Long-term tree survival and diversity of highway tree planting projects

Long-term, multi-decade research on planted tree survival in urban settings is sparse. One understudied environment highway rights-of-way (ROW), lands adjacent to high-speed, unsignalized roadways. We conducted a re-inventory of planting cohorts northern Illinois, U.S. 48 km-long near Chicago which were 10-, 21-, and 30-years old evaluate long-term patterns diversity. Using each randomly selected site along the as unit observation analysis, we compared number trees documented record drawing currently alive determine percent survival. evaluated 224 sites originally contained 2944 collected data about location. For oldest cohort, 26% still 2018 (median by species = 16%, Q1 0%, Q3 48%), while 31% 21-year-old cohort (med. 6%, 47%) 86% 10-year-old 85%, 74%, 96%). The 21- 30-year-old matches estimates other researchers, higher than expected. only location characteristic that significantly affected was traffic islands (areas between entrance/exit ramps). Species with low drought tolerance less likely be for cohort. Waterlogging tolerant more Since some had very survival, richness diversity s study areas declined initial drawings reinventory. This demonstrates challenges maintaining ROW emphasizes importance selection.