Ramzi Touchan

Interests

Teaching

Dendrochronology and Dendroclimatology

Research

Dendrochronology and Dendroclimatology

Courses

Scholarly Contributions

Journals/Publications

• Touchan, R., Black, B., Shamir, E., Hughes, M. K., & Meko, D. M. (2021). A multimillennial snow water equivalent reconstruction from giant sequoia tree rings.
• Camarero, J. J., Sánchez-Salguero, R., Ribas, M., Touchan, R., Andreu-Hayles, L. .., Dorado-Liñán, I., Meko, D. M., & Gutiérrez, E. (2020). Biogeographic, atmospheric, and climatic factors influencing tree growth in mediterranean aleppo pine forests.
• Lepley, K., Touchan, R., Meko, D., Shamir, E., Graham, R., & Falk, D. (2020). A multi-century Sierra Nevada snowpack reconstruction modeled using upper-elevation coniferous tree rings (California, USA).
• Meko, D. M., Touchan, R., Kherchouche, D., & Slimani, S. (2020). Direct versus indirect tree ring reconstruction of annual discharge of Chemora River, Algeria.
• Shamir, E., Meko, D., Touchan, R., Lepley, K. S., Campbell, R., Kaliff, R. N., & Georgakakos, K. P. (2020). Snowpack- and Soil Water Content-Related Hydrologic Indices and Their Association With Radial Growth of Conifers in the Sierra Nevada, California.
• Eastoe, C. J., Tucek, C. S., & Touchan, R. (2019). Delta C-14 AND delta C-13 IN ANNUAL TREE-RING SAMPLES FROM SEQUOIADENDRON GIGANTEUM, AD 998-1510: SOLAR CYCLES AND CLIMATE. RADIOCARBON, 61(3), 661-680.
• Fletcher, T., Touchan, R., Lepley, K., Rouini, N., Bloye, R., Tremarelli, T. S., Pena, K., & Meko, D. M. (2019). TWO RECONSTRUCTIONS OF AUGUST-JULY PRECIPITATION FOR CENTRAL NORTHERN ARIZONA FROM TREE RINGS. TREE-RING RESEARCH, 75(2), 116-126.
• Kedziora, W., Touchan, R., Meko, D., Szyc, K., Wojtan, R., Bijak, S., & Tomusiak, R. (2019). The 2019 International Summer School "Tree Rings, Climate, Natural Resources, and Human Interactions," Warsaw, Poland. DENDROCHRONOLOGIA, 58.
• Choury, Z., Shestakova, T. A., Himrane, H., Touchan, R., Kherchouche, D., Camarero, J. J., & Voltas, J. (2017). Quarantining the Sahara desert: growth and water-use efficiency of Aleppo pine in the Algerian Green Barrier. EUROPEAN JOURNAL OF FOREST RESEARCH, 136(1), 139-152.
• Coulthard, B. L., Touchan, R., Anchukaitis, K. J., Meko, D. M., & Sivrikaya, F. (2017). Tree growth and vegetation activity at the ecosystem-scale in the eastern Mediterranean. ENVIRONMENTAL RESEARCH LETTERS, 12(8).
• Coulthard, B., Touchan, R., Anchukaitis, K. A., & Meko, D. M. (2017). Tree growth and vegetation activity at the ecosystem-scale in the eastern Mediterranean. Environ. Res. Lett., 12(084008), 1-10. doi:https://doi.org/10.1088/ 1748-9326/aa7b26.
• Creasman, P. P., Touchan, H., Baisan, C. B., Bassir, H., Caroli, R., Doyle, N., Herrick, H., Koutkat, M. A., & Touchan, R. (2017). An Illustrated Glossary of Arabic-English Dendrochronology Terms and Names. Palarch Journal of the Archaeology of Egypt/Egyptology, 14(3), 35.
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  The publication illustrated glossary presents a selection of essential terms and people in the study of dendrochronology‭, ‬in Arabic and English‭. ‬It is intended to make accessible an array of related literature to Arabic readers‭, ‬in hopes that the application of tree‭-‬ring research will be more widely applied to archaeological studies‭, ‬especially in Egypt‭.‬
• Creasman, P. P., Touchane, H., Bassir, H., Caroli, R., Doyle, N., Herrick, H., Koutkat, M., & Touchan, R. (2017). An Illustrated Glossary of Arabic-English Dendrochronology Terms and Names. Journal of the Archaeology of Egypt/Egyptology, 14(3), 1-35.
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  A substantial addition to the utility of dendrochronology in the Arabic-speaking world. Some 9,000 words and 70 illustrations, providing the fundamental concepts of the field to those whose primary or only reading capability is Arabic. Virtually no material exists in Arabic, which hinders wider spread use of the methods.
• Kostyakova, T. V., Touchan, R., Babushkina, E. A., & Belokopytova, L. V. (2017). Precipitation reconstruction for the Khakassia region, Siberia, from tree rings. HOLOCENE, 9. doi:https://doi.org/10.1177/0959683617729450
