Study site and species
The study site was located in a tropical montane rain forest in
Jianfengling Nature Reserve in Hainan Island, China (Figure 1a),
adjacent to a 60-ha stem-mapping plot established in 2012 (18°53′N,
108°43′E) (Xu et al. 2015). The site receives annual
precipitation ranging 1300–3700 mm and has an average annual
temperature of 19.8 °C, with summer temperature (June-August) of 27.5°C
(Xu et al. 2015). The two tree species selected for this study
were O. semicastrata f. litchiifolia , a
rhizobia-associated species, carrying coevolved host-specific soil-borne
pathogens (Li et al. 2009) and C. patelliormis , an EcM
fungi-associated species immune to infestation of soil-borne pathogens.
These species were selected because (i ) they were commonly
occurring tree species in the region, (ii ) they demonstrated
contrasting nutrient acquisition strategies, and (iii ) their
seeds could be easily collected and readily germinated.