Integration of Unified Plant Growth Model (UPGM) into the Wind Erosion Prediction System (WEPS)

The goals of the Unified Plant Growth Model (UPGM) project are to: 1) integrate into one platform enhancements from multiple EPIC-based plant growth models, 2) further enhance the integrated UPGM model, and 3) develop a component that can be more easily linked into other agroecosystem models. Objective 3 will be covered here, specifically the development and integration of a complete UPGM module into the Wind Erosion Prediction System (WEPS). The overall design of the integrated UPGM component in the context of WEPS is presented, focusing on the need to better represent the major plant phases and growth stages within typical agricultural crops using a data-driven representation. The UPGM module was developed using object-oriented constructs available in the FORTRAN language, aiding in its modular design. This facilitates easier integration into other models and allows for future migration of the code to other languages. The incorporation of UPGM into WEPS is expected to provide more accurate plant growth simulations and thereby better predict wind erosion and hydrology effects. Development of the modular UPGM component in WEPS shows promise for incorporation into other agroecosystem models, providing greater opportunity for scientists to improve or add specific algorithms in their areas of interest. For integration with any model, a plant data structure defines mass, geometry, growth, reporting and database parameters for the growing crop and mass and decomposition parameters for crop residue. Each time a crop is planted, a new plant data structure is created, and updated daily by crop growth and residue decomposition until the total plant mass falls below a minimum threshold, at which time the data structure is destroyed. For models that do not require a full definition as defined in this structure, a model specific interface routine would need to be defined to return the exact values needed by the model. The UPGM crop growth process consists of the following: preprocesses which set values for parameters needed by growth phase processes as they progress through the growth season; a series of ordered named growth phases, using selected growth phase processes to best model the type of plant being grown; a growth routine which partitions plant biomass into root, stem, leaf and reproductive mass pools and plant geometry based on the input parameters output by the current growth phase process. Currently defined preprocesses - growing degree days, winter hardening, vernalization, chill units, cold days, freeze damage, temperature stress, warm days, and leaf and stem area changes from management; trigger conditions are checked for leaf off/leaf on, regrowth of annuals, perennials, bi-annuals and woody plants, and beginning of spring for winter annuals. Currently defined growth phase processes are: PhenologyMMS_Germination, PhenologyMMS_ShootGRG, PhenologyMMS_Basephenol, PhenologyMMS_Springphenol, PhenologyMMS_Fallphenol, WEPS_DeciduousWood, WEPS_EvergreenWood, and WEPS_ShootGrow.