Leaf traits of macrophytes in lakes: Interspecific, plant group and community patterns

In freshwater systems the differentiation between macrophyte groups and growth forms is evident. The plant functional approach was used to understand the patterns of traits seen in the macrophytes of lakes at three levels: interspecific, functional groups and communities. Leaf area (LA), leaf dry weight (LDW) and specific leaf area (SLA) were measured for 31 macrophyte species in 30 lakes in Poland. To investigate the community structure, aquatic macrophyte species were sampled in 30 lakes 100 along 145 sections at the bottoms of the lakes (depth zones at 1.0 m). In total, we collected 14 500 cover-plant samples (quadrat, area = 0.1 m2). For each sample, we estimated the coverage (%) of species by SCUBA diving. Leaf trait variation was examined via mean or community-weighted mean (CWM) comparisons at three levels: interspecific, species grouped into plant functional groups (FGs) and communities. Shifts in leaf trait values were found at the interspecific and FG levels. LA, LDW and SLA varied widely across the 31 macrophyte species and among functional groups. Our results show that there are differences between CWM trait values (LDW, LA) among communities. In summary, we found that SLA decreased with increased water pH and calcium content interspecifically and among communities. Our findings show that different functional patterns predict the functioning of plant communities and FGs in lakes. Furthermore, the diversity in functional traits appears to be part of community assembly for macrophytes. At the functional group level, there are shifts in leaf traits. In contrast, among communities, there are low variations in leaf traits.