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Tropical peatlands are a known source of methane (CH4) to the atmosphere, but their contribution to atmospheric CH4 is poorly constrained. Since the 1980s, extensive areas of the peatlands in Southeast Asia have experienced land‐cover change to smallholder agriculture and forest plantations. This land‐cover change generally involves lowering of groundwater level (GWL), as well as modification of vegetation type, both of which potentially influence CH4 emissions. We measured CH4 exchanges at the landscape scale using eddy covariance towers over two land‐cover types in tropical peatland in Sumatra, Indonesia: (a) a natural forest and (b) an Acacia crassicarpa plantation. Annual CH4 exchanges over the natural forest (9.1 ± 0.9 g CH4 m−2 year−1) were around twice as high as those of the Acacia plantation (4.7 ± 1.5 g CH4 m−2 year−1). Results highlight that tropical peatlands are significant CH4 sources, and probably have a greater impact on global atmospheric CH4 concentrations than previously thought. Observations showed a clear diurnal variation in CH4 exchange over the natural forest where the GWL was higher than 40 cm below the ground surface. The diurnal variation in CH4 exchanges was strongly correlated with associated changes in the canopy conductance to water vapor, photosynthetic photon flux density, vapor pressure deficit, and air temperature. The absence of a comparable diurnal pattern in CH4 exchange over the Acacia plantation may be the result of the GWL being consistently below the root zone. Our results, which are among the first eddy covariance CH4 exchange data reported for any tropical peatland, should help to reduce the uncertainty in the estimation of CH4 emissions from a globally important ecosystem, provide a more complete estimate of the impact of land‐cover change on tropical peat, and develop science‐based peatland management practices that help to minimize greenhouse gas emissions.

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Above ground tree biomass was estimated in Bruguiera parviflora, B. sexangula, and Rhizophora apiculata communities of a mangrove forest in Talidendang Besar, East Sumatra, Indonesia. The research was carried out from December 1990 to January 1991, and allometric relation method was used to estimate the above ground biomass of tree species having a diameter of 10 cm and over. The above ground biomass in this forest ranged from 42.94 to 89.68 t d.wt/ha in a B. parviflora community; 75.99 to 279.03 t d.wt/ha in a B. sexangula community; and 40.70 t d.wt/ha in aR. apiculata community.Key words: above !,'Tound biomass / allometric relation method / Bruguiera parviflora / Bruguiera sexangula / EastSumatra /Indonesia / mangrove forest / Rhizophora apiculata / Talidendang Besar. Cintron and Novelli (1984) stated that above ground biomass is the amount of standing organic matter per unit area at a given time, which is related to a function of productivity system, stand age and organic allocation, and exportation strategies. The estimation of above ground biomass not only provides increasingly valuable means for making comparisons among ecosystems as well as for evaluating world wide productivity patterns (Rodin and Bazilevich, 1967), but is also very important for the study of the functional aspects of forests such as primary productivity, nutrient cycling and energy flow (Hasse et al., 1985). Consequently, biomass data is important in order to understand forest ecosystem characteristics to establish the proper management system based upon the sustainable yield principle.Variability in biomass data may be attributable to stand age, stand history, or structural differences (Lugo and Snedaker, 1974), and climatic factors such as temperature and precipitation (Komiyama et al., 1988). The world literature on forest biomass and production expanded rapidly in the 1960s and 1970s. Cannell (1982 reviewed the world forest biomass data from 600 papers which were written by scientists all over the world. However, the papers on the biomass of mangrove forests were scarce. Some researchers who worked on standing biomass of mangrove forests were Golley et al.

Sebatik Island, Nunukan Regency is one of the border area of Indonesia and Malaysia. Cocoa is the major commodity in this area. The objective of this study is to analyze the index and sustainability status of cocoa in the border area of Sebatik Island. The analysis uses Multi Dimensional Scaling (MDS) method, called RAP-SEBATIK (Rapid Appraisal for Cocoa on Sebatik Island). RAP-SEBATIK was employed to visualize the status of cocoa in Sebatik Island for five evaluation dimensions. This study uses primary and secondary data. The attributes that affect sensitively on the index and sustainability status was approached using the Leverage and Monte Carlo Analysis. The analysis on the five dimensions (ecology, economy, social-cultural, infrastructure and technology, law and institutional) indicate that ecological dimension is less sustainable (46.23%), economical dimension is less sustainable (48.58%), socio-culture dimension is sustainable (75.20%), infrastructure and technology dimension is less sustainable (36.39%) and dimension of law and institutional is less sustainable (40.49%). Out of 53 attributes, there were 17 attributes need to be taken care immediately because of the sensitive affect on the increase of index and sustainability status.