Franklin Park: 150 years of changing design,disturbance, and impact on tree growth

Urban stresses are known to affect street trees growing in spatially restricted conditions, but even in relatively large parks the cumulative effects by construction, pedestrian uses, and impacts from temporary events may have deleterious long-term effects on plant health. In Columbus, Ohio, the 93 ac (42.3 ha) Franklin Park has been subjected to major construction events and site re-configuration about once per generation—at least six times in 150 years. The first recorded shade- and ornamental tree installations occurred between 1895 and 1910. Those trees, as well as those native to the park, were mapped in 1939, 1989, and again in 2000. Testing the hypothesis that cumulative disturbance reduces tree vigor and growth rate even in open-grown conditions, tree diameters were compared over the sixty year period between 1939 and 2000. Soil compaction and percolation were measured on a 50 m grid, and maps were overlain to determine where site disturbance,buildings, utility lines, paths and pavements had occurred since 1860. Only 8% of the park's surface escaped disturbance; undisturbed areas occurred only in isolated patches. For all trees, trunk diameter increase averaged 0.5 cm/year for 61 years. While late successional species (e.g., Quercus, Acer) had growth rates less than expected for open-grown specimens, many early successional species (Celtis, Populus) were less affected. Despite availability of soil nutrients and lack of canopy or understory competition, tree health was generally poor in all size classes and the majority of the trees present in 1939 were in decline by 2000.