DOI: 10.13020/76gf-n039
title: Functional leaf and stem traits of the Oaks of the Americas

description: Leaf and stem trait data: Measured interspecific variation of Quercus (L.) - totaling 15+ functional traits for 135* American oak species. Our goal was to hand-measure/characterize as many North American species as possible. Measurements include: (1) specific leaf area (SLA, mm2 mg), an important leaf economic spectrum (LES) trait associated with leaf lifespan, resource acquisition, and nutrient use (Wright et al., 2004; Reich, 2014), (2) perimeter per unit leaf area (PLA, cm−1), a leaf trait that increases with degree of lobing and decreases with leaf size and is associated with hydraulic conductance and boundary layer resistance for all species (Sack et al., 2003; Kaproth and Cavender‐Bares, 2016), (3) total length of major veins per area (cm−1), associated with leaf hydraulic function (Sack and Scoffoni, 2013), (4) leaf length (mm), (5) petiole length (mm), and (6) stem specific density (g·cm−3), associated with mechanical strength and drought tolerance (Cornelissen et al., 2003; Kunstler et al., 2015). Specimens from sunlit branches were pressed and dried alongside samples collected for herbarium specimens as part of the Oaks of the Americas Project (Hipp et al., 2018).
description: To capture interspecific variation, this data set includes 15+ functional traits for 135* American oak species. Two data files present: 
1) Petiole diameter (mm),
2) Petiole length (mm),
3) Leaf length (L; cm), 
4) Leaf Feret diameter (cm),
5) Leaf mass (g), 
6) Leaf area (A; cm2),
7) Specific leaf area (SLA; mm2 mg-1),
8) Total length of major veins per area (L/A; cm-1), 
9) Leaf perimeter length (P; cm)
10) Perimeter per unit leaf area (PLA; cm-1), 
11) Leaf lobedness (P/A)*L
12) Pubescence above (0-3),
13) Pubescence below (0-3), 
14) Stem specific density (SSD; g cm-3),
15) Stem mass (g), 
16) Stem diameter (mm),
17) Stem length (cm),
18) Stem volume (cm-3), 
19) Huber Value (stem area/leaf area) (HV; mm2 cm-2), 
20) Huber Value (stem area/leaf mass) (HV; mm2 g-1),
21) Total leaf area (cm2),
22) Total leaf mass (g).

Unless otherwise noted below, all traits were measured using functional trait methods outlined in Cornelissen et al. 2003 Handbook for functional traits or Tyree Ewers 1991. Field-collected leaf and stem samples from sunlit branches were pressed and dried. Three fully expanded leaves from each individual of each species were scanned and analyzed for leaf surface area, perimeter length and perimeter per area using ImageJ software; they were then dried and weighed for SLA. Leaf pubescence was ordinal-ranked 0-3 qualitatively, with 0 = glabrous (bare), 1 = puberlulent (minimal hair present, but not functionally dense), 2 = functionally-dense (but leaf surface still partially visible), to 3 = tomentose (hair obscuring the leaf surface). Stem specific density was derived from dry segments of stem two to three flushes proximal to the terminal meristem to ensure tissue had lignified. Stem segments with bark were measured for diameter, length and mass to calculate cylindrical volume and density. To calculate the Huber Value, the total leaf area was estimated from the mean leaf area of all three measured leaves, multipled by the total number of leaves distal to the stem cross-section. 

Species mean values come from a minimum of three individuals*, collected across the species range, with a mean of 14.0 ± 12.0 (SD) leaves measured per species. The majority of leaves were field collected between 2012 and 2014, and are now held by MIN and MOR Index Herbaria. Measurements completed during 2013 and 2014. 

*28 species had fewer than three individuals: Q. affinis, ajoensis, aliena, buckleyi, canariensis, cornelius-mulleri, dalechampii, diversifolia, dumosa, dysophylla, gentryi, germana, glaucoides, gravesii, greggii, laeta, macranthera, ocoteifolia, parvula, peninsularis, polycarpa, pumila, sadleriana, sartorii, shumardii, similis, stenbergii, x acutidens