Mangrove forest structure and condition in Northern Sumatra, Indonesia in relation to tsunami and human disturbance
1Onrizal, 2Mashhor Mansor
1Department of Forestry Sciences, Universitas Sumatera Utara
2School of Biological Sciences, Universiti Sains Malaysia
Natural and human disturbance of mangrove forests have caused many areas to vanish worldwide or degraded forests with secondary vegetation. The structure, composition, condition and regeneration status of mangrove forests with affected by the 2004 Indian Ocean tsunami and human activities in Northern Sumatra were studied during April to August 2009. Three mangrove forests were selected, i.e. Singkil’s mangrove as affected areas by tsunami, Besitang-Brandan’s mangrove as affected area by extensive cutting and Secanggang’s mangrove as conservation forests. A total of 33, 30m x 30m quadrats were set in the outer, middle and lower parts of the mangrove forests at all sampling sites. Measurements included stem diameter at breast height (DBH) and height of tree stage and sapling stage. Seedling stage trees (with stem diameter of less than 2 cm) were classified as juvenile. To assess forest condition, trees within the quadrat were classified into intact, standing dead trees (die back) and stump. The result shown that the highest number of species was found at mangrove forest as conservation area (17 species) and followed by mangrove forest at affected area by tsunami and cutting, both of them has 10 species. The highest of stem density was found at conservation forest having 1,070 stem per ha. On the other hand, the stand density of mangrove forest at affected area by tsunami and cutting area were very low (only 21% and 43%, respectively). The exploitation level of mangrove forests at cutting area was up to 37% of standing trees or 271 stumps per ha. The lowest natural regeneration was recorded at affected area by tsunami as effect of lost of mother trees. This result indicates the tsunami caused higher level of density loss rather than harvesting activities. The baseline data from this study confirm that conservation area supports a diverse mangrove forest community and can provide a valuable comparison with other more degraded mangrove forests in Northern Sumatra. Therefore, the need to improve mangrove management and replanting both affected area by tsunami and extensive cutting.
Keywords: mangrove, tsunami, disturbance, conservation, Northern Sumatra
The paper will be presented at the 22nd Pacific Science Congress, 14-17 June 2011, Kuala Lumpur Convention Center, Kuala Lumpur, Malaysia