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  A nested July-June precipitation reconstruction for the period AD 1777-2012 was developed from multi-century tree-ring records of Pinus sylvestris L. (Scots pine) for the Republic of Khakassia in Siberia, Russia. Calibration and verification statistics for the period 1948-2012 show a high level of skill, and account for a significant portion of the observed variance (>50%) irrespective of which period is used to develop or verify the regression model. Split-sample validation supports our use of a reconstruction model based on the full period of reliable observational data (1948-2012). Thresholds (25th and 75th percentiles) based on the empirical cumulative distribution 1948-2012 observed precipitation were used to delineate dry years and wet years of the long-term reconstruction. The longest reconstructed dry period, defined as consecutive years with less than 25th percentile of observed July-June precipitation, was 3 years (1861-1863). There was no significant difference in the number dry and wet periods during the 236 years of the reconstructed precipitation. Maps of geopotential height anomalies indicate that dry years differ from wet years primarily in the location of an anomalous 500 mb ridge approximately over the study area.
• Touchan, R., Anchukaitis, K. J., Meko, D. M., Kerchouche, D., Slimani, S., Ilmen, R., Hasnaoui, F., Guibal, F., Julio, C. J., Sanchez-Salguero, R., Piermattei, A., Sesbou, A., Cook, B. I., Sabir, M., & Touchane, H. (2017). Climate controls on tree growth in the Western Mediterranean. HOLOCENE, 27(10), 1429-1442.
• Cook, B. I., Anchukaitis, K. J., Touchan, R., Meko, D. M., & Cook, E. R. (2016). Spatiotemporal drought variability in the Mediterranean over the last 900 years. JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, 121(5), 2060-2074.
• Touchan, R., Kherchouche, D., Oudjehih, B., Touchan, H., Slimani, S., & Meko, D. M. (2016). Dendroclimatology and wheat production in Algeria. JOURNAL OF ARID ENVIRONMENTS, 124, 102-110.
• Touchan, R., Shishov, V. V., Tychkov, I. I., Sivrikaya, F., Attieh, J., Ketmen, M., Stephan, J., Mitsopoulos, I., Christou, A., & Meko, D. M. (2016). Elevation-layered dendroclimatic signal in eastern Mediterranean tree rings. ENVIRONMENTAL RESEARCH LETTERS, 11(4).
• Cook, E. (2015). Old World Droughts and Pluvials During the Common Era. Old World Droughts and Pluvials During the Common Era, 9. doi:e1500561
• Cook, E. R., Seager, R., Kushnir, Y., Briffa, K. R., Buntgen, U., Frank, D., Krusic, P. J., Tegel, W., van, d., Andreu-Hayles, L., Baillie, M., Baittinger, C., Bleicher, N., Bonde, N., Brown, D., Carrer, M., Cooper, R., Cufar, K., Dittmar, C., , Esper, J., et al. (2015). Old World megadroughts and pluvials during the Common Era. SCIENCE ADVANCES, 1(10).
• Meko, D. M., Friedman, J. M., Touchan, R., Edmondson, J. R., Griffin, E. R., & Scott, J. A. (2015). Alternative standardization approaches to improving streamflow reconstructions with ring-width indices of riparian trees. HOLOCENE, 25(7), 1093 –1101. doi:10.1177/0959683615580181
• Meko, D. M., Friedman, J. M., Touchan, R., Edmondson, J. R., Griffin, E. R., & Scott, J. A. (2015). Alternative standardization approaches to improving streamflow reconstructions with ring-width indices of riparian trees. HOLOCENE, 25(7), 1093-1101.
• Shah, S. K., Touchan, R., Babushkina, E., Shishov, V. V., Meko, D. M., Abramenko, O. V., Belokopytova, L. V., Hordo, M., Jevsenak, J., Kedziora, W., Kostyakova, T. V., Moskwa, A., Oleksiak, Z., Omurova, G., Ovchinnikov, S., Sadeghpour, M., Saikia, A., Zsewastynowicz, L., Sidenko, T., , Strantsov, A., et al. (2015). AUGUST TO JULY PRECIPITATION FROM TREE RINGS IN THE FOREST-STEPPE ZONE OF CENTRAL SIBERIA (RUSSIA). TREE-RING RESEARCH, 71(1), 37-44.
• Edmondson, J., Friedman, J., Meko, D., Touchan, R., Scott, J., & Edmondson, A. (2014). DENDROCLIMATIC POTENTIAL OF PLAINS COTTONWOOD (POPULUS DELTOIDES SUBSP MONILIFERA) FROM THE NORTHERN GREAT PLAINS, USA. TREE-RING RESEARCH, 70(1), 21-30.
