Data from: Phenological responsiveness to climate differs among four species of Quercus in North America

1.The timing of the seasonal activity of organisms is a tractable
indicator of climate change. Many studies in North America have
investigated the role of temperature on the onset date of phenological
transitions in temperate deciduous trees and found that the onset of
leafing and flowering in numerous species has occurred earlier in recent
years, apparently in response to higher temperatures in winter and spring.
2.Few studies have examined the climatic and biogeographic drivers of
phenological responses in water-limited ecosystems or explored
inter-specific variation in responses of phenological metrics other than
the timing of onset, such as the periodicity or duration of phenological
activity. 3.This study used phenological observations of four species of
Quercus contributed to the USA National Phenology Network database from
2009-2014 to investigate how responses to climate (temperature and
precipitation) and geographic location (latitude, longitude and elevation)
varied among two western North American species (Q. agrifolia and Q.
lobata) and two eastern and central North American species (Q. alba and Q.
rubra). 4.Within years, in species in the western, water-limited
ecosystems, the phenological phases observed here (bud break, flowers or
flower buds) tend to occur intermittently throughout the growing season,
and each event is of longer duration than the same phenophases of the
temperate-zone species, rendering a single onset date an incomplete metric
with which to track responsiveness or to compare species. By contrast, the
eastern/central U.S. species were phenologically more responsive than the
western species to spatial and temporal variation in winter, spring, and
fall precipitation and maximum temperature. 5.Synthesis: Within and
between regions these congeners exhibited a diversity of responses to
seasonal temperature and precipitation. This indicates that for predictive
model development it is critical to understand how each underlying driver
influences species that are adapted to different climatic regimes. These
results underscore the value of studying a range of phenological metrics
and species from a variety of ecosystems to better predict phenological
responses to short-term variation and to long-term change in climate.