The ecological view in urban forestry evolved
from diverse roots beginning over 100 years ago and is
currently expressed in formal programs of research and
practice. Among the most useful concepts in urban forest
ecology are structure, function, diversity, dominance,
mosaic-gradients, and ecosystems. These concepts assist
in understanding changes in ecological states that produce
changes in the distribution of benefits and costs. The
ecological history of urban forestry provides these concepts
as points of departure for two special issues of the Journal of
Arboriculture devoted to the Sacramento urban forest
ecosystem