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  A new 368-year tree-ring chronology (A.D. 1643-2010) has been developed in western North Dakota using plains cottonwood (Populus deltoides subsp. monilifera) growing on the relatively undisturbed floodplain of the Little Missouri River in the North Unit of Theodore Roosevelt National Park. We document many slow-growing living trees between 150-370 years old that contradict the common understanding that cottonwoods grow fast and die young. In this northern location, cottonwood produces distinct annual rings with dramatic interannual variability that strongly crossdate. The detrended tree-ring chronology is significantly positively correlated with local growing season precipitation and soil moisture conditions (r = 0.69). This time series shows periods of prolonged low radial tree growth during the known droughts of the instrumental record (e.g. 1931-1939 and 1980-1981) and also during prehistory (e.g. 1816-1823 and 1856-1865) when other paleoclimate studies have documented droughts in this region. Tree rings of cottonwood will be a useful tool to help reconstruct climate, streamflow, and the floodplain history of the Little Missouri River and other northern river systems.
• Edmondson, J., Friedman, J., Meko, D., Touchan, R., Scott, J., & Edmondson, A. (2014). Dendroclimatic potential of plains cottonwood (Populus deltoides Subsp. Monilifera) from the northern great plains, USA. Tree-Ring Research, 70(1), 21-30. doi:http://dx.doi.org/10.3959/1536-1098-70.1.21
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  Abstract: A new 368-year tree-ring chronology (A.D. 1643-2010) has been developed in western North Dakota using plains cottonwood (Populus deltoides subsp. monilifera) growing on the relatively undisturbed floodplain of the Little Missouri River in the North Unit of Theodore Roosevelt National Park. We document many slow-growing living trees between 150-370 years old that contradict the common understanding that cottonwoods grow fast and die young. In this northern location, cottonwood produces distinct annual rings with dramatic interannual variability that strongly crossdate. The detrended tree-ring chronology is significantly positively correlated with local growing season precipitation and soil moisture conditions (r = 0.69). This time series shows periods of prolonged low radial tree growth during the known droughts of the instrumental record (e.g. 1931-1939 and 1980-1981) and also during prehistory (e.g. 1816-1823 and 1856-1865) when other paleoclimate studies have documented droughts in this region. Tree rings of cottonwood will be a useful tool to help reconstruct climate, streamflow, and the floodplain history of the Little Missouri River and other northern river systems. Copyright © 2014 by The Tree-Ring Society.
• Meko, D. M., Touchan, R., Villanueva Diaz, J., Griffin, D., Woodhouse, C. A., Castro, C. L., Carillo, C., & Leavitt, S. W. (2014). Sierra San Pedro Martir, Baja California, cool-season precipitation reconstructed from earlywood width of Abies concolor tree rings. JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES, 118(4), 1660-1673.
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  Tree ring data are analyzed for a multicentury record of drought history in the Sierra San Pedro Martir (SSPM) of Baja California, Mexico. Climatic variation in the study area is of particular interest because the SSPM is a rich biotic environment at the southern limit of the California floristic province and the southern limit of the planetary jet stream. Future shifts in the jet stream would be expected to have amplified effect on this marginal environment. The study applies linear regression to tree ring indices of earlywood-width of Abies concolor to estimate a 353 year (1658-2010 C.E.) record of cool-season (October-April) precipitation, P, in SSPM. Time-nested regression models account for more than half the variance of grid point P in calibration periods of length 50-65 years. Cross-spectral analysis indicates strong tracking of observed P by the reconstruction over a broad range of frequencies. Robustness of the reconstruction is supported by synchrony of reconstructed P with tree ring variations in other tree species from SSPM. The reconstruction emphasizes the severity of the 1950s drought in a long-term context and the single-year intensity of droughts in the last decade: 2007 stands out as the driest reconstructed year, with a high percentage of missing rings in A. concolor. The reconstruction identifies the early twentieth century pluvial as the wettest epoch in the last 353 years in the SSPM. High-elevation tree species in SSPM may be especially well-suited to sensing snowpack-related moisture variations associated with a southerly branched jet stream and the types of weather systems active in the pluvial.
