Urban forests develop on a scale of decades or longer. However, virtually all published studies of street tree survival and growth have examined a period of 5-20 years, biasing our understanding to cohorts of recently planted saplings. Long term recruitment and attrition of trees in a realistically heterogeneous urban community has been largely ignored. In a prelude to a long-term study of urban tree dynamics, we have used historical aerial photos to document urban land uses in a small city in southeast Ohio. Land use was recorded at > 200 regularly spaced points at ca. 20 year intervals beginning in 1939. Transition matrices are presented for each of four intervals.
Over eighty years, the proportion of grassland has remained stable at ca. 35% as high-density residential area has expanded into formerly pastured land, primarily between 1950 and 1970. Cultivated land, originally the dominant land use, declined to 0 by 1970. Impermeable surfaces increased from ca. 12% to 36% with the expansion of new suburbs. Tree cover increased from ca. 20% to 30% reflecting a) natural regeneration on brown fields caused by prior collapse of small industries and abandonment of a rail line between 1940 and 1955, b) planting of saplings in newly landscaped residential areas, and c) crown expansion by street trees present at the beginning of the period. We conclude that the urban ecosystem dynamic is strongly episodic, driven by short-lived phases of economic expansion and contraction. Although this dynamic entails a high rate of individual tree attrition, forest cover may persist for several decades in economically stable neighborhoods and topographically undesirable sites.