Department of Geography and Planning

Education

Ph.D., University of Georgia, 1989 

Interests and Research

Dr. Soulé’s main area of research deals with various aspects of climate and vegetation change. He is currently wrapping up a southern California-based project dealing with “hot droughts” and the impacts of these droughts on the radial growth rates of several species of pine trees in the San Jacinto Mountains. One of the main takeaways from this project is that droughts in southern California have changed since the mid-20th century as they are almost always now combined with significantly above normal temperatures and are more intense, occurring more frequently, and lasting longer than historic droughts. Surprisingly, the research has revealed that trees growing in high elevations are thriving, despite California experiencing “megadrought” conditions for much of the 21st century.

In support of tree-ring research at ASU, Pete operates the Department of Geography and Planning’s Appalachian Tree Ring Lab with Dr. Saskia van de Gevel. The lab is available for any student that would like to conduct a research project that uses tree-ring data. Pete has been a resident of the high country since 1993 and snowboards, hikes, and plays disc golf for his leisure activities.

Pete teaches Global Climate Change (F2F and online versions), Introduction to Physical Geography (F2F and online versions), Weather and Climate (F2F and online versions), and Communicating Geographic Information (F2F and online versions).

Refereed Journal Publications

2024. Knapp, P. A., Catherwood, A. A., and Soulé, P. T.  Placing 21st Century Warming in Southern California, USA in a Multi-Century Historical Context. Atmosphere. V 15(6), 649. https://doi.org/10.3390/atmos15060649. ISI Impact Factor: 2.9. (PDF)

2024. P. A. Knapp, P. T. Soulé, T. J. Mitchell, A. A. Catherwood, and H. S. Lewis. Increasing radial growth in old‑growth high‑elevation conifers in Southern California, USA, during the exceptional “hot drought” of 2000–2020. International Journal of Biometeorology. DOI: https://doi.org/10.1007/s00484-024-02619-3. (PDF)

2024. Soulé, P. T. and P. A. Knapp. The evolution of “Hot” droughts in Southern California, USA from the 20th to the 21st century. Journal of Arid Environments 220: 105118. https://doi.org/10.1016/j.jaridenv.2023.105118. (PDF)

2022. Soulé, P. T. Temporal patterns of drought frequency and severity in North Carolina, 1920-2019 and the drought gap of the 1960s-1970s. Southeastern Geographer. DOI: 10.1353/sgo.2022.0003. (PDF)

2021. J. T. Maxwell, J. C. Bregy, S. M. Robeson, P. A. Knapp, P. T. Soulé, and V. Trouet. Recent increases in tropical cyclone precipitation extremes over the US east coast. Proceedings of the National Academy of Sciences. DOI: 10.1073/pnas.2105636118. (PDF)

2021. J. J. Jonaitis, L. B. Perry, P. T. Soule, C. Thaxton, M. F. Andrade-Flores, T. I Vargas, and L. Ticona. Spatiotemporal patterns of ENSO-precipitation relationships in the tropical Andes of southern Peru and Bolivia. International Journal of Climatology. DOI: 10.1002/joc.7058. (PDF)

2021. P. T. Soulé, P. A. Knapp, J.T . Maxwell, and T. J. Mitchell. A comparison of the climate response of longleaf pine (Pinus palustris Mill.) trees among standardized measures of earlywood, latewood, adjusted latewood, and totalwood radial growth. Trees. DOI: 10.1007/s00468-021-02093-z. (PDF)

2020. P. A. Knapp, P. T. Soulé, J.T . Maxwell, J. T. Ortegren, and T. J. Mitchell. Tropical Cyclone Precipitation Regimes Since 1750 and the Great Suppression of 1843-1876 Along Coastal North Carolina, USA. International Journal of Climatology. DOI: 10.1002/joc.6615. (PDF)

2020. A. L. Kaiser, P. T. Soulé, S. L. van de Gevel, P. A. Knapp. A. Bhuta, J. Walters, E E. Montpellier. Dendroecological Investigation of Red-cockaded Woodpecker Cavity Tree Selection in Endangered Longleaf Pine Forest. Forest Ecology and Management. V 473: 118291. (PDF)

2020. E. E. Montpellier, P. A. Knapp, P. T. Soulé, and J. T. Maxwell. Microelevational Differences Affect Longleaf Pine (Pinus Palustris Mill.) Sensitivity to Tropical Cyclone Precipitation: A Case Study Using Lidar. Tree-Ring Research. Vol. 76(2), 2020, pp. 89–93. (PDF)

2020. E. E. Montpellier, P. T. Soulé, P. A. Knapp, and L. Baker Perry. Reconstructing Summer Upper-Level Flow in the Northern Rocky Mountains using an Alpine Larch Tree-Ring Chronology. Climate Research. V 79: 207-218. (PDF)

