Preliminary dendrochronology at Muir Woods National Monument

Carroll, Allyson

During the 2014 Golden Gate National Recreation Area BioBlitz, tree-ring samples were collected from three Sequoia sempervirens (SESE) at Muir Woods National Monument, allowing for an initial dendrochronological investigation and establishment of educational material. This data provided for the first redwood tree-ring chronology at Muir Woods, spanning 1318–2013 A.D. and capturing the oldest extent of any crossdated SESE south of Mendocino County. The Muir Woods chronology correlated strongly with the nearest RCCI plot at Samuel P. Taylor State Park (r = 0.40, p < 0.001, common period 1750–2009 A.D.) reflecting a shared climate signal. Relationships between monthly climate variables (PRISM data, common period 1895–2013 A.D.) and the inter-annual tree-ring chronology (32-year spline detrended) were consistent with patterns identified at SESE locations across the range (Carroll et al. 2014). The year-to-year variation in ring widths was most sensitive to spring and summer soil moisture availability (r = 0.25, p < 0.01; average of March–August correlations with Palmer Drought Severity Index). While March (r = 0.24, p = 0.01) showed the strongest monthly correlation for precipitation, the relationship was not as strong as at other sampled locations across the range. Using station data for precipitation at Muir Woods (1941–2013 A.D.) showed a stronger March correlation (r = 0.46, p < 0.01) perhaps reflecting well maintained data collection at the national monument.