7 2 



Garden and Forest. 



Number 417. 



Rate of Growth of the Long-leaf Pine. 



THE rate of growth of the Long-leaf Pine, Pinuspalustris, 

 given in the accompanying table, is based upon the 

 measurements of sixty-five trees from various stations 

 within its range. The measurements of the individual 

 trees were extended enough to enable the Division of For- 

 estry, with a sufficient number of properly selected trees, 

 say, from 400 to 500 of a species, to make a complete investi- 

 gation regarding its growth and progessive development. 

 But while the biological laws of this species cannot be 

 determined until a greater number of trees is examined, the 

 rate of growth may be more or less clearly demonstrated 

 by the analysis of the individuals already measured. 



Height Growth. — The growth in height of Long-leaf 

 Pine is comparatively slow for the first four or five years 

 (about three or four inches); forthe next two or three years 

 the height growth has not been fully investigated, though 

 it is also said to be slow. The most rapid stage of height 

 growth begins with the seventh or eighth year, and con- 

 tinues to the 30th or 35th year, and amounts to from 16 to 

 17 inches annually. A tree 30 or 35 years old is from 37 

 to 44 feet high. From the 30th to the 50th year the annual 

 growth in height begins to lessen, and is not more than 12 

 inches. A tree 50 years old is from 56 to 60 feet high. 

 From the 50th to the 80th year the height growth rapidly 

 decreases to about six inches annually, and grows less and 

 less up to the age of from 90 to 100 years, when the tree 

 reaches its full height growth — that is, from 76 to 80 feet. 

 That Long-leaf Pine actually reaches about its full height in 

 from 90 to 100 years is easily learned from the measure- 

 ments of old trees which in from 225 to 300 years reach a 

 total height not exceeding 108 to 118 feet. 



Diameter Growth. — The diameter accretion of Long-leaf 

 Pine is rapid for the first 30 years, when its trunk thickens 

 by 1.6 inches (bark excluded) for each decade. For the 

 next 50 years there is noticed a slight decrease in the 

 diameter accretion, and for each decade only 1.4 inch is 

 produced. A tree 80 years old at breast-height is 13 inches 

 in diameter, including bark ; this decrease of diameter ac- 

 cretion continues with age, being 1. 2 inches for each decade 

 between 80 and 100 years, 0.9 of an inch between 100 and 

 120, and 0.8 of an inch between 120 and 140 years. From 

 the 140th year the diameter accretion falls very rapidly, its 

 increase not exceeding 0.3 to 0.4 of an inch for each of the 

 successive decades. 



While the diameter accretion decreases with age — that is, 

 while the rings become, narrower from the centre of the 

 tree to its periphery — the areas formed by them on the 

 cross-sections, excluding the 20 central rings, are almost 

 equal for the third, fourth, fifth and sixth decades. With 

 the seventh decade, though, there is an increase of the 

 areas, compared with those of the previous years ; that 

 increase is almost the same for the successive decades up 

 to 140 years inclusive. Thus, dividing the time of the 

 diameter growth into two periods, the areas of every 10. 

 rings on the cross-section are almost equal within the lim- 

 its of each period. It will be readily understood that each 

 ring must be thinner with the increase of diameter. 



Mass Accretion. — Speaking of mass accretion, it will be 

 more convenient to consider separately the annual increase 

 of the volume of a tree and that for certain periods. We dis- 

 tinguish two kinds of annual accretion : one, an average 

 annual increase of the mass, produced for the total age of 

 tree, which can be easily obtained by dividing the volume 

 of the tree by its age. The other, called current accretion, 

 is simply the increase of volume of a tree for a given year 

 of its age. 



From the table given below it will be seen that both 

 current and average annual accretions, being scarcely per- 

 ceptible for the first years, become gradually larger and 

 larger till they reach their maximum point, and, remaining 

 at those points for a couple of years, begin to decrease first 

 gradually and slowly, then rapidly. It will be seen, also, 

 that while the current accretion, passing its culmination 



point, becomes smaller and smaller, the average annual 

 accretion still increases, approaching the maximum and 

 becomes almost equal to the current accretion when the 

 tree is between 160 and 170 years of age. The age of a 

 tree, when its average annual accretion becomes equal 

 to the current accretion, is equal to that of the maxi- 

 mum point of the average annual accretion. The same 

 is true with regard to all species.* The difference will 

 be only in the age at which different species reach the 

 stage of maximum growth. It depends a great deal upon 

 the conditions under which the species is growing — that is, 

 soil, moisture, climatic and forestry conditions. Thus the 

 correlation between the current and average annual accre- 

 tion is of great economical value, for it determines the time 

 when a species reaches the stage of its maximum growth. 

