Semi-natural grasslands have an important conservation value in Europe but have been in continuous decline since the early twentieth century. Valuable and well-preserved semi-natural grasslands must be identified in order to plan conservation and restoration strategies. The main aim of this paper is to develop an expert system based on diagnostic species for the identification and assessment of EU semi-natural grasslands using a dataset of 3238 vegetation plots from the Iberian Peninsula (Portugal and Spain, including the French Pyrenees). The dataset was obtained by stratified resampling of a larger dataset of 12,204 vegetation plots containing other related grasslands and herbaceous vegetation types. We applied a k-means classification on the resampled dataset and selected the diagnostic species for each group of EU semi-natural grasslands in order to develop an expert classification system with definitions based on their species composition and biogeographic distribution. The expert-based classification was applied to 14 vegetation subtypes belonging to semi-natural grasslands in the Habitats Directive, corresponding to semi-dry calcareous grasslands (Habitat 6210), Nardus grasslands (6230), hay meadows (6510, 6520) and Molinia meadows on peaty soils (6410). We provide a practical and easy tool for the identification, monitoring and assessment of EU semi-natural grasslands on the Iberian Peninsula.

半自然草原在欧洲具有重要的保护价值，但自20世纪初以来一直在持续下降。为了规划保护和恢复策略，必须确定宝贵且保存完好的半自然草原。本文的主要目的是使用来自伊比利亚半岛（葡萄牙和西班牙，包括法国比利牛斯山脉）的3238个植被地块的数据集，开发一种基于诊断物种的专家系统，用于鉴定和评估欧盟半天然草原。该数据集是通过对包含其他相关草地和草本植被类型的12,204个植被地块的较大数据集进行分层重采样而获得的。我们在重新采样的数据集上应用了k均值分类，并为每组欧盟半天然草原选择了诊断物种，以便开发出基于物种组成和生物地理分布进行定义的专家分类系统。基于专家的分类适用于人居指令中属于半天然草原的14种植被亚型，对应于半干钙质草原（人居6210），豌豆土壤上的纳达斯草原（6230），干草草甸（6510、6520）和莫利尼亚草甸（6410）。我们为识别，监测和评估伊比利亚半岛上的欧盟半天然草原提供了一种实用而简便的工具。