Relative growth rate (RGR) and leaf area
Mean relative growth rate (RGR) was derived as: RGR = (logeW2 - logeW1 )/(t2 -t1 ), where W1 andW2 was the plant dry weight at the first (t1 ) and second (t2 ) harvest, respectively. At the final harvest, plant total leaf area was measured after saturation in wet tissue paper at 5℃ overnight, with a Delta-T Area Meter (Burwell, Cambridge, UK) for most species, while a 1 mm paper grid was used to calculate leaf area visually for some species with tiny leaves. Average leaf area was calculated as the ratio of total leaf area to leaf number per individual. For each species, 8-30 individuals were used for quantifying the above parameters (details see Cornelissen et al. (1996), Cornelissen, Cerabolini, Castro-Diez, Villar-Salvador, Montserrat-Marti, Puyravaud, Maestro, Werger and Aerts (2003a)).