H A R jDA^MJ-©-I>- RECORD 



Jan. Feb. Mar. Apr. May. June. July. Sept. Nov. 



„ , ^ J ?> % % % % % % % % 



Heavy bardwoods 41 38 36 36 39 35 39 38 34 



Light hardwoods 53 58 51 49 47 47 50 47 45 



Loniferous woods 60 58 59 54 60 60 60 58 58 



Average of all 51 51 49 49 49 49 50 48 48 



The reason bark peels so mucli easier in the spring is not that the 

 "sap is up," but that the cambium layer is particularly active in 

 the formation of new wood and new bark. Growth is rapid and 

 the cells newly-formed have delicate, unthickened walls readily torn 

 upon the slightest pressure. Later, growth slows down and thick- 

 walled latewood is formed. Finally there is no growth at all during 

 the resting period (winter) and the bark is tight. 



What, then, are the advantages of winter felling of hardwood 

 timber? If only the amount of moisture in the wood were consid- 

 ered, summer would appear the best cutting season. As a matter of 

 fact the user of hardwood is little concerned with the actual or 

 comparative amount of moisture in a tree when it is felled, and 

 this in spite of his insistence that material must be cut in winter 

 ' ' when the sap is down. " It is not the water in wood that causes 

 trouble; it is getting it out. Winter-cut hardwood is preferred, not 

 because of the moisture content at the time of felling, but largely 

 because of the effect of the time of year on seasoning. 



Seasoning is essentially drying. Dry wood differs from green 

 wood in other ways than the mere loss of moisture. When wood 

 dries the cell walls become thinner — they shrink — but a dry cell is 

 practically as long as it was before. The structure of wood, espe- 

 cially that of the hardwoods, is so complex that when the elements 

 composing it begin to shrink in different amounts and directions, 

 severe strains occur. Wood is somewhat plastic — otherwise it would 

 break into minute fragments upon drying. This plasticity will 

 permit slow readjustments to the new sizes and shapes of the cells, 

 but at best there will be some checking and warping, and this will 

 be increased as the rate of drying or the irregularity of it increases. 

 Coniferous woods are much simpler in structure than hardwoods and 

 can be seasoned more rapidly without serious checking. 



Loss of water from wood is wholly by evaporation from the sur- 

 face. This is very largely influenced by the temperature, so that 

 wood dries much more rapidly in summer than in winter. If sea- 

 soning proceeds too fast, checking and warping increase in geo- 

 metric ratio. Hence hardwoods felled in winter season more slowly 

 and uniformly than when cut at other seasons and for this reason 

 the material will contain fewer cheeks, which, no matter how small, 

 are a source of weakness. 



But how is increased durability of winter-felled timber accounted 

 for? There are several different problems involved. Insects and 

 fungi, which occasion nearly all the damage to timber, are not active 

 during cold weather. Consequently winter-cut material will have 

 more or less time for seasoning (depending upon the time of cut- 

 ting) before being subjected to infection. If the drying has pro- 

 ceeded far enough it may escape entirely. At any rate the chances 

 of the material getting to the mill in a sound condition will be 

 much greater. 



When trees have completed the season's growth the layer of 

 wood next the bark is denser and harder than would be the case if 

 cut while in a growing condition. In the case of poles and round 

 posts, this denser layer does not afford fungi as good a chance to 

 lodge and grow as the undeveloped wood of the cambium layer. 



The usual explanation of greater durability of winter-felled 

 material is as follows: "The reason is found in the scantiness of 

 easily decomposed chemical substances in the tissues of trees after 

 the close of the vegetative period. The sap in the tree during 

 winter consists 'almost entirely of water, and therefore does not 

 offer a favorable medium for the development of micro-organisms. 

 In summer, on the contrary, the sap contains albuminous and 

 other chemically unstable substances which, under the influence of 

 the high temperature of summer, readily ferment and favor the 

 development of decay-producing micro-organisms." (Zon, R.: 

 Methods of determining the time of year when timber was cut. 

