SYLVICULTURE. 



temperature and tlie annual rainfall seem to indicate; a discrepancy 

 between cause and effect, possibly due to forest fires. West of the 

 9oth degree of longitude, Oak, Ash and Walnut occur along rivers, 

 especially on Eastern banks. Oak also appears scattered through 

 the depressions. 



d. North Central Sub-region. Precipitations very abundant 

 from -South as well as Xorth. Average winter teihperature 30 de- 

 grees Faht. Quick change of temperature. The light-seeded, broad- 

 leaved species reach maximum in this section, also White Pine anJ 

 Hemlock. Six Maples, $ve Birches, Elms and Lindens, further Ash, 

 Butternut, Red and White Oak compose the forest. 



e. North Atlantic Sub-region. Plenty of moisture, the moun- 

 tains being close to the sea-shore, but not so much as in Lake states. 

 Average winter temperature 34 degrees Faht. at seashore. Pinus 

 rigida and mitis, Beech, Birch, Chestnut, Maples, often replaced by 

 Poplar and Willow. Spruce sets in at altitude exceeding 1,000 ft., 

 accompanied by Hemlock, White Cedar, Red Cedar, ^^^lite Pine and 

 Tamarack. 



f. North Prairial Sub-region. Dry summers, blizzardy winters 

 and more sandy soil. No Hemlock. Red Pine and Jack Pine intrud- 

 ing fom North. Scrub Oak openings. On best soil still good develop- 

 ment of Linden, Maple, Elm and Birch. Wliite Pine of poorer quality 

 than in sub-region " d." 



IV. Eastern Evergreen Forest of the moderately cold zone. 



The majority of this zone lies in Canada, in northern Lake states, 

 Maine. It occurs in North Carolina at 6,000 ft. elevation; in the 

 Adirondacks at 2,000 feet; in Maine at sea level. 



The region occupies a big belt stretched across the continent, so 

 that western and eastern flora joins hands in it. A typical tree of 

 this region, the ^^Tiite Spruce, often forms large pure forests. Other 

 species of the zone are Red Spruce, Black Spruce, Balsam-fir, Cotton- 

 woods, Canoe Birch, Hemlock, MHiite Cedar and Tamarack, the latter 

 here ootaining its optimum. 



B. The North Mexican forest. 



The North Mexican Flora intrudes, coming from MexicD, Arizona 

 and New Mexico. It is diff'erent from the Pacific flora, unimportant 

 commercially, interesting only botanically. Forest possible only at 

 altitudes exceeding 5,500 feet. Forest proper — dense forest — only at 

 8,000 feet. 



I. North Mexican sub-tropical forest. 



Characterized by Cactus, Yucca, Agave and Mesquite (Prosopis). 

 Evergreen Oaks in moist valleys. Madrona (Arbutus), a beautiful 



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