森林(forest)
以乔木为主要生物类型的复杂生态系统。在最暖和的月份气温高於10℃、年降水量大於200公厘的地方，以乔木占优势的森林便能存在。在上述气候范围内，森林能在多种多样的条件下发育形成。森林中土壤、植物和动物类型又依环境影响的悬殊而异。在凉爽的高纬度近极地地区，泰加林以耐寒的球果植物为主；在较温暖的高纬度气候条件下，由针叶树和落叶阔叶林组成的混合林占优势；在中纬度气候条件下，落叶阔叶林占优势；在赤道带潮湿的气候条件下，热带雨林得以形成，由於降雨量大，有利於常绿阔叶树种生存，而不像凉爽地区的森林主要为针叶树种。森林属世界上最复杂的生态系统之列，显示了多种多样的垂直分层结构。针叶林的结构最简单︰乔木层高约30公尺；灌木层分布不规则，甚至没有；地被层覆以地衣、苔和藓。落叶林的垂直分层结构较为复杂，其树冠层分为上、下两层，而雨林的树冠至少分为三层。生活於森林中的动物具有高度发达的听力，许多种类因环境而适应於竖向运动。因为除了地表植物外，食物稀少，许多地栖动物仅将森林当作栖身之所。森林是大自然界最有效率的生态系统，光合作用率极高，这能影响处於一系列复杂的有机联系中的动物和植物。
English version：
forest
Complex ecosystem in which trees are the dominant life form. Tree-dominated forests can occur wherever the temperatures rise above 50°F (10°C) in the warmest months and the annual precipitation is more than 8 in. (200 mm). They can develop under various conditions within these limits, and the kind of soil, plant, and animal life differs according to the extremes of environmental influences. In cool, high-latitude subpolar regions, taiga (boreal) forests are dominated by hardy conifers. In more temperate high-latitude climates, mixed forests of both conifers and broad-leaved deciduous trees predominate. Broad-leaved deciduous forests develop in midlatitude climates. In humid equatorial climates, tropical rain forests develop. There heavy rainfall supports evergreens that have broad leaves instead of the needle leaves of cooler evergreen forests. Forests are among the most complex ecosystems in the world, with extensive vertical layering. Conifer forests have the simplest structure: a tree layer, a shrub layer that is spotty or even absent, and a ground layer covered with lichens, mosses, and liverworts. Deciduous forests are more complex (the tree canopy is divided into an upper and lower story), and rain-forest canopies are divided into at least three layers. Forest animals have highly developed hearing, and many are adapted for vertical movement through the environment. Because food other than ground plants is scarce, many ground-dwelling animals use forests only for shelter. The forest is nature's most efficient ecosystem, with a high rate of photosynthesis affecting both plant and animal systems in complex organic relationships.
