Data from: A theoretical framework to quantify ecosystem pressure-volume relationships
Data files
Nov 04, 2024 version files 1.29 MB
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Alice_Mulga_biomass_data.xlsx
16.21 KB
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Cax_plot_data.xlsx
30.45 KB
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Cumberland_Plain_diameter_height_biomass_data.xlsx
57.77 KB
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GWW_dbh_height_biomass_basal_area_sapwood_all_sites_rmibKeZ.xlsx
21.99 KB
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inventory_data_CB_2012.xlsx
23.59 KB
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Litchfield_Savanna_stem_diameter_height_biomass_basal_area.xlsx
31.33 KB
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Model_plot_PV_8.R
50.05 KB
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README.md
3.78 KB
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supersite.848.1-asn_fnqr_veg_dbh-h_robson_25ha_2009-2015.xlsx
680.50 KB
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Tumbarumba_Wet_Eucalypt_diameter_height_biomass_dat_mLR4IYB.xlsx
20.86 KB
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wood_density_CB_Sp.xlsx
13.29 KB
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wood_density_RC_Sp.xlsx
338.44 KB
Abstract
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.
README: 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"
Methods
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 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. The New Phytologist, 187(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. Nature, 528(7580), 1–13. https://doi.org/10.1038/nature15539