Gravel pads of powerline towers as human-made habitats for ruderal vegetation in some Mediterranean wetlands of Egypt: Implications for management

Despite the widespread of transmission powerlines in many aquatic ecosystems of Egypt, little is known about their ecological impacts. The current study evaluates floristic composition associated with gravel pads constructed for stabilizing powerline towers in the wetlands of Burullus and Manzala. Plant cover was measured for 34 randomly selected in paired gravel pads and adjacent wetlands. Ordination analysis indicated that vegetation on the gravel pads significantly differed from that in wetlands. Thirty-two species were recorded in the gravel pad plots (more than twice the number found in wetlands). Mean species richness was significantly higher in gravel pad plots (3.8 species) than in wetland plots (1.7 species). Gravel pad plots had a significantly lower cover than wetlands of Chenopodiaceae (12.9% vs. 28.7%) and Poaceae (15.7% vs. 32.2%), while Asteraceae showed higher cover in gravel pad plots (25%) than in wetlands (6.7%). Gravel pad plots were consistently occupied by ruderals, weeds and invasive species. Regression analysis showed that total vegetation cover and diversity indices increased significantly with rises in the thickness of the gravel pads. The study highlighted the importance of gravel pad corridors for the abundance of ruderal plant species that could eventually colonize more pristine areas in the adjacent wetlands.