【英语求教,定语从句引导词省略的问题,有例句Frequentfireisafactortowhichrainforestspeciesseemunabletoadapt,althoughancientcharcoalremainsfromAmazonforestsoilsdatingpriortothearrivalofhumanssuggestthatmoist】

　　英语求教,定语从句引导词省略的问题,有例句

　　Frequentfireisafactortowhichrainforest

　　speciesseemunabletoadapt,althoughancientcharcoalremainsfrom

　　Amazonforestsoilsdatingpriortothearrivalofhumanssuggestthat

　　moistforestsalsooccasionallyburn.这句话里althoughancientcharcoalremainsfromAmazonforestsoils里的remains是定语从句修饰charcoal吗?前面为什么没有引导词啊?