前言做好农业自然资源调查和农业区划研究工作，可以为合理地开发利用农业自然资源，因地制宜地规划和指导农业生产，实现我国社会主义农业现代化提供科学依据。

1. In the first step, three large regions are divided to reflect the combined effectof hydrothermal conditions. In the northwest, the water insuficiency hampers thefunction of warmth; in the Tibetan Plateau, the low temperature hinders the fullutility of water; it is only in the monsoon area, where precipitation occurs in thewarm period, does the water-heat combination yield better results. These three regionsare of order 1.