DOI: 10.5061/dryad.ttdz08m8f
title: Climate model experiments of regional-scale tree die-off replaced by shrubs (select variables at daily time resolution): Part 4

description: 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 (GPP) 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 GPP 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 GPP in the Western US. Our results provide novel 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 4) represents selected variables from the simulations at
 daily time resolution for experiments where trees were replaced with
 shrubs.
description: This dataset has monthly averaged variables for all land and
 atmosphere fields for experiments where trees are replaced by
 shrubs. These data are climate model output from
 experiments described further in the relate manuscrip by Feng et al.
 Briefly, we conducted simulations using National Center for Atmospheric
 Research (NCAR) Community Earth System Model version 1.3 (CESM, https://www.cesm.ucar.edu/models). The CESM model couples Community Atmosphere Model version 5 (CAM5) (Neale <em>et al</em> 2012) to the Community Land Model (CLM4.5) (Oleson <em>et al</em> 2013), the CICE4 sea ice model (Hunke <em>et al</em> 2010), and implements a slab ocean with prescribed heat transport derived from a fully-coupled ocean-atmosphere simulation (Neale <em>et al</em>2012). Further details about the parameterization of the component models can be found in the papers above, as well as in the technical documentation (Oleson <em>et al</em> 2013). Year 2000 land use conditions based on satellite observations (Lawrence and Chase 2007) were used in the model setup, and the atmospheric CO<sub>2</sub> concentration was set to be constant at 400 ppm as our simulations are intended to represent approximately present-day “equilibrium” conditions in a stable climate as discussed further below. The land model component calculates surface fluxes of energy, water, and momentum which are passed to the atmospheric model. Carbon fluxes are also calculated diagnostically, and leaf area dynamically responds to photosynthesis rates through allocation of fixed carbon to leaves. This allows both surface albedo and evapotranspiration rates to vary with climate as a function of atmospheric conditions, stomatal conductance per leaf area, and leaf area. Model simulations were conducted at the spatial resolution of 1.9◦ latitude by 2.5◦ longitude for 200 years for most experiments, but only 100 years for two experiments. Climate and terrestrial variables (e.g. global surface temperature, leaf area index) reach equilibrium after approximately 40 years of model spin up. The spin up period is discarded during analysis, although it is included in the output files. This post-spinup time period (all years after year 40) can be considered “equilibrium” conditions, where variations over time represent samples over the expected internal variability of the climate system rather than a time series into the future. The CESM simulations were implemented on the NCAR Cheyenne supercomputing cluster (Computational and Information Systems Laboratory, 2017)(opens in new window), sponsored by the National Science Foundation. We conducted 15 simulations: a control with no tree die-off and 14 experimental simulations, each corresponding to the scenario of tree die-off in one of 14 most forested ecoregions in the United States (i.e. NE, MA, SE, GL, PP, AP, OZ, NR, SR, DS, GB, PN, PS, and TA Domains of the US National Ecological Observatory Network (NEON) as in Swann et al. 2018). In each experiment, all forested area in an ecoregion was replaced with shrubs. For high latitude locations we performed two experiments with two different shrub types as replacement vegetation.  Present-day tree abundance was based on satellite observations (Lawrence and Chase 2007). Thus the magnitude of tree die-off varies between experiments as a function of the present-day forest cover.  <strong>References</strong> Hunke E C, Lipscomb W H, Turner A K, Jeffery N and Elliott S 2010 <em>Cice: the los alamos sea ice model documentation and software user’s manual version 4.1 la-cc-06-012 T-3 Fluid Dynamics Group,</em> Los Alamos National Laboratory 675 500 Lawrence P J and Chase T N. Representing a new MODIS consistent land surface in the community land model (CLM 3.0). <em>J. Geophys. Res.: Biogeosciences,</em> 112(G1). Neale R B, Chen C-C, Gettelman A, Lauritzen P H, Park S, Williamson D L, Conley A J, Garcia R, Kinnison D, Lamarque J-F and Others 2012 Description of the NCAR community atmosphere model (CAM 5.0) <em>NCAR Tech. Note NCAR/TN-486+STR 289</em> Oleson K, Lawrence D M, Bonan G B and Drewniak B 2013 Technical description of version 4.5 of the Community Land Model (CLM)(No. NCAR/TN-503+ STR) <em>UCAR: Boulder, CO, USA</em> Swann A L S, Laguë M M, Garcia E S, Field J P, Breshears D D, Moore D J P, Saleska S R, Stark S C, Villegas J C, Law D J and Minor D M 2018 Continental-scale consequences of tree die-offs in North America: identifying where forest loss matters most <em>Environ. Res. Lett. </em>13 055014
description: # Climate model experiments of regional-scale tree die-off replaced by
 shrubs (select variables at daily time resolution): Part 4 Dataset DOI:
 [10.5061/dryad.ttdz08m8f](10.5061/dryad.ttdz08m8f) This dataset is ***part
 4*** of a collection of four datasets related to the same study: Part 1:
 Contains all variables from simulations where trees were replaced with C3
 grass, at a monthly averaged time resolution. It also includes time series
 for the specific variables plotted in the accompanying Feng et al.
