The article presents a discussion on the ecology of species found in Pembrokeshire Islands. It shows the comparison between the grazed and ungrazed vegetation while indicating the effect of grazing on flowering, herbs and grasses, and other life forms of plants. It explores the rapid fluctuations in grazing intensity which cause vegetation changes. The article is supplemented with details on the artificial exclusion of mammals, plant successions, ecology, and diversity. Diagrammatic representations of plant successions controlled by grazing intensity and exposure are also given.
The article reports on the Rivularia bullata-balanus community. The occurrence of this community gives rise to a number of ecological considerations especially as featuring an instance of biotic reactions and as emphasizing the relevance of considering the sea shore as a biotic community or biome. The Rivularia genus propagates both by hormogones and spores and the hormogones provides an effective method for increasing the size of the colony and the formation of new colonies. This report of the Rivularia-Balanus community gives evidence of a study of both adelophycean stages and biotic relationships in attempting to clarify problems connected with marine ecology of the littoral region.