Relative tree growth and mortality responses to the 2012 midwestern US drought in the central hardwood ecoregion
Data files
Jun 20, 2025 version files 3.21 MB
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Calculate_RelativeSensitivity.m
4.62 KB
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gr_ij.csv
1.87 MB
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HexagonCoordinates.csv
16.66 KB
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mr_ij.csv
1.30 MB
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README.md
7.45 KB
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RelativeGrowthSensitivity.csv
602 B
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RelativeMortalitySensitivity.csv
604 B
Abstract
This dataset contains relative drought-driven tree growth and mortality responses derived from the USDA FS Forest Inventory and Analysis dataset (Gray et al., 2012) in the North American central hardwood ecoregion (a region representing the four US states of Indiana, Illinois, Kentucky, and Brandt et al., 2014). Data represents a period of 2000 – 2018 and characterizes relative responses to the severe 2012 midwestern drought (Mallya et al., 2013) between co-located trees with a diameter at breast height greater than 12.7 cm. Analyses were limited to regions of the study area that experienced ‘Severe’ or ‘Extreme’ drought conditions from March to October of 2012, as defined by the US drought monitor program (Svoboda et al., 2002). Co-located trees were defined as those growing within the same discrete 875 km2 hexagonal boundary following a tessellation approach by which Forest Inventory and Analysis plots were aggregated across 560 uniform hexagons imposed over the study area.
Relative drought-driven responses were quantified among the following tree species: Acer rubrum, Acer saccharum, Carya alba, Carya glabra, Carya ovata, Carya texana, Celtis occidentalis, Fagus grandifolia, Juglans nigra, Liriodendron tulipifera, Nyssa sylvatica, Pinus echinata, Prunus serotina, Quercus alba, Quercus coccinea, Quercus rubra, Quercus stellata, Quercus velutina, Sassafras albidum, and Ulmus americana.
Dataset DOI: 10.5061/dryad.280gb5n2b
Description of the data and file structure
The files here include: (1) the georeferenced coordinate centers of each tessellated hexagon imposed across the study area (i.e., HexagonCoordinates.csv), (2) relative growth responses during drought (gr_ij) between individual species within each hexagon (i.e., gr_ij.csv), (3) Relative growth sensitivity values, which reflect a synthesized species-level characterization of the percentile difference of the number of co-located species which experienced relatively larger or smaller drought-driven growth declines (i.e., RelativeGrowthSensitivity.csv), (4) relative mortality responses during drought (mr_ij) between individual species within each hexagon (i.e., mr_ij.csv), (5) Relative mortality sensitivity values, which reflect a synthesized species-level characterization of the percentile difference of the number of co-located species which experienced relatively greater or lower drought-driven stem loss (i.e., RelativeMortalitySensitivity.csv), and (6) MATLAB code used to calculate the relative growth sensitivity and relative mortality sensitivity values of each species based on gr_ij and mr_ij, respectively (i.e., Calculate_RelativeSensitivity.m).
Analyses were limited to the 20 most abundant canopy dominant tree species within the regional Forest Inventory and Analysis dataset, which were accessed at: https://research.fs.usda.gov/products/dataandtools/fia-datamart.
Files and variables
File 1: HexagonCoordinates.csv
This file contains the georeferenced coordinates (in decimal degrees) of the tessellated 560 hexagons imposed across the study area. The unique hexagon ID is denoted in column 1, the latitude of the respective hexagon center is denoted in column 2, and the longitude of the respective hexagon center is denoted in column 3. The data file is in a comma separated value format and requires no specialized software.
File 2: gr_ij.csv
This file contains calculated relative drought-driven growth responses (i.e., gr_ij; *Equation 3) between species *i and j in each hexagon. Species i is denoted in column 1, the discrete hexagon ID where the comparison was quantified is denoted in column 2, and the relative response to species j (i.e., one of the other 19 study tree species that species i was compared to) are denoted in columns 3 ‒ 22. gr_ij values in hexagons where species i and j did not coexist in the inventory dataset or did not meet the filtering criteria are denoted as ‘NaN’. The data file is in a comma separated value format and requires no specialized software.
