Assessing seasonal richness of active flowers throughout UC Reserve sites in the 20th Century

Plant species are well documented to alter both the timing and duration of
their flowering in response to changing climate.  Plant species
often exhibit different magnitudes or directions of phenological responses
to climate changes from each other.  These shifts may have
cumulative effects on the diversity of species in flower throughout a
given flowering season, resulting in periods of high or low species
richness of actively flowering community members that differ from those
that occurred under historical conditions.   In this
study we model the effects of warming throughout the past century on the
daily species richness of actively flowering species by developing
species-specific phenoclimate models for 1,848 plant species documented to
inhabit 16 well documented plant communities across California. 
These communities encompassed a variety of distinct vegetation types,
ranging from coastal marshes and grasslands to chaparral shrublands and
mountainous conifer forests.   By examining consistent
patterns in the resultant modeled community-level flowering displays, we
demonstrate that recent warming is likely to have consistently shortened
the period in which many species flower concurrently, and that the bloom
season has advanced by nearly 5 days on average.  Accordingly,
within every flora, recent warming was predicted to increase the daily
species richness of active flowers early in the local growing season, with
corresponding reductions in species richness of active flowers later in
the growing season.  Notably, patterns of change in
community-level bloom displays were driven primarily by differences among
species in the timing of flowering onset, as termination dates tended to
advance in unison with onset dates, resulting in minor changes to
flowering duration among species.