Open Access Peer-reviewed

Vegetation Structure and Species Distribution of Mangroves along a Soil Salinity Gradient in a Micro Tidal Estuary on the North-western Coast of Sri Lanka

K. A. R. S Perera1, 2,, M. D. Amarasinghe1, S. Somaratna2

1Department of Botany, University of Kelaniya, Kelaniya, Sri Lanka

2The Open University of Sri Lanka, Nawala, Nugegoda, Sri Lanka

American Journal of Marine Science. 2013, 1(1), 7-15. DOI: 10.12691/marine-1-1-2
Published online: August 25, 2017

Abstract

Soil salinity in both coastal and inland, is known to affect vegetation structure and functions. Mangrove vegetation at Kala Oya estuary on the north western coast of Sri Lanka was selected to study the effect of soil salinity on structure, potential gross primary productivity and plant biomass of the ecosystems. Five belt-transects were laid perpendicular to the shoreline, covering 3.5 km upstream and approximately at 750 m intervals to collect data for the purpose. Vegetation structure was determined using data collected on plant species diversity, density, basal area, leaf area index and tree height. Biomass (total of above and below ground) of mangrove trees was estimated by allometric methods and potential gross primary productivity was calculated using leaf area index measured with terrestrial radiation sensor. Total of eight (8) true mangrove species were encountered in the area and highest density was recorded for Rhizophora mucronata (528 trees/ha), followed by Excoecaria agallocha (447 trees/ha) and Lumnitzera racemosa (405 trees/ha). Vegetation complexity index (CI), basal area, total tree biomass leaf area index and potential gross primary productivity measurements revealed an inverse correlation with soil salinity. Mangrove species were observed to possess varying salinity tolerance levels and Avicennia marina was the most salinity tolerant species, followed by Rhizophora mucronata, Ceriops tagal and Lumnitzera racemosa. Excoecaria agallocha was the least salt tolerant species in the area. Mangrove areas located around 2 km from the estuary mouth, where the soil salinity ranged from 8-12 mg/l, was observed to be with the highest species richness and diversity, indicating its’ ecological and conservation significance that may be considered in mangrove management decision-making for the area. Presence of a few species of terrestrial and freshwater plants among the mangroves indicates salinity changes that would have taken place due to trans-basin diversion of water to the area for irrigation purposes.

Keywords:

mangroves, soil salinity, species distribution, micro-tidal estuary
[1]  Cintron,G. and Novelli,Y.S.,1984. Methods for studying mangrove structure, In: Snedaker,S.C.and Snedaker,J.G.,(eds.) The mangrove ecosystem: research methods. United Nations Educational, Scientific and Cultural Organization, Paris, 91-113.
 
[2]  Chen, R & Twilley, R.R. 1989. A gap dynamic model of mangrove forest development along gradient of soil salinity and nutrient resources, Journal of Ecology, 86: 37-52.View Article
 
[3]  Lugo, A.E. 1980. Mangrove ecosystems: successional or steady state, Tropical succession, Biotropica supplement, 12: 65-72.View Article
 
[4]  Ukpong, I.E. 1991. The performance and distribution of species along soil salinity gradient of mangrove swamps in southeastern Nigeria, Vegetation, 95: 63-70.View Article
 
[5]  Saha, S. & Choudhury, 1995. Vegetation analysis of restored and natural mangrove forests in Sagar island, Sundarabarns, east coast of India, Indian journal of Marine sciences, 24: 133-136.
 
[6]  Kathiresan, K. Rajendran, N. & Thangadurai, G. 1996. Growth of mangrove seedlings in intertidal area of Vellar estuary southeast coastr of India. Indian Journal of Marine Sciences, 25: 240-243.
 
[7]  Suwa R, Deshar R, Hagihara, A 2009. Forest structure of a subtropical mangrove along a river inferred from potential tree height and biomass. Aquatic Botany, 91: 99-104.View Article
 
[8]  Lin, A.E. & Sternberg, L.D.S.L. 1993. Effect of salinity fluctuation on photosynthetic gas exchange and plant growth of the red mangrove (Rhizophora mangle L.). Journal of experimental botany,44 (258): 9-16.View Article
 
[9]  Karunathilake, K.M.B.C. 2003. Status of mangroves in Sri Lanka, Journal of coastal development, 7(1): 5-9.
 
[10]  Kanakaratne, M.D., Perera, W.K.T. & Fernando, B.U.S. 1983. An attempt at determining the mangrove coverage around Puttalam lagoon, Dutch Bay and Portugal Bay in Sri Lanka through remote sensing techniques, 15.1-15.9.
 
[11]  Kathiresan, K. and Khan, S.A. 2010. International Training Course on Costal biodiversity in Mangroves: Course manual, Annamalie University, India. 116-125.
 
