AN ABSTRACT OF THE THESIS OF Leslie A. Morrissey for the degree of Doctor of Philosophy in Geosciences presented on February, 6,1992. Title: Temporal and Spatial Variability of Methane Emissions from Alaskan Arctic Tundra Abstract approved: Robert E. Frenkel Methane flux was measured from northern Alaska Arctic Coastal Plain wetlands to assess the spatial and temporal variability of Arctic tundra emissions during the summers of 1987 through 1990. Initially, the role of vegetation in the release of methane from substrate to atmosphere was assessed. Methane emissions were shown to be proportional to the foliage surface area and release of methane from plants controlled by the stomata.Daily values of methane emissions and leaf conductance were correlated (r = 0.95). A satellite-derived regional methane flux estimate had 3 to 5 times greater precision than estimates based on direct expansion. Methane emissions from the tundra exhibit high temporal variability at hourly, daily, seasonal, and annual scalesof observation. Daily variabilityin methane emissions was low near the summer solstice and increased through the growing season. Strong seasonal variation in emissions was related to the position of the local water table, the amount of leaf area above the water, and plant phenological development. An interannual comparison of emissionsprovided insight into the local and regional scale responses of Arctic tundra to potential climatic warming. Methane emissions in1989, a warm year,were over three fold greater thanin 1987, a "normal"year. Temperature- dependent increases in methane emissions expected as a result of climaticwarming are projected to exceed increases due to a longer growing season. The potential for strong positive biological feedback exists whereby the enhanced emissions of methane, a greenhouse gas, to the atmosphere may further accelerate rates of regional and global climatic warming. Copyright by LeslieA. Morrissey February 6, 1992 All Rights Reserved Temporal and Spatial Variability of Methane Emissions from Alaskan Arctic Tundra by Leslie A. Morrissey A THESIS submitted to Oregon State University in partial fulfillment of the requirements for the degree of Doctor of Philosophy Completed February 6,1992 Commencement June, 1992 APPROVED: 7 '.. .... 4z e- Professor of Geography in charge of major rtment Geosciences Dean of Graduate School Date thesis is presentedFebruary 6, 1992 Typed by Leslie A. Morrissey ACKNOWLEDGEMENT There are many individuals who have supported my research efforts. Without their support,I would have never completed my studies or research. Dr.Robert Frenkel was always encouraging and enthusiastic, nearly giving his life in pursuit of science during the 1989 field season. I thank Dr. Charles Rosenfeld, Dr. Donald Zobel, Dr. David Thomas and Dr. Anita Grunder for serving onmy thesis committee and for theiradvice and suggestions which contributed to the completion of the thesis. Comments and review of the experimental design and thesisbyDr. Donald Zobel were particularly insightfuland appreciated. Dr. Don Card provided statistical guidance and review. I would like to extend my appreciation to Dr.Gerald P.Livingston for his advice, support, and friendship throughout my enlightenment. I am grateful to Dr. James Lawless and Dr. Diane Wickland who provided both financial and morale support.I also wish to acknowledge B.P. Exploration Inc. for allowing access to sites in the Prudhoe Bay region and providing logistical support. Funding for this research was provided by the Graduate Researchers Program at NASA Ames Research Center and the Interdisciplinary Research Program at NASA Headquarters. TABLE OF CONTENTS I. INTRODUCTION II. REVIEW OF METHANE PROCESSES AND EMISSIONS Methane Processes Controlling Environmental Factors Methane Emissions from Tundra Ecosystems III. OBJECTIVES AND APPROACH IV. STUDY REGION Climate and Permafrost Topography and Soils Arctic Tundra Vegetation V. GENERAL METHODS AND MATERIALS Site Selection Methane Flux Measurements Field Methods Laboratory Analyses Analytical Methods VI. CONTROLLING MECHANISM FOR RELEASE OF METHANE FROM PLANTS Plant Pathways Site Description Experimental Design Field Methods Leaf Conductance Results Experiment I Repeated Measures Experiment II Time Course Experiment III Antitranspirant Experiment IV Enclosure Discussion Comparison with Previous Stomatal Manipulation Studies Implications for Future Studies VII. ROLE OF LEAF AREA IN RELEASE OF METHANE Methods and Experimental Design Results Discussion VIII. SATELLITE-DERIVED LEAF AREA ESTIMATES Background Experimental Design and Methods Results Discussion IX. REGIONAL ESTIMATION OF METHANE FLUX Background Data Base Analysis and Results Direct Expansion Estimate LAI-based Estimate Discussion X. TEMPORAL TRENDS IN METHANE EMISSIONS Diurnal Trends Methods and Experimental Design Results Daily Trends Seasonal Trends Site Description Methods Results Abiotic Controls Interaction of Water Table and Leaf Area Discussion XI IMPLICATIONS FOR CLIMATIC WARMING Interannual Comparison Observational Background Results Growing Season Length Results and Discussion XII. SUMMARY AND CONCLUSIONS REFERENCES APPENDIX LIST OF FIGURES Figure Page 1. Key research topics and experiments (by 13 Chapter) of this dissertation. 