Foliar elemental composition and carbon and nitrogen isotope values for 339 woody species from Barro Colorado Island, Panama

Metadata – Foliar elemental composition and carbon and nitrogen isotope values for 339 woody species from Barro Colorado Island, Panama

File name – “BCI LEAF ELEMENTAL COMPOSITION with binomials.txt”, a tab-delimited text file.

Variable names, definitions, and units:

sp6 – a six-letter code used to identify species for the BCI 50-ha plot

sp4 - a four-letter code used to identify species for BCI seed trap and seedling censuses

family – plant family

genus – plant genus

species – plant species

LIGHT – values are SUN and SHADED (see definition below)

AL – aluminum concentration (μg Al / g leaf tissue)

CA – calcium concentration (mg Ca / g leaf tissue)

CU – copper concentration (μg Cu / g leaf tissue)

K – potassium concentration (mg K / g leaf tissue)

MG – magnesium concentration (mg Mg / g leaf tissue)

MN – manganese concentration (μg Mn / g leaf tissue)

P – phosphorus concentration (mg P / g leaf tissue)

ZN – zinc concentration (μg Zn / g leaf tissue)

D13C – carbon stable isotope (per mil)

D15N – nitrogen stable isotope (per mil)

C – carbon concentration (100 * g C / g leaf tissue)

N – nitrogen concentration (100 * g N / g leaf tissue)

The variable “Light” takes the values SUN or SHADED. The value SUN indicates leaves were fully exposed to direct sunlight in the forest canopy. The value SHADED indicates leaves were in the understory and received direct sunlight from small, short-lived sun flecks or when the solar disk passed in front of a hole in the canopy located to one side and not directly above the leaf. In the latter case, the foliage on the tree was oriented towards the hole in the canopy. Most species have data for both SUN and SHADED leaves. However, SUN or SHADED values are missing entirely for rare species collected in just one microhabitat and for extreme shade-intolerant species (SUN values only) and for some understory shrubs and treelets (SHADED values only).
 

Field collection methods:

We targeted the six largest and six smallest individuals of each species in the BCI 50-ha plot and collected two leaves from each individual between July 2007 and January 2008. Leaves were held on ice until oven-dried at 60 C. We determined elemental composition for a single pooled sample for each species and microhabitat, where microhabitat refers to exposure to sunlight (see the variable “LIGHT” above). To pool samples by species and microhabitat, we ground leaves the oven-dried leaves to a fine powder, weighed an equal mass of ground tissue for each individual tree, combined the weighed samples for each species and microhabitat, and mixed the combined sample thoroughly. Thus, our values represent mean values over three to six individuals for each species-microhabitat combination. 

The following article described field collection methods in greater detail: 

Wright, SJ, K Kitajima, NJB Kraft, PB Reich, IJ Wright, DE Bunker, R Condit, JW Dalling, SJ Davies, S Díaz, BMJ Engelbrecht, KE Harms, SP Hubbell, CO Marks, MC Ruiz-Jaen, CM Salvador and AE Zanne. 2010. Functional traits and the growth-mortality tradeoff in tropical trees. Ecology 91: 3664-3674.

Laboratory methods:

Nitrogen – automated elemental analyzer (dry combustion and gas chromatography, with TCD detection). 

Description of determination of total elements in plant tissue by nitric acid digestion follows:

Chemicals

1. Nitric acid, 70% (FW 63.01), Sigma 438073, ACS Reagent.

Procedure

1. Weight 200 mg of dried, ground plant tissue into a PTFE digestion vessel and add 2 mL of concentrated nitric acid.

2. Include a blank vessel (nitric acid only) and a certified reference sample (e.g. pine needles).

3. Cap the vessels and clamp into place on the metal frames. The screws should be hand-tight and then further tightened with an additional quarter turn using a hexagonal wrench. Do not overtighten as this will damage the PTFE caps.

4. Heat the samples in an oven for 6 h at 180oC.

5. In the morning, remove the samples from the oven and remove the caps in the fume hood to allow the vapour to disperse. Do not open vials until the samples are cool.

6. Transfer the digestion solution into a 50 mL volumetric flask, rinsing the PTFE vessel with deionized water to ensure quantitative transfer of elements to the flask.

7. Dilute the sample to the mark with deionized water and determine elements by inductively-coupled plasma optical-emission spectrometry (ICP–OES).