SEEDLING GROWTH PERFORMANCE OF FOUR Syzygium species IN THE SIMULATED LIGHT AND SOIL NUTRIENT ENVIRONMENTS OF A RAIN FOREST IN SRI LANKA

Abstract

Seedlings of four species of Syzygium (S. firmum, S. makul, S. operculatum, S.rubicundutn) were investigated for differences in growth and survival after one and halfyears growth in a nursery experiment. All four species co-exist in the moist evergreen rainforest 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. BothS. makul and S. operculatum arc sub canopy trees of late-successional forest alongstreamways of lower slopes and valleys.

Seedlings of each species were grown within replicated light and soil nutrient treatmentsfound in the groundstorey forest environments. The light treatments exposed seedlings toi) full sun; ii) sunlight like that at the center of a 200 m2 forest opening. iii) sunlight likethat at the center of a 400 m2 canopy opening; iv) 50% shade of sunlight with qualitysimilar to the outside edge of a 400 m2 canopy opening on the shaded side; v) 20% ofsunlight with a quality similar to the inside edge of a 400 m2 canopy opening on theshaded side and vi) I% of sunlight with a quality and amount similar to the forestunderstorey. Within each light treatment seedlings were grown with additions ofphosphorus, potassium, magnesium, al\ three combined and a control with no additionalnutrients. 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 survivaland seedling height were greatest in shelters simulating forest openings. Leaf productionwas highest in full sun and inside edge light treatments and all species had their greatestnet photosynthesis in the inside edge treatment. For nutrient treatments phosphoruspromoted greatest seedling growth in all species