Differences in perennial vs. ephemeral cover

Data are differences between the cover of perennial and ephemeral species in each plot over six censuses spanning 18 months. Values > 0 indicate higher perennial cover, whereas values < 0 indicate higher ephemeral cover. Environmental factors included wave exposure (exposed, protected) and tidal elevation (higher, lower), and experimental manipulations included screens (absent [0], present [1]), herbivores (removal, ambient), and nutrients (none, addition).