Dendrochronology of Seaside Juniper: A Paleoclimate Reconstruction of the San Juan Islands

Transcription

1 Dendrochronology of Seaside Juniper: A Paleoclimate Reconstruction of the San Juan Islands From: Dustin Gleaves, M.A. Candidate, Environmental Studies (206) gleaved@wwu.edu To: Graduate Program Committee, Huxley College Total required funding for project: $ Amount requested from Graduate Program Committees: $ Project Duration: Start date: 4/17/2017 End date: 6/1/2018 Applicant: Dustin Gleaves Approved by: Thesis committee chair Dr. Aquila Flower ( ) Thesis committee member: Dr. James Helfield ( ) Thesis committee member: Dr. Andy Bach ( )

2 Background: Seaside Juniper (Juniperus maritima) is a newly discovered species of Juniper tree endemic to the Pacific Northwest. Prior to discovery in 2007, Seaside Juniper was treated as Rocky Mountain Juniper (J. scopulorum) due to cryptic speciation (Adams, 2007). Although climate is a well known primary determinant of forest health, the effects of fluctuating climatic conditions on the growth and regeneration of Seaside Juniper have never been studied. Dendrochronology uses the measurement of annual tree ring widths as a proxy for periodic climate conditions. If successful, this study will produce a model of climate conditions over the lifespan of the sampled trees, potentially prior to instrumental measurements. No dendrochronological study of Seaside Juniper is available in published literature and no existing chronology is available from the International Tree Ring Databank (ITRBD, 2017), the primary public database of tree ring chronologies. Due to this lack of study, it is unknown if individual Seaside Junipers crossdate, defined as expressing consistent patterns of annual growth between individuals, which would indicate non-random climatic response, a crucial requirement of dendrochronological study. If Seaside Juniper expresses climate sensitivity, this represents a yet unutilized resource of dendrochronological records that could be used to elucidate long-term climate trends in the Salish Sea region. Prior studies have succeeded in correlating precipitation and temperature with the closely related Utah Juniper (J. osteosperma) (Derose et al., 2016) and Rocky Mountain Juniper growth (Spond, et al., 2014), which indicates a potential for climate sensitivity in Seaside Juniper. Purpose: I seek to produce a regional chronology of Seaside Juniper in the San Juan Islands and the surrounding mainland through field collection of tree cores from approximately 20 individual trees at each of 4 to 6 sites throughout the region, then confirm statistically if Seaside Juniper is capable of crossdating for use in more comprehensive dendrochronological study. If successful and subject trees are of sufficient age, it is also my intent to analyze the data collected in this process for use in a paleoclimate reconstruction of the San Juan Island region. The final chronologies produced will be made available on the ITRDB for public access. By quantifying the relationship between climate and the growth of the Seaside Juniper, this study will produce insights into this rare endemic species resilience under future climatic changes. Furthermore, hindcasting of past climatic conditions will reveal the history of long-term trends in climate in the Salish Sea region and provide important context for current and future climatic changes. Methods: Sites will be selected for presence of at least 20 mature and accessible Seaside Juniper individuals as determined by site locations defined by Adams (2014) and through predictive species distribution modeling followed by on-site species identification. Tree core samples will be collected from live individuals on-site using an increment borer by myself and 1 to 3 field assistants. Two cores will be taken from opposite sides of each tree at angles parallel to slope to eliminate any slope-related

3 growth (Speer, 2010) and to crossdate samples from the same individual to ensure homogeneity of growth. Samples will then be mounted to wood blocks and sanded to enhance visual contrast of ring widths. Ring widths will be measured for each core sample and crossdated to ensure accurate dating of each annual ring using Cdendro and CooRecorder, a task-specific image analysis software package. Raw ring widths will be converted to a unitless index of radial growth that can be compared among samples through the process of statistical detrending, which will also remove non-climatic signals from factors such as age-related growth trends and inter-tree competition. Statistical analysis will be performed in R using the DENDROCLIM package (Bunn, 2008). Evaluation of bivariate relationships between tree growth and climate variables (annual, seasonal, and monthly minimum, maximum, and mean temperature and total precipitation) will be performed using bootstrapped correlation analysis using the dendroclim package in R (Biondi and Waikul, 2004; Bunn, 2008; Robertson, 2011) to create a model from correlations of annual ring widths against instrumental climate data in the modern period, with statistical significance assessed via bootstrapping. Climate data will be obtained from PRISM (Robertson, 2011) via ClimateWNA (Wang et al., 2012). El Niño Southern Oscillation and Pacific Decadal Oscillation indices will be obtained from NOAA s climate research databank. Any climate variables with a significant (p<0.05) and strong (r>.2) correlative relationship with annual radial growth in the instrumental period will be considered for use in a linear regression-based hindcasting model of the climate variable. Timeline: Summer 2016 (completed): Collected complete set of cores Washington Park in Anacortes, WA. Spring 2017: Scout and collect cores on Sucia Island State Park, WA. Summer 2017: Scout and collect cores from Skagit island, San Juan Island, Shaw Island, Lopez Island, and Orcas Island sites. Fall and Winter 2017: Prepare and analyze all samples. Write Thesis. Spring 2018: Write thesis and defend.