• Slimani, S., Touchan, R., Derridj, A., Kherchouche, D., & Gutierrez, E. (2014). Fire history of Atlas cedar (Cedrus atlantica Manetti) in Mount Chelia, northern Algeria. JOURNAL OF ARID ENVIRONMENTS, 104, 116-123.
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  The first fire history of the Cedrus atlantica forest of Chelia in northern Algeria is reconstructed from samples of 14 and 12 dead fire-scarred trees from lower and upper elevation stands respectively. Superposed epoch analysis is applied to summarize mean climate conditions before, during, and after sets of fire years in both stands. Prior to 1850, C atlantica forests in both sites were characterized by high frequency and low intensity fire regimes. The sharp decline in the fire frequency after the mid-nineteenth century coincided with the promulgation of the first laws governing land and forest use in Algeria. Most fire events occurred in the summer, during the latter part of the growing season. No significant relationships were found between an October-June precipitation reconstruction and fire events. This could be due to anthropogenic and topographic factors. The findings of this study provide baseline knowledge on the ecological role of fire in the C atlantica forest. This information is vital to support ongoing ecosystem management efforts in the region. (C) 2014 Elsevier Ltd. All rights reserved.
• Touchan, R., Christou, A. K., & Meko, D. M. (2014). Six centuries of May-July precipitation in Cyprus from tree rings. CLIMATE DYNAMICS, 43(12), 3281-3292.
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  A May-July precipitation nested reconstruction for the period AD 1415-2010 was developed from multi-century tree-ring records of Pinus nigra, Pinus brutia, and Cedrus brevifolia for Cyprus. Calibration and verification statistics for the period 1917-2010 show a good level of skill, and split-sample validation over 1917-2010 supports temporal stability of the tree-ring signal for precipitation. Smoothed annual time series of reconstructed precipitation and a tally of drought events in a moving time window indicate that the calibration period is not representative of the full range of drought variability. While convective precipitation in the warm season may be driven strongly by local factors, composite maps of geopotential height anomaly for dry years and wet years support large-scale atmospheric-flow influence related to height anomalies over the broader region of northeast Africa and the eastern Mediterranean. Emerging positive trend in reconstruction residuals may be an early sign of exacerbation of drought stress on trees by recent warming in May-July. Future warming expected from increases in greenhouse gases poses a threat to forest resources in Cyprus and elsewhere in the Mediterranean.
• Touchan, R., Christou, A. K., & Meko, D. M. (2014). Six centuries of May-July precipitation in Cyprus from tree rings. Climate Dynamics, 1-12.
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  A May-July precipitation nested reconstruction for the period AD 1415-2010 was developed from multi-century tree-ring records of Pinus nigra, Pinus brutia, and Cedrus brevifolia for Cyprus. Reconstructions were interpreted climatologically.
• Touchan, R., Meko, D. M., & Anchukaitis, K. J. (2014). DENDROCLIMATOLOGY IN THE EASTERN MEDITERRANEAN. RADIOCARBON, 56(4), S61-S68.
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  Dendroclimatology in the Eastern Mediterranean (EM) region has made important contributions to the understanding of climate variability on timescales of decades to centuries. These contributions, beginning in the mid-20th century, have value for resource management, archaeology, and climatology. A gradually expanding treering network developed by the first author over the past 15 years has been the framework for some of the most important recent advances in EM dendroclimatology. The network, now consisting of 79 sites, has been widely applied in large-scale climatic reconstruction and in helping to identify drivers of climatic variation on regional to global spatial scales. This article reviews EM dendroclimatology and highlights contributions on the national and international scale.
