Functional traits and photosyntheticsis performances traits were measured from six to ten seedlings for each species (Table 1). The seedlings were measured at 12-18 months after planting, which is a typical age for seedlings used in reforestation (Snorrason, 2020). Eleven functional traits were measured from three leaves per samples, including 1) leaf area, 2) leaf fresh weight, 3) leaf dry weight, 4) specific leaf area, 5) seedling height, 6) root collar diameter, 7) leaf thickness, 8) chlorophyll content, 9) carbon content, 10) nitrogen content, and 11) carbon-to-nitrogen ratio (Table S2).  

Leaf areas were measured by using the scanner and the Fiji software (Schindelin et al., 2012; Umaña et al., 2015). Dry weights were measured after drying in a 70˚C hot air oven for 48 hr (Cornelissen et al., 2003; Garnier et al., 2001; Pérez-Harguindeguy et al., 2016). Specific leaf area (SLA) was the fraction between leaf area and dried matter, one of the most frequently studied plant traits (Cornelissen et al., 2003; Wright et al., 2004). Seedling height (H) and root collar diameter (RCD) were measured as a proxy for performance to represent plant seedling growth rate for one 2 years old (Table S2). Leaf thickness was determined using the Thickness Gauge 547 (Mitutoyo, Japan) (Onoda et al., 2011). 

The chlorophyll content was measured using the SPAD-502 Chlorophyll Meter at the leaf apex, middle, and base, avoiding major veins and margins (Coste et al., 2010). Carbon, nitrogen content, and the ratio of C and N were also determined to represent leaf chemistry. Three dried leaves for each species were used for estimating these values, using the Standard Test Methods for Determination of Carbon, Hydrogen, and Nitrogen in Analysis Samples of Coal and Carbon in Analysis Samples of Coal and Coke, CHNS-628 (LECO, USA) at the Biomass and Bio-energy Technology Division, Kasetsart Agricultural and Agro-Industrial Product Improvement Institute (KAPI). Each trait was measured with three replications (Pérez-Harguindeguy et al., 2016). 

Photosynthetic performance trait measurement 

To determine the performance traits of tree seedling photosynthesis, we measured five fully expanded leaves from each 1-year-old tree seedling before midday (Pérez-Harguindeguy et al., 2016) using the LI-6400 Portable Photosynthesis System (LICOR Inc., USA). The leaf chamber contained an LED light source at 25-30˚C air temperature and 400 ppm CO2. Intensities of light were set at 2000, 1600, 1200, 1000, 800, 600, 400, 200, 100, 50, 20, and 0 µmol · m-2 · s-1 to measure photosynthetic rate at each light intensity and generate a light response curve. The following photosynthesis parameters were estimated using the equation from Lobo et al. (2013): maximum capacity of photosynthesis (Pmax, µmol · m-2 · s-1), quantum yield (ɸ or Phi), dark respiration (Rd, µmol · m-2 · s-1), convexity index (θ or Theta), light compensation point (LCP, µmol · m-2 · s-1), and light saturation point (Qsat75, µmol · m-2 · s-1).