Seasonal Changes of Leaf Chlorophyll Content in the Crowns of Several Broad-leaved Tree Species

This study described the seasonal changes and variations of leaf chlorophyll content (chl) at different crown layers of Quercus serrata, Q. glauca, Zelkova serrata, Camellia japonica and Myrica rubra trees growing under open and shaded environments. Both leaf greenness (SPAD values) determination and chl extraction were used. Positive relationships were derived from leaf greenness and total chlorophyll (chl a+ b) per unit leaf area (mg·cm-2). The method provided reliable estimates of chl (mg· cm-2) in field experiments using intact leaf samples whose leaf greenness were continuously measured. Leaf greenness was shown to be affected by leaf thickness, age and crown position. Patterns of the seasonal changes chl a+b varied for each species. The direct relationship between chl per unit leaf area and photosynthetic photon flux density (PPFD) was not clear but the results seemed to show that chl was higher in trees under areas where lower ranges of PPFD were experienced, such as in C.japonica and Q.glauca under the shade. Measurements done in the leaves of first and second growth flushes showed that the flushing phenomenon in trees influenced the seasonal changes of chl content because of the differences in their leaf age.