Browsing by Author "Saparamadu, M.D.J.S."

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    Development of allometric equations to determine above and below ground biomass and organic carbon content in Bruguiera gymnorrhiza and Lumnitzera racemosa
    (University of Kelaniya, 2011) Perera, K.A.R.S.; Saparamadu, M.D.J.S.; Amarasinghe, M.D.
    Bruguiera gymnorrhiza and Lumnitzera racemosa are two species of true mangroves commonly found in Sri Lankan mangrove areas. Determination of amount of carbon assimilated by these two species therefore, is of considerable importance to estimate the carbon fixing capacity of Sri Lankan mangrove areas. Objective of the present study therefore, is to develop allometric relationships between biomass of stems, leaves, below and above ground roots with easily measured variables such as girth/ diameter at breast height (gbh/dbh) that can be used in estimating the carbon assimilation capacity of Sri Lankan mangrove ecosystems. The below ground biomass of trees of the two mangrove species accounted for 20 – 44 % of the total biomass of the plants. The ratio (A/B) between above (A) to below (B) ground biomass of Lumnitzera racemosa ranged 1.4 – 3.9 and that for Bruguiera gymnorhiza was 1.2 – 4.4, indicating relatively greater amount of biomass in the below ground root systems.Data on dry weight of plant components were analyzed with SPSS ver.16 and a strong positive correlation (p<0.01) and non-leaner relationship (r2 >0.80) were revealed for stems, roots, above ground and total biomass of plants with dbh of individuals of the two species. Four allometric equations were derived between biomass of different components with dbh of Bruguiera gymnorrhiza ; biomass of stem= 0.115 (dbh)2.386, biomass of root = 0.100 (dbh)2.364, above ground biomass =0.289 (dbh)2.327 and total biomass (above +below)= 0.405 (dbh)2.320 . Four other allometric equations were derived between biomass of different components with dbh of Lumnitzera racemosa; biomass of trunk= 0.098 (dbh)2.244, biomass of root = 0.118 (dbh)2.063, above ground biomass =0.114 (dbh)2.523 and total biomass (above +below)= 0.220 (dbh)2.376 . Using the organic carbon content embodied in biomass of the components of the plants of the two species, equations were altered to represent the relationship between organic carbon present and the dbh. Organic carbon content in Bruguiera gymnorhiza stem=0.0631 (dbh)2.386 and root = 0.0529 (dbh)2.364 and organic carbon content Lumnitzera racemosa trunk = 0.0546 (dbh)2.244 and root= 0.0624 (dbh)2.063 . These allometric relationships are required to estimate the amount of carbon accumulated in the plants of these mangrove species and thus the carbon assimilation capacity of the mangrove stands that comprise these mangrove species.
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    Net photosynthetic production and potential carbon assimilation capacity of mangroves of Kadolkele in Negombo estuary, Sri Lanka
    (University of Kelaniya, 2011) Perera, K.A.R.S.; Saparamadu, M.D.J.S.; Amarasinghe, M.D.
    Mangroves are considered as highly productive ecosystems that have considerable potential to serve as efficient sinks of carbon, both on short and long time scales. Magnitude of mangrove primary productivity is highly variable in space and time and it depends on factors such as tidal flushing, latitude, temperature, salinity and nutrient regimes as well as substrate characteristics. Net primary production is represented by above and below ground biomass, litter production and the rate of grazing by herbivores. Since results of very few studies on primary productivity of Sri Lankan mangroves are available, the present study was conducted with the objective of understanding the net primary productivity and magnitude of net carbon assimilation capacity of mangrove ecosystem at Kadolkele. The study was conducted at Kadolkele (7011‟42.18”- 7011‟50.48” N; 790 50‟32.08”– 790 50‟47.50” E), a relatively undisturbed natural mangrove stand extending over 13.5ha, at the northern end of Negombo estuary. Data on biomass increment and litterfall during study period were gathered from twenty 10 m x10 m permanent study plots of three belt transect of 10 m wide laid perpendicular to the shoreline. Annual increment of above and below ground biomass was calculated by girth (gbh) increment, using allometric relationships developed between gbh and biomass of mangrove trees. Biomass loss through herbivory was assumed to be negligible due to high tannin content in mangrove plant parts and thus their low palatability. Organic carbon content of each component of mangrove trees was determined by Walkey and Black wet oxidation without external heating procedure followed by colorimetric method to determine absorbance at 600 nm, using a UV- visible spectrophotometer. Annual organic carbon accumulation was calculated from NPP and organic carbon content. Relatively high values of NPP were recorded from the water-front areas of the mangrove stand and it decreased towards inland. Annual total organic carbon increment was recorded to be 1232.17 + 9.23 g m-2y-1 of which 682.80 + 7.51 g m-2y-1 was found deposited in the above ground woody parts while 396.46 + 4.65 g m-2y-1 was in the plant litter and 152.91 + 1.94 g m-2y-1 in the roots. Potential capacity of Kadolkele mangroves in assimilating and accumulating carbon is 166.66 t y-1 and this amount is equivalent to the amount of carbon emitted as CO2 by combustion of 272,694 (nearly quarter of a million) liters of diesel in motor vehicles. Assuming a motor car consumes 1200 liters of diesel per year, this mangrove stand at Kadolkele with an extent of 13.5 ha can remove atmospheric carbon produced by 227 cars during one year.