[12]  Jayakody,J.M.A.L., Amrasinghe,M.D.,Pahalawattarachchi,V. and De Silva,K.H.W.L. 2008. Vegetation structure and potential gross primary productivity of mangroves at Kadolkallle in Meegamuwa (Negombo) estuary, Sri Lanka, Sri Lanka J.Aquat. Sci. 13(2008): 95-108.
 
[13]  (Holdridge et al 1971).
 
[14]  Andrews, T.J., and Muller, G.J. 1985. Photosynthetic gas exchange of the mangrove, Rhizophora stylosa Griff., in its natural environment. Oecologia 65: 449-455.View Article
 
[15]  Clough,B.F. and .Sim, B.G 1989. Changes in gas exchange characteristics and water use efficiency of mangroves in response to salinity and vapour pressure defects, Oecologia, 79:38-44.View Article
 
[16]  Cheeseman J.M., Clough B.F., Carter D.R., Lovelock CE., Eong O.J. & Sim R.G. 1991 The analysis of photosynthetic performance in leaves under field conditions - a case study using Bruguiera mangroves. Photosynthesis Research 29: 11-22.
 
[17]  English, S.,Wilkinson, C and Basker, V. 1997. Survey manual for tropical marine resources (2nd Ed). Australian Institute of Marine Science, Townsville. pp119-195.
 
[18]  Amarasinghe, M.D. & Balasubramaniam, S. 1992. Structural properties of two types of mangrove stands on the nothernwestern coast of Sri Lanka. Hydrobiologia. 247:17-27.View Article
 
[19]  Komiyama, A., Poungparn, S. & Kata, S. 2005. Common allometric equations for estimating the tree weight of mangroves, Journal of Tropical Ecology 21: 471-477.View Article
 
[20]  Perera, K.A.R.S., Sumanadasa W.A. & Amarasinghe, M.D.2012. Carbon retention capacity of two mangrove species, Bruguiera gymnorriza (L.) Lamk and Lumnitzera racemosa Willd. in Negombo estuary, Sri Lanka. Journal of the Faculty of Graduate Studies, University of Kelaniya, Vol 1: 56-70.
 
[21]  De Silva, M. & De Silva, P.K. 1998. Status, diversity and conservation of the mangrove forests of Sri Lanka, J. South Asian Nat. Hist. Wildlife heritage trust of Sri Lanka. 3:1 79-102.
 
[22]  Joshi, H.& Ghose, M. 2003. Forest structure and species distribution along soil salinity and pH gradient in mangrove swamps of the Sundarabans, Trop. Ecol., 44(2):197-206.
 
[23]  Alongi, D.M., 2008. The energetic of mangrove forests. Springer Science Busness media B.V.
 
[24]  Clough, B.F. 1992. Primary productivity and the growth of mangrove forests. In: A.I. Robertson & D.M. Alongi, (eds.) “Coastal and estuarine studies: Tropical mangrove ecosystems” American geophysical society, USA, 225-250.View Article
 
[25]  Medina, E., Lugo, A.E. & Novelo, A. 1995. Mineral content of foliar tissues of mangrove species in Laguna de Sontecomapan (Veracruz, Mexico) and its relation to salinity, Biotropica, 27 (3): 317-323.View Article
 
[26]  Alongi, D.M., 2009. Present status and future of the world’s mangrove forests, Environmental conservation, 29: 331-349.
 
[27]  Diop, E.S., Soumare, A., Diallo, N. & Guissa, A. 1997. Recent changes of the mangroves of the Saloum river estuary, Senagal. Mangroves and Salt marches, 1: 163-172.
 
[28]  Naidoo, G. 1990. Effects of nitrate, ammonium and salinity on growth of the mangrove Bruguiera gymnorrhiza (L) Lam., Aquatic Botany, 38: 209-219.View Article
 
[29]  Koch, M.S. & Snedaker, S.C. 1997. Factors influencing Rhizophora mangle seedling development in everglades carbonate soils, Aquatic Botany, 59 (1-2): 87-98.View Article
 
[30]  Suratman M.N., 2008, Carbon sequestration potential of mangroves in southeast Asia. In: Bravo F., (ed.), Managing forest ecosystems: The challenge of climate change, Springer Science Business Media, pp.297-315.View Article
 
[31]  Perera, K.A.R.S. and Amarasinghe, M.D. 2013. Carbon partitioning and allometric relationships between diameter and total organic carbon (TOC) in plant components of Bruguiera gymnorrhiza (L.) Lamk. and Lumnitzera racemosa Willd. In microtidal estuary in Sri Lanka, International Journal of Marine Science,3: 72-78.
 
[32]  De Silva, K.H.G.M. & Balasubramaniam, S. 1984. Some ecological aspects of the mangroves on the west coast of Sri Lanka, Ceylon Journal of Science (Bio. Sci) 17 &18: 22-42.