Tree-ring analysis revealed 33 living white oaks (Quercus alba) in Iowa that began growing before 1700. We analyzed cores of wood 4 mm in diameter, each extracted from a radius of a tree trunk. The oldest white oak, found in northeastern Warren County, began growing about 1570 and is thus over 410 years old. We also found a chinkapin oak (Quercus muehlenbergii) over 300 years old. Ring widths from the white oaks are well correlated with total precipitation for the twelve months preceding completion of ring formation in July. Reconstructions of annual (August-July) precipitation for 1680-1979, based on the tree rings, indicate that the driest annual period in Iowa was August 1799-July 1800, and that the driest decade began about 1816. Climatic information of this kind, pre-dating written weather records, can be used to augment those records and provide a longer baseline of information for use by climatologists and hydrologic planners

Blasing, T. J.

Duvick, Daniel N.

Name not available

Iowa\u27s Oldest Oaks

University of Northern Iowa

Proceedings of the Iowa Academy of Science Volume 90 Number Article 9 1983 Iowa's Oldest Oaks Daniel N. Duvick Oak Ridge National Laboratory T. J. Blasing Oak Ridge National Laboratory Let us know how access to this document benefits you Copyright ©1983 Iowa Academy of Science, Inc. Follow this and additional works at: https://scholarworks.uni.edu/pias Recommended Citation Duvick, Daniel N. and Blasing, T. J. (1983) "Iowa's Oldest Oaks," Proceedings of the Iowa Academy of Science, 90(1), 32-34. Available at: https://scholarworks.uni.edu/pias/vol90/iss1/9 This Research is brought to you for free and open access by the Iowa Academy of Science at UNI ScholarWorks. It has been accepted for inclusion in Proceedings of the Iowa Academy of Science by an authorized editor of UNI ScholarWorks. For more information, please contact scholarworks@uni.edu. Proc. Iowa Acad. Sci . 90(1): 32-34, 1983 Iowa's Oldest Oaks 1 DANIEL N. DUVICK and T. J. BLASING Environmental Sciences Division, Oak Ridge National Laborarory, Oak Ridge, Tennessee 37830 Tree-ring analysis revealed 33 living white oaks (Querms alba) in Iowa that began growing before 1700. We analyzed cores of wood 4 mm in diameter, each extracted from a radius of a tree trunk. The oldest white oak, found in northeastern Warren County, began growing about 15 70 and is thus over 4 10 years old. We also found a chinkapin oak (Quercm muehlenbergii) over 300 years old. Ring widths from the white oaks are well correlated with rota! precipitation for the twelve months preceding completion of ring formation in July. Reconstructions of annual (August-J uly) precipitation for 1680-1979, based on the tree rings, indicate that the driest annual period in Iowa was August 1799-J uly 1800, and that the driest decade began about 1816. Climatic information of this kind, pre-dating written weather records, can be used ro augment those records and provide a longer baseline of information for use by climarologists and hydrologic planners. INDEX DESCRIPTORS: Oldest Trees, Tree Rings, Past Climate, Oak Trees, Dendrochronology Several oaks approaching or exceeding 300 years of age have been discovered in Iowa as a result of studies aiming ro reconstruct the climatic hisrory of the region from tree-ring widths. Prior ro this study, very few Iowa trees over 300 years old of any species have been noted. Landers (1977) has found living eastern red cedar (juniperm virginiana) over 400 years old at Palisades-Kepler State Park and a living bur oak (Quercm 1nacrocarpa) 400 years old near Sutherland in O 'Brien County. Anderson (1938) reported an eastern red cedar dating from A.D. 1516. White oak (Querms alba) was selected as the primary species for our study because it is widely distributed and long-lived . The maximum age for this species is g iven by Harlow et al. (1979) as 400-500 years and by the U.S. Department of Agriculture (1965) as 600 years. However, we could find no documentation of the trees on which these estimates are based. MATERIALS AND METHODS Site selection was made primarily by canvassing state parks and other areas in central and northeastern Iowa. The oldest trees are often found on rugged terrain, where they have survived cutting because of their relative inaccessibility and their often contorted shapes (Fig. 1), which