美国的森林资源比较丰富,森林面积居世界第四位。全国有森林面积28830万公顷,占国土面积的32.7%,人均占有森林面积3.1公顷,尤其东部和西部地区,森林更加茂密。然而,到美国的三藩、洛杉矶、纽约、费城、华盛顿等城市参观,沿途汽车奔驰在完阔的高速公路上,公路两旁看不到成行的行道树,路旁多是绿色的草坪和疏落的风景树。美国朋友告诉我们,公路两旁 The United States has abundant forest resources and ranks the fourth largest in the world in terms of forest area. The country has a total area of ​​288.3 million hectares of forest, accounting for 32.7% of the total land area and a forest area of ​​3.1 hectares per capita. Especially in the eastern and western regions, forests are more dense. However, to the United States, San Francisco, Los Angeles, New York, Philadelphia, Washington and other cities to visit the car along the Mercedes-Benz highway in the open, the roadside can not see the line of trees, the roadside is mostly green lawn and drenched landscape tree. American friends tell us that the roads are lined up