Historical Continuity

Abstract

The historical continuity of old growth urban forests in the New York, New York, and Philadelphia, Pennsylvania, metropolitan areas was analyzed to reveal the strengths and weaknesses of historical ecology methods for forest ­dynamics research. The use of paleopalynological techniques to determine forest changes in the time span of the past century to recent millennia requires thoughtful selection of the sampling site but can reveal unrecorded species losses and introductions as well as regional forest changes related to urbanization. Pre-forest clearance witness tree records provide the basis for comparison to ascertain how the modern old growth urban forest differs from the forest primeval. Historical floras from the period immediately following the forest resetting event are catalogs of arboreal ­species present at the time of old growth urban forest formation that can be used to determine subsequent species diversity changes. Forest remeasurement studies are limited because methodological uniformitarianism and actualism are difficult to achieve due to insufficient detail in recording prior field procedures. However, ­comparisons of past data and resampling results provide invaluable information on changes in the canopy, subcanopy, and sapling layers that is essential to understanding­ forest dynamics and historical continuity.