 Forestry Quarterly, Vol. Vn. 1909.) 



Assuming this statement to be correct, it could only apply to the 

 sapwood. The sap in heartwood remains practically the same the 



23 



year round, for the cells are dead, have no need of food for them- 

 selves and have lost the power of storing it up" or handling it any 

 way. Since the sapwood of no native species is naturally durable 

 when exposed to conditions favorable for decay, the prolongation 

 of life due to winter-felling would, at least, be slight. 



If there were the differences in the composition of the sap that 

 IS claimed, then it should be possible by means of chemical analysis 

 of a piece of wood to determine at what season it was felled. The 

 most painstaking investigations of the question by competent Ger- 

 man authorities have scored as many misses as hits. As a matter 

 of fact, during the resting period of the tree there is more reserve 

 food in the living wood than at any other time. The sap contains 

 less in solution in early winter, but fungi should not, on that ac- 

 count, experience any difficulty in reaching the stored food. Again, 

 many of the most destructive fungi live, not upon the sap or the' 

 cell contents, but on the cell walls— the wood substance itself. 

 They will attack the sapwood of any tree regardless of the time 

 of feUing. That heartwood of any tree is always more durable 

 than the sapwood is due to the presence in it of infiltrated sub- 

 stances, such as gums, resins, oils, pigments and tannins, which 

 were not present in such quantities in the sapwood. 



Another explanation of the alleged increased durability is as 

 follows: "During the growing season the wood of trees contains 

 sulphuric acid and potassium, both of which are solvents of carbo- 

 hydrates, starch, resins and gums; they are known to soften also 

 the ligneous tissue to a considerable degree. During the summer 

 months the wood of living trees contains eight times as much 

 sulphuric acid and five times as much potassium as it does during 

 the winter months. The presence of these two chemical substances 

 during the growing season constitutes the chief factor in dissolving 

 the natural preservatives within the wood and in preparing the 

 wood for the different kinds of wood-destroying fungi." 



Even if this explanation is correct, which' is more than doubtful, 

 it could apply only to the relative durability of sapwood, which no 

 one expects to last when exposed to conditions favorable for decay. 

 And, after all, what creditable evidence is there that the season of 

 felling aloue affects appreciably the durability of wood?— S. J. R. 



TIMBER RESOURCES OF CANADA 



It is commonly stated that Canada is a woodland country, and 

 this, as generaUy understood, means a timber country. Even the 

 statement that Canada is a woodland country needs modification, 

 according to Dr. B. E. Fernow, for at least one-third is treeless 

 tundra, to which must be added the 200,000 square miles of prairie 

 and plains country, the extensive areas above timber line, and a 

 large proportion, perhaps one-half, of the northern woodland 

 country, which is in swamps and mUskegs or otherwise open. One 

 should bear in mind, too, the unusually large areas of water surface 

 represented in the innumerable lakes which stud the vast 

 undulating interior plain. 



A closer inspection of natural forest conditions of Canada reveals, 

 first, that the country as a whole is poorly timbered; secondly, that 

 the valuable timber is unevenly distributed; thirdly, that compara- 

 tively few species are represented in the forest ; further, that within 

 the forest areas farmlands are scanty and mostly poor, and waste- 

 lands — rock barrens, swamps, bogs and muskegs — plentiful. The 

 country is vast, covering over three and a half mUlion square miles, 

 larger than the United States, and while there are endless woods, 

 really good timber is limited, say 600,000,000,000 feet. 



Of this amount of timber, half may be accredited to the Pacific 

 and half to the Atlantic side. In addition, a large amount in the 

 aggregate of pulpwood and of inferior saw material, needful for 

 local development, is found scattered through the middle portion. 

 . While an enumeration of species occurring in Canada would- show 

 a rather large total of 150, less than one-third are of commercial 

 value, and, indeed, if frequency and quantity of occurrence are kept 

 in mind as factors in determining economic importance, the number 

 of important species will be found within thirty, namely, eighteen 

 softwoods and twelve hardwoods. 



