Herbaceous plant diversity including rare aquatic species has been lost in many countries by agricultural intensification and abandonment. In paddy fields of the Lao People’s Democratic Republic (Lao PDR), irrigation facilities have been constructed rapidly since 1997. The aim of this study was to clarify the impacts of double rice cropping accompanied by the introduction of irrigation systems on herbaceous plant diversity and utilization in paddy fields of southern Lao PDR. Ground vegetation surveys and interviews were conducted in Kok Deau and Lak 30 villages in Champasak Province, and propagule bank survey was conducted in Kok Deau village. The species richness and species diversity, measured by the Shannon’s diversity index, were not significantly different between the irrigated and rainfed paddies (p > 0.05), when compared in both the wet and dry seasons. However, double rice cropping with irrigation systems affected herbaceous plant species composition in paddy fields. Increased use of chemical fertilizers in irrigated paddies resulted in predominance of tall undesirable species, such as Fimbristylis miliacea (L.) Vahl and Echinochloa colona (L.) Link. Small and frequently submerged species were dominant in the ground vegetation and propagule banks of the rainfed paddies. Since small submerged species are often sensitive to environmental changes, increase of irrigated paddy area may lead to a decrease in the variety of aquatic herbaceous plants in Lao PDR. While a total of 9 herbaceous plant species were utilized as foods in the villages, no change was recognized by farmers in species composition and frequency of utilization of paddy plants as food before and after the development of the irrigation systems.

包括稀有水生物种在内的草本植物多样性在许多国家因农业集约化和废弃而丧失。在老挝人民民主共和国 (Lao PDR) 的稻田中，自 1997 年以来灌溉设施建设迅速。本研究的目的是阐明双季稻随着灌溉系统的引入对草本植物多样性和利用的影响在老挝南部的稻田里。在占巴塞省的Kok Deau和Lak 30村进行了地面植被调查和访谈，在Kok Deau村进行了繁殖库调查。以香农多样性指数衡量的物种丰富度和物种多样性在灌溉稻田和雨育稻田之间没有显着差异（p > 0.05)，在雨季和旱季进行比较。然而，灌溉系统的双季稻影响了稻田中的草本植物物种组成。在灌溉稻田中增加使用化肥导致高大的不良物种占优势，例如Fimbristylis miliacea (L.) Vahl 和Echinochloa colona (L.) Link 。在雨养稻田的地面植被和繁殖体中，小型且经常淹没的物种占主导地位。由于小型沉水物种通常对环境变化敏感，因此灌溉稻田面积的增加可能导致老挝人民民主共和国水生草本植物种类的减少。虽然村里共有 9 种草本植物被用作食物，但农民们认为在灌溉系统发展前后，稻谷植物作为食物的物种组成和利用频率没有变化。