Seedlings were planted at each site following a randomized complete block design with four blocks. Each seed source was randomly assigned to a plot within a block. The size of each plot was about 730 m2 and contained 144 trees (12 × 12 rows of trees) in which only the 64 interior trees were considered for analyses, leaving 4 × 4 rows of border trees as a buffer zone. The total number of planted seedlings was 9216, corresponding to 144 seedlings × 4 blocks × 2 seed sources × 8 sites.