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Tang S.Y.,Hokkaido University | Hara S.,Hokkaido University | Melling L.,Tropical Peat Research Laboratory Unit | Goh K.J.,Applied Agricultural Resources Sdn Bhd 212 | Hashidoko Y.,Hokkaido University
Bioscience, Biotechnology and Biochemistry | Year: 2010

Root-associating bacteria of the nipa palm (Nypa fruticans), preferring brackish-water affected mud in Sarawak, Malaysia, were investigated. In a comparison of rhizobacterial microbiota between the nipa and the sago (Metroxylon sagu) palm, it was found that the nipa palm possessed a group of Burkholderia vietnamiensis as its main active nitrogen-fixing endophytic bacterium. Acetylene reduction by the various isolates of B. vietnamiensis was constant (44 to 68nmolh~1 in ethylene production rate) in soft gel medium containing 0.2% sucrose as sole carbon source, and the bacterium also showed motility and biofilm-forming capacity. This is the first report of endophytic nitrogen-fixing bacteria from nipa palm.

Watanabe A.,Nagoya University | Moroi K.,Nagoya University | Sato H.,Nagoya University | Tsutsuki K.,Obihiro University of Agriculture and Veterinary Medicine | And 3 more authors.
Chemosphere | Year: 2012

Wetlands are an important source of DOM. However, the quantity and quality of wetlands' DOM from various climatic regions have not been studied comprehensively. The relationship between the concentrations of DOM (DOC), humic substances (HS) and non-humic substances (NHS) in wetland associated sloughs, streams and rivers, in cool temperate (Hokkaido, Japan), sub-tropical (Florida, USA), and tropical (Sarawak, Malaysia) regions was investigated. The DOC ranged from 1.0 to 15.6mgCL-1 in Hokkaido, 6.0-24.4mgCL-1 in Florida, and 18.9-75.3mgCL-1 in Sarawak, respectively. The relationship between DOC and HS concentrations for the whole sample set was regressed to a primary function with y-intercept of zero (P<0.005) and a slope value of 0.841. A similar correlation was observed between DOC and NHS concentrations, with a smaller slope value of 0.159. However, the correlation coefficient of the latter was much larger when the data was regressed to a logarithmic curve. These observations suggest the presence of a general tendency that the increased DOC in the river waters was mainly due to the increased supply of HS from wetland soils, whereas the rate of the increase in the NHS supply has an upper limit which may be controlled by primary productivity. © 2012 Elsevier Ltd.

Kimura S.D.,Tokyo University of Agriculture and Technology | Melling L.,Tropical Peat Research Laboratory Unit | Goh K.J.,Advanced Agriecological Research Sdn Bhd
Geoderma | Year: 2012

The influence of oil palm development on tropical peat soil decomposition rate was investigated by an incubation experiment. Soil samples from soil surface and around underground water table were taken from forest site, and oil palm site at 1st and 9th year after development. The soil samples were sieved into 0-2mm, 2-8mm and 8-20mm and analyzed for carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) fluxes.The development of oil palm did not change the CO2 emissions and showed inconsistent influence on CH4 flux according to aggregate size, while significantly higher N2O emissions were found for aggregates 0-2mm at high moisture of oil palm plantation soils compared with the original forest. Nitrous oxide fluxes showed significant positive correlation with the CO2 flux, which indicated that soil organic matter decomposition was closely related to the N2O production. On the other hand, CH4 flux showed clear emission for aggregates bigger than 2mm, while aggregates size 0-2mm showed consistent CH4 uptake. These results showed that investigation of greenhouse gas emissions in tropical peat soil must take into account the aggregate characteristics of the soil, which are inhomogeneous and mixed with fresh organic matter. © 2012 Elsevier B.V.

Melling L.,Tropical Peat Research Laboratory Unit | Yun Tan C.S.,University Technology of MARA | Goh K.J.,Advanced Agriecological Research Sdn Bhd | Hatano R.,Hokkaido University
Journal of Oil Palm Research | Year: 2013

The partitioning of soil respiration (SR) to root respiration (RR) and microbial respiration (MR) was conducted using the root exclusion and closed chamber method in three ecosystems on tropical peatlands. RR was estimated by differencing SR and MR. The forest ecosystem displayed significantly higher monthly MR compared with oil palm and sago ecosystems with the highest value of 219 mg CO2 C m-2 hr-1 in May 2003. This might be attributed to its thick leaf litter and root mat, and water filled pore space which was conducive for microbial activity. The lowest range of MR, between 153 mg CO2 C m-2 hr-1 (October) and 34 mg CO 2 C m-2 hr-1 (September), was found in the sago ecosystem probably due to its high water-table. The highest RR was recorded in the forest (172 mg CO2 C m-2 hr-1), followed by oil palm (128 mg CO2 C m-2 hr-1) and sago (95 mg CO2 C m-2 hr-1). The latter might be ascribed to its slow growth rate, while the former to higher root biomass and growth rate. The annual ratio of RR to SR was 52% in the sago ecosystem and 60% to 62% in both oil palm and forest ecosystems.

Melling L.,Tropical Peat Research Laboratory Unit | Henson I.E.,7 Richmond Dale
Journal of Oil Palm Research | Year: 2011

This article presents data on greenhouse gas (GHG) exchange of tropical peat soils with emphasis on changes in emissions of gases during and following the conversion of native tropical peatlands to plantations of oil palm and other crops. The relevant GHGs are carbon dioxide (CO2), methane (CH 4) and nitrous oxide (N2O). Establishment of plantations on peat requires drainage, which, even if controlled, results in peat aeration and subsidence. Subsidence is mainly due to natural consolidation, often augmented by mechanical compaction, and is manifested as increased bulk density. Aeration causes carbon to be released as CO2. Methods for distinguishing and quantifying these processes are discussed. Exchanges of CH4 and N2O are also changed by plantation development and are influenced by management practices but the quantities involved are small and in some cases peat soils even act as a sink and not a source, of these gases. There are seasonal changes in the GHG fluxes related to both water table depth and rainfall, and emissions of CH4 and N2O can be promoted by nitrogen application. GHG exchange of reclaimed peat is dominated by CO2 despite the higher global warming potential of CH4 and N2O. Methods for estimating CO2 fluxes are reviewed and their shortcomings are examined. The importance of adequately distinguishing between emission sources, e.g. root and microbial respiration when evaluating carbon fluxes at the surface of peat soils is emphasised.

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