AN ABSTRACT OF THE DISSERTATION OF

Tara M. Hudiburg for the degree of Doctor of Philosophy in Forest Science presented on June 14, 2012. Title: Analysis of the Regional Carbon Balance of Pacific Northwest Forests Under Changing Climate, Disturbance, and Management for Bioenergy

Abstract approved:

Beverly E. Law

Atmospheric carbon dioxide levels have been steadily increasing from anthropogenic energy production, development and use. Carbon cycling in the terrestrial biosphere, particularly forest , has an important role in regulating atmospheric concentrations of carbon dioxide. US West coast forest management policies are being developed to implement forest bioenergy production while reducing risk of catastrophic . Modeling and understanding the response of terrestrial ecosystems to changing environmental conditions associated with energy production and use are primary goals of global change science. Coupled carbon-nitrogen process models identify and predict important factors that govern long term changes in terrestrial carbon stores or net ecosystem production (NEP). By quantifying and reducing uncertainty in model estimates using existing datasets, this research provides a solid scientific foundation for evaluating carbon dynamics under conditions of future climate change and land management practices at local and regional scales. Through the combined use of field observations, remote sensing data products, and the NCAR CESM/CLM4-CN coupled carbon-, the objectives of this project were to 1) determine the interactive effects of changing environmental factors (i.e. increased CO2, nitrogen deposition, warming) on net carbon uptake in temperate forest ecosystems and 2) predict the net carbon emissions of West Coast forests under future climate scenarios and implementation of bioenergy programs. West Coast forests were found to be a current strong carbon sink after accounting for removals from harvest and fire. Net biome production (NBP) was 26 ± 3 Tg C yr-1, an amount equal to 18% of Washington, Oregon, and California fossil emissions combined. Modeling of future conditions showed

increased net primary production (NPP) because of climate and CO2 fertilization, but was eventually limited by nitrogen availability, while heterotrophic respiration (Rh) continued to increase, leading to little change in net ecosystem production (NEP). After accounting for harvest removals, management strategies which increased harvest compared to business-as-usual (BAU) resulted in decreased NBP. Increased harvest activity for bioenergy did not reduce short- or long-term emissions to the atmosphere regardless of the treatment intensity or product use. By the end of the 21st century, the carbon accumulated in forest regrowth and wood product sinks combined with avoided emissions from fossil and fire were insufficient to offset the carbon lost from harvest removals, decomposition of wood products, associated harvest/transport/manufacturing emissions, and bioenergy emissions. The only scenario that reduced carbon emissions compared to BAU over the 90 year period was a ‘No Harvest’ scenario where NBP was significantly higher than BAU for most of the simulation period. Current and future changes to baseline conditions that weaken the forest carbon sink may result in no change to emissions in some forest types.

©Copyright by Tara M. Hudiburg June 14, 2012 All Rights Reserved

Analysis of the Regional Carbon Balance of Pacific Northwest Forests Under Changing Climate, Disturbance, and Management for Bioenergy by Tara W. Hudiburg

A DISSERTATION

submitted to

Oregon State University

in partial fulfillment of the requirements for the degree of

Doctor of Philosophy

Presented June 14, 2012 Commencement June 2013

Doctor of Philosophy dissertation of Tara W. Hudiburg presented on June 14, 2012.

APPROVED:

Major Professor, representing Forest Science

______Head of the Department of Forest Ecosystems and Society

Dean of the Graduate School

I understand that my dissertation will become part of the permanent collection of Oregon State University libraries. My signature below authorizes release of my dissertation to any reader upon request.

Tara W. Hudiburg, Author

ACKNOWLEDGEMENTS

First of all, I would like to thank my major professor, Beverly Law, for supporting me and providing the necessary guidance in order for me to complete my degree. Bev’s faith in my ability and her encouragement in my pursuit of a PhD have been essential to my success. I would also like to thank Peter Thornton for patiently teaching me how to become an ecosystem ‘modeler’. I would also like to thank my other committee members, Richard Waring and Dominique Bachelet for their continued support and genuine interest in my research and success. I would like to extend a very special thanks to my peers at OSU and the greater scientific community, especially Sebastiaan Luyssaert for his quantitative assistance and mentorship and Terralyn Vandetta without whom I would never have been able to run a single model simulation on the Linux cluster. Finally, I want to thank my family; my parents, Ron and JoAnne Hudiburg and my husband Kris. Your confidence, support, and encouragement were essential. And last of all, my children Quinlan and Mackenzie, for understanding and patience when I was unable to play with you because I was too busy working on my dissertation. This research was supported by the U.S. Department of Energy Biological and Environmental Research Terrestrial Carbon Program (Award # DE-FG02-04ER64361) and the DOE Global Change Graduate Fellowship. This study is part of a regional North American Carbon Program project. Special thanks to Catharine van Ingen for her assistance with database organization and implementation, and to Microsoft for database design funding through an E-Science grant and a Microsoft Research graduate student internship. We would like to thank the PNW-FIA regional office for their assistance and cooperation in compiling the database and James Sulzman for programming consultation.

CONTRIBUTION OF AUTHORS

For Chapter 2, Tara Hudiburg designed and implemented the study with guidance from Beverly Law and Sebastiaan Luyssaert. Tara Hudiburg, Sebastiaan Luyssaert, and Beverly Law co-wrote the paper and Sebastiaan contributed to parts of the analysis. Christian Wirth provided essential data and methods for the analysis and valuable comments on the manuscript. For Chapter 3, Tara Hudiburg and Beverly Law designed, implemented and co-wrote the paper. Tara Hudiburg did the analysis and Peter Thornton provided guidance and valuable comments on the manuscript. For Chapter 4, Tara Hudiburg designed and implemented the study with guidance from Beverly Law and Peter Thornton. Tara Hudiburg, Sebastiaan Luyssaert, Beverly Law, and Peter Thornton co-wrote the paper.

TABLE OF CONTENTS

Page

Chapter 1: Introduction……………………………………………………… 2

Chapter 2: Regional CO2 implications of forest bioenergy production ……. 9

Chapter 3: Evaluation and improvement of the Community Land Model (CLM 4.0) in Pacific Northwest Forests ………………………………….. 25

Chapter 4: Long-term effects of bioenergy harvest on the carbon balance of Pacific Northwest forests under changing climate and climate-related disturbance 57

Chapter 5: Conclusion……………………………………………………… 104

Bibliography……………………………………………………………… 110

Appendices………………………………………………………………. 122