Figure 1.
Tree-ring characteristics of Sequoia sempervirens and Sequoiadendron giganteum.
(A) Crossdated SESE annual rings with marks beginning 1900 (three dots far right) and ending 1960 (one dot far left). (B) Crossdated SEGI annual rings with same years and marks as panel A. (C) Area of tight SESE annual rings, including missing rings. (D) SESE ring wedging, where discontinuous rings merge. (E) SESE spiral compression wood. (F) SESE annual rings from northernmost location (JS) showing 1739 event. After large 1738 ring (*), 1739 and 1740 are 1-cell-wide micro-rings merged with 1738 latewood, 1741 and 1742 rings are tight, and 1750 ring is marked with two dots on left. (G) SEGI annual rings from GF showing 1580 event, marked with one dot. Of 12 cores collected from the largest SEGI sampled, this is the only core showing 1580. (H) Two fire scars on core collected 45 m above ground in SESE rainforest (JS). Black boxes in upper right of each panel cover 1 mm2.
Figure 2.
Average annual precipitation, elevation, and geographic distribution of 14 locations for two redwood species.
Filled circles are Sequoia sempervirens locations and open circles are Sequoiadendron giganteum locations. Precipitation values for each location are 114-year averages (1895–2008) at 800-m resolution using PRISM data [36]. Red-shaded areas indicate native ranges of Sequoia sempervirens (left) and Sequoiadendron giganteum (right), and stars denote sampling locations.
Table 1.
Characteristics and tree-ring sampling intensity for two species at 14 locations.
Figure 3.
Classification system for crossdating confidence based on annual resolution.
Marker years are denoted in blue. Examples are drawn from Sequoia sempervirens ring-width data. (A) High crossdating confidence or continuous annual resolution with no or few missing rings. (B) Moderate crossdating confidence (orange). Although missing rings are placed in their most likely location, alternative positions are possible (e.g., 3 missing rings between 1918–1926). Also assigned to sections of miniscule growth (e.g., missing rings among micro-rings). (C) Bounded with no annual resolution (red). Total number of missing rings in a section deduced from surrounding crossdating, but there is no indication of their most likely placement, often due to many missing rings (e.g., 20 missing rings between 1890–1935). (D) Crossdating cessation (purple). No annual resolution for a section where crossdating terminated and interior rings are neither resolved nor bound by known markers (e.g., crossdating progressed towards pith and ceased at 1928, leaving an undated section of core with a minimum ring count).
Figure 4.
Standardized tree-ring chronologies and sample depths for eight Sequoia sempervirens locations.
Blue lines indicate ring-width indices for each location, using series >50 years in length with high crossdating confidence and detrended with a 32-year cubic smoothing spline. Pink shading denotes difference between total number of series sampled and number of series with high crossdating confidence. Tree sample sizes indicated in gray.
Figure 5.
Standardized tree-ring chronologies and sample depths for six Sequoiadendron giganteum locations.
Blue lines indicate ring-width indices for each location, using series >50 years in length with high crossdating confidence and detrended with a 32-year cubic smoothing spline. Red shading denotes difference between total number of series sampled and number of series with high crossdating confidence. Tree sample sizes indicated in gray.
Table 2.
Statistical characteristics of standard tree-ring chronologies for two species at 14 locations.
Figure 6.
Correlations among redwood tree-ring chronologies and relationships with Euclidean distances between locations.
Values in cells are % variance explained (100×r2) for pairwise correlations over a 259-year common period (1750–2008). Locations arranged by latitude from north (left and top) to south (right and bottom) within species.
Table 3.
Correlations between tree-ring indices of SESE and SEGI and six other western North American tree species.
Figure 7.
Summary of climate sensitivities for eight Sequoia sempervirens locations.
Bootstrapped correlations and response functions of residual tree-ring chronologies against monthly Palmer Drought Severity Index (PDSI), precipitation, and maximum and minimum temperature conducted over a 114-year common period (1895–2008). Thicker black lines indicate correlation values. Thin dotted lines represent cutoff for statistical significance (P<0.01). Colored circles show months with significant correlations and response functions. Grey lines and blue circles represent minimum temperature. Letters indicate 20 months from March of previous year to October of current year. Locations arranged by latitude from north (top) to south (bottom).
Figure 8.
Correlations between residual tree-ring chronologies and reconstructed summer cloudiness for eight Sequoia sempervirens locations.
Summer cloudiness (i.e., airport fog with cloud base ≤400 m elevation) reconstructed by Johnstone and Dawson [42] for June–September over a 108-year common period (1901–2008). Dotted line represents cutoff for statistical significance (P<0.01).
Figure 9.
Summary of climate sensitivities for six Sequoiadendron giganteum locations.
Bootstrapped correlations and response functions of residual tree-ring chronologies against monthly Palmer Drought Severity Index (PDSI), precipitation, and maximum and minimum temperature conducted over a 114-year common period (1895–2008). Thicker black lines indicate correlation values. Thin dotted lines represent cutoff for statistical significance (P<0.01). Colored circles show months with significant correlations and response functions. Grey lines and blue circles represent minimum temperature. Letters indicate 18 months from May of previous year to October of current year. Locations arranged by latitude from north (top) to south (bottom).
Figure 10.
Summary of radial growth sensitivity to summer drought indices for two species at 14 locations.
Correlations of residual Sequoia sempervirens and Sequoiadendron giganteum tree-ring chronologies against regional and state summer drought (average June–September PDSI) indices conducted over a 114-year common period (1895–2008). Dotted line represents cutoff for statistical significance (P<0.01). Locations arranged by latitude from north (left) to south (right) within species.
Figure 11.
Visual comparison of southernmost Sequoia sempervirens (LH) tree-ring index and Central Coast California summer drought index.
Summer drought is average June through September PDSI from the National Climatic Data Center for CA04 (Central Coast California). Both indices standardized by their standard deviates. Note discrepancies after known forest fires in 1985 and 1999 (arrows).