Development and Climatic Analysis of a 456-Year Tree Ring Chronology from Northeast Ohio, USA

1. DEVELOPMENT AND CLIMATIC ANALYSIS OF A 456 YEAR TREE RING CHRONOLOGY FROM NORTHEAST OHIO, USA DEVELOPMENT AND CLIMATIC ANALYSIS OF A 456 YEAR TREE-RING CHRONOLOGY FROM NORTHEAST OHIO, USA Introduction Tree-ring series developed from old growth oak forests in Northeast Ohio are sensitive records of past moisture variability and have been used, together with a larger network of chronologies, to reconstruct drought histories on a continental scale. Here we describe the development and extension of ring-width records for Northeast Ohio from living oaks and from timbers in historical buildings. 409 series from 10 old growth remnant forests and 16 historical sites are combined into a regional ring-width chronology that spans AD 1550-2005. These series are positively correlated with summer precipitation, the summer Palmer Drought Severity Index and streamflow in the region. The five most-narrow rings (1699, 1748, 1810, 1839 and 1895) are inferred to have been extremely dry summers. Years 1699 and 1810 are linked to high latitude cooling associated with large-scale, volcanic events recognized in ice cores, but are of uncertain origin. Living trees show a general increase in ring-width over the last 150 years that is poorly understood, but may be related to the widespread forest disturbance and recovery after settlement in the early 1800s. Development of this record together with a more regional analysis and mapping of extreme years and long-period trends are ongoing. This work is leading to new insights into understanding drought and forest growth in the North American Midwest. Lehmann, Sophie1, Belding, Elyssa1, Wiles, Gregory1, and Brush, Nigel2 (1) Department of Geology, The College of Wooster, 1189 Beall Ave, Wooster, OH 44691 (2) Geology, Ashland University, 401 College Ave, Ashland, OH 44805 Figure 4: This graph represents the entire span of the NEO chronology (1550-2005) as standardized indices of tree ring width variability. The five narrowest rings in the chronology are indicated with asterisks (1895, 1839, 1748, 1699 and 1810). 1895 is a major drought year and correlates with the second driest year in Ohio. The narrow rings of 1699 and 1810 are concurrent with large-scale volcanic events of unknown origin, suggesting a link of cooling at higher latitudes in the Northern Hemisphere (D’Arrigo and Jacoby, 1999) and drought. Interestingly, similar large-scale volcanically induced cooling and drying are not part of the observational record. Perhaps the years 1748 and 1838 could also be years of low moisture not related to volcanic induced events. Methods and Procedure An increment borer allows us to core a 5 mm cross section from living trees while a chainsaw is used to collect cross-sections of timber from fallen structures and discarded beams. In order to sample houses and historical structures, an electric hand corer extracts a core from a beam in an old structure with no harm. All the cross-sections and cores in the Northeast Ohio (NEO) Chronology were brought back to the Wooster Tree Ring Lab where they were sanded and analyzed under a dissecting microscope for the ring-widths. Determining the age of the outermost ring differs depending on where the sample came from. The outermost ring on cores extracted from living trees are dated to the most recent growing season. The age of the outermost ring on dead trees cannot be determined until all the rings are measured, thus, the data from such a location are formed into a floating chronology without a calendar date. The successive annual widths are measured to the nearest 0.001 mm. Each location is then crossdated (Fig. 1) against each other and the formed master chronology to check for strong correlation within the series. Figure 5:The NEO ring-width series was compared with a long monthly (1888-2003) precipitation record from the Ohio State Agricultural and Development Center located centrally in the study area. A common period of 112 years was used to correlate monthly temperature and precipitation values for the dendroclimatic year starting in March of the previous year through October of the year of growth. The strongest correlations are with June and July precipitation of the growth year with a correlation of 0.48 (p<0.0001). A strong negative relationship with June temperatures is also noted and is likely due to the high intercorrelation of temperature in June with precipitation. Cooling in June is associated with wetter conditions favorable for tree growth. Comparison with mean summer PDSI series with a common 104-year period (1900-2003) yields a correlation of 0.43 (p<0.0001). Figure 3:The cropped raw ring width chronology is divided into the chronologies of living oaks and timber from historical structures in the area. While the series count is strong after the early 1600s, before this time there are minimal series and therefore earlier data must be considered with caution. The NEO chronology is