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The increasing global demand for vegetable oils has resulted in a significant increase in the area under oil palm in the tropics during the last couple of decades, and this is projected to increase further. The Roundtable on Sustainable Palm Oil discourages the conversion of peatlands to oil palm and rubber plantations. However, our understanding of the effects on soil organic carbon (SOC) stocks and associated greenhouse gas (GHG) emissions of land use conversion is incomplete, especially for mineral soils under primary forests, secondary forests, rubber and other perennial plantations in the tropics. In this review we synthesised information on SOC stocks and GHG emissions from tropical mineral soils under forest, oil palm and rubber plantations and other agroecosystems across the tropical regions. We found that the largest SOC losses occurred after land use conversion from primary forest to oil palm and rubber plantations. Secondary forest and pasture lands showed lower SOC losses as well as total GHG (CO2, N2O and CH4) emissions when converted to oil palm and rubber plantations. However, due to the limited data available on all three GHG emissions, there remains high uncertainty in GHG emissions estimates, and regional GHG accounting is more reliable. We recommend long-term monitoring of oil palm and other perennial plantations established on tropical mineral soils on different soil types and regions on SOC stock changes and total GHG emissions and evaluate appropriate management practices to optimise production and sustainable economic returns, and minimise environmental impact. [ABSTRACT FROM AUTHOR]

The African oil palm (Elaeis guineensis) is relatively well adapted to the pedoclimatic conditions of central Amazonia. The clayey uplandsoils of the region are well supplied with nitrogen, although they are deficient in most other nutrients. Under these conditions, oil palm does not respond to N fertilization with yield increases. In this research, the N status of a central Amazonian upland soil was evaluated after having supported a productive oil palm plantation for 15 years without N fertilization. Mineral N in the upper 2 m of soil showed pronounced spatial patterns, with very low concentrations close to the palms, indicative of efficient N uptake by the palms, and evidence for nitrate leaching into the subsoil in the inter-tree spaces despite the near-absence of a leguminous cover crop during the previous tenyears. The pronounced increases of mineral N with increasing tree distance were explained by increases in N mineralization and a strong decrease in fine root length density of the palms, especially in the subsoil. Failure of the palms to fully occupy the available soil volume with their roots was apparently related to fertilizer placement close to the stem base, which over the years had led to steep fertility gradients between the soil under the trees and the inter-tree spaces.Broadcast fertilization would have presumably favored a more extensive lateral root development of the palms, and consequently improved nutrient and water uptake from the inter-tree spaces. The incomplete soil occupation by the palm roots also suggests that young oil palms can be associated with shade tolerant crops without much risk of root competition. These conclusions may be valid also for other tree cropsand may help to reduce nitrate leaching and consequently the need for N fertilization in Amazonian tree crop agriculture. [ABSTRACT FROM AUTHOR]

Crassignathadanaugirangensis sp. n. (Araneae: Symphytognathidae) was discovered during a tropical ecology field course held at the Danau Girang Field Centre in Sabah, Malaysia. A taxonomic description and accompanying ecological study were completed as course activities. To assess the ecology of this species, which belongs to the ground-web-building spider community, three habitat types were surveyed: riparian forest, recently inundated riverine forest, and oil palm plantation. Crassignathadanaugirangensis sp. n. is the most abundant ground-web-building spider species in riparian forest; it is rare or absent from the recently inundated forest and was not found in a nearby oil palm plantation. The availability of this taxonomic description may help facilitate the accumulation of data about this species and the role of inundated riverine forest in shaping invertebrate communities.

A study was conducted to determine the distribution of ants in the crowns of oil palms on 2 plantations (Mpundu and Mondoni) in southwestCameroon (a total of 615 oil palms). Six dominant species [Crematogaster gabonensis (Emery), Tetramorium aculeatum (Mayr), Oecophylla longinoda (Latreille), Monomorium sp., Pheidole megacephala (F.), and Paratrechina sp.] were distributed in a mosaic pattern. C. gabonensis was the most frequent ant species in Mpundu (86% of the oil palms), whereas in Mondoni it was in competition with T. aculeatum (45.8% of the oil palms of the 6 parcels of land) and was recorded at alower rate (51.1%). On 3 parcels in Mondoni, T. aculeatum was the most frequent; whereas on 2 others, C. gabonensis was the most frequent, and in the last parcel these 2 species were evenly distributed. Therefore, oil palm plantations shelter dominant ant mosaics as do plantations of other trees of economic interest and tropical forests. The percentages of oil palms occupied by one or the other of the 2 most frequent dominant ants recorded in 12 parcels were compared with the rate of attack by Coelaemenodera minuta Uhmann. Low rates of attack bythe hispine beetle were recorded for parcels where the percentages of oil palms occupied by C. gabonensis were high; the opposite was true for parcels where the percentages of oil palms occupied by T. aculeatum were high. [ABSTRACT FROM AUTHOR]