Site and Soil Characteristics Driving White Oak Decline in the Chicago Region

Abstract Background A widespread trend of declining and dying mature oaks has been observed in the Chicago region since 2019. While there have been studies on the stress-physiology of white oaks and the epidemiology of decline diseases, there have not been any studies focusing on the relationship between predisposing abiotic site and soil characteristics and white oak decline in the Chicago metro area. The objective of this study was to determine if site and soil characteristics are significantly related to white oak decline in the Chicago region. Methods Soil and site characteristics were compared between 66 healthy and declining trees of the white oak group on 32 sites in the summer of 2023. During site visits, deep pedon samples, composite soil samples, fine roots for oomycete detection, site characteristics, tree health assessments, and site management information were collected. DAS-ELISA Phyt tests and soil lab analyses were conducted. Results Low micronutrient levels, compaction, elevated soil sodium, and poor drainage appear to be the most relevant predisposing abiotic site characteristics for white oak decline through ANOVA and GLMMs. The ELISA Phyt tests were 88% positive for both healthy and declining trees. Conclusions Results from this study can help arborists and urban foresters improve management and treatment design and implementation for white oaks, improve our understanding of the predisposing factors influencing the health of managed trees, and improve future planting guidelines.