Patterns of floristic composition of Mediterranean meadows and mesophytic grasslands in eastern Continental Portugal

It is becoming increasingly necessary to gain a deeper understanding of the ecological gradients underlying the floristic pattern of meadows and grasslands, because their distribution area and dynamics may be affected by the increased dryness resulting from climate change. Thus, the objectives are (1) to identify community types in <i>Molinio–Arrhenatheretea</i> meadows and <i>Stipo giganteae–Agrostietea castellanae</i> grasslands in Eastern Continental Portugal; (2) to recognize those communities that configure habitat types of the European Union Habitats Directive; (3) to establish environmental gradients underlying their spatial variation. Combining the Braun–Blanquet approach with numerical analysis, 292 relevés and 448 species were classified and ordered using two-way indicator species analysis (Twinspan classification) and canonical correspondence analysis (CCA). Partial CCA was applied to assess the relative influence of land use factors. About 17 community types were identified and those floristic patterns were mainly related to environmental gradients linked to pedological factors and humidity gradients. Based on biogeography and the determination of diagnostic species, four new phytosociological associations were proposed: <i>Mentho pulegii–Cyperetum badii</i> ass. nova hoc loco; <i>Trifolio resupinati–Menthetum suaveolentis</i> ass. nova hoc loco; <i>Mentho suaveolentis–Holcetum lanati</i> ass. nova hoc loco and <i>Festuco amplae–Brachypodietum phoenicoidis</i> ass. nova hoc loco.

当前，愈发有必要深入理解草甸与草原的植物区系格局背后的生态梯度，因为二者的分布范围与动态变化可能受到气候变化引发的干旱加剧的影响。据此，本研究的目标如下：（1）识别葡萄牙大陆东部的<i>Molinio–Arrhenatheretea</i>草甸与<i>Stipo giganteae–Agrostietea castellanae</i>草原的群落类型；（2）界定符合欧盟《生境指令》（Habitats Directive）所规定生境类型的群落；（3）阐明驱动其空间变异的环境梯度。本研究将布劳恩-布朗奎特法（Braun–Blanquet approach）与数值分析相结合，采用双向指示种分析法（two-way indicator species analysis, Twinspan分类法）与典范对应分析（canonical correspondence analysis, CCA）对292个植被样方与448个物种进行分类与排序；并通过偏典范对应分析（Partial CCA）评估土地利用因子的相对影响。本研究共识别出约17个群落类型，其植物区系格局主要与土壤因子相关的环境梯度及湿度梯度密切相关。基于生物地理学研究与特征种的确定，本研究提出4个全新的植物社会学群丛：<i>Mentho pulegii–Cyperetum badii</i> 新群丛（ass. nova hoc loco）、<i>Trifolio resupinati–Menthetum suaveolentis</i> 新群丛（ass. nova hoc loco）、<i>Mentho suaveolentis–Holcetum lanati</i> 新群丛（ass. nova hoc loco）以及<i>Festuco amplae–Brachypodietum phoenicoidis</i> 新群丛（ass. nova hoc loco）。