GROWTH PERFORMANCE OF FOUR Syzygium species IN THE SIMULATED LIGHT AND
SOIL NUTRIENT ENVIRONMENTS OF A RAIN FOREST IN SRI LANKA
H K Gamage* , B M P Singhakumara* , P M S Ashton**
* University of Sri Jayewardenepura; ** Yale University,
New Haven, USA.
Seedlings of four species of Syzygium (S. firmum, S. makul, S. operculatum,
S. rubicundum) were investigated for differences in growth and survival
after one and half years growth in a nursery experiment. All four species
co-exist in the moist evergreen rain forest of South western Sri Lanka.
S. firmum is a canopy tree on valleys to midslopes. S. rubicundum is considered
a canopy tree of late-successional forest on hill mid slops. Both S. makul
and S. operculatum are sub canopy trees of late-successional forest along
streamways of lower slopes and valleys.
Seedlings of each species were grown within replicated light and soil
nutrient treatments found in the groundstorey forest environments. The
light treatments exposed seedlings to i) full sun; ii) sunlight like that
at the center of a 200 m2 forest opening. iii) sunlight like that at the
center of a 400 m2 canopy opening; iv) 50% shade of sunlight with quality
similar to the outside edge of a 400 m2 canopy opening on the shaded side;
v) 20% of sunlight with a quality similar to the inside edge of a 400
m2 canopy opening on the shaded side and vi) 1% of sunlight with a quality
and amount similar to the forest understorey. Within each light treatment
seedlings were grown with additions of phosphorus, potassium, magnesium,
all three combined and a control with no additional nutrients. At the
end of one and half years seedlings were measured for net photosynthesis,
height increment, leaf number and survival.
Seedling survival for all species was low in the forest understorey treatment.
Both survival and seedling height were greatest in shelters simulating
forest openings. Leaf production was highest in full sun and inside edge
light treatments and all species had their greatest net photosynthesis
in the inside edge treatment. For nutrient treatments phosphorus promoted
greatest seedling growth in all species.
Department of Forestry and Environmental Science,
of Sri Jayewardenepura,Sri Lanka. 1999. All rights reserved.