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|Title:||A simulation model for growth of the submersed aquatic macrophyte hydrilla (Hydrilla verticillata (L.f.) Royle)|
|Authors:||Aquatic Plant Control Research Program (U.S.)|
Best, E. P. H.
Boyd, William A.
|Publisher:||Environmental Laboratory (U.S.)|
Engineer Research and Development Center (U.S.)
Abstract: A simulation model for the biomass dynamics of the submersed macrophyte Hydrilla venicillata (dioecious biotype) is presented. The model HYDRIL is based on carbon flow within a 1-m² water column. It includes several aspects that affect biomass dynamics, such as latitude, seasonal changes in climate, pH and oxygen effects on CO2 assimilation rate at light saturation, wintering strategies, grazing (removal of aboveground and tuber biomass), and mechanical control (removal of aboveground biomass). The characteristics of the community and of the site can be easily modified by the user. HYDRIL incorporates insights into the processes affecting the dynamics of a Hydrilla community in relatively shallow, hard water (0.1- to 2.5-m depth; DIC concentration > 0.8 mmol). It has been calibrated on data pertaining to a Hydrilla community in Lake Orange, Florida. At that site, no aboveground wintering biomass is present and growth starts from the tuber bank. Peak biomass is reached late in August and tuber formation takes place in autumn, replenishing the tuber bank. HYDRIL simulates the dynamics of plant biomass and tuber bank density at Lake Orange well over a period of 1 to 5 years. It has been used to calculate plant biomass and tuber density for .other sites in subtropical (Florida) and tropical (India) areas, where it simulated biomass ranges similar to those measured in the field. Sensitivity analysis shows that peak biomass of a Hydrilla community is most sensitive to changes in photosynthetic activity at light saturation and very sensitive to changes in light-use efficiency. Sensitivity analysis indicates that changes in climate greatly affect the simulated data on peak biomass and, although less, tuber numbers. Peak biomass proved sensitive to changes in water transparency and, to less extent, in water depth, while tuber weights and numbers were not in 1-year simulations. However, simulations indicated that all three parameters were sensitive on a longer term (periods > 1 year). The model can be used as a tool to predict the dynamics of a Hydrilla community over 1- to 5-year periods. Running the model with different parameter values specific for any particular site and/or treatment, e.g., biomass removal to a certain water depth, helps in gaining insight into the predominant mechanisms regulating submersed plant dynamics.
|Rights:||Approved for public release; distribution is unlimited.|
|Appears in Collections:||Technical Report|