File 3: RelativeGrowthSensitivity.csv
This file contains a calculated relative growth sensitivity metric (Equation 4) that is defined at the species-level. Column 1 denotes the species and column 2 denotes the relative growth sensitivity value. Relative growth sensitivity quantifies the percentile difference of the number of species which experienced greater or more reduced relative growth than their neighbors during drought. A positive relative growth sensitivity value indicates growth was more strongly reduced by drought while a negative value indicates greater growth tolerance. The data file is in a comma separated value format and requires no specialized software.
File 4: mr_ij.csv
This file contains calculated relative drought-driven mortality responses (mr_ij; Equation 7) between species i and j in each hexagon. Species i is denoted in column 1, the discrete hexagon ID where the comparison was quantified is denoted in column 2, and the relative response to species j (i.e., one of the other 19 study tree species that species i was compared to) are denoted in columns 3 ‒ 22. mr_ij values in hexagons where species i and j did not coexist in the inventory dataset or did not meet the filtering criteria are denoted as ‘NaN’. The data file is in a comma separated value format and requires no specialized software.
File 5: RelativeMortalitySensitivity.csv
This file contains a calculated relative mortality sensitivity metric (Equation 8) that is defined at the species-level. Column 1 denotes the species and column 2 denotes the relative mortality sensitivity value. Relative mortality sensitivity quantifies the percentile difference of the number of species which experienced greater or more reduced stem loss during drought than their neighbors. A positive relative mortality sensitivity value indicates greater mortality than their neighbors during drought while a negative one indicates greater survival. The data file is in a comma separated value format and requires no specialized software.
Code/software
Calculate_RelativeSensitivity.m is the code used to quantify the species-level relative growth sensitivity and relative mortality sensitivity metrics. gr_ij.csv and mr_ij.csv are the input files and RelativeGrowthSensitivity.csv and RelativeMortalitySensitivity.csv are the output files. The file can be opened and manipulated with various software (i.e., NotePad, NotePad++) but the code is written to be executed in MATLAB version R2023a: https://www.mathworks.com/products/new_products/release2023a.html.
We emphasize that executing this code is not necessary to access the relative drought-driven tree growth and mortality responses quantified in this work as the input and output files are included within this dataset as comma separated value formats and requires no specialized software.
Access information
Data was derived from the following source:
The US Department of Agriculture Forest Service, Forest Inventory and Analysis Database and were accessed at: https://research.fs.usda.gov/products/dataandtools/fia-datamart
References
Brandt, L., He, H., Iverson, L., Thompson, F. R., Butler, P., Handler, S., … & Westin, S. (2014). Central Hardwoods ecosystem vulnerability assessment and synthesis: a report from the Central Hardwoods Climate Change Response Framework project. Gen. Tech. Rep. NRS-124. Newtown
Brzostek, E. R., Dragoni, D., Schmid, H. P., Rahman, A. F., Sims, D., Wayson, C. A., … & Phillips, R. P. (2014). Chronic water stress reduces tree growth and the carbon sink of deciduous hardwood forests. Global change biology, 20(8), 2531-2539.
Gray, A. N., Brandeis, T. J., Shaw, J. D., McWilliams, W. H., & Miles, P. D. (2012). Forest inventory and analysis database of the United States of America (FIA). Biodiversity and Ecology, 4, 225-231.
Mallya, G., Zhao, L., Song, X. C., Niyogi, D., & Govindaraju, R. S. (2013). 2012 Midwest drought in the United States. Journal of Hydrologic Engineering, 18(7), 737-745.
Sheil, D., Burslem, D. F., & Alder, D. (1995). The interpretation and misinterpretation of mortality rate measures. Journal of Ecology, 331-333.
Svoboda, M., LeComte, D., Hayes, M., Heim, R., Gleason, K., Angel, J., … & Stephens, S. (2002). The drought monitor. Bulletin of the American Meteorological Society, 83(8), 1181-1190.
