ERDC/EL TR-07-14, Carbon-Flow-Based Modeling of Ecophysiological Processes and Biomass Dynamics of Submersed Aquatic Plants

A dynamic simulation modeling approach to describing carbonflow-based, ecophysiological processes and biomass dynamics of freshwater submersed aquatic plant species has been developed. The models describe major, carbon-flow-based ecophysiological processes and biomass dynamics of four common freshwater species and how these are influenced by factors such as light, temperature, current velocity, dissolved inorganic carbon availability, oxygen concentration, and human influences such as management measures (changes in turbidity, mechanical harvesting, grazing, flooding). The model species are Vallisneria americana [model VALLA], Potamogeton pectinatus [POTAM], Hydrilla verticillata [HYDRIL], and Myriophyllum spicatum [MILFO]. These plant species are similar in growth strategy but differ significantly in morphology and physiology. The same modeling approach was followed for all species, with species-characteristic morphology and physiology incorporated in four separate models. V. americana and P. pectinatus are considered as desirable, and H. verticillata and M. spicatum as invasive species in parts of the United States. In the models, phenology is tied to day-degree sum. This enables simulations for different sites and climates facilitating model operation. The models contain unique descriptions of (1) speciescharacteristic vertical distribution of shoot biomass in the water column; (2) recalculation procedures of vertical distribution with daily changes in water level; (3) ibidem with daily removal of shoot biomass at various levels within the water column; (4) species-characteristic epiphytic light interception; (5) species-characteristic effects of current velocity on photosynthesis; (6) removal of periodic shoot and tuber/root crown biomass; and (7) relationships of plant process parameters with site-specific climate by linkage with formatted weather files and calculation of latitude-specific effects on day length. Sensitivity analysis showed that the models are very sensitive to changes in process parameters influencing carbon flow. A good fit was found between simulated and measured biomass in the field. The models can be used to simulate the daily changes in plant processes, biomass, and persistence under various site-specific conditions and management scenarios over a 1to 5-year period of four submersed aquatic vegetation species, in climates varying from temperate to tropical. DISCLAIMER: The contents of this report are not to be used for advertising, publication, or promotional purposes. Citation of trade names does not constitute an official endorsement or approval of the use of such commercial products. All product names and trademarks cited are the property of their respective owners. The findings of this report are not to be construed as an official Department of the Army position unless so designated by other authorized documents. DESTROY THIS REPORT WHEN NO LONGER NEEDED. DO NOT RETURN IT TO THE ORIGINATOR. ERDC/EL TR-07-14 iii