Competition and integration in a clonal woody shrub

Several studies have examined plant competition in a clonal context over the past 20 years. Few have done so with woody clonal plants, however, preferring instead to work with herbaceous species. This study examines competition and the physiological integration of a clonal woody species, Vaccinium stamineum, in its natural habitat. This is a woody shrub common in the eastern United States whose primary mode of reproduction is asexual in the southeastern sandhills region. Clones of V. stamineum were either left as natural, integrated units or rhizomes were severed to create the non-integrated treatment group. These integrated and non-integrated clones were subjected to either low or high competition intensities, and their growth and survivorship subsequently measured. The individual ramets were also mapped on a regular basis, permitting a spatial analysis of the expansion or contraction of the clones. This coupling of a spatial component with the growth and survivorship measurements allows for a rigorous comparison of responses of integrated and non-integrated clones under differing competitive environments. Integrated clones produced more new ramets and greater vertical growth on existing ramets than non-integrated clones, at all treatment levels. The level of competition affected the growth and asexual reproduction of the clones, both integrated and non-integrated, but did so asymmetrically, with non-integrated clones experiencing more negative effects. This experiment suggests that, for woody species, integration in clonal plants conveys an advantage in environments with both high and low competition intensities.