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The study was done to determine and analyze the stand structure of replanted mangroves and aboveground biomass of 7 year's old replanted mangrove. The physical characteristic and standing crop biomass of a mangrove forest, sited at the Pulau Layang-Layang at Kelantan Delta, Tumpat were studied. There were two types of replanted mangrove species; Rhizophora mucronata and Rhizophora apiculata. The R. mucronata trees dominated this forest. Five physical characteristics were studied: diameter (cm), length (m) (for root and branch only), height (m), distance (m) (for root only), and DBH (cm) (for stem only). The estimate of increment for 7 year's old root was 43 roots. The increment of length was 1.06 m, the distance was 0.85 m and height of root formation was 0.66 m. Meanwhile the increment of diameter was dt 1.83 cm, dm 1.98 cm and dl 2.62 cm. Subsequently, the height of tree and DBH estimate increment was 5.22 m and 4.44 m followed by the diameter of stem formation dt 0.63 cm, dm 3.35 cm and d10 5.55 cm. The estimate increment of primary branches was 35 branches. The height and length increment were 2.15 m and 1.47 m respectively. Furthermore for the diameter of formation primary branch was dt 1.38 cm, dm 1.60 cm and dl 1.81 cm. For the aboveground biomass, the estimate increment was 10.62 kg for root, 5.60 kg for stem, 8.38 kg for primary branch, 6.67 kg for secondary branch, 6.77 kg for leaves and 0.06 kg for fruits. In sapling, the root constitutes the largest component of the aboveground biomass.
Keywords: Mangrove, aboveground biomass, Kelantan Delta
Mangrove is derived from the word "mangal" and "mangue" in the Portuguese word. In Malay, mangroves are commonly referred as "Bakau" or "Hutan Paya Laut". The word "Bakau" is referring to two species of vegetation only: Rhizophora apiculata (Bakau Minyak) and Rhizophora mucronata (Bakau Kurap) (Mohd Lokman and Sulong, 2001). Mangrove is a type of forest growing along tidal mudflats and along shallow water areas extending inland along rivers, streams and their tributaries where the water is generally brackish. The mangrove ecosystem is dominated by mangrove trees as the primary producer interacting with associated aquatic fauna, social and physical factors of the coastal environment (Melana et al., 2000). Mangroves protect the coast from erosion, surge storms, especially during hurricanes, and tsunamis. Their massive root system is efficient at dissipating wave energy. Likewise, they slow down tidal water enough that its sediment is deposited as the tide comes in and are not re-suspended when the tide leaves, except for fine particles (Mastaller, 1997).
Mangrove usually considered being wastelands, unhealthy and human alike. Despite its smelly reputation, a mangrove forest is a very dynamic and highly productive ecosystem. To quantify this productive term 'net primary productivity' is employed. According to Field, 1996 productivity is the net annual primary productivity is the amount of plant biomass that and it generated per unit area per year. Term productivity that it is used is 'biomass' accumulation. Biomass can be defined as the sum total of all of the components of a tree, below ground as well as above ground and is therefore usually measured by estimation (Hogarth, P.J, 1999). Meanwhile, aboveground biomass is the amount of standing organic matter per unit area at a given time. The amount of standing biomass stored in a forest is a function of the system's productivity, age and organic matter allocation and exploitation strategies. (Cintron and Schaeffer, 1984).
Aboveground biomass (AGB) includes the trunk, branches, stems and leaves. In mature trees of all species the trunk constitutes the largest component of the AGB (Ross et. al 1999). Rhizophora species had generally higher AGB than all other species (Saenger and Snedaker, 1993 in Ross et. al., 1999) but this may result from their dominance of forests at low latitudes. Total aboveground production is usually estimated by a combination of allometry and litter collection. (Ross et. al, 1999). Allometric relationships are described for estimating leaf biomass, branch biomass, stem biomass and total above-ground biomass from measurements of stem diameter (DBH) in the mangrove species. (Clough and Scott, 1989).
The main objectives of this study are (i) to determine the physical characteristic 7 years old of replanted mangroves and (ii) to determine the aboveground biomass for 7 years old of replanted mangroves. This study can give more information to better understand the dynamics of organic matter cycling in the mangroves; it is important to know the amount of biomass that is present in the vegetation covering at a given time. The results from this study are expected to be helpful to improve knowledge about the physical characteristics and biomass of mangrove especially for replanted mangrove where it then can be used as a guideline for mangrove replanting in the future.
