SIMULATION OF VEGETATION GROWTH IN RIPARIAN ECOSYSTEMS

Abstract

Land between agricultural production areas and streams can be important for mitigating pollutants reaching water supplies. However, there is little information available on management for effective control of upland runoff of sediment, nutrients, and pesticides. In an effort to provide a decision-making tool for managing stream-side areas, a riparian ecosystem model has been developed to simulate processes of water movement and nutrient dynamics. An important component of this model is the growth of vegetation. The riparian area is divided into three zones parallel to the stream. In the direction of the uplands, each zone represents an increasing level of management intensity. Vegetation is characterized as grass, an herbaceous/shrub mixture, evergreen trees, or deciduous trees. In forested areas, two canopy layers are simulated in competition with each other for water, light, and nutrients. Photosynthates are dynamically allocated to the plant organs and a reserve pool. Litterfall is a function of biomass and phenology. Vegetation serves to reduce water flow into the stream, act as a physical barrier against erosion, provide carbon for nutrient immobilization and denitrification in the soil, and sequester nutrients in the roots and canopy.