This continuing research program includes six topics: 1) a 20-year perspective of several scales of disturbance on three species of kelp that will be continued with long term demographic studies in five areas; 2) thinning experiments searching for thresholds necessary for understory persistence in different regions; 3) evaluation of intra- and interspecific density effect on kelp growth, reproduction, recruitment, and survivorship; 4) an experimental evaluation of fundamental vs. realized niches of kelps in the presence of a strong competitive dominant, and 5) the effects of long shore and cross shore gradients, especially light and temperature with regard to succession theory. The investigators are also (6) using outplants to evaluate some adaptive tactics of four species of relatively rare kelps that have very different life histories. For most of the experiments they will use triplicated clearings at each of four depths and modules with different densities of sporophytes to evaluate regional and density thresholds on growth, time and intensity of reproduction, recruitment, and survivorship.