Using data of making observations of the herbage turning green on the typical steppe and themeteorological conditions at the same time, the main limiting factor of the herbage turning greenis heat conditions.
利用典型草原牧草返青和气象要素平行观测资料分析认为，牧草返青的主要限制因子是热量条件，只有当０～３０ｃｍ土壤水分总贮存量低于２０ｍｍ时，水分才产生制约作用。