Effects of land cover and water availability on brittlebush (Encelia farinosa) flowering phenology and its pollinator community.

Phenology is the seasonal timing of environment-mediated events such as
growth and reproduction. Phenology is quantified by determining time of onset
and end of events, duration, and number of flowers (Augspurger 1983, Rathcke and Lacey
1985). Studies of flowering and leafing phenology have dramatically increased
during the last few decades due to growing concerns over global climate change and because
phenology is a highly sensitive indicator that researchers can use to study the effects of
climate change at multiple scales (Chuine et al. 2000, Sparks and Menzel 2002, Peuelas
et al. 2004, Williams and Abberton 2004). Urban climatic conditions are
considered similar to the changing global climate conditions; therefore, many researchers
study urbanized areas as smaller scale experiments, or models, of global climate change
(Ziska et al. 2003). Concerns over climate change are not the only reasons for
studying urban ecosystems. It is important to create urban environments
resilient to social, economic, and ecological collapse. The literature of flowering phenology in urban environments suggests that
spring-blooming plants in urban environments located in temperate, Mediterranean, and
boreal ecosystems in North America, Europe, and China tend to bloom earlier in the city
than in the surrounding un-urbanized habitat (Roetzer et al. 2000, Fitter and Fitter 2002,
White et al. 2002, Ziska et al. 2003, Zhang et al. 2004). Moreover, non-woody
plants, early spring bloomers, and insect-pollinated plants in these environments tend to
be more sensitive than woody plants, mid- or late-spring bloomers, and wind-pollinated
plants (Fitter and Fitter 2002, Traidl-Hoffman et al. 2003). Finally,
temperature (Heat Island Effect) has been assumed to be the cause of earlier flowering in
the urban environments since the large-scale advancement of flowering has been strongly
correlated with global warming. Study of flowering phenology in urban ecosystems is important
because changes in phenology may have wide-reaching consequences. Explicit study
of the potential consequences of any changes in flowering phenology in urbanized areas has
not been widely addressed; however, general ecological consequences from phenological
changes due to global climate change have been hypothesized and studied, such as earlier
and extended pollen allergy season (e.g., Van Vliet et al. 2002, Traidl-Hoffman et al.
2003, Ziska et al. 2003) and mis-matches in synchronized inter-specific interactions
(e.g., Kudo et al. 2004). These effects of global climate change may be similar
to changes and consequences in urban ecosystems. Other potential consequences
include effects on: individual fitness (e.g. offspring production and
viability); intra-specific interactions (e.g., genetic mixing); plant inter-specific
interactions (e.g., resource competition); non-plant inter-specific interactions (e.g.,
pests, pollinators, pathogens, herbivores); economics (e.g., any agriculture occurring
near or within cities, including the floral industry and crops that require pollination by
native organisms; also, private gardens); and human health (e.g., pollinosis,
psychological well-being/appeal).