DOI: 10.5061/dryad.wdbrv15w2
title: Simulations disentangling temperature vs. VPD effects on tropical forest GPP

description: Tropical forest photosynthesis can decline at high temperatures due to (1)
 biochemical responses to increasing temperature and (2) stomatal responses
 to increasing vapor pressure deficit (VPD), which is associated with
 increasing temperature. It is challenging to disentangle the influence of
 these two mechanisms on photosynthesis in observations, because
 temperature and VPD are tightly correlated in tropical forests.
 Nonetheless, quantifying the relative strength of these two mechanisms is
 essential for understanding how tropical gross primary productivity (GPP)
 will respond to climate change, because increasing atmospheric CO2
 concentration may partially offset VPD-driven stomatal responses, but is
 not expected to mitigate the effects of temperature-driven biochemical
 responses. We used two terrestrial biosphere models to quantify how
 physiological process assumptions (temperature acclimation of
 photosynthesis and dynamic hydraulic stress) and functional traits (e.g.
 maximum xylem conductivity) influence the relative strength of modeled
 temperature vs. VPD effects on light-saturated GPP at an Amazonian forest
 site, a seasonally dry tropical forest site, and an experimental tropical
 forest mesocosm. By simulating idealized climate change scenarios, we
 quantified the divergence in GPP predictions under model configurations
 with stronger VPD effects compared to stronger direct temperature effects.
 Assumptions consistent with stronger direct temperature effects resulted
 in larger GPP declines under warming, while assumptions consistent with
 stronger VPD effects resulted in more resilient GPP under warming. Our
 findings underscore the importance of quantifying the role of 
 direct temperature and indirect VPD effects for projecting the resilience
 of tropical forests in the future, and demonstrate that the relative
 strength of temperature vs. VPD effects in models is highly sensitive to
 plant functional parameters and structural assumptions about
 photosynthetic temperature acclimation and plant hydraulics.
description: This dataset contains model output from simulations using the
 Functionally Assembled Terrestrial Ecosystem Simulator (FATES; Koven et
 al. 2020) and the Community Land Model version 5 (CLM5; Lawrence et al.
 2019).
description: # Simulations disentangling temperature vs. VPD effects on tropical forest
 GPP This repository contains model code to run Functionally Assembled
 Terrestrial Ecosystem Simulator (FATES) and Community Land Model version 5
 (CLM5) simulations, and it contains model output from these simulations. 
 ## Description of the data and file structure This dataset is organized
 into several zipped files: `model_output`, `model_code`, `input_files`,
 and `case_directories`. #### Model Output The `model_output` file contains
 multiple directories, each of which contains model output from a different
 simulation. Simulations are named according to the convention
 `ModelConfiguration_Site_MeteorologicalForcing_Number.` There are eight
 model configurations: * `FATESdef` (default FATES: both photosynethic
 temperature acclimation and plant hydraulics are off) * `FATESH` (FATES
 with photosynethic temperature acclimation off and plant hydraulics on) *
 `FATESA` (FATES with photosynethic temperature acclimation on and plant
 hydraulics off) * `FATESAH` (FATES with both photosynethic temperature
 acclimation and plant hydraulics on) * `CLM5` (default CLM5: both
 photosynethic temperature acclimation and plant hydraulics are on) *
 `CLM5minusH` (CLM5 with photosynethic temperature acclimation on and plant
 hydraulics off) * `CLM5minusA` (CLM5 with photosynethic temperature
 acclimation off and plant hydraulics on) * `CLM5minusAH` (CLM5 with both
 photosynethic temperature acclimation and plant hydraulics off) There are
 three sites:  * `K67` (kilometer 67) * `B2` (Biosphere 2) * `MXTes`
 (Tesopaco) There are multiple meteorological forcings, including the
 historical meteorology, synthetic meteorologies to isolate different
 drivers, and idealized climate treatments. These meteorological forcings
 are described in more detail in the corresponding manuscript in Global
 Change Biology: * `historical`: historical meteorology observed at the
 site * Synthetic meteorological forcing to isolate different drivers *
 `isolateTBOT` * `isolateTBOTandVPD` * `isolateTBOTandVPDandPRECTmms` *
 `isolateVPD` * `decreaseRH` * Idealized climate treatments *
 `increaseTemp` * `increaseTempdecreaseRH` *
 `increaseTempdecreaseRH_highCO2` * `increaseTemp_highCO2` *
 `increaseTempincreaseVPD` * `increaseVPD` Within each simulation
 directory, there are three folders: `lnd`, `logs`, and `rest`. `lnd`
 contains model output from the land model and contains two subdirectories:
 `hist` and `proc`. `hist` contains the raw model output, and `proc`
 contains postprocessed model output such that each file is a time series
 for a single variable. Each variable is described in the netcdf
 metadata. `rest` contains the restart file for each year of the
 simulation, which can be used to continue the simulation for additional
 years. `logs` contains the log files from the simulation runs which
 produced the model output. #### Model Code The `model_code` file contains
 the Functionally Assembled Terrestrial Ecosystem Simulator (FATES) and
 Community Land Model version 5 (CLM5) model code and the run scripts used
 to generate individual simulations. There are three subdirectories within
 this folder: `run_scripts`, `ctsm_FATES_03Jan2022_derecho`,
 `ctsm_FATES_03Jan2022_acclimOff_derecho`. `run_scripts` contains the run
 scripts used to generate individual simulations,
 `ctsm_FATES_03Jan2022_derecho` contains CLM5 and FATES code used to run
 the majority of simulations. `ctsm_FATES_03Jan2022_acclimOff_derecho`
 contains a modified version of CLM5 where photosynthetic temperature
 acclimation was turned off. We thank all scientists and software engineers
 who contributed to the development of CLM5 and FATES. CLM5 and FATES code
 is also available on GitHub at
 [https://github.com/ESCOMP/CTSM](https://github.com/ESCOMP/CTSM) and
 [https://github.com/NGEET/fates](https://github.com/NGEET/fates),
 respectively. #### Input Files The `input_files` file contains the custom
 input files necessary to run the model. There are three subdirectories:
 `B2`, `K67`, `MXTes`, and `param_files.` `B2`,`K67`, and `MXTes` contain
 site-specific model input files for Biosphere 2, kilometer 67, and
 Tesopaco, respectively. `param_files` contains general parameter files.
 #### Case Directories The `case_directories` folder contains the case
 directories for each model simulation. These case directories contains
 information about how each simulation was configured, e.g. namelists and
 which input files were used.