Clonal integration improves the tolerance of Carex praeclara to sand burial by compensatory response.

A pot experiment was conducted to examine effects of clonal integration on response of rhizomatous sedge Carex praeclara to local sand burial at different depths. In the experiment, we used clonal fragment consisting of four successive ramets. The two proximal ramets (older) and their offspring, referred as the proximal part, remained unburied while the two distal ramets (younger) and their offspring, referred as the distal part, were either unburied (control) or buried by sand at depth of 7, 14 or 21 cm (sand burial treatment). The rhizomatous connection between the proximal and distal parts was either severed or intact. Severing rhizome dramatically decreased survival of the distal part with increasing sand burial depth. Severing rhizome and sand burial had negative effects on plant performance such as biomass accumulation, number of ramets and number of leaves in the distal part. A cost-benefit analysis based on performance measures showed that the proximal part supported its interconnected distal part and did not incur any costs from this resource export. When connected to the distal part subject to sand burial, the photosynthetic efficiency of the proximal part was enhanced with increasing sand burial depth. The results suggest that the compensatory response (such as photosynthetic and photochemical traits) promoted by the mechanism of source-sink feedback regulation might ameliorate negative effects of sand burial on survival and growth of C. praeclara. Clonal integration, which is one of the functionally important consequences of clonal growth, contributes significantly to the species to withstand local sand burial and successfully inhabit in a desertified alpine habitat, Northwest Sichuan plateau, China.