2. North Slope of Alaska with the Prudhoe Bay 21 studyareahighlighted. 3. The Arctic Coastal Plain, west of Prudhoe 25 Bay, Alaska. 4. Relationship between leaf conductance and 48 methane flux for taiga Carex sites measured from June 10 - 18, 1990. Values represent the mean and standard error determined from replicate measurements from three sites.From lower left to upper right, the values represent observations on June 10, 11, 17, 18, and 16, respectively. 5. In situ relationship of leaf conductance 50 (mean and standard error of the mean) over time, following foliage enclosure in an opaque chamber. 6. Experimental design for the clipping 71 experiments. In the firstexperiment (a), following clipping the remaining plants consist of intact leaves and stems. In the second experiment (b), the inner air spaces of the leaves and stems were exposed to the atmosphere following clipping of the tops of the plants. Repeated measurement of methane emissions 72 following systematic reduction of foliage with leaves of remaining plants left intact. Two curvilinear relationships relating flux and leaf area index are evident. Repeated measurement of flux following 74 systematic clipping of the tops of the foliage exposing the inner air spaces of the aerenchyma tissue of the plant to the atmosphere. Relationship between leaf area and 95 satellite radiance for Landsat MSS band 2(a),3(b), and 4(c). Relationship between leaf area index and 97 satellite-derived NDVI values calculated from Landsat MSS bands 2 and 3. Image of NDVI values for the Prudhoe Bay 98 region showing the amount of vegetation ranging from dark unvegetated areas to white areas with high leaf area index values. 12. Diurnal trend of methane emissions for the summer solstice on June 25-26, 1989 (a); corresponding air temperature (b); and solar radiation (c). Site 1 is unvegetated; sites 2-4 are vegetated. 13. Diurnal trend of leaf conductance for August 13 - 14, 1989 at Prudhoe Bay, Alaska. 14. Location of seasonal sites at Prudhoe Bay, Alaska. 15. Seasonal trend in methane emissions (a), soil temperature at 10 cm depth (b), and thaw depth (c) for the nine seasonal sites at Prudhoe Bay (plotted as mean and standard error of the mean). 16. Relationship between methane emissions and leaf area index for nine seasonal sites (including one outlier, 52W). 17. Relationship between methane emissions and LAI near the summer solstice (June 25-26, 1989) and at peak growth (August 9, 1989) based on diurnal and seasonal data respectively. 18. Methane emissions (a), water table position above surface (b), and precipitation (c)for the seasonal sites grouped by anaerobic (solid line) and aerobic substrate (dashed line). Standard error of the mean shown by error bars. 19. Relationship (r = 0.85) between methane 150 emissions and soil pH at 10 cm depth for seasonal sites at Prudhoe Bay, Alaska. 20. Relationship between methane emissions and 151 soil temperature at 10 cm depth for seasonal sites at Prudhoe Bay, Alaska. A linear relationship is evident for the five anaerobic sites (+), but not for the four intermittently aerobic sites (o). 21. Relationship between methane emissions 155 and leaf area for nine seasonal sites including an adjusted leaf area for site 52W based on foliage area exposed above the water surface. 22. Summer temperature regimes for Prudhoe 162 Bay, Alaska. Seasonal temperature trends (a) and cumulative temperature above 0°C (b). A "normal" year is represented by 1987 while 1989 represents a warm year. LIST OF TABLES Table Page 1. Methane fluxes from Carex spp. before and 51 following antitranspirant application at Prudhoe Bay and Fairbanks sites. 2. Methane fluxes from Carex aauatilis before 55 and after a two hour enclosure in an opaque chamber. 3. Leaf conductances of Carex aauatilis before 56 and after a two hour enclosure in an opaque chamber. 4. Landsat MSS post calibration values for 89 dynamic ranges, after Markham and Barker (1986). 5. Radiance and NDVI values for MSS data 92 related to average one-sided leaf area index. 6. Summary statistics for field-determined 93 one-sided green leaf area and NDVI sites at Prudhoe Bay, Alaska. 7. Summary of relationships between one-sided 94 green leaf area index and Landsat Multispectral Scanner (MSS) radiance