Vegetation structure and potential gross primary productivity of mangroves at Kadolkele in Meegamuwa (Negombo) estuary, Sri Lank
J.M.A.L. JAYAKODY, M.D. AMARASINGHE*, V. PAHALAWATTAARACHCHI AND K.H.W.L. DE SILVA
The potential gross primary productivity of the mangrove stands at Kadolkele in Meegamuwa (Negombo) estuary was studied in relation to vegetation structure with a view to understanding the salient structural components that affect functioning of mangrove ecosystems. Structure of mangrove stands under study was characterized with plant species richness, plant (stem) density, frequency of occurrence of constituent species, plant basal area and height. The structural complexity index values calculated from above parameters revealed a statistically significant (p < 0.01) positive relationship with the potential gross primary productivity of the mangrove stands that has been calculated using data on absorption of photosynthetically active radiation (PAR) by the stands that were measured using a light meter with a quantum sensor. Leaf area index (LAI) values were calculated using absorption data and potential gross primary productivity was estimated using an assimilation coefficient. Mean values of structural parameters were used to ordinate the mangrove sites through principal component analysis. Ordination showed a productivity gradient among the mangrove sites where species richness, stem density, plant height and leaf area index were the key factors that affect potential gross primary productivity of mangrove stands.