AN ABSTRACT OF THE THESIS OF Hio Peter Eilers III for the degree Doctor of Philosophy (Name of Student) Degree) in Geography presented on November 16, 1974 (Major Department) (Date) Title: PLANTS, PLANT COMMUNITIES, NET PRODUCTION AND TIDE LEVELS: THE ECOLOGICAL BIOGEOGRAPHY OF THE NEHALEM SALT MARSHES, TILLAMOOK COUNTY, OREGON Abstract approved: Robert E. Frenkel Nehalem Bay is located on the northern coast of Oregon in Tillamook County and contains approximately 243 ha of salt marsh. The Nehalem marshes occur as islands and land-tied units. West Island is the largest marsh island with an area of 82.9 ha and a maximum eleva- tion of 3.079 m above mean lower low water. Three divisions on West Island based on inundation period have been identified: intertidal marsh, below mean high water; transitional marsh, from MHW to 2.76 m above MLLW; and extratidal marsh, above 2.76 m. West Island may be further subdivided into four topographic units based on the steepness of the elevation gradient: edge marsh, from.the lower margin to 2.00 m; low marsh, 2.00 to 2.36 m; transitional marsh, 2.36 to 2.76 m; and high marsh, 2.76 m and above. Creek density is low for the lower intertidal marsh, for the edge marsh, and.for the higher extratidal marsh; and is high for the upper intertidal and transitional marsh. Salt marsh vegetation-on West Island was sampled by harvesting above- ground biomass along seven transects at two-month intervals from May of 1972 to September of 1972. Plant species diversity increases with elevation and each species displays a particular elevation range. Analysis of dry-weight data by an ordination routine suggests the presence of 11 plant communities along the elevation gradient on West Island. Plant communities named by dominant species are Triglochin, Scirpus, Carex (tall and short phases), Carex-Deschampsia-Triglochin, Triglochin-Deschampsia, Carex-Deschampsia-Triglochin-Agrostis, Juncus- Agrostis, Juncus-Agrostis-Festuca, Aster-Potentilla-Oenanthe, Carex- Aster-Oenanthe, and Picea-Salix. Plant communities are readily identified by signatures on aerial photographs. Net aerial production on West Island increases with elevation and varies from a minimum of 518 g/m2/yr for the Triglochin community to a maximum of 1936 g/m2/yr for the Aster-Potentilla-Oenanthe community. The community mean net aerial productivity is 1388 g/m2/yr. More than 90 percent of the intertidal marsh net aerial production is removed to the estuary as organic detritus, and net aerial production in the high marsh is rapidly incorporated into marsh soil. It is estimated that approxim- ately 56 percent of all net aerial production on West Island is transported to the estuary by the tides. It is recommended that salt marshes be preserved in their natural state and new salt marshes be created to ensure the continued high productivity of estuarine ecosystems in Oregon. Plants, Plant Communities, Net Production and Tide Levels: The Ecological Biogeography of the Nehalem Salt Marshes, Tillamook County, Oregon by Hio Peter Eilers III A THESIS submitted to Oregon State University in partial fulfillment of the requirements for the degree of Doctor of Philosophy June 1975 APPROVED: Professor of Geography in charge of major Head of Department of Geography Deanof Graduate School Datethesis is presented November 16, 1974 Typed by Kay Eilers for Hio Peter Eilers III ACKNOWLEDGMENTS I am grateful to those who have supplied information, exchanged ideas, and provided support at various stages in the completion of this study. I would especially like to thank Dr. Robert E. Frenkel for his guidance, encouragement, and insight from the inception of this work. Also, I would like to acknowledge Dr. David McIntire for his assistance with species diversity measures, Dr. Roderic Mitchell for aid in the implementation of the SIMORD program, and John Casad for donating his time and airplane for aerial reconnaissance. Many others were also very helpful including Gordon Newman, Roy Sunquist, and Alice Parker at the Portland District Corps of Engineers; Eleanor Wimber, Frank Knight, and Oscar Klein at Nehalem; and Mark Harbert and Stanley Hamilton at the Division of State Lands. Above allI would like to express gratitude to my wife Kay who has been an able assistant in the field, typist, critical reviewer of draft copy, and an endless source of encouragement. This study was supported in part by the Oregon Division of State Lands and the National Science Foundation. TABLE OF CONTENTS I. INTRODUCTION 1 Scope and Objectives 1 The Salt Marsh as a Study Area 2 Location 2 Development and Drainage 3 Floristics 4 Zonation 6 Ecosystem Structure and Function 8 World Classification 10 II. SURVEY OF NORTH AMERICANCOASTAL SALTMARSHES 16 Coastal Salt Marshes of Eastern North America 16 Nova Scotia and Eastern Canada 16 New England to New Jersey 17 Southeastern and Gulf Coasts 18 Coastal Marshes of Western North America 20 Pacific Coast Spartina Marshes 22 North Pacific Coast Marshes 38 Summary of Pacific Coast Salt Marsh Literature 48 Selection of the Study Area 49 III. THE STUDY AREA AND ENVIRONMENTAL FACTORS 51 General Description. 