make them undesirable for lumbering. Old white oaks (older than about 200 years) can usually be distinguished from younger trees by the twisted and gnarled appearance of the crown and by the spiral bark contours and burls, or knots, o.i;1 the trunk (Fig. 2). Although we have not searched outside of central and northeastern Iowa, old oaks could probably be found in other parts of the state, especially m eastern and southern Iowa where white oaks are common. Ring-width data are obtained by using an increment borer ro remove a core of wood about 4 mm in diameter from two or more radii of the trunk, at breast height, about 1.25 m above the ground. This procedure does not harm the tree, though pruning spray is often applied as an added precaution after a core is extracted. The tree core is preserved by gluing it into a fitted groove in one side of a core-mounting stick, a piece of wood about 1 cm 2 on the ends and cut a few mm longer than the core robe mounted. The cores are sanded down until the ring structure is clearly visible. The rings are dated by calendar year, measured, and analyzed for climatic information con-tent. More detail on the sampling and laborarory procedures is found in Stokes and Smiley (1968). Further information on the tree-climate relationships and their applications is found in Fritts ( 1976). 1 Research supported by the National Science Foundation, Ecosystem Studies Program, under lnreragency Agreement DEB8 l- l53 16 with the U.S. Deparcmenr of Energy under Contract W-7405-eng-26 with Union Carbide Corporation. Publication No. 2014, Environmenral Sciences Division, ORNL RESULTS Table l lists the 34 white oaks (and one chinkapin oak, Quercm muehlenbergii) for which the actual or estimated beginning of g rowth (pith date) is prior to 1700. Fig. 3 shows the locations of the nine sites where these trees are found . The oldest white oak is located on a ridge top in northeastern Warren County. One core taken from this tree crosses the pith which formed in 1573 . In that year the tree was a sapling about 1. 25 m tall (the height at which the core was taken), so the acorn would have germinated several years earlier, probably before 1570. This living tree is now at least 410 years old . It g rew quite slowly in its first 200 years and more rapidly after about 1780 when its competition for light and water may have been reduced by the death of neighboring trees. Only one other white oak has been found which appears to have begun growing before 1600 . This tree is in White Pine Hollow in northeastern Iowa. The center of this tree has unfortunately rotted, preventing determination of the exact pith date (this was also the case for several of the other trees listed). The earliest ring on a core from this tree was dated at 1630. The pith date was estimated to be 1580, using the curvature of the innermost rings and assuming a growth rate similar to that observed on the inner part of the core. Fig. l. The first author using a Swedish increment borer to extract a core of wood from a contorted white oak growing on a steep bluff slope. 1Duvick and Blasing: Iowa's Oldest OaksPublished by UNI ScholarWorks, 1983!OW NS OLDEST OAKS 33 Fig. 2. Bole of a white oak over 340 years old showing burls, gnarled limbs, and spiral bark contours typical of old oaks. Cores passed through the piths of only four of the trees listed in Table 1 (those with the first ring indicated as "pith "). Only one of the white oaks was dead when sampled (tree no. 9, Table 1). The pattern of wide and narrow rings near the outermost edge of the core was compared with recen.t rings of cores from living trees to obtain a cross-match to determine lhe year in which the dead tree put on its last ring . In this way we determined that the tree died afrer the growing season of 1975 but prior to the growing season of 1976. Of the nine Iowa sites where we found trees daring to before 1700, the largest numbers of old trees were in Ledges (ten trees) and Pammel (eight trees) State Parks. At these parks, as well as at many of the ocher sites, the oldest trees were on ridge tops and upper slopes of rugged, ravine-dissected uplands bordering major river valleys. The area at Pammel where the oldest trees were found was described as a virgin forest by the park ranger. One chinkapin oak represents the only species besides white oak included in our list. This was the only chinkapin oak sampled, but several other potentially old chinkapin oaks were seen at the Ledges sire. 6. 