DOI: 10.5061/dryad.qrfj6q5p7
title: Data from: A theoretical framework to quantify ecosystem pressure-volume relationships

description: Water potential’ is the biophysically relevant measure of water status in
 vegetation relating to stomatal, canopy, and hydraulic conductance, as
 well as mortality thresholds; yet this cannot be directly related to
 measured and modelled fluxes of water at plot- to landscape-scale without
 understanding its relationship with ‘water content’.  The
 capacity for detecting vegetation water content via microwave remote
 sensing further increases the need to understand the link between water
 content and ecosystem function.  In this review, we explore how
 the fundamental measures of water status, water potential and water
 content, are linked at ecosystem scale drawing on the existing theory of
 pressure-volume (PV) relationships. We define and evaluate the concept and
 limitations of applying PV relationships to ecosystems where the quantity
 of water can vary on short timescales with respect to plant water status,
 and over longer timescales and over larger areas due to structural changes
 in vegetation. As a proof of concept, plot-scale aboveground vegetation PV
 curves were generated from equilibrium (e.g. predawn) water potentials and
 water content of the above ground biomass of nine plots including tropical
 rainforest, savanna, temperate forest, and a long-term Amazonian
 rainforest drought experiment. Initial findings suggest that the stored
 water and ecosystem capacitance scale linearly with biomass across diverse
 systems, while the relative values of ecosystem hydraulic capacitance and
 physiologically accessible water storage do not vary systematically with
 biomass.  The bottom-up scaling approach to ecosystem water
 relations identified the need to characterise the distribution of water
 potentials within a community; and also revealed the relevance of
 community-level plant tissue fractions to ecosystem water relations.
  We believe that this theory will be instrumental in linking our
 detailed understanding of biophysical processes at tissue-scale to the
 scale at which land surface models operate and at which tower-based,
 airborne and satellite remote sensing can provide information.
description: The main data used in the analyses were plot-level forest
 inventories.  Seven of the eight sites were in Australia, where the
 inventories were undertaken by CSIRO. The original data sets and protocol
 are available on the TERN (Terrestrial Ecosystem research Network)
 website: https://portal.tern.org.au. The non-Australian site was in Amazonian rainforest in<em> </em>Floresta Nacional de Caxiuanã, Brazil, and is the site of a long-term throughfall exclusion experiment.  Both the experiment and inventory methodologies are described in da Costa et al. (2010) and Rowland et al. (2015). The actual data are in their original raw form, although the data sets have been subsetted in some cases to represent a fraction of the original area.  For example 1 hectar out of 25 for the Robson Creek site, or only the data representing the most recent collection. Related works: da Costa, A. C. L., Galbraith, D., Almeida, S., Portela, B. T. T., da Costa, M., de Athaydes Silva Junior, J., Braga, A. P., de Gonçalves, P. H. L. L., de Oliveira, A. A. R., Fisher, R., Phillips, O. L., Metcalfe, D. B., Levy, P., Meir, P., Silva Junior, J. D. A., Braga, A. P., de Gonçalves, P. H. L. L., de Oliveira, A. A. R., Fisher, R., … Meir, P. (2010). Effect of 7 yr of experimental drought on vegetation dynamics and biomass storage of an eastern Amazonian rainforest. <em>The New Phytologist</em>, <em>187</em>(3), 579–591. https://doi.org/10.1111/j.1469-8137.2010.03309.x Rowland, L., Da Costa, A. C. L. C. L. L., Galbraith, D. R. R., Oliveira, R. S. S., Binks, O. J. J., Oliveira, A. A. R. A. R. R., Pullen, A. M. M., Doughty, C. E. E., Metcalfe, D. B. B., Vasconcelos, S. S. S., Ferreira, L. V. V., Malhi, Y., Grace, J., Mencuccini, M., & Meir, P. (2015). Death from drought in tropical forests is triggered by hydraulics not carbon starvation. <em>Nature</em>, <em>528</em>(7580), 1–13. https://doi.org/10.1038/nature15539
description: # README The files described below are associated with the publication
 '*A theoretical framework to quantify ecosystem pressure-volume
 relationships*' (Binks et al. 2014, Global Change Biology). The data
 files contain forest inventory data including tree diameter at breast
 height and height - explained in more detail below. The R scripts contain
 code for the analysis and generation of plots in the study. **R SCRIPTS**
 * All code is included in the three R scripts 'Model plot PV 8'
 and 'Some figures', and 'Equilibrium soil water potential
 script'. Descriptions of each script follow: Script: **Model plot PV
 8** The script is broken into sections with the main model at the top.
 Following the model are sections in which the data for each site is
 organised for the model - this includes a 'simulated forest'
 used for generating figure 2. The organisation for plot-level data varies
 across sites depending on what data were available. To execute the script:
 i) the dataframe (df) must first be prepared for a given site (execute
 code under heading of each site to the line where it is states "#
 Model..."), ii) run the model on the dataframe
 [PV_mod(df,plot.size,df_name)]. The dataframe, df, is the one generated
 per site in the previous step. The plot size is typically 1 hectare (10^4
 m2), but for sites cax_a, cax_b and CB is only 80^2 m2. A site-specific
 name must be included in the model function, e.g. CB_mod. iii) Leaf/canopy
 water was added separately for each site in section 'Adding leaf area
 water content'. This requires the additional parameters: leaf area
 index (LAI), leaf-level hydraulic capacitance (leaf_cap), leaf-level
 saturated water content (leaf_sat_WC), and leaf turgor loss point
 (leaf_TLP). A sub-model is used to add the canopy-level water content. The
 final section of the script includes the script for figures 2, 3, 5 and 6
 in the main manuscript. Script: **Some figures** A script plotting the
 following figures: SI 6.1, 6.2 Fig. 4 Script: **Equilibrium soil water
 potential script** Calculation and plotting of SI 1.1 Proof that
 Jensen's Inequality applies to the relationship between water
 potential and water content. **DATA FILES** * The data for each site is in
 an excel file referenced in the R script 'Model plot PV 8' *
 Each excel file has i) a data tab, and ii) an 'Information' tab
 which describes the columns and states the units. * The R script can
 access the excel files directly. * The plot-level inventory data include
 the following information about the trees: diameter at breast height,
 height, and wood density. The exceptions are the Cow Bay and Robson Creek
 site which have species-level wood density in separate files. **Files**: *
 Plot inventory of the 'Alice Mulga' savanna site "Alice
 Mulga biomass data" * Plot inventory of the rainforest site in the
 Brazilian Amazon in Caxiuana National Park "Cax plot data" *
 Plot inventory data of the temperate forest site 'Cumberland
 Plain' "Cumberland_Plain_diameter_height_biomass_data" *
 Plot inventory data of tropical rainforest site 'Cow Bay'
 "inventory data CB 2012" * Plot inventory data of tropical
 savanna site 'Litchfield'
 "Litchfield_Savanna_stem_diameter_height_biomass_basal_area" *
 Plot inventory data of the tropical rainforest site 'Robson
 Creek'
 "supersite.848.1-asn_fnqr_veg_dbh-h_robson_25ha_2009-2015" *
 Plot inventory data for temperate forest site 'Tumbarumba'
 "Tumbarumba_Wet_Eucalypt_diameter_height_biomass_dat_mLR4IYB" *
 Plot inventory data for temperate forest site 'Great Western
 Woodland'
 "GWW_dbh_height_biomass_basal_area_sapwood_all_sites_rmibKeZ" *
 Species-level wood density of the species at Cow Bay "wood
 density_CB_Sp" * Species-level wood density of the species at Robson
 Creek "wood density_RC_Sp"