Hurley Pasture Model

About the HPM

The Hurley Pasture Model is a dynamic, process-based model of carbon and nitrogen inputs, cycling and fate in cool temperate grassland. It covers plants, animals, and soils and their interaction. It simulates the responses of temperate grasslands to the environment (eg light, temperature, daylength, rainfall, CO₂) and to management (eg fertiliser input, supplements, irrigation, cutting/grazing, stock numbers and animal physiological type). It contains a plant/soil water submodel of the physics and biology of water movement. A thorough description of the original structure of the model can be found in Thornley (1998) Grassland Dynamics: an ecosystem simulation model, CAB International (view attached). Some major updates and developments have been made since that date, and these are incorporated, and annotated, in the HPM.csl programme (see link below). A list of all the kinds of processes covered by HPM is included at the start of the programme. A precis of the background and ‘provenance’ of the model (with references), and a recent example of its application, can be found in Parsons et al (2016) CAB Reviews*.

The model rigorously and dynamically tracks the rates of inputs and outputs/fate of both the C (carbon) and N (nitrogen) cycles, and the resulting C and N ‘states’ (eg organic matter sequestration and mineral ‘N, C’ pools) on a time scale from diurnal, to centuries. Outputs and responses to changes in environment or management, or in the biological traits of plants, large animals, and soil organisms, can be studied both in the short-term, in which case many responses will be transient, or longer term, as the responses move toward new sustainable, dynamic steady states. This is only made possible by the level of detail at which the model operates.

* Parsons, A.J., Thornley, J.H.M., Rasmussen, S. & Rowarth, J. S. (2016) Some clarification of the impacts of grassland intensification on food production, nitrogen release, greenhouse gas emissions and carbon sequestration: using the example of New Zealand. CAB Reviews: Perspectives in Agriculture, Veterinary Science, Nutrition and Natural Resources,2016, 11, No. 054.doi:10.1079 / PAVSNNR201611054.

Access to the HPM program/code

The source code for the Hurley Pasture Model is available for educational and research purposes. Please see Technical details, before downloading from the menu.