of available moisture. Following spring denuding, Fucus recovered at FE (the most exposed recolonization 

 station) in 8 months, at WP (2nd most exposed) in 14 months, at FS (2nd most sheltered) in 19 months, 

 and at GN (the most sheltered) in 29 months. After autumn denuding, the time needed for Fucus 

 abundance in the recolonization strips to approach that in the controls at FE, WP, FS, and GN were, 

 respectively, 16, 24, .36, and 36 months. Delay was attributed to the requirement for surface heterogeneity 

 to provide refuges from grazing; Littorina littorea prevent Fucus from establishing itself on smooth surfaces 

 (Lubchenco 1983). The community of the mid intertidal recovers (in terms of Fucus canopy) in as little 

 as S months (when denudation occurs prior to barnacle set, at an exposed station), or as long as 3 years 

 (when denudation occurs after barnacle set, at a sheltered station). 



Recovery of the low intertidal (re-establishment of a Chondrus canopy) takes longer than recovery of 

 high or mid intertidal areas (Fig. 14). Chondrus propagates vegetatively from a basal crust; if the upright 

 axes are removed (e.g., by scraping or freezing) but the crust left intact, recovery of uprights may be rapid 

 (MacFarlane 1956). If, however, the crust is removed (e.g., by our methods of scraping and burning), 

 repopulation mu.st occur by settlement of spores. For Chondrus, repopulation initiated by spores is a slow- 

 process. After both spring and autumn denudings, Chondrus at GN and WP reached a maximum of only 

 5% cover after 30 months. In fact, during each 30 month experiment, the highest abundance of Chondrus 

 at any recolonization station was ca. 10% at FS after the autumn denuding. 



Recovery of a Chondrus population involves long-term survival of relatively slow growing individuals. 

 This strategy is at the opposite end of a spectrum from that of ephemeral algae, that settle and grow 

 quickly whenever conditions are favorable. It also implies that even short-term periodic exposure to lethal 

 conditions will preclude re-establishment of Chondrus at FE. 



Even under favorable conditions, interspecific competition for space from Fucus vesiculosus may 

 partially explain the slow recovery rate of Chondrus. Regardless of the time of year in which denuding 

 occurred, Fucus was the first perennial macroalga to colonize the low intertidal, and usually developed 

 into a dense canopy (Fig. 15). FoUowing experimental denudation of areas in dense Chondrus beds, 

 Lubchenco (1980) reported that Fucus colonized and persisted for at least 3 years. Chondrus settled and 

 grew under the Fucus canopy. Lubchenco predicted that when Fucus senesced (after its 3-5 year lifespan), 

 Chondrus would remain and exclude further Fucus settlement. In other words, Fucus initially out-competes 

 Chondrus, but eventually Chondrw; would dominate the low intertidal. Data from recolonization transects 



42 