2. STUDY AREA
Kelantan Delta, Tumpat is a large delta that has been developed by the river, with sand spits and sand bars common at close to the outlets of larger distribution channels. Besides the sand spit, mangrove swamps and tidal flat are present within the larger river mouth. The uniqueness of this study area is that, the Kelantan Delta was only delta that located in Kelantan and it has a very dynamic ecosystem. Kelantan Delta covers approximately 1300 ha and comprises 17 islands namely P. Emas, Pulau Layang-Layang, P. Che Minah, P. Ekor Che Tahir, P. Che Soh, P. Terendak, P. Che Lah, P. Timun, P. Tongkang, P. Suri, P. Haji Nik Mat, P. Seratus, P. Beluru, P. Renjuna, P. Che Tahir, P. Rulah and Tg. Kuala or Tg. Duff (Kasawani, 2003 as cited by Faezah Nor, Z. 2006). Kelantan state's climate regime is influenced by the northeast and southeast monsoons that blow from late November to March and from June to September respectively. The estimated total amount of rainfall was 2647 mm per annum with heavy rainfall during the Northeast monsoon (November to March). The temperature ranged from 22.7ËšC to 32.9ËšC with an estimated mean of 26.8ËšC. The humidity of the region was estimated to be about 83.7% (Malaysian Meteorological Service, 1999).
Figure 1: Location of sampling site in Kelantan Delta, Tumpat.
The study was conducted in P. Emas, Tumpat. This island consists of 7 years' old replanted mangroves. The trees were selected base on the health of the tree. In this study 4 trees were selected in this area randomly. The type of tree that were going be studied were R. mucronata. This study was divided into two parts which were physical characteristic and aboveground biomass.
3.1 Physical Characteristics
For physical characteristics, three parameters were measured which are roots structure, stem structure and primary branch structure. For root structure, number of roots, height, diameter, distance and length were measured where each root were labeled with plaster that shows the number identification. This way is important for researcher to detect each root either had measured or not measured, also avoid the mistake and confuse in getting the data. For stem structure, diameter of stem, total height and diameter at breast-height (DBH) were measured. The diameter of the stem at breast height (DBH) is a measurement at a height of approximately 1.3 m, or above the highest prop-root. Meanwhile, diameter, length and height were measured for the primary branch structure.
3.2 Aboveground biomass
There are two main approaches to biomass determination, clear-cut and allometric techniques. Clear-cutting is only recommended in young or shrub stand. Allometric measurement is preferred for tall forests. (Cintron and Schaeffer, 1984). The clear-cut technique is easy but it is recommended only for sapling growth. The trees were cut off at ground level, separated into components and weighed separately. The most often-used components are wood (stem and branches), prop roots, leaves, flowers and fruits. The harvest materials were weighed in the field and samples were taken of each compartment for dried and calculation of the dry/green weight ratios. This material should be dried to constant weight in an oven at 70° C. (Cintron and Schaeffer, 1984).The total harvested dry-weight of each component was calculated from the ratio of dry-weight to fresh weight of the corresponding sub samples.
3.3 Statistical Analysis
In this study, correlation and linear regression were used to determine the relationship the physical parameter of mangrove structures. Correlation and linear regression also used to determine the relationship between d10 and other component of biomass.
4. RESULTS AND DISCUSSION
4.1 Root Structure
From this study the mean value of root length was 1.06m. R. mucronata grows well in soft mud too and is believed to be among the few that can survive complete daily inundation. They function to provide aerial ventilation but more importantly provide added support to the lower part of the trunk (Mastaller, 1997). They also are having a highly efficient sediment trapping mechanism and considered as an important sink of suspended sediment, thus important for maintaining coastal stability and finally will prevent the erosion. (Katherisan and Bingham, 2001). From the result, the distances between the roots and wide distribution play important role for sediment trapping mechanisms. The high radius of root will trap more sediment than the lower radius. Besides, their massive root system is also efficient at dissipating wave energy. Numerical model of wave attenuation showed that substantial attenuation of wave energy occurred within the mangrove forest with attenuation strongly dependent on the diameter of mangrove roots and on the spectral characteristics of the incident waves (Katherisan and Bingham, 2001). From the result, the diameter of root has the moderate correlation between dl and dt (r = 0.626). It proves that the wave energy will reduce by the correlation of the diameter.
