自然火源是在森林生态系统形成以前就存在的。地球上的森林生态系统形成之后,火就作为一个自然因子参与森林生态系统的演变。火是一个重要生态因子,可以从以下几部分论述:一、火的发生需要一定的生态条件 Natural sources of fire existed before the formation of forest ecosystems. After the formation of forest ecosystems on Earth, fire has been involved as a natural factor in the evolution of forest ecosystems. Fire is an important ecological factor, which can be discussed from the following aspects: First, the occurrence of fire requires certain ecological conditions