Table 1.

Description of the selected functional traits, trait functional dimensions, mean–ranges and global reference ranges

Trait (abbreviation)	Units	Description	Trait function (dimension)	Trait mean ± SD ( ${\bar{Q}}_{> 0.1}$ – ${\bar{Q}}_{< 0.9}$ )	Reference range	References
Fibre wall thickness (FWT)	µm	^a Double wall between adjacent fibres ^b Resistance of internal and external stresses ^c Greater walls, higher hydraulic safety	Water exploitative safety (wood)	5.54 ± 1.52 (3.24–8.55)	4–12	Madsen and Gamstedt (2013); Scholz et al. (2013); Sorieul et al. (2016)
Hydraulically weighted diameter (d_h)	µm	^a Sum of circle conduits diameters d divided by the number of conduits N in a surface area ${(\sum \frac{d^{4}}{N})}^{0.25}$ ^b Conductance of conduits ^c Larger weighted diameters, higher hydraulic efficiency	Water exploitative efficiency (wood)	58.64 ± 22.39 (31.23–105.74)	1–300	Scholz et al. (2013); Rosell et al. (2017)
Leaf area (LA)	mm²	^a Projected area of a leaf ^b Light interception, energy and water balance ^c Larger LA, cheaper tissues and high water demands	Investment in tissues Water exploitative efficiency (leaves)	1.25 × 10⁴ ± 2.15 × 10⁴ (1.05 × 10³–5.77 × 10⁴)	1–>20×10⁶	Pérez‐Harguindeguy et al. (2013); Díaz et al. (2016)
Leaf dry matter content (LDMC)	mg g⁻¹	^a Dry mass per unit of lamina surface area ^b Tissue investments and carbon‐gain strategies ^c Higher LDMC, robust tissues	Investment in tissues (leaves)	379.38 ± 91.31 (209.46–533.64)	50–700	Pérez‐Harguindeguy et al. (2013); Díaz et al. (2016)
Leaf thickness (L_th)	Mm	^a Leaf mesophilic density (or thickness) ^b Physical strength and leaf longevity ^c Thicker leaves, higher tissue investments	Investment in tissues (leaves)	0.21 ± 0.06 (0.13–0.33)	0.11–0.74	Pérez‐Harguindeguy et al. (2013); Onoda et al. (2011)
Maximum vessel area (VA_max)	µm²	^a Average conduit surface area of the last VA percentile (>75, Q₃–Q₄) ^b Hydraulically efficiency ^c Greater conduits, higher water flows but higher conduits embolism risk	Water exploitative efficiency (wood)	2942.59 ± 2623.32 (589.12–8904.27)	7853–31415	IAWA et al. (2007); Scholz et al. (2013)
Pit area (PA)	µm²	^a Pit aperture surface area ^b Air–water interfaces for conduits ^c Larger pits, higher water flows but higher conduits embolism risk	Water exploitative efficiency (wood)	19.68 ± 16.30 (4.37–55.15)	12–78	IAWA et al. (2007); Scholz et al. (2013)
Pit diameter aperture (DA_pit)	µm	^a Horizontal pit membrane diameter ^b Embolism resistance inter‐conduits ^c Smaller and denser pits, higher hydraulic safety	Water exploitative safety (wood)	2.90 ± 1.19 (1.38–5.38)	0.5–7	Scholz et al. (2013); Li et al. (2016); Helmling et al. (2018)
Specific leaf area (SLA)	mm² mg⁻¹	^a Area of a fresh leaf divided by its oven‐dry mass ^b Carbon capture and leaf longevity ^c Higher SLA, lower tissue investments	Water exploitative efficiency (leaves)	15.39 ± 7.33 (7.24–32.22)	<1–300	Wright et al. (2004); Pérez‐Harguindeguy et al. (2013)
Vessel area (VA)	µm²	^a Average conduit surface area ^b Hydraulic conductivity ^c Greater conduits, higher hydraulic efficiency but lower hydraulic safety	Water exploitative efficiency and safety (wood)	1676.93 ± 1484.11 (391.73–5094.72)	196–37600	Olson and Rosell (2013); Scholz et al. (2013)
Vessel density (VD)	vessels mm⁻²	^a Number of conduits per cross‐sectional area ^b Resistance to strength and vessel implosion ^c Higher density, higher hydraulic safety	Water exploitative safety (wood)	71.71 ± 50.54 (15.22–181.83)	1–1000	Chave et al. (2009); Scholz et al. (2013); Jacobsen et al. (2005)
Wood density (WD)	g cm³	^a Oven‐dry mass divided by saturated volume of the wood section ^b Wood stability, aboveground biomass construction and carbon‐gain strategies ^c Harder woods, lower water demands and higher tissue investments	Investment in tissues Water exploitative safety (wood)	0.63 ± 0.15 (0.32–0.84)	0.1–1.2	Chave et al. (2009); Pérez‐Harguindeguy et al. (2013)
Wood anhydrous density (WD₀)	g cm³	^a Oven‐dry mass divided by anhydrous volume of the wood section ^b Wood stability ^c Greater wood anhydrous densities, higher tissue investments	Investment in tissues (wood)	0.72 ± 0.17 (0.38–0.96)	0.1–1.5	Chave et al. (2009); Pérez‐Harguindeguy et al. (2013)
Water content at maximal capacity (WC_max)	kg kg⁻¹	^a Free and fixed water capacity in cells. $[(1.5 ‐ {WD}_{0}) \times 1.5 {WD}_{0}] + {WC}_{fsp}$ (Water content at fibre saturation point); ${WC}_{fsp} = \frac{1}{WD} ‐ {\frac{1}{WD}}_{0}$ ^b Shrinkage and swelling of xylem cells ^c Higher water content, lower xylem mechanical resistance	Water exploitative efficiency (wood)	1.05 ± 0.61 (0.53–2.54)	0.2–5.0	Guevara (2001); Berry and Roderick (2005)
Xylem potential hydraulic conductivity (K _p)	Kg m⁻¹ s⁻¹ MPa⁻¹	^a Theoretical specific xylem hydraulic conductivity per cross‐sectional area. $\frac{{π ρ}_{ω}}{128 η} \times \sum d_{h}^{4} \times VD$ ; $ρ_{ω}$ =998.2 kg m^‐3; $η$ = 1.002 × 10^–9 MPa s^–1; d_h and VD by m units ^b Water exploitation abilities ^c Higher potential conductivity, higher hydraulic efficiency	Water exploitative efficiency (wood)	25.09 ± 43.78 (2.25–113.72)	0.3–200	Chave et al. (2009); Poorter et al. (2010); Méndez‐Alonzo et al. (2012)

^{^a}

Trait‐based ecology definition and method of calculation.

^{^b}

Trait association to functions and mechanisms of a tree.

^{^c}

Trait association to hydraulic safety‐efficiency trade off of a tree.