We have the clearest understanding of how plants are adjusting
the timing of their activity in temperate ecosystems in Europe
and the United States; our knowledge of ecosystems on other
continents is sparser. Even so, some long-term observational
datasets do exist in semiarid, arid, and arctic ecosystems, and
they all reveal similar patterns, with general trends of advancing
springtime phenology and variability from one species to the
next. Around the globe, evidence of species shifting their phe-
nology in response to rapidly changing conditions is piling up.
Intriguingly, however, she also reports:
But not all plants are shifting their springtime activity earlier in
the year. Some are exhibiting the opposite response, delaying
their springtime activity. For example, in North Dakota, nanny-
berry, smooth sumac, and black walnut now flower approximately
10 days later than in the first half of the 1900s. And many
other species seem not to care much about changing condi-
tions and persist in undergoing springtime activity at the same
time that they have in decades past. This is especially true in
the Southern Hemisphere. Approximately 70 percent of the
species evaluated in a comprehensive study in Australia and
New Zealand showed no evidence of changes in phenology.
Informally, UCFS Members share their own anecdotal observations
along the lines of, "Tree species X is blooming earlier than ever!" To
understand why phenological changes are happening has numerous
implications–both personal and professional—for urban foresters
and affiliated professionals. On a personal level, getting outside,
looking at plants, shifting focus away from one's own problems for a
Phenology data
undergirds the
USA-NPN Pheno
Forecasts that give
you the optimal time
to treat for pests.
Phenology tracking
is also a great way
to engage the public
with your urban
forestry program.
26 CityTREES
