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FORESTRY INVESTIGATIONS U. S. DEPARTMENT OF AGRICULTURE. 



Light-needing and quicker-growing kinds show similar conditions to those grown on good soil, 

 and here, therefore, early thinnings are desirable. In these cases the thinnings have also to bo 

 repeated oftenest, especially during the period of prevalent height accretion. Absolute rules as 

 to the time for interlucations and their periodical repetition evidently can not be given. The 

 peculiar conditions of each individual case alone can determine this. The golden rule, however, 

 is early, often, moderately. The right time for the beginning of these regular and periodical 

 interlncations is generally considered to have arrived when the natural thinning out before 

 mentioned commences and shows the need of the operation. This occurs generally when the 

 crop has attained the size of hop poles. At this stage the well-marked difference in size of the 

 suppressed trees will point them out as having to fall, and there will not be much risk of making 

 any gross mistakes. Until the trees have attained their full height the thinning should remain 

 moderate. From this time forward it will prove expedient to open out the stock more freely 

 without ever going so far as to thin severely. Within the last few years new and revolutionary 

 ideas regarding principles and methods to prevail in thinnings are gaining ground, which we have 

 not space here to discuss. 



UNDER-PLANTINCJ. 



All these manipulations experience modifications according to circumstances, different species 

 and soil conditions requiring different treatment. One of the most interesting modifications, the 

 results of which in a given district were fully exhibited, is the v. Seebach management in beech 

 forests. Such a management, which contemplates the production of heavier timber in the shortest 

 time, tries to take advantage of the increase in accretion due to an increase of light which is 

 secured by severe thinning, and in order to prevent the drying out of the soil by such severe 

 thinning a cover of some shady kind is established by sowing or planting. This cover gradually 

 dies off under the shade of the old timber, the crowns closing again after a number of years. The 

 rate of growth in a stand of 70 to 80 years was thereby increased from 51 cubic feet per acre and 

 year to 77 cubic feet per acre and year, while a neighboring stand, otherwise the same but not so 

 treated, increased by only 60 cubic feet, distributed over a larger number of trees. 



The same method is applied to the production of heavy oak timber. In this case the oak 

 growth is thinned out when about 60 years old and "underplanted" with beech. It may also be 

 applied to older growths with advantage, as appears from the following results: 



A stand of oaks 150 to 160 years old in 1846 was thinned to 96 trees per acre, averaging 

 37 cubic feet of wood per tree, the cleared space being "underplanted" with beech and spruce. 

 In 1887 the oaks, now 190 to 200 years old, of which 59 trees only were left, contained 50 cubic 

 feet in the average, thus growing during the last forty years more than one-half as much as 

 during the one hundred and fifty to one hundred and sixty years previous to the operatioii, i. e., 

 doubling the rate of growth. In this case, under the light-foliaged oaks, some of the beech and 

 spruce developed sufficiently to furnish marketable material. 



With Scotch pine it has been found in one case that while the average accretion of a stand 

 120 years old under ordinary condition was about 59 cubic feet per acre and year the yield by 

 thinning included a stand underplanted with beech showed an accretion of 100 cubic feet per 

 acre and year, besides much better log sizes and earlier supply of saw timber. 



Translated into money an example from Bavaria may be cited as follows: 



Ou 1 acre of pine 80 years old, iinderplantod at a cost of $2.85 per acre with beech now 40 years old, there 

 were found 



Supposing tills stand to be left forty years longer, it may be figured that the pine would bring W50 and Hi.- 

 beech ^120; total per aero, $770, of which $4!) was yielded in thinnings. White pine without iunlergro\vi:>v s 

 expected to produce only $520 per acre when 120 years old. 



