Towards a better understanding of the role of rhizomes in mature woody plants: the belowground system of Quercus coccifera

摘要

Key message Vegetative regeneration and horizontal spreading, supported by a large bud bank dependent on rhizome length, are specific functions of Quercus coccifera rhizomes, while anchoring and storing reserves are also root functions. The ability to reproduce vegetatively through rhizomes has mainly been ignored in woody species and the roles attributed to them are little documented, despite their importance at the ecological level. In this study, the author provides basic information on the rhizomatous species Quercus coccifera. Specifically, three plots from a Mediterranean basin garrigue dominated by Q. coccifera were excavated to a depth of 30 cm. Their belowground components and spatial distribution were described, and the belowground biomass, starch concentration, specific root and rhizome lengths and bud density were measured according to five diameter classes. A conspicuous, dense network of rhizomes comprised the greater portion of the total belowground biomass (68%) but the lower portion of its total length (39%), with a corresponding abundant presence of large rhizomes and a greater length of fine roots. The roots had the higher mean starch concentration, but within the five diameter classes, neither the starch concentration differed between roots and rhizomes nor did the specific length of the roots and rhizomes differ for any of the diameter classes. The rhizomes had a high bud density, which depends on their growth in length. In conclusion, along with the roots, the rhizomes play a significant role in anchoring Q. coccifera to the soil and storing reserves. Moreover, the high bud density found in rhizomes supports their specific function in vegetative regeneration, while also highlighting the bud bank's dependence on rhizome growth in length and thus its role in plant horizontal spreading.