Plant–Plant Interactions in Coastal Dunes

Abstract

Biotic interactions among plants have long been recognized as important in determining community structure and dynamics (Pickett 1980). Interactions range from negative to positive and function simultaneously. The result is a balance among mechanisms that cause a gradient of potential effects. In general, it is accepted that as the abiotic stress increases, so will the importance of positive interactions, and the opposite occurs when physical stress is reduced, and the importance of competition is expected to increase (Bertness and Callaway 1994). In coastal dunes, in particular, high environmental heterogeneity generates the possibility of the occurrence of a wide variety of interactions among plants. The number of studies on plant–plant interactions in these environments has increased during the last decades (see Table 13.1) and has shown that both positive and negative interactions are important, although the abiotic environment exerts an important control as well. However, although the successional gradients and dynamics have been widely studied in these environments (for example, Cowles 1899; Yarranton and Morrison 1974; Lichter 2000), there have been few studies of the relative impact of the different interactions during different successional stages. In this chapter we will focus on the most studied plant–plant interactions of the literature on coastal dunes: facilitation, competition, and epiphytism. We will review the information reported in the literature and will include our own data, to test the prediction that positive interactions are more frequent during the environmentally harsh early successional stages, when the sand is highly mobile, while competition and epiphytism become more frequent as the system stabilizes and the plant cover increments.