Ecology of the urban forest—Introduction to part I

This first of two special issues on urban forest ecology offers new empirical work describing forest structure and composition. Four avenues of inquiry are pursued in this introductory paper with the purpose of setting the contributions of the special issue in context of the existing literature. First, in temperate regions of the world, it is likely 60–80% of a city's area supports enough trees to meet conventional definitions of “forest”. Second, the geographical distribution of canopy cover is understood best as dependent upon the historical development of the city and its division into land-use sectors. Third, physiognomy is poorly understood and varies widely depending on the amount and kind of human intervention in the colonization and regeneration processes. Fourth, dominance and diversity are likely to be hotly debated questions of urban forest structure because of lack of agreement as to what constitutes a “good” composition. Finally, a typology of urban forest structure is needed to be followed by historical explanations of how biology and human agency combine to bring about these structures.