5 • • 4 .1 3 •2 l. Pommel State Park 2. Lake Ahquabi State Park 3. Northeastern Warren County 4 . Johnston 5. Ledges State Park 6. Woodman Hollow State Preserve 7. White Pine Hollow State Preserve 8. Merritt Forest State Preserve 9. Yellow River State Forest Fig. 3. Sites in Iowa containing old oaks. The scarcity of old oaks in Iowa is largely due to the face chat most of Iowa's forests have been cut since the state was settled in the mid-1800's. Numerous stands were found in which many of the trees sampled had pith dates that clustered between 1850 and 1885. At that time the original forest may have been clearcut, or nearby settlers put out prairie fires, allowing the trees to invade former prairie areas (Thomson and Herrel, 1981). In some cases, isolated trees over 200 years old were found surrounded by stands of younger trees that began growing shortly after settlement, and the older trees show a sharp increase in ring width about the same time. These older trees, which were left after the original forest was cut, g rew more rapidly in the absence of competition from neighboring trees. RECONSTRUCTING PAST CLIMATE The width of each year's ring is strongly influenced by the total amount of precipitation during the 12-month period preceding completion of ring formation (roughly from the preceding August through the concurrent July). In a dry year, reduced soil moisture can slow the tree's physiolog ical processes, resulting in less radial growth, while in a wet year more growth occurs. High temperatures in spring and summer reduce growth by causing increased respiration which consumes photosynthate and by increasing water loss through evapo-transpiration. Thus, the narrowest rings are usually formed in hot dry years. Ring-width chronologies developed from cores taken at the Pam-mel, Ledges, and Johnston sites in central Iowa were used by Duvick and Blasing ( 1981) to estimate annual (August-] uly) precipitation for Iowa, for each year since 1679-80. (Hereafter, the latter calendar year of the 12-month period is given. Thus, 1680 would imply August 1679 through July 1680.) In that study the ring-width series from 2Proceedings of the Iowa Academy of Science, Vol. 90 [1983], No. 1, Art. 9https://scholarworks.uni.edu/pias/vol90/iss1/934 PROC. IOWA ACAD. SCI. 90(1983) Table I. Iowa oaks growing before 1700 (all white oaks except as indicated) Rank Estimated pith date First ring on core Location 1573 1573 N.E. Warren County (Actual) (Pith) 2 1580 1630 White Pine Hollow 3 1630 1650 Yellow River Forest 4 1630 1657 Yellow River Forest 5 1634 1634 Pammel State Park (Actual) (Pith) 6 1640 1642 Pammel State Park 7 1640 1647 Pammel State Park 8 1640 1652 Pammel State Park 9 1645 1654 Johnston (Died 1975) 10 1650 1653 Pammel State Park 11 1650 1654 Johnston 12 1650 1662 Ledges State Park 13 1670 1676 Ledges State Park 14 1670 1680 Pammel State Park 15 1673 1673 Ledges State Park (Actual) (Pich ) 16 1673 1673 Ledges State Park (Actual) (Pith) 17 1675 1687 Yellow River Foresc 18 1675 1692 Ledges State Park (Chinkapin Oak) 19 1675 1695 Woodman Hollow 20 1676 1677 Pammel State Park 21 1680 1683 Ledges State Park 22 1680 1685 Yellow River Foresc 23 1680 1694 Ledges State Park 24 1680 1694 Ledges Seate Park 25 1680 1694 Johnston 26 1680 1698 White Pine Hollow 27 1680 1700 Johnston 28 1680 1710 Pammel Stace Park 29 1685 1698 Woodman Hollow 30 1685 1687 Ledges Scace Park 31 1690 1702 Lake Ahquabi 32 1690 1706 Whice Pine Hollow 33 1690 1714 Merritt Foresc Preserve 34 1695 1705 Merritt Foresc Preserve 35 1698 1704 Ledges Scace Park each core was first statisrically filtered to remove low-frequency variations due to factors such as tree age and competition effects. The climatic reconstruction indicated that droughts have occurred regularly throughout the last 300 years, with about the same frequency in presettlement and postsettlement times. Since 1874, the first year of statewide precipitation records, the five driest years in both the actual and reconstructed series have been, in chronolog ical order, 1894, 193 1, 1934, 1956, and 1977. The reconstruction indicates that the 10 driest years since 1680, listed from driest to least dry, were 1800, 1934, 1894, 1736, 1743, 1977, 1704, 1956, 193 1, and 1940. For the most recent dry year, 1977, the estimated value of 60.0 cm compares with a measured value of55. 