Description: This dataset is part of a research project that aims to study how bark and wood traits shape species ecological strategies at the seedling stage in four tropical forests in Colombia.  These forests are located in the municipalities of Jabiru (Tolima), Cotove (Antioquia), Colorados (Bolivar) and Tyrona (Magdalena). Detailed information on the location of these forests can be found in: https://doi.org/10.1111/ele.13659 

Date: 6 February, 2024

Dataset Title: Bark traits of tropical dry forests seedlings

Dataset Creators: A. Gonzalez-Melo & M.N. Umaña

Dataset Contact: Andres Gonzalez agonzm@umich.edu

Funding: NSF DEB-2016678 & NatGeo explorers, both granted to M.N. Umaña 

Methodological details

Study sites: Information on the location and environmental conditions of the four study sites can be found in: https://doi.org/10.1111/ele.13659 

Trait measurement:

This dataset contains measurements of three bark traits and seven wood traits measured for 41 seedling species from tropical dry forests. Between two and six seedlings (i.e., 20-70 cm in height, and less than 1 cm in diameter) per species were collected in four mature dry forest in Colombia.

Inner and outer bark thickness were measured manually, at the same stem point, using the ImageJ 1.52 software, and total bark thickness was calculated as the sum of inner and outer bark thickness.

Wood density was calculated, for each stem segment, as fresh volume over dry mass. Fresh volume was measured by the water displacement method, and dry mass was determined after oven-drying the samples to a constant mass at 103º C  Cross and tangential anatomical sections (10-15 µm thick) were cut from each stem segment using a rotary microtome with disposable blades (Leica RM2255; Leica Microsystems, Wetzlar, Germany). Anatomical sections were stained in AstraBlue (for 10 min) and Safranine O (for 10 min). Then, they were gradually dehydrated in ethanol series for 1 min each (50%, 75% and 96%), dipped in solvent and mounted on slides with Eukitt mounting medium (Electron Microscopy, Hatfield, PA, USA). Anatomical slides were photographed using a camera (Axiocam 305 color, Zeiss, Germany) mounted on a light microscope (Axio Scope A1, Zeiss). From each anatomical slide, one 100x tangential photograph was taken, while one 10x and one-to-three 40x (depending on stem diameter) photographs were taken in the cross section. To take cross-sectional photographs, we selected in each anatomical slide a representative area covering, in general, most of the radial variation (i.e., from pith to bark) in wood structure, and avoiding visible injuries or tension wood.
 
In these anatomical photographs, we measured eight wood anatomical traits related to transport, storage and mechanical support. To measure the fractions (i.e., % of stem cross-sectional area) of vessels, fibers and parenchyma cells, we first manually colored each cell type in the 10x cross-section photographs using a drawing pad (Wacon CTL-472; China) and Photoshop CS4 (Adobe Systems Incorporated, USA). Then, we calculated the fractions automatically using the batch function in the ImageJ 1.52 software (http://rsb.info.nih.gov/ij/). When the distinction between fibers and axial parenchyma cells in the cross-sectional photographs was problematic, due to fiber dimorphism and/or thick-walled parenchyma, we checked tangential images to verify the categorization of these cell types. 
 
To measure fiber wall thickness (Fwt), each 40x cross-sectional photograph was divided in four equal sections, and 20 fibers per section were randomly selected and measured, for a total of 80 fibers in each photograph. Intervessel pit diameter aperture (Dpm) was measured,  in the 100x tangential photographs, as the horizontal pit membrane diameter at its widest point, in 20 pits per vessel and three vessels per photograph. Mean hydraulically weighted vessel diameter (Dh) was measured, in one 10x cross-sectional photograph per individual, as: Dh= (∑ D4/n)1/4, where D is the average of the major and minor axis for each vessel cross-section, and n is the total number of vessels measured . We measured on average 142 vessels per photograph (range 15-455). Fwt, Dpm and Dh were measured in ImageJ.

Csv file description:

The csv file has two sheets. The first one, contains scientific names, plots where the seedlings were collected, as well as species mean and standard deviation values of three bark traits and seven wood traits. The second one, contains a table with the units, abbreviations and description of the traits measured.

Abbreviations	Units	Description	
Ibt	𝛍m	Inner bark thickness	
Obt	𝛍m	Outer bark thickness	
Tbt	𝛍m	Total (i.e., inner + outer) bark thickness	
WD	g/cm3	Wood density. Oven-dried mass over fress volume	
Ff	%	Fiber fraction. Percentage of stem cross-section allocated to fibers	
Vf	%	Vessel fraction. Percentage of stem cross-section allocated to vessels	
Tpf	%	Total parenchyma fraction. Percentage of stem cross-section allocated to total (axial + radial) parenchyma cells	
Dh	𝛍m	Vessel lumen diameter. Hydraulically weighted vessel diameter	
Dpm	𝛍m	Pit membrane diameter aperture. Intervessel pit diameter aperture	
Fwt	𝛍m	Fiber wall thickness