一 前言 森林是陆地生态系统中物种组成最多,层次结构最复杂,下垫面的空间最高,生产力最大,基因资源最丰富的再生资源的生态系统。它和草原生态系统、农田生态系统、沼泽生态系统、荒漠生态系统和水域生态系统等,构成了自然界的整体,并构成为各种不同的自然景观。森林在环境保护、防止污染、维护自然景观、减缓水旱灾害、保 Foreword Forests are the ecosystems of terrestrial ecosystems that have the largest species composition, the most complex structures, the highest space in the underlying surface, the largest productivity and the most abundant genetic resources. It and the grassland ecosystem, farmland ecosystems, swamp ecosystems, desert ecosystems and water ecosystems constitute the nature of the whole, and constitute a variety of different natural landscapes. Forests protect the environment, prevent pollution, maintain natural landscape, and ease floods and droughts