UNIVERSITY OF CALIFORNIA Los Angeles Southern California Climate and Vegetation Over the Past 125,000 Years from Lake Sequences in the San Bernardino Mountains A dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Geography by Katherine Colby Glover 2016 © Copyright by Katherine Colby Glover 2016 ABSTRACT OF THE DISSERTATION Southern California Climate and Vegetation Over the Past 125,000 Years from Lake Sequences in the San Bernardino Mountains by Katherine Colby Glover Doctor of Philosophy in Geography University of California, Los Angeles, 2016 Professor Glen Michael MacDonald, Chair Long sediment records from offshore and terrestrial basins in California show a history of vegetation and climatic change since the last interglacial (130,000 years BP). Vegetation sensitive to temperature and hydroclimatic change tended to be basin-specific, though the expansion of shrubs and herbs universally signalled arid conditions, and landscpe conversion to steppe. Multi-proxy analyses were conducted on two cores from the Big Bear Valley in the San Bernardino Mountains to reconstruct a 125,000-year history for alpine southern California, at the transition between mediterranean alpine forest and Mojave desert. Age control was based upon radiocarbon and luminescence dating. Loss-on-ignition, magnetic susceptibility, grain size, x-ray fluorescence, pollen, biogenic silica, and charcoal analyses showed that the paleoclimate of the San Bernardino Mountains was highly subject to globally pervasive forcing mechanisms that register in northern hemispheric oceans. Primary productivity in Baldwin Lake during most of its ii history showed a strong correlation to historic fluctuations in local summer solar radiation values. Rapid organic perturbations in the Baldwin Lake core were coeval with Dansgaard- Oeschger (D-O) events from the North Atlantic, which were evident in records from the Santa Barbara Basin. The predominant vegetation signal at Baldwin Lake was one of temperate conifer forest expansion during moist conditions, and contraction during dry conditions. This expansion and contraction was paced with summer insolation fluctuations during Marine Isotope Stage 5 (110,000 – 71,000 years BP), before a regime change towards more rapid, shorter-lived hydroclimate extremes. Wildfire is an important agent of landscape change throughout the Valley’s history, with two hiatuses during cold and moist conditions from 25,000 – 14,000 years BP, and arid conditions 7,000 – 3,000 years BP. Taken together, this multi-proxy dataset suggests that paleoclimatic changes in alpine southern California have been highly sensitive to three climate drivers: 1) shifts in local summer insolation, 2) rapid warming in the North Atlantic, and 3) changes in the strength of the California Current. The record also showed a wide range of possible moisture states in southern California’s past that vary from present conditions, including multi-millennial states of long-term aridity and pre-glacial deep lake conditions. iii The dissertation of Katherine Colby Glover is approved. Thomas Welch Gillespie Matthew E. Kirby Marilyn Raphael Glen Michael MacDonald, Committee Chair University of California, Los Angeles 2016 iv For my family — John, Mom, Dad, Andrew, Olivia, and Athena. v Table of Contents 1. Introduction . 1 2. Palynology in California: Vegetation and Climate Change Patterns over the past 130 kyr. 7 2.1 Abstract . 7 2.2 Introduction . 8 2.3 Present-Day Climate Dynamics and Vegetation . 9 2.3.1 Ocean-Atmosphere Dynamics. 9 2.3.2 Ecoregions and their dominant vegetation . 11 2.3.2.1 Mediterranean Ecoregion . 14 2.3.2.2 Temperate Desert Ecoregion . 16 2.3.2.3 Tropical-Subtropical Arid Southwest. 17 2.4 The Nature of the Pollen Record . 18 2.4.1 Pollen as a Proxy: Preservation Dynamics and Sources of Bias . 18 2.4.2 Current Data Quality and Availability . 21 2.5 Patterns of Change . 22 2.5.1 The Record from the Last Interglacial (MIS 5e, 130 – 120 ka). 22 2.5.2 The Record from the Last Glacial Maximum (26 – 19 ka) . 27 2.5.3 The Holocene (10 – 0 ka) . 28 2.6 Summary . 31 2.6.1 Review Questions . 