The Effects of Rhizome Severing on the Clonal Growth and Clonal Architecture of Scirpus maritimus

Abstract

Physiological integration is a major component of growth in many clonal plants. However, in many species, integration is disrupted by clone fragmentation due to habitat perturbation and herbivory. The consequences of such clone fragmentation remain poorly studied. The purpose of this paper is to quantify the effects of rhizome severing on ramet size variation, clonal growth and clonal architecture in Scirpus maritimus, a rhizomatous perennial, in which ramet size increases with the successive iterations that occur in each year of growth, causing marked intra-generation ramet-size variability. We first compared the development of a ramet generation, from a single sprouted tuber, either left to grow naturally or artificially severed. Intact clones consisted of ramets of various size and occupied most of the container. Severed clones formed more numerous but smaller ramets, with shorter rhizomes, and remained strongly clumped in the centre of the container. Resource translocation between ramets may promote spatial propagation of S. maritimus clones by successively increasing the size and the colonisation capacity of the late formed ramets. A comparison of the sprouting of one-year-old tubers showed that in intact clones, smaller tubers remained dormant while larger tubers sprouted. In severed clones, all tubers sprouted. The weight of sprouted tubers was significantly correlated with first shoot length, ramet number and total biomass. In the intact clones, resource translocation both from dormant to sprouted tubers and between sprouted tubers may partially buffer the effect of sprouted tuber weight. Release of buds from dormancy, due to rhizome severing, may be an important component of the response to frequent local perturbation and clone fragmentation by herbivore activity in S. maritimus since it will permit rapid re-colonization after such disturbance.