Relative tree growth and mortality responses to the 2012 midwestern US drought in the central hardwood ecoregion

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  â€˜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.
Rela..., 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 â€’ BA_i,0)/BA_i,0] Ã— 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 spec..., # **Relative tree growth and mortality responses to the 2012 midwestern US drought in the central hardwood ecoregion.**

Dataset DOI: [10.5061/dryad.280gb5n2b](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-le...,