the tree surveys, see the appendix.