Climate model experiments of regional-scale tree die-off replaced by C3 grass (all monthly data fields): Part 1

Climate change is triggering regional-scale alterations in vegetation
including land cover change such as forest die-off. At sufficient
magnitudes, land cover change from forest die-off in one region can change
not only local climate but also vegetation including agriculture elsewhere
via changes in larger-scale climate patterns, termed an “ecoclimate
teleconnection”. Ecoclimate teleconnections can therefore have impacts on
vegetative growth in distant regions, but the degrees to which the impact
decays with distance or directionally diffuses relative to the initial
perturbation are general properties that have not been evaluated. We used
the Community Earth system model to study this, examining the implications
of tree die-off in 14 major US forested regions. For each case, we
evaluated the ecological impact across North America as a function of
distance and direction from the location of regional tree die-off. We
found that the effects on gross primary productivity generally decayed
linearly with distance, with notable exceptions. Distance from the region
of tree die-off alone explained up to ~30% of the variance in many
regions. We also found that the gross primary productivity impact was not
uniform across directions and that including an additional term to account
for direction to regional land cover change from tree die-off was
statistically significant for nearly all regions and explained up to ~40%
of the variance in many regions, comparable in magnitude to the influence
of El Nino on gross primary productivity in the Western US. Our results
provide insights into the generality of distance decay and directional
diffusion of ecoclimate teleconnections and suggest that it may be hard to
identify expected impacts of tree die-off without case-specific
simulations. Such patterns of distance decay, directional diffusion, and
their exceptions are relevant for cross-regional policy that links forests
and other agriculture (e.g. US Department of Agriculture). The data in
this specific dataset (part 1) represents all variables from the
simulations where trees were replaced by C3 grass at monthly averaged time
resolution as well as the timeseries of the specific variables plotted in
the accompanying  Feng et al. publication in ERL.