Here we present the result from a two-year field experiment in which we transplanted seedlings of 14 woody species representing three contrasting functional types(broad-leaved evergreen, deciduous and coniferous species) along a light gradient into the understory of a subtropical forest in southwestern China. We assessed mortality and measured the growth rate of all transplanted individuals at intervals. To further understand the mechanisms leading to seedling mortality and growth, we examined three functional traits of transplanted individuals (SLA, leaf mass ratio, wood density).

Seedlings of each species were sown in spring 2007 in a nursery near the field sites. We set up 6 quadrats at each of the two sites along a light gradient. Quadrats 1, 4, 7, 9 and 11 were in low light, quadrats 2, 5, 8 and 12 in high light and quadrats 3, 6 and 10 were in the open (simulating a forest gap). In August 2007, we transplanted four seedlings of each species into each of the 12 quadrats in a random pattern. A field map was drawn for each quadrat to help locating each seedling in the following surveys. We then checked the survival of seedlings two weeks after transplanting and found that all seedlings survived. We revisited each quadrat in March 2008, August 2008, January 2009 and July 2009, documented seedling survival, height and stem diameter (at 2 cm above ground) for all seedlings which were still alive.Light (light availability and quality) and soil factors (water and nutrient content, pH) were quantified in each quadrat.At each census date, after recording survival, the height of surviving seedlings was measured from the ground to the highest shoot tip above ground and the diameter was measured on the stem at 2 cm above ground with calipers. In July 2009, all the surviving seedlings were harvested after all the non-destructive measurements had been taken. In the laboratory, each seedling was separated into leaf, stem and root fractions. Then we measured SLA, WD and LMR.

The study was carried out from August 2007 to July 2009 at two forest sites near Dujiangyan, Sichuan, SW China. The prevailing vegetation type is secondary, mixed coniferous and broad-leaved subtropical forest. The climatic conditions are subtropical with a dry winter (November–April) and a warm and rainy summer (May–October). The annual average temperature is 15.2 °C and July average temperature is 25 °C. The mean annual precipitation is 1341 mm and the annual average relative humidity is above 80%.

August 2007 to July 2009

The 14 species studied are commonly found in subtropical forest in Dujiangyan. We included 6 evergreen broad-leaved, 6 deciduous broad-leaved and 2 evergreen coniferous species representing 9 families.