Seed coating experiment
To examine the effect of seed coats on native seed germination success, we used two formulations of seed coats and one control (i.e., raw seed without any treatment). The two formulations refer to seeds encrusted with mixtures of clay powder and biochar powder at ratios of 7:3 (clay-dominant) and 4:6 (biochar-dominant) in weight respectively. The biochar composed of mixed woods, mainly Acacia confusa ,Dimocarpus longan and Bauhinia  spp. The wood debris is heated up to approximately 500 °C in a low oxygen environment for 30 minutes to create the biochar. Large seeds (over 10 mm in diameter) were treated using a sweet dumpling rotating machine (Model YX-65, China), while small and medium-sized seeds (3-5.9 mm; 6-9.9 mm in diameter) were treated using a DIY modified centrifuge (EBA 8, Hettich, Germany).
Seeds were planted on three landslide sites between April and June 2020 (Figure. 1a). Within each site, there were nine plots (each 1.6 m by 1.8 m), and the plots were at least 2 m from each other (Figure 1b). Within each plot, we further divided it into six equal grids as six species were tested (Table 1). We planted 24 seeds per grid for each species (Figure 2a). There were three replicate plots for each of the two treatments and the control, hence nine plots per site.