7 cm. The estimated precipitation for 1800 was 51. 3 cm , or at least 4 cm less than either the estimated or actual values for 1977 . Normal annual precipitation (1920-1979) for Iowa is 80. 2 cm . The driest decade in Iowa in the 20th century, in both the actual and reconstructed precipitation series, was 193 1-40 which includes the dust bowl years. Five decades comparable to or drier than the 1930's are indicated between 1680 and 1979. These are 1696-1705, 1735-1744, 1791-1800, 1816-1825, and 1886-1895. Actual cli-matic records indicate that 1886-95 was about as dry as 1931-40. In even the driest decades, drought years are often separated by occasion-al moist years (e.g., 1932 and 1935). Precipitation for the very wet years appears to be estimated less accurately than for dry years because excess rainfall runs off and factors other than moisture become limiting to tree growth. H owever, the widest rings are usually formed during wet years. Periods indicated to have been especially wet include 1726-1733, 1745-1747, 1774-1781, 1802-1807, 183 1-1837, 1875-1885, 1902-1909, and 1941-1947. The actual precipitation records covering the last three of these periods confirm that they were in fact wetter than normal. Further details and comparisons of reconstructed and recent climate are given by Duvick and Blasing (1981). Analysis of annual rings of Iowa's oldest trees has contributed to a better understanding of the region's hydrologic history, providing long-term estimates of the expected frequencies of extreme events (e.g. , dust bowl type situations). However, dust-bowl droughts or other extreme events may become more, or less, frequent in future centuries if, for example, the global climate warms in response to increasing amounts of atmospheric carbon dioxide. Extending the climatic record back in time can also help scientists identify the mechanisms which cause the climatic fluctuations we observe. Solar activity, for example, has been indirectly measured (by sunspot numbers) since before 1700 . Dates of large volcanic eruptions (e.g., Tambora in 1815) have also been recorded for hundreds of years. Both of these mechanisms are suspected of influencing climate on time scales of decades to centuries. However, continuous written records of climate are available in most places for only about the last hundred years. Therefore, if we are to substantiate or refute these hypothesized causes of climatic change, we must extend the climatic record by indirect means. Ring widths of old trees are extremely useful for this purpose. The climatic study outlined above provides an example of how the preservation of our oldest trees has more than just aesthetic value. These trees are living records of their environmental histories, and we can learn nothing from those histories if the records are destroyed . ACKNOWLEDGMENTS We thank the Iowa State Conservation Commission for permission to sample trees in state parks and preserves. W e also thank Bill Gilbert, H. R. Delcourt, and D . C. West for their helpful comments on earlier drafrs of this paper. REFERENCES ANDERSON, W. A. 1938. The oldesc Iowa tree. Proc . Iowa Acad. Sci. 45:73-74. DUVICK, D. N., and T. J . BLASING. 198 1. A dendroclimatic reconstruc-tion of annual precipitation amounts in Iowa since 1680. Water Resour. Res. 17: 1183- 1189. FRITIS, H . C. 1976. Tree rings and climate. Academic Press, London. HARLOW, W. M., E. S. HARRAR, and F. M. WHITE. 1979. Textbook of dendrology. McGraw-Hill Book Company, New York. LANDERS, R. Q. 1977. Dendrochronology in Iowa - An introduction. Unpublished manuscript for class instruction, Iowa Scace University, Ames, Iowa. STOKES, M. A., and T. L. SMILEY. 1968. An introduction ro tree-ring dating. Univers ity of Chicago Press , Chicago. THOMPSON, G. W., and H . G. HERTEL. 1981. The forest resources of Iowa in 1980. Proc. Iowa Acad. Sci. 88:2-6 U. S. DEPARTMENT OF AGRICULTURE, Forest Service. 1965 . Silvicsof forest trees of the United Scares. Agriculture Handbook No. 27 1. Washingron, D.C. 3Duvick and Blasing: Iowa's Oldest OaksPublished by UNI ScholarWorks, 1983

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Iowa\u27s Oldest Oaks

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