Relative growth and relative growth sensitivity
To calculate relative growth (gr_ij) we first quantified species-specific growth in each hexagon as a relative growth rate across three successive inventories from 2000 – 2018. The relative growth rate equation (RGR_i) was expressed as (Brzostek et al., 2014):
RGR_i = [(BA_i,1 ‒ BA_i,0)/BA_i,0] × 100 (Equation 1)
where BA_i,0 is the species-specific tree basal area at the initial inventory and BA_i,1 is the species-specific tree basal area at the next inventory. Next, the impact of drought on RGR_i was characterized as a rate change parameter, ΔRGR_i (% growth/year), whereby RGR_i after 2012 was subtracted by the RGR_i of the conspecific individuals occupying the same hexagon prior to drought disturbance. Specifically, ΔRGR_i was quantified as:
ΔRGR_i = RGR_i,post_drought ‒ RGR_i,pre_drought (Equation 2)
where RGR_i,post_drought is species-specific relative tree growth following drought (when BA_i,1 was sampled during the years 2012−2018; Equation 1) and RGR_i,pre_drought is the relative tree growth of the same species and locations from two successive inventories during a non-droughted period (i.e., when BA_i,1 was sampled during the years 2000−2011; Equation 1). gr_ij is then calculated as the pairwise difference between corrected growth rates between species i and j, expressed as:
gr_ij = ΔRGR_i ‒ ΔRGR_j (Equation 3)
Relative growth sensitivity (%) was then quantified as:
Relative growth sensitivity_i = [(n_gr_ij<0 ‒ n_gr_ij>0)/n_tot] × 100 (Equation 4)
where n_gr_ij<0 are the number of co-occurring species that experienced lower growth reductions and n_gr_ij>0 are the number of species whose growth was more limited by drought. n_gr_ij<0 and n_gr_ij>0 were determined by a one sample t-test of the species-specific gr_ij comparisons. n_tot is the number of species that were able to be compared.
Relative mortality and relative mortality sensitivity
To calculate relative mortality (mr_ij), we first quantified species-specific mortality in each hexagon as a stem loss rate (m_i) across three successive inventories from 2000 – 2018 using the following equation (Sheil et al., 1995):
m_i = [1 ‒ (N_i,1/N_i,0)^(1/t)] × 100 (Equation 5)
where N_i,0 is the species-specific number of live stems at the initial inventory (at year = t_0) and N_i,1 is the species-specific number of live stems at the next inventory (at year = t_1). The variable t (years) is the difference in time between inventory periods, and equal to t_1 – t_0. Next, we evaluated the impact of drought as a change in stem loss rate (Δm_i) (% stem loss/year), where species-specific m_i after 2012 were subtracted by m_i quantified in the same hexagon during previous non-drought periods. The Δm_i equation took the following form:
Δm_i = m_i,post_drought ‒ m_i,pre_drought (Equation 6)
where m_i,post_drought is a species-specific drought-driven stem loss rates (when N_i,1 was sampled during the years 2012−2018; Equation 5) and m_i,pre_drought is the stem loss rate for the same species and locations from two successive inventories during a non-droughted period (when N_i,1 was sampled during the years 2000−2011; Equation 5). mr_ij is then calculated as the pairwise difference between corrected stem loss rates between species i and j, expressed as:
mr_ij = Δm_i ‒ Δm_j (Equation 7)
Relative mortality sensitivity (%) was then quantified as:
Relative mortality sensitivity_i = [(n_mr_ij>0 ‒ n_mr_ij<0)/n_tot] × 100 (Equation 8)
where n_mr_ij>0 are the number of co-occurring species that experienced lower drought-driven stem loss change and n_mr_ij<0 are the number of species that experienced greater drought-driven stem loss change. n_mr_ij>0 and n_mr_ij<0 were determined by a one sample t-test of the species-specific mr_ij comparisons. n_tot is the number of species that were able to be compared.