Growth and Mortality 



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^<r 



ONE o£ the most significant figures in the 

 appraisal of the forest situation is the rate 

 of current timber growth. This figure re- 

 flects the net effect of stocking, stand condition and 

 thriftiness of the growing stock. Contrasted with 

 drain it is an indicator of probable trend in inven- 

 tory volumes. 



Current Annual Net Growth 



Approximately 720 million cubic feet of new 

 vokmie, includino 1,200 million board feet of saw- 

 timber material, are added to the timber stands 

 in the Lake States region each year (table 18). 



The average growth per acre in cubic feet in the 

 Lake States is one-third less than in the Pacific 

 Northwest, and only about half that reported in 

 the South. It is considerably less also than in the 

 New England and Central States regions {39). 



The average growth per acre of saw timber in this 

 region is only one-third as large as in the Pacific 

 Northwest, one-fourth as large as in the South. 



j Taiu.f, \H.— Estimated net arniual sirowlh in the Lake Slates 



i 



j region, by stand class, 1950 





All timber 



Saw timb 



er 



Stand class 



All 



Soft- 



Hard- 



All 



Soft- 



Hard- 





species 



wood 



wood 



species 



wood 



wood 





Million 



Mittion 



Million 



Million 



Million 



Million 





cubic 



cubic 



cubic 



cubic 



cubic 



cubic 





feet 



feet 



feet 



feet 



feet 



feet 



Old-growth saw timhcr 



30 



10 



20 



100 



30 



70 



Second-growth saw timber.. 



80 



20 



60 



320 



80 



240 



Pole timber 



280 



65 



215 



570 



160 



410 



Seedlings and saplings, and 















poorly stocked and de- 

















330 



85 



245 



210 



90 



120 







Total 



720 



180 



540 



1 . 200 



360 



840 







The relatively short growing season, and the 

 extent of low site swampland place the Lake States 

 at a comparative disadvantage with some of the 

 other regions but do not fully account for the differ- 



Forest Resources of tlie Lal<e States Region 



ences in annual growth. The low rate in this 

 region is primarily a result of heavy mortality, and 

 the excessively large proportion of acreage in de- 

 forested or newly restocked condition. 



Because in most parts of the region the timber 

 is so young, more than half of the annual growth 

 consists of so-called "ingrowth," that is, volume 

 credited to trees which have just reached minimum 

 merchantable size. In Clearwater County, Minn., 

 for example, the survey made in 1949 showed that 

 63 percent of the current annual growth was newly 

 recogni/cd volume of trees which had just entered 

 the (i-inch diameter class. In the case of saw timber, 

 ()7 ]3crcent was volume credited to trees which had 

 just attained minimum saw-timber size. The trees 

 involved may be 30 years or more of age when they 

 first attain pole-timber size. Thus ingrowth credits 

 to the current year new volume which actually has 

 accrued over a longer period. Obviously, not all 

 of this kind of growth is ready for immediate con- 

 version into timber jjroducts. 



Moriality 



Roughly 700 million cubic feet of timber, includ- 

 ing 1,000 million board feet of saw-timber size 

 succiunbs to suppression, fire, or natural enemies 

 in a typical year (table 19). 



Suppression and Delerioralion 



As trees grow in size, they compete more and 

 more with each other for food, light, and water. 

 Many are stippressed and killed in the process. For 

 example, a fairly well-stocked 20-year-old jack jjirie 

 stand loses half of its trees through suppression 

 before it reaches 30-year age and half of the re- 

 mainder before it reaches 50-year age. Many of 

 these dying trees would be usable for pulpwood, 

 posts, and fuel wood if salvaged at the right time. 



In old stands, especially those degraded by previ- 

 ous high grading logging operations, the losses from 

 dying trees and from the advance of rot, cracks, and 



27 



