[1] We measured gas fluxes of carbon dioxide (CO 2 ), methane (CH 4 ), and nitrous oxide (N 2 O) from the soil surface to the atmosphere under various land uses in Sumatra, Indonesia, from September 1997. Four land-use types, i.e., old-growth forest, logged-over forest, burned site after logging, and rubber plantation site, were selected. One loggedover forest was clear-cut and burned in the middle of the experiment. An incubation experiment was also performed to measure the potential of these three gases' emissions by using intact soil cores

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To determine the means and variations in CH4 uptake and N2O emission in the dominant soil and vegetation types to enable estimation of annual gases fluxes in the forest land of Japan, we measured monthly fluxes of both gases using a closed‐chamber technique at 26 sites throughout Japan over 2 years. No clear seasonal changes in CH4 uptake rates were observed at most sites. N2O emission was mostly low throughout the year, but was higher in summer at most sites. The annual mean rates of CH4 uptake and N2O emission (all sites combined) were 66 (2.9–175) µg CH4‐C m−2 h−1 and 1.88 (0.17–12.5) µg N2O‐N m−2 h−1, respectively. Annual changes in these fluxes over the 2 years were small. Significant differences in CH4 uptake were found among soil types (P < 0.05). The mean CH4 uptake rates (µg CH4‐C m−2 h−1) were as follows: Black soil (95 ± 39, mean ± standard deviation [SD]) > Brown forest soil (60 ± 27) ≥ other soils (20 ± 24). N2O emission rates differed significantly among vegetation types (P < 0.05). The mean N2O emission rates (µg N2O‐N m−2 h−1) were as follows: Japanese cedar (4.0 ± 2.3) ≥ Japanese cypress (2.6 ± 3.4) > hardwoods (0.8 ± 2.2) = other conifers (0.7 ± 1.4). The CH4 uptake rates in Japanese temperate forests were relatively higher than those in Europe and the USA (11–43 µg CH4‐C m−2 h−1), and the N2O emission rates in Japan were lower than those reported for temperate forests (0.23–252 µg N2O‐N m−2 h−1). Using land area data of vegetation cover and soil distribution, the amount of annual CH4 uptake and N2O emission in the Japanese forest land was estimated to be 124 Gg CH4‐C year−1 with 39% uncertainty and 3.3 Gg N2O‐N year−1 with 76% uncertainty, respectively.

We measured fluxes of three greenhouse gases (N 2 O, CO 2 and CH 4 ) from soils of six different land-use types at 27 temporary field sites in Jambi Province, Sumatra, Indonesia. Study sites included natural and logged-over forests; rubber plantation; oil palm plantation; cinnamon plantation; and grassland field. The ranges of N 2 O, CO 2 and CH 4 fluxes were 0.13-55.8 µg N m −2 h −1 ; 1.38-5.16 g C m −2 d −1 ; −1.27-1.18 mg C m −2 d −1 , respectively. The averages of N 2 O, CO 2 and CH 4 fluxes at 27 sites were 9.4 µg N mrespectively. The values of CO 2 and CH 4 fluxes were comparable with those in the reports regarding other humid tropical forests, while the N 2 O flux was relatively lower than those of previous reports. The N 2 O fluxes in each soil type were correlated with the nitrification rates of soils of 0-5 cm depth. In Andisols, the ratio of the N 2 O emission rate to the nitrification rate was possibly smaller than that of the other soil types. There was no clear relationship between N 2 O flux and the soil water condition, such as water-filled pore space. Seventeen percent of CH 4 fluxes were positive; according to these positive fluxes, we did not find a good correlation between CH 4 uptake rate and soil properties. Although we performed a chronosequence analysis to produce some hypotheses about the effect of land-use change by a limited amount of sampling at one point in time, further tests are required for the future.

An incubation experiment was conducted to examine the effects of the phosphorus (P) application on nitrous oxide (N2O) and nitric oxide (NO) emissions from soils of an Acacia mangium plantation in Indonesia. The soils were incubated with and without the addition of P (Ca[H2PO4]2; 2 mg P g soil−1) after adjusting the water‐filled pore space (WFPS) to 75% or 100%. The P addition increased N2O emissions under both WFPS conditions and NO emissions at 75% WFPS. Some possible mechanisms are considered. First, the P addition stimulated nitrogen (N) cycling, and N used for nitrification and/or denitrification also increased. Second, the P addition could have relieved the P shortage for nitrifying and/or denitrifying bacteria, producing N2O and NO. Our results suggest that the application of P fertilizer has the potential to stimulate N2O and NO emissions from Acacia mangium plantations, at least when soils are under relatively wet conditions.

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