Environmental drivers of plant assemblages: are there differences between palustrine and lacustrine wetlands? A case study from the northern Apennines (Italy)

Mountain wetlands are among the most vulnerable habitats in the Mediterranean basin. Their conservation requires knowledge of plant species assemblages and their environmental drivers. In this study, we investigated what the main environmental factors driving species composition in mountain wetlands are. Differences in environmental control and floristic composition between palustrine and lacustrine wetlands were explored. We used a dataset of 168 vegetation plots (relevés), sampled at 45 mountain wetlands in the northern Apennines (central Italy). Direct ordination showed that water depth, geology type and altitude were the main factors responsible for species distribution. The most important gradient was linked to soil moisture, with hygrophilous species increasing with moisture levels. Indicator Species Analysis underlined a clear distinction in the distribution of aquatic plants between wetland subsystems. Geology and rainfall affected species assemblages in lacustrine and palustrine subsystems. Indirect ordination and Generalized Additive Models revealed that plant species and their attributes significantly changed in the wetland subsystems with an increase in hydrophytes with increasing rainfall in palustrine wetlands and a decrease in thermophilous species along an altitudinal gradient in lacustrine wetlands. Management and conservation guidelines for northern Apennines wetlands are suggested.