Given more attention在这里相当一个条件壮语从句。可改写为 If it had been given more attention,the trees could have grown better. 此句是针对过去的虚拟语气,从句If it had been given more attention时态用过去完成时;主句the trees could have grown better用结构could have+动词的过去分词. 另外,过去分词做壮语可以表被动或完成,在此表被动,the trees是动作的承受者。