Data from: Phenology differences between native and novel exotic-dominated grasslands rival the effects of climate change

1. Novel ecosystems can differ from the native systems they replaced. We
used phenology measures to compare ecosystem functioning between novel
exotic-dominated and native-dominated grasslands in the central US. 2.
Phenology, or timing of biological events, is affected by climate and land
use changes. We assessed how phenology shifts are being altered by exotic
species dominance by comparing remotely sensed Normalized Difference
Vegetation Index (NDVI) within growing seasons at exotic- and
native-dominated sites along a latitudinal gradient. Exotic species were
dominated by the C3 species functional group in the north and the C4
species functional group in the south. 3. Date of senescence was an
average of 36 days later in exotic than native-dominated grasslands, and
this effect was consistent across latitudes. 4. Exotic-dominated
grasslands greened up an average of 10.7 days earlier than
native-dominated grasslands, but this effect was highly dependent on
latitude and the plant functional group that dominated at that latitude.
Greenup differed between native and exotic sites the most in central and
northern regions that had dominant C3 grasses. 5. We estimated the effects
of an increase in global temperatures on green-up and senescence with a
space-for-time substitution, and by comparing growing degree day
differences between historical average temperatures and +2.5° C. Green-up
was significantly earlier and senescence was significantly later with a
2.5 ° C increase in temperature. The native-exotic difference was
significantly greater than the difference due to increased temperature for
senescence, but not for green-up. 6. Synthesis and applications. Native to
exotic plant conversions in central US grasslands have led to highly
altered phenology, especially in terms of senescence, and this effect
should be considered along with global warming in models moving forward.
This conversion will have to be considered in developing estimates of how
global change will affect phenology in locations where exotics are
present, especially in cases where their abundance is increasing
concurrent with climate change. Global change models and policy should
consider exotic species invasion as an additional widespread factor behind
changes in phenology.