©Copyright 2010 Clinton Stewart Wright Effects of Disturbance and Fuelbed Succession on Spatial Patterns of Fuel, Fire Hazard, and Carbon; and Fuel Consumption in Shrub-dominated Ecosystems Clinton Stewart Wright A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy University of Washington 2010 Program Authorized to Offer Degree: School of Forest Resources University of Washington Graduate School This is to certify that I have examined this copy of a doctoral dissertation by Clinton Stewart Wright and have found that it is complete and satisfactory in all respects, and that any and all revisions required by the final examining committee have been made. Chair of the Supervisory Committee: _______________________________________________________ David L. Peterson Reading Committee: _______________________________________________________ James K. Agee _______________________________________________________ Donald McKenzie _______________________________________________________ David L. Peterson Date: _____________________________________ University of Washington Abstract Effects of Disturbance and Fuelbed Succession on Spatial Patterns of Fuel, Fire Hazard, and Carbon; and Fuel Consumption in Shrub-dominated Ecosystems Clinton Stewart Wright Chair of the Supervisory Committee: Professor David L. Peterson School of Forest Resources A state and transition approach was used to model and map fuelbed, fire hazard, and carbon change under different management and fire regimes for the Okanogan- Wenatchee National Forest in central Washington. Landscape metrics showed different patterns of change over time depending upon the metric considered and the fire and management regime modeled. Fuelbeds characteristic of older forest conditions became more common during the first ~100 years of simulation (coverage increased 5 – 20%), except in those locations where wet forests subject to stand-replacement fire occur (coverage decreased 6 – 12%). In general, mean fuelbed patch size decreased (mean patch size 12 – 18 ha smaller in year 200), and patches of like type became more aggregated (contagion index increased 2 – 4% in year 200) under current and elevated fire and management regimes; absence of management did not cause the same level of change in mean fuelbed patch size. Low fire hazard patches tended to become larger and occupy more of the landscape over time, whereas high fire hazard patches generally became smaller and less common. Management activities had only small effects on mean patch size and landscape class composition; however, simulated management generally produced landscapes with less aggregated patches. The Okanogan-Wenatchee National Forest could be expected to be a sink for carbon, much of it in pools of dead material, for at least ~100 years if the current fire and management regime persists. If, as expected, annual area burned increases, the Forest is likely to become a source of carbon. Management activities that encourage preservation of large, fire-resistant trees could mitigate projected carbon releases if annual area burned increases. Fuel consumption predictions are necessary to accurately estimate fire effects, including pollutant emissions during wildland fires. Fuel and environmental measurements on a series of operational prescribed fires were used to develop models for predicting fuel consumption in big sagebrush (Artemisia tridentata) and pine flatwoods ecosystems. Models predicted independent consumption measurements within 2% (fall) and 5% (spring) for big sagebrush fires, and 8% (dormant season) and 67% (growing season) for pine flatwoods fires. A general model for predicting fuel consumption in shrub-dominated types is also proposed. TABLE OF CONTENTS Page LIST OF FIGURES .............................................................................................................................iii LIST OF TABLES ............................................................................................................................... v CHAPTER 1: INTRODUCTION ......................................................................................................... 1 CHAPTER 2: REVIEW OF LANDSCAPE SUCCESSION MODELS ...................................................... 3 Summary ................................................................................................................................... 3 Introduction .............................................................................................................................. 3 Objective .................................................................................................................................... 4 Model Classifications .............................................................................................................. 5 Methodological ................................................................................................................... 5 Computational .................................................................................................................... 6 Ecological ............................................................................................................................. 7 Modeling Approaches ............................................................................................................. 8 Methods for Simulating Succession ................................................................................. 8 Methods for Integrating Disturbance ............................................................................ 13 Conclusions ............................................................................................................................ 17 CHAPTER 3: EFFECTS OF DISTURBANCE AND FUELBED SUCCESSION ON SPATIAL PATTERNS OF FUEL, FIRE HAZARD, AND CARBON ....................................................................................... 24 Summary ................................................................................................................................. 24 Introduction ............................................................................................................................ 25 Fuel Succession ................................................................................................................. 27 Fuel Mapping .................................................................................................................... 28 Characterizing Fuels ........................................................................................................ 28 Objectives and Questions ..................................................................................................... 31 Methods ................................................................................................................................... 31 Overview ........................................................................................................................... 31 Study Area ......................................................................................................................... 32 Modeling Framework ...................................................................................................... 34 Fuelbed Succession Simulation Experiment ................................................................. 44 Landscape Metrics ............................................................................................................ 45 Carbon Stock ..................................................................................................................... 47 Data Analysis .................................................................................................................... 47 Results ..................................................................................................................................... 49 Fuels .................................................................................................................................... 49 Fire Hazard ........................................................................................................................ 51 Carbon ................................................................................................................................ 54 Discussion ............................................................................................................................... 55 Landscape Composition .................................................................................................. 55 i Landscape Change ........................................................................................................... 58 Landscape Heterogeneity ................................................................................................ 61 Modeling Limitations ....................................................................................................... 64 Implications and Conclusions ......................................................................................... 67 CHAPTER 4: FUEL CONSUMPTION IN SHRUB-DOMINATED ECOSYSTEMS ................................. 86 Summary ................................................................................................................................. 86 Introduction ............................................................................................................................ 86 Prescribed Fire and Big Sagebrush ................................................................................