rainfall but otherwise maintained ambient light and temperature (light transition rate was over 90% and temperature inside and outside the glass house differed by < 0.3℃). Summer climate in this site is typically hot and wet; the average rainfall total and temperature from June to September is 141 mm and 29.9℃, respectively. Over recent decades, the frequency of high temperature (~ 40℃) and low precipitation during the mid-summer season has increased (from Meteorological Bureau of Nanchong (http://sc.cma.gov.cn/ds/nc/)). After 8 weeks of clonal propagation, 180 cuttings (90 males and 90 females) of similar size (15 cm in length and 0.5 cm in diameter) were chosen randomly from all cuttings across populations and transplanted to plastic pots (15 cm × 20 cm) filled with 8 kg homogenized soil (1 cutting per pot). Surface soil (0-20 cm) was collected from farmland near the experimental site. Soil was sifted with a 0.35 mm diameter sieve. The soil was a Cambisol (pH 7.