Technical Abstract: Landscape scale hydrologic models can be improved by incorporating realistic, process-oriented plant models for simulating crops, grasses, and woody species. The objective of this project was to present some approaches for plant modeling applicable to hydrologic models like SWAT that can affect the accuracy in the simulating several components of the water and nutrient biogeochemical cycles. First, we described some unique aspects of the general plant model ALMANAC. Next, we described how a revised version of the ALMANAC model simulated complex successional changes in forest ecosystems. Finally, we discussed alternative physiological and physical process simulation techniques that could increase simulation accuracy in SWAT-type models.