• Touchan, R., Touchan, R., Anchukaitis, K. J., Anchukaitis, K. J., Shishov, V. V., Shishov, V. V., Sivrikaya, F., Sivrikaya, F., Attieh, J., Attieh, J., Ketmen, M., Ketmen, M., Stephan, J., Stephan, J., Mitsopoulos, I., Mitsopoulos, I., Christou, A., Christou, A., Meko, D. M., & Meko, D. M. (2014). Spatial patterns of eastern Mediterranean climate influence on tree growth. HOLOCENE, 24(4), 381-392.
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  The first large-scale network of 79 tree-ring chronologies in the Eastern Mediterranean and Near East (EMNE; 33 degrees N-42 degrees N, 21 degrees E-43 degrees E) is described and analyzed to identify the seasonal climatic signal in indices of annual ring width. Correlation analysis and cluster analysis are applied to tree-ring data and gridded climate data to assess the climate signal embedded in the network in preparation for climate field reconstructions and formal proxy/model intercomparison experiments. The lengths of the 79 combined chronologies range from 89 to 990 years. The monthly correlations and partial correlations reveal a pervasive positive association with May, June, and sometimes July precipitation, positive correlations with winter and spring (December through April) temperatures, and negative relationships with May through July temperature, although as expected, there are site-to-site exceptions to these general patterns. Cluster analysis suggests three groups of sites based on their association with climate. The chronologies for the EMNE have coherent seasonal precipitation and temperature signals across a fairly broad geographical domain. The predominant signal is a positive growth response to May-June precipitation. Collectively, the findings suggest that the network can be exploited to develop season-specific field reconstructions of precipitation and drought history in the EMNE.
• Griffin, D., Woodhouse, C. A., Meko, D. M., Stahle, D. W., Faulstich, H. L., Carrillo, C., Touchan, R., Castro, C. L., & Leavitt, S. W. (2013). North American monsoon precipitation reconstructed from tree-ring latewood. GEOPHYSICAL RESEARCH LETTERS, 40(5), 954-958.
• Griffin, D., Woodhouse, C. A., Meko, D. M., Stahle, D. W., Faulstich, H. L., Carrillo, C., Touchan, R., Castro, C. L., & Leavitt, S. W. (2013). North American monsoon precipitation reconstructed from tree-ring latewood. Geophysical Research Letters, 40(5), 954-958.
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  Abstract: The North American monsoon is a major focus of modern and paleoclimate research, but relatively little is known about interannual- to decadal-scale monsoon moisture variability in the pre-instrumental era. This study draws from a new network of subannual tree-ring latewood width chronologies and presents a 470-year reconstruction of monsoon (June-August) standardized precipitation for southwestern North America. Comparison with an independent reconstruction of cool-season (October-April) standardized precipitation indicates that southwestern decadal droughts of the last five centuries were characterized not only by cool-season precipitation deficits but also by concurrent failure of the summer monsoon. Monsoon drought events identified in the past were more severe and persistent than any of the instrumental era. The relationship between winter and summer precipitation is weak, at best, and not time stable. Years with opposing-sign seasonal precipitation anomalies, as noted by other studies, were anomalously frequent during the mid to late 20th century. © 2013. American Geophysical Union. All Rights Reserved.
• Heinrich, I., Touchan, R., Linan, I. D., Vos, H., & Helle, G. (2013). Winter-to-spring temperature dynamics in Turkey derived from tree rings since AD 1125. CLIMATE DYNAMICS, 41(7-8), 1685-1701.
• Touchan, R., Meko, D. M., Ballesteros-Canovas, J. A., Sanchez-Salguero, R., Julio Camarero, J., Kerchouche, D., Muntan, E., Khabcheche, M., Blanco, J. A., Rodriguez Morata, C., Garofano-Gomez, V., Martin, L. A., Alfaro-Sanchez, R., Garah, K., Hevia, A., Madrigal-Gonzalez, J., Sanchez-Miranda, A., Shestakova, T. A., Tabakova, M., , , ., et al. (2013). DENDROCHRONOLOGY COURSE IN VALSAIN FOREST, SEGOVIA, SPAIN. TREE-RING RESEARCH, 69(2), 93-100.
