RESUMEN

The predicted increase of drought intensity in South-East Asia has raised concern about the sustainability of rubber (Hevea brasiliensis Müll. Arg.) cultivation. In order to quantify the degree of phenotypic plasticity in this important tree crop species, we analysed a set of wood and leaf traits related to the hydraulic safety and efficiency in PB260 clones from eight small-holder plantations in Jambi province, Indonesia, representing a gradient in local microclimatic and edaphic conditions. Across plots, branch embolism resistance (P50) ranged from -2.14 to -2.58 MPa. The P50 and P88 values declined, and the hydraulic safety margin increased, with an increase in the mean annual vapour pressure deficit (VPD). Among leaf traits, only the changes in specific leaf area were related to the differences in evaporative demand. These variations of hydraulic trait values were not related to soil moisture levels. We did not find a trade-off between hydraulic safety and efficiency, but vessel density (VD) emerged as a major trait associated with both safety and efficiency. The VD, and not vessel diameter, was closely related to P50 and P88 as well as to specific hydraulic conductivity, the lumen-to-sapwood area ratio and the vessel grouping index. In conclusion, our results demonstrate some degree of phenotypic plasticity in wood traits related to hydraulic safety in this tropical tree species, but this is only in response to the local changes in evaporative demand and not soil moisture. Given that VPD may increasingly limit plant growth in a warmer world, our results provide evidence of hydraulic trait changes in response to a rising evaporative demand.

Asunto(s)

Hevea , Madera , Madera/fisiología , Goma , Suelo , Hojas de la Planta/fisiología , Árboles/fisiología , Sequías , Agua/fisiología , Xilema/fisiología

RESUMEN

With the prospect of climate change and more frequent El Niño-related dry spells, the drought tolerance of oil palm (Elaeis guineensis Jacq.), one of the most important tropical crop species, is of major concern. We studied the influence of soil water availability and palm height on the plasticity of xylem anatomy of oil palm fronds and their embolism resistance at well-drained and seasonally flooded riparian sites in lowland Sumatra, Indonesia. We found overall mean P12 and P50 values, i.e., the xylem pressures at 12% or 50% loss of hydraulic conductance, of -1.05 and - 1.86 MPa, respectively, indicating a rather vulnerable frond xylem of oil palm. This matches diurnal courses of stomatal conductance, which in combination with the observed low xylem safety evidence a sensitive water loss regulation. While the xylem anatomical traits vessel diameter (Dh), vessel density and potential hydraulic conductivity (Kp) were not different between the sites, palms in the moister riparian plots had on average by 0.4 MPa higher P50 values than plants in the well-drained plots. This could largely be attributed to differences in palm height between systems. As a consequence, palms of equal height had 1.3 MPa less negative P50 values in the moister riparian plots than in the well-drained plots. While palm height was positively related to P50, Dh and Kp decreased with height. The high plasticity in embolism resistance may be an element of the drought response strategy of oil palm, which, as a monocot, has a relatively deterministic hydraulic architecture. We conclude that oil palm fronds develop a vulnerable water transport system, which may expose the palms to increasing drought stress in a warmer and drier climate. However, the risk of hydraulic failure may be reduced by considerable plasticity in the hydraulic system and the environmental control of embolism resistance, and a presumably large stem capacitance.

Asunto(s)

Embolia , Suelo , Sequías , Humanos , Indonesia , Agua , Xilema

RESUMEN

Palm oil is a promising source of cooking oil and biodiesel. The demand for palm oil has been increasing worldwide. However, concerns exist surrounding the environmental and socio-economic sustainability of palm oil production. Indonesia is a major palm oil producing country. We explored scenarios for palm oil production in Indonesia until 2050, focusing on Sumatra, Kalimantan and Papua. Our scenarios describe possible trends in crude palm oil production in Indonesia, while considering the demand for cooking oil and biodiesel, the available land for plantations, production capacity (for crude palm oil and fresh fruit bunches) and environmentally restricting conditions. We first assessed past developments in palm oil production. Next, we analysed scenarios for the future. In the past 20years, 95% of the Indonesian oil palm production area was in Sumatra and Kalimantan and was increasingly cultivated in peatlands. Our scenarios for the future indicate that Indonesia can meet a considerable part of the global and Asian demand for palm oil, while avoiding further cultivation of peatlands and forest. By 2050, 264-447Mt crude palm oil may be needed for cooking oil and biodiesel worldwide. In Indonesia, the area that is potentially suitable for oil palm is 17 to 26Mha with a potential production rate of 27-38t fresh fruit bunches/ha, yielding 130-176Mt crude palm oil. Thus Indonesia can meet 39-60% of the international demand. In our scenarios this would be produced in Sumatra (21-26%), Kalimantan (12-16%), and Papua (2%). The potential areas include the current oil palm plantation in mineral lands, but exclude the current oil palm plantations in peatlands.