186 



Canadian Forestry Journal, April, 1919 



THE MAKING OF A SPRUCE TREE 



ARTICLE No. 3. 



By Dr. C. D. Horve, Faculty of Forestry, University of Toronio. 



The white spruce in the St. Maurice Valley, 

 Quebec, produced an enormous crop of seed 

 in 1917. The cones were so abundant near the 

 top of the trees that they hid the foliage from 

 view and at a distance the trees seemed to be 

 wearing light brown hoods. In some cases the 

 branches were broken down by the weight of the 

 cones. In the fall of 1918, however, one could 

 hardly find a white spruce cone containing seed 

 in the St. Maurice Valley. It may be three, five, 

 or seven years — probably the latter, before the 

 >vhite spruce again seeds heavily in that dis- 

 trict. The same holds for the other spruces 

 and for most of our evergreen cone-bearing 

 trees; big seed years come at intervals and be- 

 tween times they seed only scatteringly as a rule. 

 It may be mentioned, parenthetically, that the 

 long interval between seed-bearing has a very 

 important influence upon forest nursery practice 

 and tree planting. Owing to thoughtless news- 

 paper agitation the public may be misled into 

 believing that large forest planting schemes 

 can be carried into effect upon short notice. On 

 the contrary, seed is plentiful and cheap only in 

 years of heavy fruiting; a year or two after it 

 is usually scarce and expensive, and often un- 

 attainable at any price. That is practically the 

 situation this year with regard to both pine and 

 spruce seed. It will be two years at the earliest 

 and it may be four or six years before another 

 heavy seeding of these species occurs. 



Fruiting Intervals. 



One explanation of the cause of fruiting at in- 

 tervals is that seed production requires large 

 quantities of stored food and usually it requires 

 several years to accumulate a sufficient supply. 

 Just before seeding all the storage places in a 

 tree are filled to overflowmg and after seedmg 

 they are drained. It takes several seasons for a 

 tree to fill in storehouses to capacity and since 

 seed production requires large quantities of re- 

 served food supply, productive years are separ- 

 ated by non-productive years. The production 

 of offspring draws upon the reserves of a tree 

 as it does upon the reserves of any other mother. 



hence there follows an mterval of recuperation 

 and after that an mterval of accumulation of 

 food material. The length of the interval may 

 depend upon the weather during the growing 

 season. If two seasons favorable for the ac- 

 cumulation of reserve food follow one another, 

 then the seed years may be three years apart. 

 If, however, seasons unfavorable for food ac- 

 cumulation, such as abnormally dry, cold or 

 cloudy seasons, then it may be five or seven 

 years before the tree can acquire sufficient re- 

 served food to produce a seed crop. 



Years of Heavy Yield. 



The years of strikmgly abundant seed pro- 

 duction usually occur at the longer intervals 

 and the phenomenon extends over wide areas. 

 For example, the heavy seeding of white spruce 

 in 1917 apparently covered the provinces of 

 Quebec and New Brunswick and probably the 

 whole range of the species in Eastern Canada. 

 The medium-sized seed crops usually occur at 

 the shorter intervals and the interesting thing 

 about it is that these secondary waves of pro- 

 duction are often localized in their distribution. 

 For example, the medium-sized seed crop of 

 white pine in the St. Maurice, the Rouge, the 

 Gatineau valleys might occur in three different 

 years. Thus, if seed production depends upon 

 weather conditions as suggested in the para- 

 graph above, the trees must be sensitive and re- 

 sponsive to local variations in climate in order 

 to fruit in different years in adjacent valleys. 

 Still more locally, on a square mile of forest 

 one might find a few trees in favorable positions 

 every year bearing a crop of seeds. Thus, it 

 would appear that some trees are more sensitive 

 than others to the seed producing influences or 

 else that such influences are very irregular in 

 their distribution, both in time and space. 



The growing realization of the importance 

 of securing good reproduction of spruce and pine 

 in our forests will doubtless lead to an investiga- 

 tion of peculiarities of seed production. 



(To be continued) 



