Publications by R.H. Gardner

Understanding global fire dynamics by classifying and comparing spatial models of vegetation and fire

Wed, 02 May 2007

Comparison of the sensitivity of landscape-fire-succession models to variation in terrain, fuel pattern, climate and weather

Tue, 20 Jun 2006

The purpose of this study was to compare the sensitivity of modelled area burned to environmental factors across a range of independently-developed landscape-fire-succession models. The sensitivity of area burned to variation in four factors, namely terrain (flat, undulating and mountainous), fuel pattern (finely and coarsely clumped), climate (observed, warmer & wetter, and warmer & drier) and weather (year-to-year variability) was determined for four existing landscape-fire-succession models (EMBYR, FIRESCAPE, LANDSUM and SEM-LAND) and a new model implemented in the LAMOS modelling shell (LAMOS(DS)). Sensitivity was measured as the variance in area burned explained by each of the four factors, and all of the interactions amongst them, in a standard generalised linear modelling analysis. Modelled area burned was most sensitive to climate and variation in weather, with four models sensitive to each of these factors and three models sensitive to their interaction. Models generally exhibited a trend of increasing area burned from observed, through warmer and wetter, to warmer and drier climates with a 23-fold increase in area burned, on average, from the observed to the warmer, drier climate. Area burned was sensitive to terrain for FIRESCAPE and fuel pattern for EMBYR. These results demonstrate that the models are generally more sensitive to variation in climate and weather as compared with terrain complexity and fuel pattern, although the sensitivity to these latter factors in a small number of models demonstrates the importance of representing key processes. The models that represented fire ignition and spread in a relatively complex fashion were more sensitive to changes in all four factors because they explicitly simulate the processes that link these factors to area burned.

A classification of landscape fire succession models: Spatial simulations of fire and vegetation dynamics

Fri, 24 Sep 2004

A classification of spatial simulation models of fire and vegetation dynamics (landscape fire succession models or LFSMs) is presented. The classification was developed to provide a foundation for comparing models and to help identify the appropriate fire and vegetation processes and their simulation to include in coarse scale dynamic global vegetation models. Other uses include a decision tool for research and management applications and a vehicle to interpret differences between LFSMs. The classification is based on the four primary processes that influence fire and vegetation dynamics: fire ignition, fire spread, fire effects, and vegetation succession. Forty-four LFSMs that explicitly simulated the four processes were rated by the authors and the modelers on a scale from 0 to 10 for t their inherent degree of stochasticity, complexity, and mechanism for each of the four processes. These ratings were then used to group LFSMs into similar classes using common ordination and clustering techniques. Another database was created to describe each LFSM using selected keywords for over 20 explanatory categories. This database and the ordination and clustering results were then used to create the final LFSM classification that contains 12 classes and a corresponding key. The database and analysis results were used to construct a second classification key so managers can pick the most appropriate model for their application based on computer resources, available modeling expertise, and management objective.

Strategy for a fire module in dynamic global vegetation models.

Tue, 18 May 2004

Strategy for a fire module in dynamic global vegetation models

Michael Fosberg, Wolfgang Cramer, Victor Brovkin, Rich Fleming, Robert Gardner, Malcolm Gill, Johann Goldammer, Robert Keane, Peter Koehler, Jim Lenihan, Ron Neilson, Stefen Sitch, Kirsten Thornicke, Sergey Venevski, Michael Weber and Uwe Wittenberg

A series of experimental fires was conducted to document point-source fire growth burning on full-tree harvested jack pine (Pinus banksiana Lamb.) sites with a feathermoss (Pleurozium schreberi (B.S.G.) Mitt.) duff layer. Results showed that the time for any of the fires to reach equilibrium spread rates was constant despite the fuel moisture codes and fire behavior indices of the Canadian Forest Fire Weather Index (FWI) System calculated at the time of the fires. Two relationships were developed (linear and nonlinear) for average (wind lulls included) and peak wind conditions. The linear prediction for peak wind conditions estimates that equilibrium spread rates may be achieved as quickly as 22.3 minutes after ignition. The fire depended upon a continuous feathermoss duff layer, and not the slash fuel component, for its spread. Hydraulic (moisture dependent) and thermal properties of the feathermoss surface layer contributed to the rapid drying experienced even after large amounts of precipitation had fallen.