植树绿化能保持水土、防风固沙、调节气候,直接或间接地促进农业发展,为工业、基本建设、人民生活提供原材料,这是人所共知的。城市植树绿化,除上述作用外,还有其特殊意义的是能改善卫生条件。多种树可以调节气温,使空气湿润,冬暖夏凉。最重要的是树木在有光照的条件下吸收二氧化碳同时放出氧气,供人体的需要。另外树木还能吸 Tree planting and afforestation can keep water and soil, prevent wind and sand, regulate climate, directly or indirectly promote agricultural development, and provide raw materials for industry, infrastructure, and people’s lives. This is well known. Urban afforestation, in addition to the above-mentioned functions, has its special significance in improving sanitation. A variety of trees can regulate the temperature, so that the air is moist, cool in winter and cool in summer. The most important thing is that the trees absorb carbon dioxide in the light and emit oxygen for human needs. In addition, trees can suck