南岭森林3种常见树种光合-蒸腾作用特性

Photosynthesis and Transpiration Characteristics of Three Typical Tree Species in the Forests of Nanling Mountains,Northern Guangdong

应用便携式光合作用系统Licor-6400对南岭森林3个常见树种的光合和蒸腾作用日进程进行了测定.结果表明:(1)藜蒴Castanopsis fissa日均光合速率为(4.33±0.17)μmol.m-2s-1,日均蒸腾速率为1.57 mmol.m-2s-1,日均水分利用效率(WUE)为(3.02±0.07)μmol/mmol;羊角杜鹃Strophanthus divaricatus日均光合速率为(6.41±0.20)μmol.m-2s-1,日均蒸腾速率为(2.36±0.16)mmol.m-2s-1,日均水分利用效率为(2.74±0.06)μmol/mmol;香樟Cinnamomum camphora日均光合速率为(9.28±0.39)μmol.m-2s-1,日均蒸腾速率为(3.15±0.16)mmol.m-2s-1,日均水分利用效率为(3.18±0.07)μmol/mmol.(2)日光合速率峰值出现时间因树种与林冠位置而异,藜蒴顶部在9:22左右出现,中部在10:30左右,下部在11:40左右;羊角杜鹃顶部在10:30左右出现,中部在11:30左右,下部在14:40左右;香樟顶部在10:22左右出现,中部在10:30左右,下部在13:30左右.(3)蒸腾速率日变化典型"双峰"曲线峰值出现时间因树种、林冠位置而略有差异,藜蒴下部第一峰值出现在11:40左右,第二峰值在13:30左右;羊角杜鹃顶部第一峰值出现在10:30左右,第二峰值在14:30左右;香樟顶部第一峰值出现在10:30左右,第二峰值在12:30左右.(4)水分利用效率因不同树种而异,同一树种水分利用效率因叶片所处林冠不同位置而异.

Evapotranspiration of forest canopy plays a significant role in the evaluation of ecological benefits from a forest ecosystem. This paper conducted some measurements, with a portable photosynthesis system Licor-6400, on three typical tree species, namely, Castanopsis fissa, Strophanthus divaricatus and Cinnamomum camphora within the forest ecosystem of Nanling Mountains, northern Guangdong Province, in order to determine their photosynthetic characteristics in diurnal patterns at canopy level. Results show that the daily average photosynthetic rate of the first species is （4.33±0. 17）μmol·m-2s-1, its average daily transpiration rate 1.57mmol·m-2s-1 , and its daily water-use efficiency （3.02q-0.07）μmol/mmol; that the daily average photosynthetic rate of the second species is （6.41 ± 0. 20） μmol·m-2s-1 , its daily average transpiration rate 2. 36 mmol · m-2 s-1, and its daily average water-use efficiency （2. 74 ± 0. 06） μmol/mmol; and that the daily average photosynthetic rate of the third species is （9. 28 μ0. 39） μmol·m-2s-1, its daily average transpiration rate （3.15± 0.16） mmol · m- 2·s- 1, and its daily average water-use efficiency （3.18 ± 0.07） μmol/mmol. The results also show that the time for the peak values of their daily photosynthetic rates varies with tree species and canopy heights; that the maximum photosynthetic rate of the first species appears at about 9：22 at the top, about 10：30 in the middle and about 11：40 in the lower parts, that of the second at about 10：30 at the top, about 11：30 in the middle and about 14：40 in the lower parts, and that of the third at about 10：22 at the top, about 10：30 in the middle and about 13：30 in the lower parts; that the diurnal change of transpiration rates displays a double peak pattern, subject to noon depression phenomena and to the difference of tree species and canopy heights; and that for the first species, the first peak time arrives at about 11：40 and the second at about 13：30; for the second species, the first at about 10：30 and the second at about 14：30; and for the third species, the first at about 10：30 and the second at about 12：30. The results still show that their water-use efficiency also changes with tree species and that of the same species varies with the different canopy heights of the leaves.