Leaf Color Transformation of 5 America Introduced Quercus spp. in Autumn and Winter

Five introduced species of 4-year oak seedlings including Quercus nigra, Q. nuttallii, Q. shumardii, Q. uercus palustris, Q. phellos were used to measure the contents of chlorophyll, carotenoids, anthocyanin and soluble sugar in leaves. The air temperature and humidity changes during the experiment were recorded synchronously. The relationship between the change of pigment content in leaves and environmental factors was studied. The results showed that with the decreasing of air temperature, contents of chlorophyll a and b in leaves of 5 oak species decreased significantly first and then slowly, and the content of anthocyanin presented a trend of fluctuant rise. The chlorophyll a content in descending order was as follows: Q. palustris > Q. nigra > Q. shumardii > Q. nuttallii > Q. phellos. During the test period from October 12 to November 5, the chlorophyll b of Q. nuttallii, Q. shumardii and Q. phellos decreased the most. Variations of carotenoid contents exhibited significant increase in Q. phellos, while fluctuated in the other 4 species. The average temperature had a significantly negative correlation with anthocyanin in 5 oak species(P<0.01), and there was a significant positive correlation between anthocyanin and soluble sugar content in Q. nigra and Q. phellos. This concluded that lower temperature accelerated the accumulation of anthocyanin in leaves of 5 oak species in autumn and winter and directly affected the change of leaf color.