On the annular growth pattern in Scirpus maritimus in an intertidal wetland: extension of the concept of cyclic development to within-clone spatial dynamics

In a seminal work on community organization and succession, A.S. Watt prese nted evidence to show that some plant communities are in dynamic but cyclic al equilibrium with their environment. Watt held that the resultant vegetat ion may have a patchy structure made up of different developmental phases r anging from "youngest" to "oldest" (termed "juvenile", "mature", "senile", and "slack"). At any given location, the vegetation repeatedly cycles throu gh these phases over time. We extend Watt's concept of cyclic succession an d phasic development to the study of within-clone spatial dynamics in Scirp us maritimus L. (Cyperaceae) colonizing an early succesional brackish-water environment. Specifically, we hypothesized that shoot populations of S. ma ritimus could be categorized into distinctive phases based on stem density and height and that differences in the developmental stage may be driven by a combination of biotic and abiotic controls. Data indeed show the existen ce of a strong annular banding pattern for stem density and height. The clo ne centres were characterized by a slack phase surrounded by bands of senil e, mature, and juvenile phases. Clone boundaries were highly truncated, typ ical of a phalanx growth strategy. Further analysis revealed that the chemi cal and physical environment varies between phases within clones, which may drive within-clone stem dynamics. We conclude with a model of phasic clona l growth for S. maritimus that posits the effects of demographic density-de pendence and physico-chemical environmental control on annular growth and w ithin-clone spatial dynamics.