北国寒冷,冰封雪飘,草木凋零。然而,塑料温棚内却别有洞天。走进塑料温棚,春意盎然,黄瓜、蕃茄、豆角、青椒……枝繁叶茂,果实累累,一派丰收景象。相隔一层薄膜,为何内外两重天?论光照,北京地区冬日阳光强度一般为3～4万勒克司,光照时间达17—9小时,仍够喜光果菜之需。看热量,阳光最弱的12月太阳辐射日总量仍有191卡/厘米~2·日。这些热量,薄膜棚可以充分接纳并积 North cold, snow drift, vegetation withered. However, the plastic greenhouse there is another cave. Into the plastic greenhouse, spring, cucumber, tomato, beans, green peppers ... ... leafy, fruitful, one of the harvest harvest scene. Separated by a thin film, why the two days of internal and external light? On the Beijing winter sun intensity is generally 3 to 40,000 lux, light time up to 17-9 hours, still enough light food needs. Looking at calories, the weakest sun in December total solar radiation is still 191 cal / cm ~ 2 · day. These heat, film shed can be fully received and plot