Heterogeneitv in urban ecosystems: Patterns and process

Heterogeneity in urban ecosystems derives from a combination of natural and engineered landscape features, as well as behavior of human individuals and institutions. Modern urban regions in North America and elsewhere are no longer uniformly compact and densely populated but have extended into surrounding regions and include intricate mixes of residential, commercial, and residual agricultural, forest, and other managed and unmanaged vegetated areas. Compared to less developed ecosystems, heterogeneity in water, carbon, nutrient, and energy cycling may be enhanced, specifically over the short distances associated with urban development patterns. We review conceptual approaches to characterizing and representing heterogeneity in urban ecosystems and illustrate some of the main sources of heterogeneity resulting from interactions within and between urban patch networks, with special reference to examples drawn from the Baltimore Ecosystem Study.