MODELING RESOURCE-ALLOCATION IN POTAMOGETON-PECTINATUS L

In the present study, a simulation model of the life cycle of Potamoge ton pectinatus L. (sage pondweed) is presented to analyze the implicat ions of resource allocation for longterm survival. The model is calibr ated on field observations of P. pectinatus. The model is simple and c an be used as a tool to improve understanding of the dominant mechanis ms in resource allocation and long-term survival. The model is used to test the hypothesis that the resource allocation to the tubers at low er photon flux density increases and that, consequently, sloughing of the vegetation is enhanced. Simulations indicate that the increased re source allocation to the tubers under low photon flux density can expl ain the observed biomass development and tuber bank size adequately at various light conditions in Lake Veluwe in The Netherlands. Only at t he highest shading was the calculated production much lower than the a ctual production. Apparently, other mechanisms, such as an increase in photosynthesis with increased tuber formation, are involved. An incre ase in the resource allocation to tuber production under low photon fl ux density led to a lower biomass of the vegetation during the growing season, but seems an appropriate strategy in terms of reproductive ou tput and long-term survival of the population.