2.2 Species collection and storage
We focused on 10 native species spanning different successional stages (pioneer and late successional) and a large variety of seed size with a diameter ranging from 3 to 13 mm (Table 1). These species were selected based on the fruiting cycles of local trees and the availability of sufficient quantities of seeds at the time of the study. The major fruiting season of Hong Kong’s vegetation is in the winter dry season (September to March), during which we collected seeds of each species from at least three mother trees. The collected seeds were cleaned and capsule separated within a week after collection. The successional characteristics of these species were assigned according to information in the literature (Zhuang & Corlett, 1997, Kammesheidt, 2000; Han, 2001).
To minimize the negative effect of long storage time, a suitable storage method is needed to keep the seeds viable. We stored the recalcitrant seed species such as Machilus breviflora, Sterculia lanceolataand Fagaceae family in wet sand beds in refrigerators kept at 5 to 10 °C, following the storage suggestion from the Chinese Forestry Ministry (2001). Orthodox seeds were stored in unzipped plastic bags at room temperature. Summer fruiting species storage did not exceed three weeks to ensure their quality. The seeds were not subjected to treatments to break dormancy. To ensure seed viability and quality, we screened out any floating, unhealthy seeds prior to storage and planting. The planting experiment was conducted in spring when the climate was wet and warm. Additionally, we planted plain seeds in an outdoor nursery as controls of seed viability at the same time with the field experiment.
2.3 Experimental design