Effects of sand burial in integrated clonal systems of the invasive Carpobrotus edulis

Abstract

ABSTRACT Sand burial represents one of the most common stresses for plant performance in coastal sand dunes. Clonal plants inhabiting sand dunes frequently experience situations in which the sand can bury part of the clone while other modules remain unburied. Here we present a field experiment in a coastal sand dune testing the effect of sand burial in the clonal Carpobrotus edulis. In the experiment, apical ramets were either or not subjected to burial in sand to a depth of 90% ramet height, and connected basal ramets were not subjected to sand burial. Sand burial significantly reduced survival and growth of apical ramets. Interestingly, we found a non-local plastic response in basal ramets that was dependent on the conditions experienced by their apical ramets. Thus, when apical ramets remained unburied a developmentally programmed division of labour was found. In this situation, basal ramets specialized in the acquisition of soil-based resources while apical ramets specialized in aboveground expansion. On the contrary, when apical ramets were subjected to sand burial, basal ramets increased the production of photosynthetic structures. This response could alleviate the light stress suffered by the buried apical ramets. We demonstrate that burial stress suffered by apical ramets of C. edulis triggered a compensatory response in their connected unburied ramets. This result highlights the importance of considering modular plasticity to understand plant responses to sand burial stress.