Aims Seed germination is affected by both provenance and habitat conditions (light, temperature, etc.). Then natural regeneration capacity of Korean pine (Pinus koraiensis) is determined by its seed germination, which is the key to restore the broadleaved Korean pine forest—a regional climax community. This study aimed to reveal the effects of light and temperature on seed germination of Korean pine with different provenances.
Methods Germinations of the P. koraiensisseeds produced in the year were investigated in both field and lab from three provenances in China (i.e. Qingyuan, Liaoning Province; Changbai Mountain, Jilin Province; and Yichun, Heilongjiang Province). Specifically, for field survey, seed germination data were obtained from both forest canopy gap and forest understory in different seasons. While for lab experiment, the seed germination in growth chamber were recorded under three light intensities (i.e. 200, 20 and 0 μmol·m-2·s-1, L200, L20 and L0 hereafter) and two temperature conditions (i.e. 25 and 15 °C).
Important findings Results showed that no seeds germinated in spring (May) under natural conditions. In comparison, the seed germination percentages (GP) from three provenances were relatively low ranging from 1.8% in understory to 33.7% in canopy gaps in summer (July) and autumn (September). However, we found that the GP were significantly higher in the canopy gap than in the understory in summer. Besides, lab experiments showed that the GP were relatively high (ranged from 32% to 77%) for spring and summer seeds under suitable light and temperature conditions (L200, 25/15 °C) in growth chamber, but the GP were very low for autumn seeds (<2%). At 25 °C condition, the GP and germination values (GV) were significantly higher under L200 than those under L20 and L0 conditions for all the three provenances. At 15 °C condition, the response of GP and GV was consistent with that of 25 °C for seeds from Qingyuan, while the GP and GV were the highest under L0 and L20 conditions for seeds from Changbai Mountain and Yichun, respectively. Under all light intensities, GP and GV from three provenances were all higher under 25 °C than those under 15 °C. In conclusion, temperature is essential for seed germination of P. koraiensis, and the seeds from Changbai Mountain and Yichun might require higher accumulated temperature to break dormancy. Moreover, light helps promote seed germination at relatively high temperature condition (25 °C). However, the impacts of light and temperature were provenance-dependent. More specifically, the light impacts on germination were reduced at lower temperature conditions for seeds collected from Changbai Mountain and Yichun. Our study indicated that the poor regeneration of Korean pine natural forests might attribute to the unsuitable light and temperature conditions for seed germination.