ARCHIVED CONTENT: In December 2020, the CZO program was succeeded by the Critical Zone Collaborative Network (CZ Net) ×


Models developed, or co-developed, by Calhoun CZO PIs have direct application to CZ function.  These include the Penn State Integrated Hydrologic Model (PIHM), the Maximum Entropy Production model (MEP), and Soil Organic Carbon, Erosion, Replacement, and Oxidation model (SOrCERO).  Other models, previously used by Calhoun CZO PIs, include the Distributed Hydrology Soil-Vegetation Model (DHSVM), and Triangulated Irregular Network (TIN)-based Real-time Integrated Basin Simulator with VEGetation Generator for Interactive Evolution (tRIBS-VEGGIE).


The CHILD model is widely used for the simulation of landscape evolution.

CN reforest dynamics

Coupled dynamics of tree and soil C and N during reforestation following land abandonment
Calhoun reforestation was unique: 30% biomass was lost after age 35. Models are used to explore explanations of this behavior.

Dynamic Persistence

Dynamic Persistence of Alternative States
Following disturbance, ecosystems start recovering along trajectories that will eventually lead to a stable state.

Optimal Sensing

Topographically-derived spatial soil moisture model and application to optimal sensor location
A topographically-explicit soil moisture model is developed and applied to cluster watershed into homogeneous sampling regions

Plant-soil feedback

Bistable plant-soil dynamics and biogenic controls on the soil production function
A coupled soil-plant model was developed, exhibiting bistability driven by positive feedback between vegetation and soil.


tRIBS Model
tRIBS (TIN-based Real-Time Integrated Basin Simulator) is a fully distributed physically-based hydrologic model.


Triangulated Irregular Network-based Real-time Integrated Basin Simulator-Erosion and C Oxidatition
Spatially- and depth-explicit physically-based model of hydro-geomorphic processes and of soil organic carbon dynamics.