Abstract: Using spectrophotometry method and portable chlorophyll meter SPAD-502, the chlorophyll content and SPAD value of main greening tree species in northwestern Liaoning Province were measured, and the relationships between chlorophyll content and SPAD value were investigated in the present study. The results showed that chlorophyll a/b ranged from 2.35 to 3.83. When the euclidean distance was 10, the greening tree species could be divided into 3 groups: 6 low, 29 medium, and 20 high chlorophyll a/b tree species. The mean was 2.50, 2.97 and 3.52, respectively, and the differences were significant(P<0.05). Low chlorophyll a/b indicated better using of weak light for plant. The above results showed the shadetolerance for tree species in northwestern Liaoning Province. The unit fresh weight, unit area chlorophyll content, and SPAD value varied in ranges of 0.73-4.61 mg·g^-1, 0.21-0.99 g·m^-2 and 29.42-75.51, respectively, with the variation coefficients of 43.6%, 35.2% and 23.0%, respectively. The SPAD value was insignificantly correlated with unit fresh weight chlorophyll b and chlorophyll a+b content(P>0.05), but was significantly positively correlated with unit area chlorophyll a, chlorophyll b, and chlorophyll a+b content(P<0.001). Furthermore, the relationship was ranked as: chlorophyll a(R=0.67)>chlorophyll a+b(R=0.61)>chlorophyll b(R=0.56). These results indicated that chlorophyll content of main greening tree species was lower in northwestern Liaoning Province. SPAD values could be used to represent the difference in interspecific unit area chlorophyll content, but could not reflect the unit weight chlorophyll content. Tree choice and allocation could be made properly according to shade tolerance.

Key words: chlorophyll, SPAD, shade tolerance, tree choice