Clonal architecture and patch formation of Potamogeton perfoliatus L. : in response to environmental conditions

Keywords submersed macrophyte, P. perfoliatus, clonal architecture, spatial growth, shoot density, rhizome, biomass allocation, growth plasticity, foraging, allometry, sediment, porewater, nutrients, fertilization, clonal integration, individual-based model, Lake Constance Clonal growth governs the aboveground growth pattern of submerged clonal macrophytes. The research project provides detailed data on the architectural growth rules of Potamogeton perfoliatus L. (perfoliate pondweed) such as rhizome spacer lengths, biomass allocation, branching frequencies, branching angles, as well as maps of rhizome networks and their seasonal development in Lake Constance. Besides architectural reasons, the causes for different sizes and shapes of P. perfoliatus patches are dependent on nutrients, light conditions, and clonal integration. Branching was positively related to both irradiation and nutrient supply. Rhizome spacer lengths were negatively related to nutrient supply and positively related to irradiation. Rhizome allocation tended to increase with irradiation and shoot allocation tended to decrease with irradiation. Root allocation was higher at low nutrient supply. Clonal growth was further complicated because the species showed complex sharing of of resources between older and younger ramets, aiming at optimal resource partitioning. We present an individual-based clonal model which is able to simulate seasonal growth of Potamogeton patches. Furthermore, it shows that architectural growth affects patch characteristics: both rhizome spacer lengths and growth of rhizome axes relative to those in the previous year considerably determine patch density and patch expansion rates. All results on clonal architecture are discussed in the light of foraging theory and allometric rules.