The data needed by the research are collected from relevant materials and field sampling , including the soil saturation hydraulic conductivity , soil bulk density , various kinds of chemical parameters of soil layer ( such as organic nitrogen , organic phosphorus and soluble phosphorus ) , the transformation of organic carbon content of soil layer and the land use in 1993 etc . 笔者两次参加对研究区的实地考察，并进行相关数据的收集和实测，包括1993年土地利用、土壤饱和导水率、土壤容重和土壤各种化学参数(如有机氮、有机磷和可溶性磷等) ，以及后来所进行的土壤层有机碳含量的转化等。
