2020 CSDMS meeting-079

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Transient semi arid ecosystem dynamics using Landlab ecohydrology models

Erkan Istanbulluoglu, University of Washington Seattle Washington, United States. erkani@u.washington.edu

Ecohydrological modeling capacity of Landlab is introduced and illustrated using examples that couple components for local soil moisture and plant dynamics with spatially explicit cellular automaton-based (CA) plant establishment, mortality, fire and grazing. Several key features of arid and semiarid ecosystems are discussed. Coexistence of tree-grass cover on north facing slopes (NFS) and shrub cover on south facing slopes (SFS) in central New Mexico is attributed to the competitive advantage of trees due to their longer seed dispersal range against shrubs in cooler and more moist NFS. Incorporating a rule on the inhibitory effects of shrubs on grasses enhance modeled shrub cover, while both trees and grasses are favored when runon is included in the local soil moisture model. Feedbacks among livestock grazing, grassland fire frequency and size, resource redistribution and woody plant encroachment are investigated using different ecohydrologic model configurations. These feedbacks are manifested in a three-phase woody plant expansion processes in the model, with rates of encroachment controlled by the state transition probabilities in relation to plant susceptibility to fires, grazing, and age-related mortality. A critical area of woody plant emerges in the model with which a negative feedback between fire size and woody plant expansion begins. Our results underscore the need for developing models that emphasize local and non-local plant interactions for modeling transient ecosystems.