SYLVICULTURE 



advance growth types are further bastardized with shelterwood 

 types. 



Paragraph LIII. The advance growth compartment type of natural 

 seed regeneration. 



A. The type is applicable only where large areas exhibit on 

 strong soil a uniform advance growth, consisting of seedlings, of 

 saplings and possibly of small poles. 



Previous to lumbering, the leaf canopy consists of two tiers: 

 an upper tier formed by the parents (or step-parents) and a lower 

 tier formed by the advance growth. Lumbering removes the upper 

 tier entirely and leaves the low^er tier intact — if possible. 



In the safety of the lower tier lies the great difficulty of the 

 system, especially on rough ground, in handling heavy logs of the 

 superstructure, in dealing with cheap stumpage, in cutting soft 

 woods characterized by small healing power and in the absence of 

 an intricate system of transportation. 



Where the upper story of trees consists of say 10,000 feet b. m. 

 per acre, or of more, the ground is literally littered with logs or 

 boles during the logging operations, and the advance growth has but 

 a slight chance to survive the death of its progenitors. 



B. Actual application: The type is found, in rare cases, abroad 

 under the misnomer of a moditied " selection system," where and 

 when the logger returns for a wholesale removal of mature trees, 

 at intervals of about twenty years, to the same compartments. 



The type is also practical where prolific seed years produce, 

 in mild sites and on strong soil, a uniform advance growth in even- 

 aged Beech or Firwoods, without any previous human interfei'ence 

 with the leaf canopy overhead (so-called regeneration from a com- 

 plete-growing stock). 



In the Uniie^. States, compact advance growth is rarely found^ 

 possibly so in the case of Tsuga heterophylla. The destruction of 

 the superstructure, however, usually followed by fires, tends to anni- 

 hilate every vestige of advance growth. 



C. Advantages: 



Where the system can be carried through, it offers the following 

 advantages : 



I. Concentrated logging. 



II. Well-preserved productiveness of the soil. 



III. Soil never idling, but producing without any delay. 



120 