4.2 Stem structure
Figure 2: (a) Lower correlation of stem between heights and dt, (b) Higher correlation of stem between heights and d10.
Stems have four main functions which are supports for and the elevation of leaves flowers and fruits. The stems keep the leaves in the light and provide a place for the plant to keep its flowers and fruits. The Rhizophora sp. falls to single stem trees. The stem height always depend with the diameter, expecially d10. It is because the increasement of the height depend on the diameter of the stem. Figure 2 proved that height and d10 has the proportionate relationship y = 0.612x + 1.823. The y value in the equation shows the height and the x value show the d10. Meanwhile the height and dt also has the proportionate relationship y = 0.1763x + 5.1098. The y value in the equation shows the height and the x value show the dt.
4.3 Primary branch structure
The functions of the branch are almost same with the stem, such as provide support and transport the fluid. Not only that, it also act as to reduce resistance to wind (Raven, 1981). From this study, the total number of the entire primary branch for four trees was 131 and ranging 28 to 38 per trees. Not only the stem, primary branch also have high and very high correlation between diameter and height. The correlation between dl and length (r = 0.89) show the high correlation; marked relationship. For the correlation between dt and length (r = 0.91) and dt and dl (r = 0.94), both of them show very high correlation; very dependable relationship. All the correlation show proportionate relationship, which means that if the length increase, the diameter also increases inversely. For the mangrove area, they are often exposed to storms and strong winds because the shoreline is open. The high velocity winds from the storm also destroy much of the canopy cover of the mangrove. Then, branch play important role to reduce resistance to wind. The diameter and length will increase the strength of branch to strong wind and also help to increasing the peat accumulation capacity of the forest.
4.4 Aboveground Biomass
Aboveground Biomass Component (kg)
10.26 ± 0.01
5.6 ± 0.03
8.38 ± 0.03
6.67 ± 0.04
6.77 ± 0.02
Table 1: The estimate increment and standard error of Aboveground Biomass
Aboveground biomass is the amount of standing organic matter per unit area at a given time. The amount of standing biomass stored in a forest is a function of the system's productivity, age and organic matter allocation and exploitation strategies. (Cintron and Schaeffer, 1984). For the aboveground biomass, the estimate increment was 10.62 kg for root, 5.60 kg for stem, 8.38 kg for primary branch, 6.67 kg for secondary branch, 6.77 kg for leaves and 0.06 kg for fruits respectively (Table 1). In sapling the root constitutes the largest component of the aboveground biomass. Compare to mature tree of all species the trunk constitutes the largest component of the AGB (Ross et. al 1999). The correlation showed that the biomass exceeded 0.90 and showed very high correlation (r = 0.94) d10 and biomass of root (r = 0.97), d10 and biomass of secondary branch (r = 0.98), d10 and biomass of leaves (r = 0.94) and d10 and total biomass (r = 0.99). For the meantime only d10 and primary branch show high correlation (r = 0. 74). All the physical parameter of the root in this study such as diameter, height, distance and long has the correlation between each other. The whole component plays the vital role and it will contribute to the biomass of the tree.
5. CONCLUSION AND RECOMMENDATION
The increment of length, distance, height, diameter for dt, dm, and dl, of root structure were 1.06 m, 0.85 m, 0.66 m, 1.83 cm, 1.98 cm and 2.62 cm respectively. For stem structure, the increment for height, DBH and diameter of stem formation for dt, dm and d10 were 5.22 m, 4.44 m, 0.63 cm, 3.35 cm and 5.55 cm respectively. Meanwhile, the estimate increments of number of branches, height, length and diameter formation of dt, dm and dl for primary branches structure were 35 branches, 2.15 m, 1.47 m, 1.38 cm, 1.60 cm and 1.81 cm respectively. For the aboveground biomass, the estimate increment was 10.62 kg for root, 5.60 kg for stem, 8.38 kg for primary branch, 6.67 kg for secondary branch, 6.77 kg for leaves and 0.06 kg for fruits. In sapling the root constitutes the largest component of the aboveground biomass. In conclusion, the study on physical characteristics and aboveground biomass for replanted mangrove is useful as a guideline to manage mangrove area where it can predict the increment of growth and biomass of the mangrove tree every year. Further studies should be conducted in order to fully utilize the potentials of this natural resource.