2019. P. T. Soulé and P. A. Knapp. Radial Growth Rate Responses of Western Juniper (Juniperus Occidentalis Hook.) to Atmospheric and Climatic Changes: A Longitudinal Study from Central Oregon, USA. Forests. DOI: 10.3390/f10121127. (PDF)

2019. E. E. Montpellier, P. T. Soulé, P. A. Knapp, and J. T. Maxwell. Dendroclimatic Assessment of Ponderosa Pine Radial Growth along Elevational Transects in Western Montana, U.S.A. Forests. DOI: 10.3390/f10121094. (PDF) 

2019. J. C. Bregy, J. T. Maxwell, S. M. Robeson, J. T. Ortegren, P. T. Soulé, and P. A. Knapp. Spatiotemporal Variability of Tropical Cyclone Precipitation Using a High-resolution, Gridded (0.25° x 0.25°) Dataset for the Eastern United States, 1948–2015. Journal of Climate. DOI: https://doi.org/10.1175/JCLI-D-18-0885.1.

2019. P. T. Soulé, and P. A. Knapp. A 400-Year Reconstruction of Wintertime Arctic Sea-Ice Extent Using a High-Elevation, Mid-Latitude Tree-Ring Record. International Journal of Biometeorology. DOI: 10.1007/s00484-019-01739-5 IJBM-D-18-00345R1. (PDF)

2019. P. T. Soulé, J. T. Maxwell, and P. A. Knapp. Climate-Growth Responses from Pinus ponderosa Trees Using Multiple Measures of Annual Radial Growth. Tree-Ring Research. V. 75: 25-33. (PDF)

2018. M. A. Eck, L. B. Perry, P. T. Soulé, J. W. Sugg, and D. K. Miller. Winter Climate Variability in the Southern Appalachian Mountains, 1910-2017. International Journal of Climatology. DOI: 10.1002/joc.5795. (PDF)

2018. Montpellier, E. E., Soulé, P. T., Knapp, P. A., and Shelly, J. S. Divergent Growth Rates of Alpine Larch Trees (Larix lyallii Parl.) in Response to Microenvironmentalvariability. Arctic, Antarctic, and Alpine Research. V. 50:1, e1415626-1. (PDF)

2017. Maxwell, J. T., Knapp, P. A., Ortegren, J. T., Ficklin, D. L., and Soulé, P. T. Changes in the Mechanisms Causing Rapid Drought Cessation in the Southeastern United States. Geophysical Research Letters. V. 44: 24. (PDF)

2017. Knapp, P. A. and Soulé, P. T. Spatio-Temporal Linkages between Declining Arctic Sea-Ice Extent and Increasing Wildfire Activity in the Western United States. Forests. V. 8:313. DOI: 10.3390/f8090313. (PDF)

2016. Knapp, P. A, Maxwell, J. T., and Soulé, P. T. Tropical Cyclone Rainfall Variability in Coastal North Carolina Derived from Longleaf Pine (Pinus palustris Mill.): AD 1771–2014. Climatic Change. V. 135: 311-323. (PDF)

2016. D. Austin, S. L. van de Gevel, and P. T. Soulé. Forest Dynamics and Climate Sensitivity of an Endangered Carolina Hemlock Community in the Southern Appalachian Mountains, U.S.A. Botany. V. 94: 301-309. (PDF)

2016. P. A. Knapp, J. T. Maxwell, J. T. Ortegren, and P. T. Soulé. Spatio-Temporal Changes in Comfortable Weather Duration in the Continental U.S. and Implications for Human Wellness. Annals of the Association of American Geographers . V. 106: 1-18. (PDF)

2015. D. Martin, L. B. Perry, D. Miller, and P. T. Soulé. Snowfall Event Characteristics From a High-elevation Site in the Southern Appalachian Mountains, USA. Climate Research. V. 63: 171-190.

2015. P. T. Soulé and P. A. Knapp. Analyses of Intrinsic Water-use Efficiency Indicate Performance differences of Ponderosa Pine and Douglas-fir in Response to CO2 Enrichment. Journal of Biogeography. V. 42: 144-155. (PDF)

2014. P. B. White, P. T. Soulé, and S. van de Gevel. Impacts of Human Disturbance on the Temporal Stability of Climate-Growth Relationships in a Red Spruce Forest, Southern Appalachian Mountains, USA. Dendrochronologia. V. 32: 71-77. (PDF)

2013. P. T. Soulé and P. A. Knapp. “Radial Growth Rates of Two Co-occurring Coniferous Trees in the Northern Rockies during the Past Century. Journal of Arid Environments. V. 94: 87-95. (PDF)

