chnrcoal pig iron indusrry (Willard 1916). ..... to scarring with time, and fires in li"lter years might have been Jess likely to cause a sci"lr than earlier fires.
USDA 7-7§
United States Department of Agriculture
Proceedings
Forest
11th Central Hardwood Forest Conference
Service
North Central Forest Experiment Station
General Technical Report NC - 188
Columbia, Missouri March 23-26, 1997
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d =0.0001). so the data could not tx: modeled with a normal distribution. Alternatively, t11e Wei bull d istribution did model the fire-inlet val data adequately (K-S d-statistic =0.222, Prob. > d = 0.2270). The observed fire intervals and cnlculated Weibull function for all fires and only major fires an: shown in Figure 2. The median and the short and long probable intetval values (Table 2) ind1cate that fire was like ly to return to the Oreton site every 3 to 4 years. and that annual !ires were unusual, as was an intervaJ of more than 12 ye;:u-s between fires. Majo r fires (T able 2) occurred about half the time (every 7 to 8 years). It was un usual to ha ve major fires in successive years, or for more than 24 years to pass between major fires.
JPersonal communication, 11112196. Kevin Smith, Research Plant Physiologist, Northeastern Forest Experiment Station, Louis C. Wyman Forest Sciences Lal>oratory, PO Box 640, Durham, NH 03824-06110.
175
II th Central Hardwood Conference
Table 1. Fire years, number of scars, fire interval, and season of fire of individual fires atlhe Oreton site, Vinton County, Ohio, 1856 to 1995. Fires occurred in 22 separate years. Major fires were designated where 25% of all samples or at least two cross sections had a fire scar during a given year. Seasons were designated as D = dor:nant, E = early spring (probably mid 10 late April), S = late spri ng/s um mer (probably May to mid July). (The* denotes significantly long (p < 0.05) intervals.)
Year
1871 1875
Number of trees scarred
Fire interval (years)
2 4 l l
1876 1877
1885 1895 1896 1897 1898 1902 1913 1915
1919 1923 1925 1927 1953
1954 1974 1984 1985 1988
Major fire interval (years)
Season
D D D D D E D D E
2
8
14
6
10
10
4
4
II 2
II
E
2
12
4 4
4
D
2 2 26*
6 2
I
G 2 7 2 2 I
3 2
3
D
1
2QY 10
[)
H
E D
I
2
s
s 57~
D
I
s
3
0 0
1989
Most fires burned during the donnant season (69%; 33 scars) and tlurine spring when the earlywood was fanning (25.0%; 12 scars); only 6% (3 scars) burned during the summer when latewood was forrmng. The X 2 distribution of the scars during the dormant, spring . :llld late spring/summer seasons. W"S not different (X 2 = 1.82, 2 d. f.) from wildfire occurrences in rhe Vinton County :Jrea (figure 3). 1ln1s, my e;:slimates of the periods during which scars formed probably are accura1e. f-igure 4 illustrates the relationship between fire and c limate from 1895 to 1995. If climate conditions affect fire occurrence, then more lire events should occur on the bottom half of the graph (drier than nonual conditions). There are nine fire events above the mean antl nim· below. l)onnant-season fi1cs usually m:cur in spt ing but can occur in autumn. 11ws in Figure 4, aurumn dormant ·season frres would not be expected to show a relationship to spring climate and would only add error to climate/fire relationships in thts graph. However early wood fires do occur in the spring. Pigure 4 .shows Lhal five e:u·lywood fires happened when precipitation was average or above average but that only three occurred bt:low the average level. Thus, there was no obvious relationship between precipitation and the occurrence of spring fire. This observation is consistent with that of Haines and otbe1s (l9.15), who countcrintullively found more spri ng fires in nonctrought than in dwugh t years on the Wayne National Forest. Conversely, they fou nd more amumn fires during drought years than in nondrought years. Tne data available here cannot illustrate such relationships.
l llh Central Hardwood Conference
176
________________________________...
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20 25 30 35 110 riRE INTERVAL(fi){YEARSJ
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figure 2. Distriburion of fire frequencies, with accornp3 nying Wc.:ibull prouabi lity distriuut.ions. Scale and shape parameters are shown in the equations. where p > fi =exp( (fi/b)"c), b =scale parameter, c =shape parameter; (a) frequencies for all fires . before and after U1c fire suppression era ( 1930); (b) frc·qucncies fo r major fires (25% of samples are sc:11red . or at least two samples). The only major fire after the fire suppression era is the longest imcrvnl (57 years).
Table 2. Fire intervals (years) at Oreton, Vinton County, Ohio 1856 to 1995. Data are Wcibull, not no1mally distributed. The Wei bull intervals indicate significantly (p < 0.05) sho•tor lone inte rvals between fire:;. Major fires are define
