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美国国土面积900万公里~2,森林覆被率34%,用材林约31亿亩,占有林地的3/4。在用材林中,针叶林和阔叶林各占一半。由于美国气候和土壤条件优越,天然林茂密,生长良好,森林资源比较丰富。美国最大的维尔豪斯木材公司,拥有森林20多万公顷,其中80～100年生的花旗松林,平均高25～30米,平均胸径30厘米左右,每亩蓄积量20米~3,出材量8米~3。美国有三大林区:西北部、东部和东南部。西北部林区又划分为西海岸和内陆两个区。西海岸林区,雨量充沛,主要树种是花旗松,其次有云杉、冷杉、铁杉、落叶松、侧柏,形成针叶树混交林。内陆区比较干旱,主要树种有西部白松、西部黄松、小干松、落叶松,形成针叶纯林或混交林。东部
The United States has a land area of 9 million km2, a forest cover rate of 34% and a timber forest of about 3.1 billion mu, accounting for 3/4 of the total forest land. In timber forests, conifers and broadleaf forests each account for half. Due to its superior climatic and soil conditions, dense natural forests and good growth, the United States has abundant forest resources. Woods, the largest American woodhouse, owns more than 200,000 hectares of forests. Among them, 80 to 100 years old Douglas fir forests have an average height of 25-30 meters, an average diameter of about 30 centimeters and an accumulation volume of 20-30 meters per mu 8 meters ~ 3. There are three major forest areas in the United States: northwest, east and southeast. Northwest Forest is divided into two areas on the west coast and inland. The west coast of the forest area, abundant rainfall, the main species is Douglas fir, followed by spruce, fir, hemlock, larch, arborvitae, coniferous forest. The inland areas are relatively arid. The main tree species are western white pine, western pine, small dry pine, and larch, forming pure needles or mixed forests. east