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Popondetta, Papua New Guinea

Wakelin S.A.,Agresearch Ltd. | Gerard E.,Agresearch Ltd. | van Koten C.,Agresearch Ltd. | Banabas M.,Papua New Guinea Oil Palm Research Association | And 2 more authors.
Pedobiologia | Year: 2016

The conversion of grassland to oil palm is expected to increase throughout tropical regions where oil palm grows. Given the extent of land use change, there are concerns associated with impacts on ecosystem function and nutrient cycling. For this work, soil samples were collected in Papua New Guinea from 15 sites with oil palm (planted on grassland) and adjacent remnant grassland. Using DNA-based approaches, bacterial and fungal community composition was assessed in each sample, along with abundance of genes involved in key nitrogen cycling steps: nitrification (bacterial and archaeal amoA genes), nitrite reduction (nirS gene), and nitrous oxide reduction (nosZ gene). Across all microbial properties measured, variation among sites was greater than variation due to land use change. This was driven by among-site variation in soil physicochemical properties, particularly total soil organic carbon content and δ 13C, electrical conductivity, exchangeable calcium, potassium and magnesium content, and extractable phosphorus content. The results suggest that in this environment, routinely measured soil properties such as soil pH, organic carbon, and exchangeable cation contents may serve as indicators for the effects of land use and management on soil microbial community composition and functioning. © 2016 Elsevier GmbH. Source


Goodrick I.,James Cook University | Nelson P.N.,James Cook University | Banabas M.,Papua New Guinea Oil Palm Research Association | Wurster C.M.,James Cook University | Bird M.I.,James Cook University
GCB Bioenergy | Year: 2015

Oil palm (Elaeis guineensis Jacq.) crops are expanding rapidly in the tropics, with implications for the global carbon cycle. Little is currently known about soil organic carbon (SOC) dynamics following conversion to oil palm and virtually nothing for conversion of grassland. We measured changes in SOC stocks following conversion of tropical grassland to oil palm plantations in Papua New Guinea using a chronosequence of plantations planted over a 25-year period. We further used carbon isotopes to quantify the loss of grassland-derived and gain in oil palm-derived SOC over this period. The grassland and oil palm soils had average SOC stocks of 10.7 and 12.0 kg m-2, respectively, across all the study sites, to a depth of 1.5 m. In the 0-0.05 m depth interval, 0.79 kg m-2 of SOC was gained from oil palm inputs over 25 years and approximately the same amount of the original grass-derived SOC was lost. For the whole soil profile (0-1.5 m), 3.4 kg m-2 of SOC was gained from oil palm inputs with no significant losses of grass-derived SOC. The grass-derived SOC stocks were more resistant to decrease than SOC reported in other studies. Black carbon produced in grassfires could partially but not fully account for the persistence of the original SOC stocks. Oil palm-derived SOC accumulated more slowly where soil nitrogen contents where high. Forest soils in the same region had smaller carbon stocks than the grasslands. In the majority of cases, conversion of grassland to oil palm plantations in this region resulted in net sequestration of soil organic carbon. © 2014 John Wiley & Sons Ltd. Source


Dewhurst C.F.,Papua New Guinea Oil Palm Research Association | Pilotti C.A.,Papua New Guinea Oil Palm Research Association
Australian Entomologist | Year: 2012

The native base-borer weevil, Sparganobasis subcruciata Marshall, is recorded for the first time from tissues of cultivated oil palm (Elaeis guineensis Jacq.) in Papua New Guinea. Adults, larvae, pupae and damage are illustrated. Evidence suggests that attack is initiated by odours produced by fungal decay of palm tissues caused by Ganoderma boninense Pat. and secondary decomposers or by Thielaviopsis paradoxa (de Seynes) in oil palm frond axils. Source


Nelson P.N.,James Cook University | Banabas M.,Papua New Guinea Oil Palm Research Association | Nake S.,Papua New Guinea Oil Palm Research Association | Goodrick I.,James Cook University | And 2 more authors.
Soil Research | Year: 2014

Impacts of palm oil industry expansion on biodiversity and greenhouse gas emissions might be mitigated if future plantings replace grassland rather than forest. However, the trajectory of soil fertility following planting of oil palm on grasslands is unknown. We assessed the changes in fertility of sandy volcanic ash soils (0-0.15m depth) in the first 25 years following conversion of grassland to oil palm in smallholder blocks in Papua New Guinea, using a paired-site approach (nine sites). There were significant decreases in soil pH (from pH 6.1 to 5.7) and exchangeable magnesium (Mg) content following conversion to oil palm but no significant change in soil carbon (C) contents. Analyses to 1.5m depth at three sites indicated little change in soil properties below 0.5m. There was considerable variability between sites, despite them being in a similar landscape and having similar profile morphology. Soil Colwell phosphorus (P) and exchangeable potassium (K) contents decreased under oil palm at sites with initially high contents of C, nitrogen, Colwell P and exchangeable cations. We also assessed differences in soil fertility between soil under oil palm (established after clearing forest) and adjacent forest at two sites. At those sites, there was significantly lower soil bulk density, cation exchange capacity and exchangeable calcium, Mg and K under oil palm, but the differences may have been due to less clayey texture at the oil palm sites than the forest sites. Cultivation of oil palm maintained soil structure and fertility in the desirable range, indicating that it is a sustainable endeavour in this environment. © CSIRO 2014. Source

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