The effects of different light and temperature conditions on seed germination of two keystone species (Picea asperata and Betula albo-sinensis) in subalpine coniferous forests were studied by simulating environmental conditions in climatic chambers. The results indicated that the optimal temperature of seed germination for both species was 25 degrees C, with the germination rate of 88.8 +/- 8.4% and 30.8 +/- 10.4%, respectively. Through multiple comparisons with Tukey's HSD, B. albo-sinensis was more sensitive to temperature than P. asperata. Seeds of P. asperata could germinate when the temperature reached 10 degrees C, but those of B. albo-sinensis could not, which implied that the latter as a pioneer species of subalpine coniferous forest areas needed higher lowest temperature for seed germination. Day and night temperature difference (15 degreesC/10 degrees C, 20 degrees C/15 degrees C and 20 degrees C/10 degrees C) had significant effect on the germination rates of tested seeds, which was the highest under 20 degrees C/15 degrees C. A wide range of day and night temperature difference seemed to be unfavorable to the seed germination of B. albo-sinensis. Light intensity also had a marked effect on the germination rates of test seeds. Under 20% transmittance, the germination rate of P. asperata and B. albo-sinensis was the highest, being 83.0 +/- 6.6% and 29.2 +/- 5.5%, respectively, and the initiation time and regularity of germination were the best as well. Furthermore, B. albo-sinensis was less sensitive to light than P. asperata, which was determined by the life behavior of tree itself.