Influence of the difference of management on the weed vegetation around paddy fields in valley in hill land

The vegetations on footpaths, levees and abandoned paddy located within the same valley were compared with each other, in an attempt to clarify the ecological properties of the weed communities which have been exposed to the continuous and periodic disturbance related to rice cropping such as trampling, cutting by farmers. The sample consisting of 119 species in 132 quadrats were classified by TWINSPAN. The stand groups containing Zoysia japonica, Imperata cylindrica and Miscanthus sacckariflosus corresponded to the footpath, the levee and the abandoned paddy communities, respectively. The above-ground parts of the vegetation in the footpath that frequently destructed was dominated by small creeping weeds like Z. japonica, Triforium renews, and moreover tree seedlings and tall-growing competitive erect and tussock-form weeds were involved in this vegetation. I. cylindrica super-dominated on the levees where cutting had been practiced once a year. In abandoned paddy, M, sacchariflorus formed the framework of this community, and short-growing weeds like Oenanthe javanica, Eqmsetum aruense and climbers coexisted. Abandoned paddy may not be suitable for germination of tree seeds dispersing from surrounding forest because of the high humidity. Therefore, weed community on the humid abandoned paddy seems to be relatively stable. To characterize the successional stability of vegetation, Index of Vegetation Condition (IVC) was defined for each stand based on the difference of relative plant height of each component species with dominant species of the stand. This index suggested that the stability of weed vegetation in the studied area does not correspond the values of diversity index (H'). The IVC value decreased with increasing intensity of disturbance in this valley.