Interspecific competition promotes root foraging of a clonal plant via physiological integration

Abstract Root foraging is a common response of plants to heterogeneous soils. Individuals (ramets) of clonal plants are often connected, allowing resource and signal sharing, and thus cooperative responses to environmental heterogeneity. However, it remains unknown how intraspecific and interspecific competition on a ramet influences root foraging of its connected ramet in heterogeneous soils. We grew a younger ramet of the stoloniferous herb Fragaria pentaphylla either in a heterogeneous environment consisting of high- and low-nutrient soil patches or a homogeneous environment containing an even mixture of the two soils, and its connected older ramet in a homogeneous, high-nutrient soil. The older ramet grew alone or with a ramet of the same or a different species (Duchesnea indica, Hydrocotyle sibthorpioides, or Centella asiatica). Regardless of competition, the younger ramet of F. pentaphylla exhibited root foraging in the heterogeneous soil, with a stronger response when its older ramet grew with C. asiatica than when it grew alone. However, growing with other species did not influence root foraging. Root, shoot, and total mass of the younger ramet and the whole clone of F. pentaphylla were higher in the heterogeneous than in the homogeneous soil when the older ramet grew with D. indica or H. sibthorpioides, but such effects disappeared when it grew alone, or with F. pentaphylla or C. asiatica. Our findings suggest that interspecific competition can promote root foraging of clonal plants in heterogeneous soils, but such an effect is context-dependent and not necessarily associated with performance promotion.