31 2.6.2 Best Practices for Palynological Data . 33 3. Insolation and North Atlantic Climate Forcing in alpine S. California since 125 ka . 34 3.1 Abstract . 34 3.2 Introduction . 35 3.3 Setting . 36 3.4 Materials and Methods . 39 3.4.1 Core recovery and Initial Core Description (ICD) . 39 3.4.2 Chronologic control . 39 3.4.3 Sedimentary Analyses . 40 3.4.4 Biogenic Silica (BSi) . 44 3.5 Results and Proxy Interpretation . 44 3.5.1 Age Model. 44 3.5.2 Sedimentology and Summary of Proxy Data . 44 3.5.3 Relationships and Environmental Interpretation from proxy data . 45 3.6 Discussion . 52 3.6.1 Baldwin Lake’s Environmental Change from 125 – 10 ka . 52 3.6.2 Important Climatic Drivers in California . 54 3.6.2.1 Orbital-Scale Radiative Forcing . 54 3.6.2.2 Millennial-Scale Forcing during MIS 3. 56 vi 3.6.3 Pacific- and North Atlantic-induced events . 59 3.7 Conclusions . 66 4. Terrestrial Organics, Vegetation, and Wildfire in alpine Southern California 120 – 10 ka . 68 4.1 Abstract . 68 4.2 Introduction . 69 4.3 Background . 70 4.3.1 Setting and Biogeographic Importance . 70 4.3.2 Prior Work. 71 4.4 Materials and Methods . 73 4.4.1 Stable Isotope Analysis . 73 4.4.2 Palynology. 73 4.4.3 Charcoal . 74 4.5 Results . 77 4.5.1 Stable Isotopes. 77 4.5.2 Fossil Pollen . 77 4.5.3 Charcoal . 80 4.6 Discussion . 84 4.6.1 Does isotopic data reveal organic matter source? . 84 4.6.2 Climate change from pollen data . 85 4.6.3 Linkages between wildfire, vegetation, and climate drivers . 88 4.6.4 The Role of the Pacific . 89 4.7 Conclusions . 91 5. Holocene Vegetation, Wildfire, and Hydroclimatic History from Lower Bear Lake . 95 5.1 Abstract . 95 5.2 Introduction . 96 5.3 Background . 97 5.4 Materials and Methods . 98 5.4.1 Stable Isotope Analysis . 98 5.4.2 Charcoal Analysis . 100 5.4.3 Mollusk identification, and geochemical analysis . 101 5.4.4 Fossil Pollen Data . 102 5.5 Results . 102 5.5.1 Bayesian Age Modeling. 102 5.5.2 Charcoal . 104 5.5.3 Mollusk Identification, Stable Isotope, and Trace Element Data . 104 5.5.4 Fossil Pollen . 107 5.6 Discussion . 107 5.7 Conclusions . 114 6. Dissertation Conclusions . 117 7. References . 120 vii List of Figures and Tables Figure 1.1. Location of paleoclimatic records mentioned in Ch 1 . 4 Figure 2.1. West Coast ecoregions and Pacific dynamics . 10 Figure 2.2. Palynological sites in California that date to at least 2 ka . 13 Table 2.1. Modern climate, vegetation characteristics in California’s three ecoregions . 15 Table 2.2. Palynological sites in California dating to at least 2 ka, by climate events . 22 Figure 2.3. Patterns of ecosystem change since the last interglacial at key sites . 25 Table 2.3. Summary of California’s palynological response to climate change during MIS 5e and LGM . 26 Table 2.4. Summary of California’s palynological response to Holocene climate change . 29 Figure 3.1 Location map of lacustrine records in Big Bear Valley . 38 Table 3.1 Baldwin Lake core (BDL12) chronologic control . 41 Figure 3.2 Bacon 2.2 age-depth model for BDL12 . 42 Figure 3.3 Sedimentological data of BDL12 by depth . 46 Table 3.2 Multi-proxy results summary, with paleoenvironmental conditions and events . 47 Figure 3.4 BDL12 multi-proxy data plotted by age . 50 Figure 3.5 Dansgaard-Oeschger events in the North Atlantic, California margin, and at terrestrial Southern California sites . 57 Figure 3.6 Paleoclimatic records throughout the Great Basin, California, U.S. Southwest 60 Figure 3.7 California, Great Basin, and U.S. Southwest response to D-O events. 62 Figure 4.1 Schematic of charcoal deposition, and BDL12 sampling strategy . 76 Figure 4.2 Bulk organic matter, biogenic silica, and molar C:N data from BDL12 . 78 Figure 4.3 Pollen diagram of terrestrial taxa with cluster analysis and pollen zonation . 79 Table 4.1 Key changes within BDL12 pollen zones . 81 Figure 4.4 Pollen diagram of aquatic, tracer, and pollen group sums . 82 Figure 4.5 BDL12 charcoal and pollen summer, with potential drivers . 83 Figure 4.6 Comparison of Lake Elsinore and BDL12 pollen data 35 – 10 ka . 86 Figure 4.7 Comparison of BDL12 conifers to global and California marine records . 90.