EELATTVE RESISTANCE OF TREE SEEDLINGS TO EXCESSIVE HEAT H 



Table 4. — Fourth test of heat resistance: Exposure to radiation from electric 

 coil 90 to 92 days after sowing, seedlings potted in sand. 



. [Six seedlings used in each pot, except where noted.] 





Maxi- 

 mum 



Maxi- 

 mum 

 soil 

 tempera- 

 ture. 



Expo- 

 sure. 



Number of seedlings dead, mortally injured, 

 slightly injured, and uninjured, by species. 1 



Pot Xo. tempera- 

 ! ture in 

 air. 



Western 

 yellow- 

 pine. 



Lodgepole Douglas 

 pine. fir. 



Engehnann 

 spruce. 





° F. 

 110.8 



111.4 



111.4 



115. 7 



118.0 



133.3 



135.0 



142.7 



142.6 



146.8 



152.2 



154.4 



161. 1 



° F. 

 107.0 



102.0 



105.5 



105.5 



112. 1 



119.5 



130.2 



119.0 



141.8 



123.0 



121.5 



126.8 



144.8 



Min. 



128 



7S 

 30 

 87 

 30 

 30 



35 



15 



50 



12 



15 



12 



30 



0-0-O-6 

 0-0-0-6 

 0-0-0-6 

 0-0-0-6 

 0-0-0-6 

 0-0-0-6 



\ 0-0-3-3 



0-0-1-5 



/F(2) C(2) 

 I 3-0-2-1 



3 0-O-2-2 



\ 1-1-2-2 



\ 0-1-4-1 



/ E (5) 

 \ 4-0-1-1 



0-0-0-6 

 0-0-0-6 

 0-0-0-6 

 0-0-0-6 

 0-0-0-6 

 0-0-0-6 



c ri) 



1-0-0-5 



0-0-1-5 



B(l) 

 3-0-0-3 



3 0-0-0-2 

 } 0-0-2-4 



} 0-0-1-5 



D (1) 

 3-0-1-2 



0-0-0-6 

 0-0-0-6 



0-0-2-4 



0-0-0-6 



0-0-1-5 



0-0-2-4 



E (2) 

 1-0-3-2 



0-0-5-1 



F(2) C(2) 

 3-1-2-0 



J E f4) 

 \ 3 2-0-2-l 



/E(2) C(3) 

 I 3-1-1-1 



f E(4) 

 \ 2-2-2-0 



E(5)*C(1) 



6-0-0-0 



0-0-0-6 

 C-0-0-6 

 0-0-0-6 

 0-0-0-6 

 0-0-0-6 



F(l) 



10 



2 , . 



9 „ 



1 _ 





9-' 



102 



5 2 



2-0-1-3 

 1-0-1-4 

 3 (1) 



8 



2-1-1-2 

 E(l) 





3 0-0-0-3 

 B (1) 



4 



2-2-0-2 



B (2) 



6 



2-0-3-1 

 C (2) 





2-3-0-1 





133.5 



119. 9 | 42. 5 





Total 



8-2-15-51 



7-0-5-' 2 



1 7-4-20-36 



1 ;-6-6-52 













Grand total 



43-12-46-201 













Averaee 5 . __ 



149.0 



122 6 



1 3 R 



1-2-9-10 I 0-0-4-16 I 7-3-10-3 1 5-2-4-10 



Total* 















Grand total 5 .... 





13-7-27-39 







1 











1 Capital letters indicate immediate condition of seedlings following exposure; figures in parenthesis 

 indicate number of seedlings so affected, as follows: 



A=Young needles cooked; B = Slightly injured; C = Seriously injured; D = Badly burned; E = Cooked; 

 F = Killed. 



_ The four numbers under each species indicate the final condition, in the following order: Dead seed- 

 lings; injured seedlings that will die; injured seedlings that will live; uninjured seedlings. 



2 Second exposures given these pots, after two days' observation showed no apparent injury from first 

 exposure. 



3 Owing to mishap after the exposure, only 4 yellow pine, 2 lodgepoles, 5 firs, and 3 spruce were left in 

 pot 8 for final observation. 



4 This injured seedling plainly was protected by the leaves of a taller seedling, but died eventually. 



3 These averages and totals aro for pots 10, 8, 7, and 4 apart, whose period of exposure makes possible a 

 comparison with earlier tests. 



Of 156 lodgepole seedlings used in the three tests. 15, or 10 per 

 cent, died or were injured so severely that death was only a matter 

 of time; 31, or 19 per cent, of the 160 western yellow-pine seedlings; 

 53, or 33 per cent, of the Engehnann spruce seedlings; and 78, or 

 49 per cent, of the Douglas fir suffered likewise. 



The point clearly brought out by these tests was the great re- 

 sistance of lodgepole pine, which surpassed even yellow pine. Al- 

 though it is a well-known fact that lodgepole reproduction is most 

 easily secured and thrives best on open burned areas, where extremes 



