Abstract:

Plants can benefit from heterogeneous environments via disproportionately increasing resource harvesting in resource-rich patches. Their initial growing positions with respect to resource patches may thus have important influences on their performance and relative competitive ability. Such impacts may differ between species with contrasting spatial architectures. However, the potential influence of initial growing positions in heterogeneous environment on plant growth and competition has largely been ignored.

We grew the phalanx plant Carex neurocarpa and the guerrilla plant Bolboschoenus planiculmis alone or in competition in a heterogeneous environment consisting of high- and low-nutrient soil patches. In treatments without competition, one ramet of each species was grown in either a high- or a low-nutrient patch in the heterogeneous environment. In treatments with competition, a ramet of the target species was grown in either a high- or a low-nutrient patch, and a ramet of the competitor species was grown in the same patch as the target species or an adjacent patch with a different nutrient level.

Without competition C. neurocarpa produced more biomass and ramets when initially grown in a high-nutrient patch than when initially grown in a low-nutrient patch. With competition, these differences disappeared. Consequently, competitive intensity on C. neurocarpa was higher when it initially grew in a high-nutrient patch than when it initially grew in a low-nutrient patch. These impacts were independent of the initial position of its competitor. By contrast, the initial positions of B. planiculmis did not influence its growth or competitive response. Therefore, in heterogeneous environments, initial growing positions of clonal plants may influence their performance in competition-free environments and may also affect their relative competitive ability, and these effects may depend on spatial architecture of the plants.

Key words: clonal plant,  competition,  environmental heterogeneity,  guerrilla,  patchy environment,  phalanx