Plant spatial patterns and functional traits interaction along a chronosequence of primary succession: evidence from a central Alpine glacier foreland

The main aim of this study was to elucidate the roles of terrain age and spatial self-organisation 34 as drivers of primary succession using high-resolution assessment of plant composition, 35 functional traits and landscape metrics. 36 We sampled 46 plots, 1m × 1m each, distributed along a 15-70 year range of terrain ages on the 37 foreland of the Nardis glacier, located in the southern central Alps of Italy. From existing 38 databases, we selected nine quantitative traits for the 16 plant species present, and we measured a 39 set of seven landscape metrics, which described the spatial arrangement of the plant species 40 patches on the study plots, at a 1 cm × 1 cm resolution. We applied linear models to study the 41 relationships among plant communities, landscape metrics and terrain age. Furthermore, we used 42 RLQ-analysis to examine trait-spatial configuration relations. To assess the effect of terrain age 43 variation on trait performance, we applied a partial-RLQ analysis approach. Finally, we used the 44 fourth-corner statistic to quantify and test relations between traits, landscape metrics and RLQ 45 axes. 46 Surprisingly, linear models revealed that neither the plant composition nor any of the landscape 47 metrics differed among the three classes of terrain age distinguished, viz. 15-41 y, 41-57 y and 48 57-66 y, respectively. Further, no correlations were detected between trait patterns and terrain 49 age, however, the floristically defined relevé clusters differed significantly with regard to several 50 landscape metrics and suggestive relationships between increasing patch diversity and traits 51 connected to growth rate were detected. 52 We conclude that (i) terrain age below 70 years is not a good predictor for neither plant 53 composition nor spatial configuration on the studied microhabitat and (ii) the small-scale 54 configuration of the plant species patches correlates with certain functional traits and with plant 55 composition, suggesting species-based spatial self-organisation.