2013. J. T. Maxwell, J. T. Ortegren, P. A. Knapp, and P. T. Soulé. Tropical Cyclones and Drought Amelioration in the Gulf and Southeastern Coastal United States. Journal of Climate. DOI: 10.1175/JCLI-D-12-00824.1. (PDF)

2013. P. A. Knapp, P. T. Soulé and J. T. Maxwell. Mountain Pine Beetle Selectivity in Old-Growth Ponderosa Pine Forests, Montana, USA. Ecology and Evolution. DOI: 10.1002/ece3.522. (PDF)

2012. G. M. Kelly, B. F. Taubman, L. B. Perry, J. P. Sherman, P. T. Soulé, and P. J. Sheridan. Relationships between Aerosols and Precipitation in the Southern Appalachian Mountains. International Journal of Climatology. DOI: 10.1002/joc.3632. (PDF)

2012. G. M. Kelly, L. B. Perry, B. Taubman, and P. T. Soulé. Synoptic Classification of Precipitation Events in the Southern Appalachian Mountains. Climate Research. V. 55: 1-15. link

2012. P. White, S. van de Gevel, and P. T. Soulé. Succession and Disturbance in an Endangered Red Spruce-Fraser Fir Forest in the Southern Appalachian Mountains, North Carolina, U.S.A. Endangered Species Research. V. 18: 17-25. (PDF)

2012. J. T. Maxwell, P. T. Soulé, P. A. Knapp and J. T. Ortegren. Drought-Busting Tropical Cyclones in the Southeastern Atlantic United States: 1950–2008. Annals of the Association of American Geographers. V. 102: 259-275. (PDF)

2011. P. A. Knapp and P. T. Soulé. Reconstructing Annual Area Burned in the Northern Rockies, USA: AD 1626-2008. Geophysical Research Letters. V. 38: L17402. DOI: 10.1029/2011GL048119 (PDF)

2011. J. T. Maxwell and P. T. Soulé. Drought and Other Driving Forces Behind Population Change in Six Rural Counties in the United States. Southeastern Geographer. V. 51: 133-148. (PDF)

2011. J. T. Ortegren, P. A. Knapp, J. T. Maxell, W. Tyminski, and P. T. Soulé. Ocean-Atmosphere Influences on Low-Frequency Warm Season Drought Variability in the Gulf Coast and Southeastern U.S.A. Journal of Applied Meteorology and Climatology. V. 50: 1177-1186. (PDF)

2011. P. T. Soulé and P. A. Knapp. Radial Growth and Increased Water-Use Efficiency for Ponderosa Pine Trees in Three Regions in the Western United States. The Professional Geographer. V. 63: 1-13. (PDF)

2011. P. T. Soulé. Changing Climate, Atmospheric Composition, and Radial Tree Growth in a Spruce-Fir Ecosystem on Grandfather Mountain, North Carolina. Natural Areas Journal. V. 31: 65-74. (PDF)

2010. P. A. Knapp and P. T. Soulé. Increasing Water-Use Efficiency and Age-Specific Growth Responses of Old-Growth Ponderosa Pine Trees in the Northern Rockies. Global Change Biology. V. 17: 631-641. DOI: 10.1111/j.1365-2486.2010.02209.x. (PDF)

2009. J. T. Maxwell and P. T. Soulé. Drought in the United States during 2007: Historical Perspectives. Climate Research. V. 38: 95-104. (PDF)

2008. P. A. Knapp and P. T. Soulé. Use of Atmospheric CO₂-Sensitive Trees May Influence Dendroclimatic Reconstructions. Geophysical Research Letters. DOI: 10.1029/2008GL035664. (PDF)

2008. P. T. Soulé and P. A. Knapp. Does an August Singularity Exist in the Northern Rockies of the United States? Journal of Applied Meteorology and Climatology. DOI: 0.1175/2007Jamc1735.1. (PDF)

2007. P. T. Soulé and P. A. Knapp. Topoedaphic and Morphologic Complexity of Mortality and Foliar Damage Within Western Juniper Woodlands Following an Extreme Meteorological Event. Journal of Biogeography. V. 34: 1927-1937. (PDF)

2007. P. A. Knapp and P. T. Soulé. Trends in Mid-Latitude Cyclone Frequency and Occurrence During Fire Season in the Northern Rockies: 1900-2004. Geophysical Research Letters. 34, L20707. DOI: 10.1029/2007GL031216. (PDF)

2006. P. T. Soulé and P. A. Knapp. Radial Growth Rate Increases in Naturally Occurring Ponderosa Pine Trees: A Late-20th Century CO₂  Fertilization Effect? New Phytologist. V. 171 (2006): 379-390. (PDF)

2006. P. T. Soulé. A Comparison of 30-yr Climatic Normals for the Southeastern United States. Southeastern Geographer. V. 45 (2005): 16-24. (PDF)