 publication in Environmental Research Letters (ERL)
 [[https://doi.org/10.5061/dryad.stqjq2c8j](https://urldefense.com/v3/__https://doi.org/10.5061/dryad.stqjq2c8j__;!!K-Hz7m0Vt54!i7nYlnE0GWoD-8XfyK6avWBoTt0vp31R7NQgXopp8HyuY-G31AoFz_Aqu8pgLWEx_mVa_SltTOmy$)]. Part 2: Contains selected variables from simulations where trees were replaced with C3 grass, at a daily time resolution [[https://doi.org/10.5061/dryad.z8w9ghxqr](https://urldefense.com/v3/__https://doi.org/10.5061/dryad.z8w9ghxqr__;!!K-Hz7m0Vt54!i7nYlnE0GWoD-8XfyK6avWBoTt0vp31R7NQgXopp8HyuY-G31AoFz_Aqu8pgLWEx_mVa_Rt6xHxG$)]. Part 3: Contains all variables from simulations where trees were replaced with shrubs, at a monthly averaged time resolution [[https://doi.org/10.5061/dryad.5hqbzkhh0](https://urldefense.com/v3/__https://doi.org/10.5061/dryad.5hqbzkhh0__;!!K-Hz7m0Vt54!i7nYlnE0GWoD-8XfyK6avWBoTt0vp31R7NQgXopp8HyuY-G31AoFz_Aqu8pgLWEx_mVa_edlwt__$)]. Part 4: Contains selected variables from simulations where trees were replaced with shrubs, at a daily time resolution [[https://doi.org/10.5061/dryad.ttdz08m8f](https://urldefense.com/v3/__https://doi.org/10.5061/dryad.ttdz08m8f__;!!K-Hz7m0Vt54!i7nYlnE0GWoD-8XfyK6avWBoTt0vp31R7NQgXopp8HyuY-G31AoFz_Aqu8pgLWEx_mVa_fUEi49U$)]. ## Description of the data and file structure This dataset presents climate model output for 16 experiments and 1 control run simulated using the Community Earth System Model. In each experiment, tree cover is modified for an ecoregion of the US described by NEON domains ([https://www.neonscience.org/field-sites/about-field-sites](https://www.neonscience.org/field-sites/about-field-sites)). See further description of the experiments and model information in the accompanying paper. Data is presented in NetCDF files, which contain metadata information that describes variable names, units, and grid information. The data are global and additionally have a time dimension. The files are tarballs which contain the NetCDF files. The NetCDF files contain time series of individual variables for each of our 14 experiments and a control run.  Experiment files are named by the NEON domain number, as well as the plant functional type number of the plant type that replaced trees in a given domain. Relationship between NEON domain numbers to the names used in our paper (names and numbers are also listed on maps provided by NEON): | NEON Domain | Abbreviation | Domain Number | | :---------------- | :----------- | :------------ | | Northeast | NE | 1 | | Mid Atlantic | MA | 2 | | Southeast | SE | 3 | | Great Lakes | GL | 5 | | Prairie Peninsula | PP | 6 | | Appalachians | AP | 7 | | Ozarks | OZ | 8 | | Northern Plains | NP | 9 | | Central Plains | CP | 10 | | Southern Plains | SP | 11 | | Northern Rockies | NR | 12 | | Southern Rockies | SR | 13 | | Desert Southwest | DS | 14 | | Great Basin | GB | 15 | | Pacific Northwest | PN | 16 | | Pacific Southwest | PS | 17 | | Tundra | TU | 18 | | Taiga | TA | 19 | For example, for surface pressure (PS), the first number (15) refers to the "Great Basin" domain, and the second number (11 or 12) refers to the plant type to which trees were converted, with 11 referring to deciduous broadleaf shrub temperate and 12 referring to deciduous broadleaf shrub boreal. The daily files are given in 50-year increments, with the numbers indicating the years covered by each file, for this example, years 51-100. ``` cnh_neon_15_to_11.cam.h1.PS.00510101-01001231.nc ``` Additional metadata about the variables including units are contained in the metadata of the netCDF files. | Variable Abbreviation | Variable Name | | :-------------------- | :---------------------------------------------------- | | LHFLX | Surface Latent Heat Flux | | PRECC | Convective Precipitation | | PRECL | Large Scale Precipitation | | PS | Surface Pressure | | RHREFHT | Relative Humidity at the Reference Height | | SHFLX | Surface Sensible Heat Flux | | TREFHT | Air Temperature at the Reference Height | | TREFHTMN | Minimum Daily Air Temperature at the Reference Height | | TREFHTMX | Maximum Daily Air Temperature at the Reference Height |