Study site and seedling censuses
The study site is located in the Gutianshan 24-ha subtropical Forest Dynamic Plot (GTS FDP; 29.25°N, 118.12°E) with altitude varying from 446.3 to 714.9 m above sea level, in Zhejiang province, China. The climate there is seasonal with wet season from March to June and two dry seasons from July to August and from October to February (Lai et al. 2009). The plot is censused every five years for all trees with diameter at breast height (d.b.h.) ≥ 1 cm. The seedling survival dataset was from the seedling monitoring network which initiated in May 2006 in GTS FDP (Chen et al. 2010, Wang et al. 2020). The plot contained 169 census stations with three 1 m2 seedling plots in each station. The first 130 stations were arranged by a stratified random design and the subsequent 39 stations were placed in naturally occurring tree fall gaps. For each plot of the 169 stations, all the seedlings (< 1 cm d.b.h.) were tagged, identified to species, and measured for height. The statuses (alive or dead) of all seedlings recorded in May from 2009 to 2015 were used in this study. This resulted in six one-year intervals for seedling survival. After matching the tree species with transcriptomic data (see next section below), we obtained 4009 seedlings from the 2009-2010 interval, 3802 seedlings from the 2010-2011 interval, 3660 seedlings from the 2011-2012 interval, 3239 seedlings from the year 2012-2013 interval, 3202 seedlings from the year 2013-2014 interval and 2576 seedlings from the year 2014-2015 interval, and a total of 7718 unique seedlings belonging to 81 woody species across the 2009–2015 period were used in our analysis. We also determined the survival rates of each station and the top 20 dominant seedling species with more than 100 recorded seedling individuals in GTS FDP.