• Griffin, D., Meko, D. M., Touchan, R., Leavitt, S. W., & Woodhouse, C. A. (2011). Latewood chronology development for summer-moisture reconstruction in the US Southwest. Tree-Ring Research, 67(2), 87-101.
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  Abstract: Tree-ring studies have demonstrated that conifer latewood measurements contain information on long-term North American monsoon (NAM) variability, a hydroclimatic feature of great importance to plants, animals, and human society in the US Southwest. This paper explores data-treatment options for developing latewood chronologies aimed at NAM reconstruction. Archived wood samples for five Douglas-fir (Pseudotsuga menziesii, Mirb. Franco) sites in southeastern Arizona are augmented with new collections. The combined dataset is analyzed along with time series of regionally averaged observed precipitation to quantify the strength of regional precipitation signal in latewood time series and to identify ways of increasing the signal strength. Analysis addresses the signal strength influences of including or excluding "false" latewood bands in the nominal "latewood" portion of the ring, the necessary adjustment of latewood width for statistical dependence on antecedent earlywood width, and tree age. Results suggest that adjusted latewood width chronologies from individual sites can explain around 30% of the variance of regional summer (July-August) precipitation - increasing to more than 50% with use of multiple chronologies. This assessment is fairly insensitive to the treatment of false latewood bands (in intra-annual width and δ 13C variables), and to whether latewood-width is adjusted for dependence on earlywood-width at the core or site level. Considerations for operational chronology development in future studies are (1) large tree-to-tree differences in moisture signal, (2) occasional nonlinearity in EW-LW dependence, and (3) extremely narrow and invariant latewood width in outer portions of some cores. A protocol for chronology development addressing these considerations is suggested. © 2011 The Tree-Ring Society.
• Garfin, G. M., Garfin, G. M., Garfin, G. M., Hughes, M. K., Hughes, M. K., Hughes, M. K., Liu, Y., Liu, Y. u., Liu, Y., Burns, J. M., Burns, J. M., Burns, J. M., Touchan, R., Touchan, R., Touchan, R., Leavitt, S. W., Leavitt, S. W., Leavitt, S. W., Zhisheng, A., , Zhisheng, A., et al. (2005). Exploratory temperature and precipitation reconstructions from the Qinling Mountains, North-Central China. Tree-Ring Research, 61(2), 59-72.
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  Abstract: February-April (FMA) temperature at Foping (1879-1989) and July-August (JA) precipitation at Xian (1895-1988) have been reconstructed using total ring width (TRW) and maximum latewood density (MXD) from trees in the Qinling Mountains, at the northern limit of the East Asian monsoon, in central China. The Xian JA precipitation reconstruction, albeit short, represents the first well-replicated, crossdated dendroclimatic reconstruction of summer monsoon precipitation for this region. Reconstructed Xian precipitation shows significant positive relationships with historical evidence from the region. The key feature of the precipitation reconstruction is prolonged summer drought during the late 1920s and early 1930s. The Foping reconstruction displays warmer-than-average FMA temperatures during this time period. These exploratory reconstructions, along with a previous reconstruction from Huashan, demonstrate the complexity of attempting dendroclimatic reconstructions from this region. Our results indicate that further attempts to locate long-lived conifers from here can result in an extended well-calibrated and verified reconstruction of summer monsoon precipitation. Copyright © 2005 by the Tree-Ring Society.

Presentations

• Touchan, R., Kherchouche, D., Anchukaitis, K. J., Oudjehih, B., Touchane, H., Slimani, S., & Meko, D. M. (2015, December). Dendroagricultural Signal in Algeria. American Geophysical Union Fall Meeting. San Francisco: American Geophysical Union.

Others

• Meko, D. M., Woodhouse, C. A., & Touchan, R. (2014, August). Klamath/San Joaquin/Sacramento Hydroclimatic Reconstructions from Tree Rings. Final Report to California Department of Water Resources, Agreement 4600008850. http://www.water.ca.gov/waterconditions/docs/tree_ring_report_for_web.pdf