considered a regional record of June and July rainfall, mean summer PDSI, and August and September stream flow. Therefore, we consider the NEO chronology as a record of warm season precipitation and drought from 1650 to 2005. Decades of decreased precipitation occurred in the early 1800s about the same time of settlement in the region and of a cooling that is well-documented for the Northern Hemisphere (Briffa et al., 2002). A raw ring width plot of the composite 409 living series reveals a significant increase in growth following the early 1800s (intercorrelation of 0.549). A comparison of raw ring widths between living trees (n=233; total time span 1605-2006 AD) and historical samples (n=179; total time span 1550-1891 AD) shows that the increase in growth is found solely in the living trees as the historical samples show a more expected (biologically and geometrically) decrease in growth with age. This step change in growth in the living trees may partly be the result of a reduction in competition after selective logging. The early decades of the 1800s are an interval of major changes across the study region in the form of conversion of forests to agriculture and selective logging. This frequency rise in living trees is evident and we cannot rule out the potential fertilization effect of nearby agriculture fields that surrounds many of the living tree sites or the possible high nitrogen fallout and fertilization from coal burning in the region over the past century. Some of this change in growth may be the result of exogenous factors like climate change or elevated CO2. A similar observation in increasing raw ring widths of white and chestnut oaks has been found over much of the eastern U.S. (Pederson, 2005). • Conclusions • *This continuing work has extended tree-ring chronologies from Northeastern Ohio spanning from 1550-2006. This suggests the possibility of further regional extension in NEO. • *The Midwestern climate changes can be better revealed by analyzing these proxies with records of meteorological events from the area. • * Narrow rings in this record correlate with large-scale volcanic events suggesting regional cool summers or Midwest drought associated with this cooling. • *Rings prior to the early 1800’s show a decrease in ring width as they age, while rings after this period leading up to the present are widening. This maybe due to the increase in CO2, BACKGROUND AND LOCATION OF SITES The annual tree-ring widths from crossdated sites forms a regional chronology spanning 456-years extending as far back as 1550 with fewer than 10 rings. The NEO Regional master chronology has been formed from 26 sites which produced 409 of series from old-growth structural site series. Sites were initially concentrated in Wayne County and the positive correlation between these locations allowed consideration of sites in neighboring counties. The NEO chronology (Fig. 2) reveals an ever-widening climatic region, constantly increasing replication of annual ring-growth, climatic signals, and reoccurring pointer years. References -Briffa, K. R., T. J. Osborn, F. H. Schweingruber., P. D. Jones, S. G. Shiyatov, and E. A. Vaganov, 2002, Tree-ring width and density data around the Northern Hemisphere: Part 2, spatio-temporal variability and associated climate patterns. The Holocene 12(6):759-789. -Cook, E.R. and P.J. Krusic, 2004, North American Summer PDSI Reconstructions. IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series # 2004-045. NOAA/NGDC Paleoclimatology Program. -Cook, E.R. and L.A. Kairiukstis. 1990. Methods of Dendrochronology. Dordrecht: Kluwer Academic Publishers. 394 p. -Grissino-Mayer, H. D., 2001, Evaluating crossdating accuracy: a manual and tutorial for the computer program COFECHA. Tree-Ring Research 57:205-221. -Mosley-Thompson, E., T. A., Mashiotta, L. G., Thompson, 2003, High resolution ice core records of late Holocene volcanism: current and future contributions from the Greenland PARCA cores. Volcanism and the Earths’ Atmosphere Geophysical Monograph 139:153-164. -Pederson, N. 2005, Climatic Sensitivity and Growth of Southern Temperate Trees in the Eastern US: Implications for the Carbon Cycle. Ph.D. Thesis. Columbia University, New York, NY. Pederson, N. E. R. Cook, G. C. Jacoby, D. M. Peteet, K. L. Griffin., 2004, The influence of winter temperatures on the annual radial growth of six northern-range-margin tree species. Dendrochronologia 22:7-29. -Stokes, M. A. and Smiley, T. L., 1968, An introduction to tree-ring dating: Tucson: University of Arizona Press. -http://www.ncdc.noaa.gov/paleo/pdsi.htm Acknowledgements This work was supported in part by the Environmental Analysis and Action Program (EAA) at the College of Wooster funded by the Henry Luce Foundation as well as funding from Ed Cook. We thank The Wilderness Center in Wilmot, the Ohio Department of Natural Resources, The Nature Conservancy, Shawn Godwin, Paul Locher, Wayne College, Dave Taggart, and Susan Burt for permission to sample living trees and historical structures.