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By: Bagus Dwi Rahmanto

I am a Master's student in the Graduate School for International Development and Cooperation, Hiroshima University. My research interest is related about carbon stored in mangrove forest. My research topic is “Carbon Stock Estimation and Population Distribution in Post-Harvesting Mangrove Concession Area through Seed-Tree Method Application”.

Introduction
Forests sequester and store more carbon than any other terrestrial ecosystem hence are an important natural ‘brake’ on climate change. When forests are cleared or degraded, their stored carbon is released into the atmosphere as carbon dioxide (CO2) (Gibbs et al., 2007). Mangroves are unique tropical and sub tropical plants that grow with their roots partly or wholly submerged in brackish water (Tomlinson, 1986). Mangrove forest is well known as a unique ecosystem and it has also important function in supporting our human life. The various functions of mangrove are physical function (e.g. to prevent intrusion, abrasion and also strong wind), biological function (e.g. as spawning area for fish, shrimp, shell, and nesting habitat for birds and various biota and producer of weathering material that become important source of food for life in the surrounding), chemical function (e.g. as place for organic material decomposition process and other chemical process related with mangrove soil) and economical function (e.g. fuel, wood and fisheries land). Among the most important of these functions is ecosystem carbon storage, but poorly quantified (Murdiyarso et al., 2009). The estimated carbon stock in the mangrove ecosystem is relatively large. It is a high-potential ecosystem as carbon sinks in brackish water.
According to Murdiyarso et al. (2009), Ecosystem C-stocks of sampled mangrove forests ranged from 437 Mg C ha-1 to 2186 Mg C ha-1. This C storage is exceptionally high compared with upland tropical forests-which typically store between 150 and 500 Mg C ha-1 (Murdiyarso et al., 2002) and is perhaps second only to renowned C-stocks of peat swamp forest (Page et al., 2002). According to Donato et al. (2011) that mangrove deforestation generates emissions of 0.02-0.12 Pg carbon per year-as much as around 10% of emissions from deforestation globally, despite accounting for just 0.7% of tropical forest area. Therefore, mangrove ecosystem also important for climate changes mitigation.
Mangrove forest is typical forest in Indonesia which has the capacity to absorb green house gas. In Indonesia, its area reach approximately between 2.5 millions – 4.5 million hectares, exceeding Brazil (1.3 million ha), Nigeria (1.1 million ha) and Australia (0.97 million ha) (Spalding, M.D., Blasco, F. and Field, C.D., eds., 1997).  Indonesia is a country with the largest extent of mangrove forest; it covers about 49% of mangrove area in Asia and in the world (FAO, 2005).
In Indonesia, mangrove forest is managed to several forms, one of which is as a concession forest area. Mangrove forest concession is a concession system that is given to appointed company (concession holder) to exploit and manage the concession area of particular mangrove forests outside of the protected zones. Seed-tree method” is the only obligatory option for the concession holder to be applied in their logging activity in order to guarantee a sustainable regeneration of the mangroves. Technically, this silviculture system simply keeps the selected seed-trees as source of seed production to maintain their natural regeneration. The primary advantage of this method is that seed source for trees with the best phenotypes can be retained (Nyland, 1996 in Forest Encyclopedia Network, 2011).
Applying a silviculture system in forest management influences the population distribution in forest floors. Certainly, it may affect the species composition, population distribution and forest structure and carbon stock.  Few studies have estimated the carbon stock in the logged-over mangrove forest through seed-tree method application. Hence, it still will be interesting to study on carbon stock and population distribution after harvesting activity at various age classes. The purposes of this study are to obtain the dynamic of carbon stock and changing of tree distribution in the logged-over mangrove forest. Through this research we can also identify how much carbon stock lost due to logging activities and trend of carbon stock increment. We can also obtain the development of population distribution and regeneration process on the logged-over mangrove forest.

Research Question

  1. How much carbon stored in logged-over mangrove forest through seed-tree method application?
  2. How much tree carbon stocks loss due to logging activity by seed-tree method application?
  3. How about the soil carbon stock, is the implementation of seed-tree method will affect to soil carbon stock as well?
  4. How is the changing of population distribution after logging activity by implemented the seed-tree method?

Research Objectives

  1. To estimate above and below ground carbon stock in logged-over mangrove forest at various age levels and in the natural mangrove forest through seed-tree method application.
  2. To obtain population distribution both in logged-over mangrove forest and natural mangrove forest.

Expected Outcome

  1. This research result can be used as source information for stakeholder to manage and utilize mangrove area sustainably.
  2. Enrich information about carbon stock estimation on mangrove forest in Indonesia
  3. The result could be used as basic data related carbon trade schemes.

Study Site
This research was conducted in logged-over mangrove forest and natural mangrove forest in PT. Bina Ovivipari Alam Semesta’s concession area, West Kalimantan, Indonesia. The observation is based on their logging history within 5 months, 1, 2, 3, 4, 6 and 7 years after logging sites PT. Bina Ovivipari Semesta (PT. BIOS) is a concession holder of 10,100 ha mangrove forest. The concession area is divided into two blocks, i.e. ‘Bumbun’ block (4,070 ha) and ‘Selat Sech’ block (6,030ha). Geographically, Bumbun block lies between 109º8.3’00” – 109º29.2’00 E and 0º27.9’00” – 0º53.2’00” S, and Selat Sech block lies between 109º36’00” – 109º41.6’00” E and 0º54.7’00”-0º58.6’00” S (PT. BIOS, 2009). 


Figure 1. Mangrove Forest Concession Sites of PT. BIOS, West Kalimantan, Indonesia

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