 The rotation for Long-leaf Pine, should it depend on the 

 stage of maximum growth, would lie between 160 and 170 

 years. 



rate of growth of the long-leaf pine. 



(Published in advance by permission of the Division of Forestry.) 



Age. 



EE-S 



J3 D^r 



10 

 20 



30 

 40 



5° 

 60 

 70 

 80 

 90 

 100 



120 



140 

 160 

 180 



Ins. 



[Feet. 



2 I 





3.8 





5 5 





7.0 16 



8.1! 24 



9 6 34 



1 1 -5 44 



130 52 



14.5! 56 



16 60 



18.0 



65 



'9-5 



72 



20.5 



80 



21.3 



85 



Feet. 

 9 

 23 

 57 

 48 

 56 

 62 



67 

 72 

 76 

 80 



87 



93 



98 



103 



Volun 



Tree. ! Log. 



Cubic 

 feet 



12 



1 20 



3 35 

 7.06 



10.75 



15.26 

 24. l6 

 33.18 



43-57 



55.85 



76.87 

 96.44 

 112. 3 

 122.0 



Cubic 



feet. 



5.6. 



9- 3o 



13-99 

 23 1 1 

 32 27 

 42 66 

 5494 

 7587 



95-49 



in. 5 



121 .2 



Periodical accretion. 



ISt 

 2d 



3d 



4th 



5 tl, 



6th 



7th 



8th 



9th 



10th 



nth 



121I1 



13th 



14th 



15th 



16th 



17th 



18th 



Ins. 



Feet 



i-4 

 1.8 

 1.6 



9 

 14 

 14 



1 .2 



II 



1 .2 



8 



i-4 

 1.6 

 1.6 



6 

 5 

 5 



1 .2 



4 



1 .2 



4 



1 .8 



7 



1.6 



6 



0.8 



5 



0.7 



5 



Sq're 

 feet. 

 O OI 



o 04 



O.07 

 O.OS 

 O.08 

 O. 12 



o. 17 

 o. 19 



O.I6 



Cubic 

 feet. 

 O 

 I 

 2 



3 

 3 

 4 



12 



08 

 15 



7i 

 69 



5i 



8.90 



9.02 



10 39 



Cub 

 teet. 

 OOI 



Cub. 

 feet. 

 O.OI 



II 

 21 



37 

 37 

 45 



O. 17,12 .28 



o. 56 



O 30 21 .02 O.64 



O 

 O 

 O 



o 



o 

 0.89 



90 



1 .04 



1-23 

 1.05 



o 29 19 620.69 0.98 



o. 16 



15 . 86lo.700.79 



10.7 0.67 



0.53 



But in fixing the rotation there ought to be taken into 

 consideration the so-called stage of maximum value — that 

 is, the stage when a cubic foot in the tree has its greatest 

 value. For instance, one cubic foot in a tree 160 years old 

 is worth $0.05 ; the same cubic foot in the same tree when 

 it is 180 years old will be worth $0.07. With age the tree 

 increases not only its mass, but also the value of the mass 

 laid up previously, because the boards made from the old- 

 est tree, being of a larger size, will bring a larger price. 

 For Long-leaf Pine under the conditions of its present 

 growth a rotation of 200 years is suggested as being the 

 most economical that can be adopted. 



In the table is shown the increase of volume for every 

 ten years ; we call it periodical accretion. A close exam- 

 ination of the figures given will give an idea as to the rate 

 of volume growth of Long-leaf Pine. 



Quite different would be the case under forestry manage- 

 ment. In our records of tree measurements there are two 

 whose environments in the forest are the same as those that 

 would take place under management. Tree No. 314 (see 

 table below), fifty-three years old, is from a moderately 

 dense forest, the crowns of the trees being equally closed 

 from all sides, thus forming a favorable roof-cover for that 

 age. A Long-leaf Pine up to 90 to 100 years — that is, when 

 it has reached its full height — being surrounded by 

 neighbors of the same age — is competing with them for 



* A niiithematic.il proof of this law is given by Eger in AUg. Forst und JagJzeititng 

 01-1842, p. 175. Another, by means of calculus, is found there for 1870, p. 482. 



