NATURAL REGENERATION OF DOUGLAS FIR. 3 
different parts of the region. These relations are brought out by 
Figure 1 and Table 1. The limits of the range of Douglas fir are 
shown in Figure 2. 
The climatic units into which the Douglas fir region of Oregon 
and Washington’ has been divided in Table 1 are based on weather 
records taken at the regular Weather Bureau stations. Although 
the weather records often are not taken at points typical of the 
forest regions, the averages of the records taken at all stations of 
each region are reliable indices of the relative differences between 
its climatic characteristics and those of other regions similarly 
determined. 
TABLE 1.—Vemperature and precipitation in the Douglas-fir region of Oregon 
and Washington based on records through periods of 5 to 64 uears with an 
average of about 16 years.* 
Mean : 
Mean | Highest | Lowest | temper-| . Mean | Maxi- 
annual ern annual mum 
per- | temper- ature as 
temper- | “stur a rare growing precipi- | annual 
ature. : ; Sensor tation. rainfall. 
Washington: FIDE oe vias WIDE Inches. | Inches. 
IWies OM@AScaAd CSaee ee ee aaa 50. 2 105 —6 56. 5 | 55. 56 2151. 56 
Hast of Cascadeseics cess coon seats 47.7 108 — 30 61.3 14,75 8 35.77 
Oregon: 
WiestronC@ascadess au ae ee oni tee 51.1 | 108 —16 57. 4 59. 51 4167. 29 
Southwestern section............-...-. 52.7 110 —4 63. 1 31. 44 5 62. 66 
HastaoniCascades eae se Gee eae 56.5 119 —27 63. 6 14. 55 6 43.65 
oat Annual Latest | Earliest 
Precipita- 
Minmiam | tion durme) Ueto) Ol Cate date 
rainfall. | growing | C2YS1n the hs 1s 
Season growing frost in | frost in 
season. spring. | autumn. 
Washington: i Inches. Inches. 
Wiest Of; Oascad esi iis tose ys ye eyes Baca ee 715.00 18. 66 8199} Apr. 6! Oct. 30 
- MAST ON CASCAMeS set sabi accesso o oe eae 5 « 93.71 2. 69 135 | May 25] Sept 30 
regon: 
IWieS TOL @ascadesiias sae ois yu eeee 10 15, 53 17.29 197.) Apr Wi lOctymal 
Southwestern’section: - 352-2. 22¢ 5.5... 2. IST 99 4. 90 164 | May 7:| Oct. 13 
Hastof Cascadesyorss ees gee se ee cess ee 12 4, 60 3. 21 142 | May 18] Oct. 2 
1United States Department of Agriculture, 8 The length of the growing season does not coin- 
Weather Bureau records. For location of regions cide with the average dates of earliest and latest 
see figure 1. frosts due to the variation of the length of the 
2 Clearwater, Jefferson County, 1899. periods through which records were taken. 
3 Lyle, Klickitat County, 1894. 9 Ellensburg, Kittitas County, 1898. 
4 Glenora, Tillamook County, 1896. 10 Roseburg, Douglas County, 1913. 
5 West Fork, Douglas County, 1896. 11 Ashland, Jackson County, 1905. 
6 The Dalles, Wasco County, 1858. 12 Umatilla, Umatilla County, 1898. 
7 Port Townsend, Jefferson Veguney. 1889. 
In western Oregon and Washington Douglas fir is not exacting 
in its choice of site, except as it 1s influenced by altitude and lati- 
tude. This is chiefly because there is enough precipitation, especially 
during the long favorable growing season, to insure the establishment. 
of the seedling and to enable it to compete successfully with other 
species of trees and with shrubs. The longer growing season on 
the west side not only enables the Douglas fir to continue growth 
through a longer period, but it also insures better maturity, so 
that there is Tess frost injury than on the east side. Its best. 
development is below the altitude of 3,000 feet, although in Oregon 
it produces good timber trees up to about 4,300 feet. Its crowth is 
