Overview of the SALUS (Systems Approach to Land Use Sustainability) Model Development

Paustian, K.

Presented at the All Scientist Meeting (1998-07-21 to 1998-07-22 )

The SALUS model is designed to simulate agroecosystem dynamics, including plant growth and development, soil water and heat flux and soil organic matter and nutrient fluxes, over short (growing season) to medium (several decades) time horizons. Its development was prompted by the need for an improved analysis of ecosystem responses to management and climate perturbations in complex cropping systems, including the opportunity to simulate many “non-conventional” management regimes. A major objectives has been to combine the attributes of daily-based functional crop growth models (e.g. CERES) with those of detailed biogeochemical models (e.g. Century) in order to represent both fine-scale, within season variability in plant, water and nutrient dynamics as well as longer-term feedbacks between management, soil characteristics and productivity. The project is a collaboration between investigators at Michigan State University (MSU) and Colorado State University (CSU).The model was written in Fortran-90, which affords a number of technical advantages including better ‘encapsulation’ of program components, availability of complex data structures and explicit pointers and dynamic memory allocation. These attributes facilitate a more modular design compared to Fortran-77 based models and dynamic memory allocation allows several cropping systems to be run simultaneously, for example, spatially distributed applications linked through GIS.Major enhancement over antecedent models (CERES, Century) include multi-year simulations of crop growth using generic structures parameterized for specific species and varieties, a ‘full’ plant C balance including root turnover, exudation and respiration, simulation of soil organic matter and nutrient turnover through the entire profile, ‘time-to-ponding’ concepts to represent effects of within day variability of precipitation intensity effects on runoff and water balance, and an enhanced set of management options. A prototype graphical program has been developed to manipulate and plot model output.The model is currently running on UNIX, PC and Mac platforms. Model testing is underway, utilizing a variety of data from the KBS-LTER and other data from KBS experiments. We plan to complete this first comprehensive testing of the model in 1998, to be followed by submission of a paper describing and documenting the model, and additional collaborative papers using the model for interpretation and analysis of data from the LTER and other KBS experiments. Following completion of these analysis, we will conduct a cross-site application of the model for a set of long-term agricultural field experiments across the US to investigate interactions between management, crop growth and soil organic matter dynamics. Future objectives on which limited work has begun include incorporation of phosphorus dynamics and development of a user-friendly graphical user interface.SALUS Modeling Group: Brian Baer (MSU), Rodolfo Delgado (CSU), Aris Gerakis (MSU), Kendrick Killian (CSU), Keith Paustian (CSU), Joe Ritchie (MSU), Urs Schultress (MSU)Return to Contents

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