Figure legends
Figure 1. Two simplified examples of the effect of turf species on
canopy-forming macroalgae. A) In this example, the canopy kelp is
negatively affected by two species that live in the understory below.
This competitive effect can be measured experimentally, through the
removal of the turf and crust understory. If the abundance (or biomass,
etc.) of the canopy increases in the absence of the turf and crust
species, the interaction is estimated as competitive. B) However, if
these species facilitate the canopy kelp, then the removal of turfs and
algal crusts should have a negative effect on the canopy.
Figure 2. Locations of the studies included in the meta-analysis, by
study type. On the right is the distribution of studies in the Northeast
Pacific Ocean, where a high density of studies have been conducted.
Figure 3. The overall effect of different turf functional groups on the
canopy (kelps and Fucales combined). Each point in grey represents an
individual measured interaction, with means and 95% confidence
intervals in black. If log response ratio (LNRR) is negative, then the
effect of turf species on the canopy is facilitative. If LNRR is
positive, then the effect is competitive.
Figure 4. The experimental effect of different turf functional groups on
the canopy, by depth. Each point is a raw data point, scaled in size by
the study sample size, with 95% confidence intervals shaded around each
line. Note that the slope and intercept of the coralline crust and
non-coralline turf lines do not statistically differ from zero.
Figure 5. Across latitude (top), mixed evidence for increasingly
facilitative interactions at higher latitudes. Below, patterns across
life history stage (raw data in grey, means and 95% confidence
intervals for the mean in black). For life history stage, observations
were collected primarily on the recruit canopy stage (see Results:
Observational studies). Plot across latitude includes only coralline
turfs, plot across life history includes all canopy and turf taxa.