4 Budget: Requested Funding Purchase Anticipated Source Price Quantity Total Ferry transit* Washington State Ferries $ $ Gas reimbursement (est.) Various gas stations $ $68.75 Garmin GPSmap 64 Amazon.com $210 1 $210 Camping fees** San Juan County Parks & WA state Parks $28 14 $392 Backpacking tent rental AS Outdoor center $ $7.50 Sleeping pad rental AS Outdoor center $ $2.00 Backpacking stove rental AS Outdoor center $ $2.50 *Ferry transit based on 2 round trips, 4 people, in 2 vehicles and 1 trailer Total requested funding: $ **Camping fees based on 7 nights with 4 people using 2 sites per night. Site costs of San Juan County Parks and Moran State Park range from $20 to $40 per night. $28 represents average cost per night. Required Funding Not Requested Purchase Anticipated source Anticipated Funding Price Quantity Total Food per diem in field research (per person) Various Self $20 28 $560 American Association of Geographers conference American Association of Geographers Dean s Fund for Sustainability $155 1 $155

5 Air Fare - Round trip Seattle to New Orleans United Airlines Ross Travel Grant $435 1 $435 Lodging (per night) St. James Hotel Dean s Fund for Sustainability (partial) $128 5 $640 Food per diem AAG conference Various Self $20 5 $100 Required funding not requested: $1890 Works Cited Adams, R. P. (2007). Juniperus maritima, the seaside juniper, a new species from Puget Sound, North America. Phytologia, 89(3), Biondi, F., & Waikul, K. (2004). DENDROCLIM2002: a C++ program for statistical calibration of climate signals in tree-ring chronologies. Computers & Geosciences, 30(3), Bunn, A. G. (2008). A dendrochronology program library in R (dplr). Dendrochronologia, 26(2), Cybis Elektronik, CDendro and CooRecorder., Derose, R. J., Bekker, M. F., Kjelgren, R., Buckley, B. M., Speer, J. H., & Allen, E. B. (2016). Dendrochronology of Utah Juniper (Juniperus osteosperma (Torr.) Little). Tree-Ring Research, 72(1) Gedalof, Z. E., & Berg, A. A. (2010). Tree ring evidence for limited direct CO2 fertilization of forests over the 20th century. Global Biogeochemical Cycles, 24(3). Grissino-Mayer, H. D. (2001). Evaluating crossdating accuracy: a manual and tutorial for the computer program COFECHA. Tree-ring research. ITRDB. Retrieved April 4, 2017, from Peterson, D. W., & Peterson, D. L. (2001). Mountain hemlock growth responds to climatic variability at annual and decadal time scales. Ecology, 82(12), Robertson, C. (2011). Dendroclimatology of yellow cedar (Callitropsis nootkatensis) in the Pacific Northwest of North America.

6 Speer, J. H. (2010). Fundamentals of tree-ring research. University of Arizona Press. Spond, M. D., van de Gevel, S. L., & Grissino-Mayer, H. D. (2014). Climate-growth relationships for Rocky Mountain juniper (Juniperus scopulorum Sarg.) on the volcanic badlands of western New Mexico, USA. Dendrochronologia, 32(2), Stanton, S. (2009). Western dwarf mistletoe and prescribed fire behavior a case study from Crater Lake National Park. Northwest Science, 83(3), Wang, T., Hamann, A., Spittlehouse, D., and Murdock, T. N. (2012). ClimateWNA High-resolution spatial climate data for western North America. Journal of Applied Meteorology and Climatology 61: