ECOPHYSIOLOGY OF TWO LIANA SPECIES Calamus ovoideus AND Coscinium fenestratum UNDER DIFFERENT CANOPY REMOVAL TREATMENTS

Abstract

Calamus ovoideus Thw. and Coscinium fenestratum Colbr. are naturally growing economicallyimportant liana species, around the Sinharaja MAB reserve, Sri Lanka. Growth performance andphysiological attributes of these species were examined using plants established in 1991 underthree different canopy removal treatments ina Pinus caribaea plantation in the buffer zone ofSinharaja forest. They were 3 pine rows and 1 pi lie row removed, 3 pine rows under plantingand the Pinus underplanting control where the initial light intensities were 22, 10, 5 and 3mol/m21 day respectively.

The results showed that height after 8 years and the annual height increments were significantlyhigher among the three canopy removal treatments compared to that in the closed canopy controlfor both species. In C. ovoideus greatest height was in the three-pine rows removal treatment andleast in the closed canopy under planting . .In contrast, Cifenestratum showed no significantheight difference among the three canopy removal treatments compared to the control. The meanroot collar diameter after 8 years and its increments in C. fenestratum were significantly higherin the canopy removal treatments compared to that of the control. In the physiological studies,both species showed significant differences in their net photosynthetic rate and stomatalconductance when grown under different light regimes. The higher photosynthetic rate of C.ovoideus was in the one pine removed treatment ar.d in C. fenestratum it was in the three pinerows removed treatment.

After 8 years of establishment, for both study species the three and one pine rows removed andthree pine rows underplanting treatment were better than the Pinus underplanting (closedunderstorey) treatment. This study revealed that these liana species could be successfullyintroduced to the monocuIture Pinus caribaea plantations in the lowland wet zone of Sri Lanka.