Table 2.
The ecological significance for each functional trait measured.
| Trait | Code | Ecological significance | Unit |
|---|---|---|---|
| Leaf thickness | LT | Thicker leaves with higher LMA, longer leaf lifespan and lower relative growth rate (Wright et al. 2004, Westoby and Wright 2006) | μm |
| Palisade mesophyll thickness | PT | Palisade and spongy mesophylls are the main tissues for efficiently intercepting and transmitting light, thus optimizing photosynthesis (Terashima et al. 2011) | μm |
| Spongy mesophyll thickness | ST | μm | |
| Stomatal density | SD | More stomata per area enables greater CO2 assimilation and promotes growth and competition (Tanaka and Shiraiwa 2009) | no. mm−2 |
| Guard cell length | GCL | Larger guard cells and stomata result in large pores, enabling greater CO2 assimilation and promoting growth and competition (Hetherington and Woodward 2003) | μm |
| Leaf density | LD | Less dense leaves are associated with lower LMA and thus higher potential relative growth rate, and dense leaves with higher LMA, longer leaf lifespan and lower relative growth rates (Niinemets 2001, Westoby and Wright 2006) | kg m−3 |
| Leaf mass per area | LMA | A lower LMA is associated with shorter leaf lifespan and higher resource acquisition capacity, indicating a fast-growth strategy (Wright et al. 2004) | g cm−2 |
| Leaf size | LS | LS is thought to affect water loss. Smaller leaves have thinner boundaries, enabling leaves to keep cool especially when transpiration cooling is not possible during drought (Wright et al. 2017) | cm2 |
| Leaf dry matter content | LDMC | Lower LDMC is related to lower LMA and thus higher potential relative growth rate. Lower LDMC may also be linked with drought tolerance in certain ecosystems (Niinemets 2001) | g g−1 |
| Nitrogen concentration | N | Higher N concentrations per leaf area or mass are linked with more rapid photosynthetic rate per leaf area or mass, respectively (Wright et al. 2004) | mg g−1 |
| Phosphorus concentration | P | Higher P concentrations per leaf area or mass are linked with more rapid photosynthetic rate per leaf area or mass, respectively (Wright et al. 2004) | mg g−1 |
| Potassium concentration | K | K content was measured because it is involved in osmotic regulation in cells and is considered to be important for regulating stomatal opening (Benlloch-González et al. 2008) | mg g−1 |
| N/P ratio | N/P | N/P is expected to detect the nature of nutrient limitation, with N/P <14 indicating N limitation, while N/P >16 P limitation (Koerselman and Meuleman 1996) | |
| Stable carbon isotope composition | δ13C | To estimate the efficiency of long-term water use in natural vegetations (Farquhar et al. 1989) | ‰ |
| Stomatal conductance | g s | Higher gs leads to higher potential CO2 assimilation rate and thereby greater productivity and competition (Franks and Beerling 2009) | mol m−2 s−1 |
| Area-based light-saturated photosynthetic rate | A a | Higher Aa relates to greater productivity and competition (Franks and Beerling 2009) | μmol m−2 s−1 |
| Mass-based light-saturated photosynthetic rate | A m | Higher Am relates to greater productivity and competition (Franks and Beerling 2009) | nmol−2 g−1 s−1 |
| Photosynthetic nitrogen use efficiency | PNUE | It is inversely related to the leaf lifespan, positively related to photosynthesis (Poorter and Evans 1998) | μmol mol−1 s−1 |
| Photosynthetic phosphorus use efficiency | PPUE | It is inversely related to the leaf lifespan, positively related to photosynthesis (Poorter and Evans 1998) | mmol mol−1 s−1 |
| Photosynthetic water use efficiency | WUEi | Indicator of instantaneous water use efficiency; it is negatively related to the PNUE, PPUE (Santiago et al. 2004) | μmol mol−1 |
| Leaf vein density | D vein | Higher vein densities would increase leaf hydraulic conductance and potentially photosynthetic rate and growth (Sack and Scoffoni 2013) | mm mm−2 |
| Wood density | WD | WD is strongly related to the mechanical strength and capacity to prevent vessel implosion, water storage capacity and life history strategy (Hacke and Sperry 2001, Chave et al. 2009) | g cm−3 |
| Vessel density | VD | VD is related to hydraulic transportation capacity; the higher the VD, the higher the water transport efficiency (Hacke and Sperry 2001, Chave et al. 2009) | no. mm−2 |
| Hydraulically weighted vessel diameter | D h | Vessel diameter is related to hydraulic transport efficiency and is inversely related to the cavitation resistance (Hacke and Sperry 2001) | μm |
| Theoretical hydraulic conductivity | K t | Higher hydraulic conductance is related to higher stomatal conductance and higher photosynthetic carbon gain (Brodribb and Feild 2000, Santiago et al. 2004) | kg m−1 s−1 MPa−1 |