2.1 Experimental Design
Our experiment investigated community responses to soil and climate variation using standardized communities composed of three species:Dactylis glomerata L., Plantago lanceolata L.¸ andLotus corniculatus L. Species were selected based on wide climatic tolerances and a global distribution, being naturalized on six continents (Seipel et al. 2012). These species are considered non-invasive, making them attractive for coordinated studies (Alexander and Edwards 2010). The experimental communities represent a variety of herbaceous lifeforms (graminoids, non-leguminous forbs, and legumes), with limited functional overlap (Dı́az and Cabido 2001). These species are well suited to experimental studies due to relatively short life cycles and being readily manipulated. Consequently, these species can be used as a common currency for plant community dynamics across coordinated studies.
Seeds used in this study were sourced from Rieger-Hofmann in central Germany to reduce variability in genetic origin. We partitioned the effects of local soil from climatic effects by including a reference substrate treatment (vermiculite mixed with 4g Osmocote fertilizer) at each site. Vermiculite is a suitable substrate comparable to potting soil (Wilfahrt et al. 2021). Plants used in the experiment were reared in a greenhouse in Bayreuth, Germany for four weeks before being transported to field sites in summer 2017 (Fig. 1 ). The selected locations were Bayreuth, Germany (350 m a.s.l.); Fendt, Germany (550 m a.s.l.); Graswang, Germany (850 m a.s.l.); Esterberg, Germany (1300 m a.s.l.); Stubai, Austria (1850 m a.s.l.); and Furka, Switzerland (2440 m a.s.l.). These locations represent a wide geographical, climatic, and soil compositional range (Table 1 ).