Study of the measurement to preserve agricultural field as tertiary nature with the aim of coexisting the natural environment

在日本农村地区，保持了丰富的自然环境，即“次生自然”，以平衡农业种植。然而，近年来，一些农田被集约化管理，以保持高生产力，同时严格保护作为生物栖息地的环境。这一集约型领域可以归类为“第三性质”。本研究的目的是通过实地考察两种环境的平衡和变化。2003年，第一个试验点设在花卷市花川-筑美沼泽区附近的野生虹膜田。2004年，工地被转移到伊萨瓦平原的汉诺基池塘。第二块场地由面积1公顷的小型养殖场池塘和周围未开垦的潮湿低地组成。因此，在这个场地上开发的政府项目，既将稻田的土地整理作为“三级自然”，又将湿地保护作为“二级自然”。岩手大学的四名研究人员完成了整个项目的田野工作。藤井博士测量了场地和周围稻田土壤水分的时间变化，竹原博士探索了同一地点的植被特征。然后栗岛博士观察了气象和水文特性。此外，武田博士考察了耕作田地的机械能，另外两位研究人员为我们的活动提供了田野数据。在田野数据和热烈讨论的基础上，我们思考了“湿地为第二自然”和“生产田地为第三自然”之间的生态关系。我们希望这些学术工作能够对保持农田高产所需的投入能量进行定量检验。

In the rural area of Japan, ample natural environment, namely "secondary nature", has been maintained so as to balance agricultural cultivation. However, some agricultural field is recently managed intensively to keep high productivity with strict preservation of environment as a biotope. This intensive field may be categorized as "tertiary nature". This study aimed to examine the balance and change of both environments through the field works.In 2003,first test site was set on wild iris field beside Hanawa-tsutsumi swamp area in Hanamaki-city. Then site was moved to Hannnoki-pond in Isawa Plain in 2004. Second site is composed of small farm pond of 1ha area, and surrounding wet lowland uncultivated. Thus the governmental, project developed on this site aims both the land consolidation of paddy field as "tertiary nature" and the conservation of wet land as "secondary nature".Four researchers in Iwate University fulfilled the field works for the full term of this project. Dr.Fujii measured the temporal change of soil moisture of the site and surrounding paddy field, and Dr.Takehara explored the vegetation characteristics on the same location. Then Dr.Kurashima observed the meteorological and hydrological properties. Besides them, Dr.Takeda examined the mechanical energy to cultivate the field, and other two researchers supplied the field data to support our activities.On the basis of the field data and heated discussion, we considered the ecological relationship between "wet land as a secondary nature" and "productive field as a tertiary nature". We hope these academic works would lead to a quantitative examination on the input energy to keep agricultural field with high productivity.