51 Location 51 HumanSettlements 51 NehalemMarshes 54 Ownership 55 Climate 56 NehalemRiver 59 Geology 62 Non-Marsh Vegetation 63 Chronological Changes in Marsh Morphology 63 The 1891 Chart 64 The 1914 Survey 67 The Second Navigational Chart 68 Diking and Grazing 72 Changes 1939 to 1972 73 Progradation and Retrogradation 1939 to 1972 82 Marsh Topography 90 Survey and Hypsometric Map of West Island 90 Topographic Units on West Island 91 The Tides 101 GeneralNature and Available Data 101 Observed Versus Predicted Tide Levels 103 Tidal Surfaces on West Island 107 TABLE OF CONTENTS (cont.) Inundation and Exposure Periods 109 Significance to the Distribution of Salt Marsh Plants 109 Inundation Periods 110 Exposure Periods 115 Sediments and Soils 120 Sediment Sources and Sedimentry Processes 120 Sediments and Soils on West Island 122 Water Salinity 144 Sampling 144 Seasonal Contrasts 144 Depressions on West Island 146 Hydrology 147 Creek System Development 147 Channel Migration and Terrace Development 148 Classification of Creek Systems 149 Drainage Pattern and Subdivisions on West Island 149 Creek Morphology and Hydraulic Geometry of West Island 152 Creek Channels and Tidal Submergence on West Island 159 III. SALT MARSH VEGETATION ON WEST ISLAND 162 Area Versus Gradient Approach 162 Vegetation Study in General 162 Previous Investigations of North American Pacific Coast Salt Marshes 164 Basis for the Present Study 164 Methods of Vegetation Data Collection 165 Location of Transects and Sample Points 165 Sample Quadrat Size 167 Plot Sampling and Laboratory Procedure 168 Vegetation Data Analysis and Results 174 Individual Species and Stands 174 Plant Communities 206 Net Production 262 Determining Net Productivity 266 Net Productivity in the West Island Marsh 267 Fate of Net Aerial Production 306 Determining Disappearance of Net Aerial Production 307 Disappearance of Net Aerial Production and Elevation 309 Disappearance of Net Aerial Production and Plant Communities 314 V. DISCUSSION 316 Plant Succession 316 A Model for Salt Marsh Progradation and Vertical Accretion 317 TABLE OF CONTENTS (cont.) IV. SUMMARY AND CONCLUSIONS 321 Summary 321 Conclusions 323 Elevation and Associated Tide Levels 323 Plant Communities and Photographic Signatures 324 Developmental History Since 1875 324 Value of Salt Marshes at Nehalem Bay 324 VII. EPILOGUE 326 Implications of the Study for Management 326 Preservation 326 Conservation 327 Creation of New Marsh 328 Areas of Needed Research 331 REFERENCES 333 APPENDICES I--Area, Disturbance and Disturbance Rating for Oregon Coastal Salt Marshes 353 II--Species Dry Weight and Cover for Stand Sampling Locations in the West Island Salt Marsh, Nehalem Bay, Oregon 356 III--Selected Computer Maps of West Island, Nehalem Bay, Oregon 363 LIST OF TABLES Table Page 1 World classification of salt marshes (compiled from Champman, 1960). 12 2 Mean daily temperatures for summer (July-September) and winter (January-March) and mean annual rainfall for selected stations on the Pacific Coast of North America. 23 3 Vertical distribution of dominant salt marsh species in Palo Alto, California; elevation in feet above mean lowerlow water (after Hinde, 1954). 34 4 Plant species reported by Johannessen (1962), MacDonald(1967:151), and Stock (1972:22) for Oregon salt marshes. 42 5 Average salinity, average pH and plant species of the five mosquito habitats identified by Frohne (1953). 47 6 Area and percent of total area of salt marsh units in NehalemBay, Oregon. 55 7 Meanmonthly temperature and precipitation for Astoria, Seaside, andTillamook, Oregon (data from United States Environmental Data Service, 1967). 57 8 Aerial photographic coverage of the Nehalem salt marshes: C) Chickering Co., Eugene, Oregon; E) U.S. Army Corps of Engineers, Portland District; S) U.S.D.A. Soil Conservation Service; T) taken in conjunction with the present study (vertical and obligues); TC) Oregon Tax Commission, Salem, Oregon. 75 9 Topographic units on West Island, Nehalem Bay, based on discontinuities in the elevation gradient. Ele- vational range is in reference to MLLW. 95 10 Maximum annualexposure periods and exposure zones for elevations above MLLW in the Nehalem marshes, Nehalem Bay, Oregon (calculated from predicted tide levels for Brighton, Oregon; from N.O.A.A., 1972). 118 LIST OF TABLES(cont.) Table Page 11 Description of soil samples collected at various elevations on West Island, Nehalem Bay; October 2, 1972 (measurement in meters; Munsell color notation is for moist condition). 125 12 Salinity, pH, and estimated elevation above MLLW of soil samples collected August 20-21, 1971, at Nehalem Bay, Oregon. 134 13 Salinity in parts per thousand and elevation in meters above MLLW of free soil water samples collected April 29, 1973, on West Island, Nehalem Bay, Oregon. 141 14 Location and salinity of surface water samples collected in April of 1973 and September of 1972 at Nehalem Bay, Oregon.