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Oil palm plantations have rapidly expanded over the last 30 years, and now occupy 10% of the world’s permanent cropland. The growth of one of the world’s most efficient and versatile crop has alleviated poverty and increased food and energy security, but not without side effects. Losses of forest biodiversity hits the news. Although equally important, climate change issues have not reached this limelight. Data on greenhouse gas emissions associated with oil palm production is limited, especially for the potent greenhouse gas nitrous oxide (N2O). This paper provides an overview of the data availability, and identifies knowledge gaps to steer future research to provide the data required for climate change models and more accurate international and national nitrous oxide emission accounting.

Oil palm and rubber expansion is a main driver of the widespread deforestation of tropical rainforests taking place in South-East Asia, particularly in Indonesia. The replacement of forests with monoculture plantations of rubber and oil palm reduces biodiversity and carbon pools but also modifies canopy structure, which is an important determinant of microclimate. There is, however, a lack of quantitative information characterizing the effect of such land transformation on microclimate. We report the first medium-term observations of below-canopy microclimatic conditions (air temperature, relative humidity, vapour pressure deficit and soil temperature) across forest, jungle rubber agroforest, oil palm and rubber monoculture plantations in Sumatra/Indonesia. The data set covers a period of approximately three years (2013–2016) and includes one of the strongest El Nino-Southern Oscillations (ENSO) of the last decades. Forests were up to 2.3 and 2.2 °C cooler than oil palm and rubber monocultures respectively. The monocultures were also drier (11.9% and 12.8% less in oil palm and rubber respectively) and had higher vapour pressure deficit (632 Pa and 665 Pa higher in oil palm and rubber respectively) than the forest, while differences in soil temperature were less pronounced. Conversion from forest to other land uses, especially to monocultures, also amplified the diurnal range of all microclimatic variables studied. Jungle rubber stands out as the transformed land-use system that maintains more stable microclimatic conditions. Our results indicate that canopy openness is a key driver of below-canopy microclimate, and hence could be used in climate models to better evaluate climatic feedbacks of land-use change to rubber and oil palm. The ENSO event of 2015 led to warmer and drier conditions than in the previous two years in all four land-use systems, especially in the forest (up to 2.3 °C warmer, 8.9% drier and up to 351 Pa more during ENSO). The relative effect of ENSO was lower in the monoculture plantations, where below-canopy microclimate is generally more similar to open areas. Forests exhibited the largest differences with the pre-ENSO years, but still maintained more stable microclimatic conditions (lower temperatures and vapour pressure deficit and higher relative humidity) due to their higher climate regulation capacity. During ENSO, microclimatic conditions in jungle rubber were comparable to those in the monocultures, suggesting that while forests buffered the increase of temperature, jungle rubber might have surpassed its buffering capacity to extreme events. This capacity of buffering extreme climatic events should be considered when assessing the effects of land-use change.

Rice paddy fields are one of the largest anthropogenic sources of methane (CH 4 ), the second most important anthropogenic greenhouse gas (GHG) after carbon dioxide (CO 2 ). For this reason most studies on the GHG budget in these agricultural systems focus on the evaluation of CH 4 production. However, these systems also exchange other GHGs with the atmosphere, such as CO 2 and nitrous oxide (N 2 O). To estimate the total global warming potential (GWP) of rice cultivation, a field experiment was carried out in a Mediterranean rice paddy field in the Po Valley (Italy), the largest rice producing region in Europe. For two consecutive years, ecosystem CO 2 and CH 4 fluxes were assessed using the eddy covariance technique and CH 4 and N 2 O fluxes were measured with closed chambers. The net biome productivity indicated a nearly carbon (C) neutral system in 2009 while it accumulated C in 2010, due to the application of organic fertilizers and the midseason drainage of the otherwise flooded field, the latter having the additional benefit of leading to lower water consumption. The rice paddy field acted as a strong GHG source with a GWP of 1148 g CO 2- eq m −2 yr −1 in 2009 and decreased four-fold in 2010 (289 g CO 2- eq m −2 yr −1 ). In both years, the site was a large CH 4 source. Differences in the GHG budget between the two years of measurements were mainly caused by the lower CH 4 emissions in 2010 (21.0 g CH 4 m −2 compared to 37.4 g CH 4 m −2 in 2009), probably driven by drainage of the otherwise flooded field in the middle of the growing season during 2010 and moderately larger CO 2 uptake. The increased N 2 O fluxes (29%), had a marginal contribution to the GWP. However, midseason drainage, which needs to be evaluated in combination with the concurrent application of organic fertilizers, resulted in small decreases of yield. Our results therefore suggest that an adequate management of the water table level reduces CH 4 fluxes and has the potential to decrease the GWP and water losses through evapotranspiration of rice paddy fields, confirming that full GHG budgets should be assessed in combination with yields in order to develop and evaluate effective mitigation strategies.

Oil palm plantations have expanded rapidly in recent decades. This large-scale land-use change has had great ecological, economic, and social impacts on both the areas converted to oil palm and their surroundings. However, research on the impacts of oil palm cultivation is scattered and patchy, and no clear overview exists. We address this gap through a systematic and comprehensive literature review of all ecosystem functions in oil palm plantations, including several (genetic, medicinal and ornamental resources, information functions) not included in previous systematic reviews. We compare ecosystem functions in oil palm plantations to those in forests, as the conversion of forest to oil palm is prevalent in the tropics. We find that oil palm plantations generally have reduced ecosystem functioning compared to forests: 11 out of 14 ecosystem functions show a net decrease in level of function. Some functions show decreases with potentially irreversible global impacts (e.g. reductions in gas and climate regulation, habitat and nursery functions, genetic resources, medicinal resources, and information functions). The most serious impacts occur when forest is cleared to establish new plantations, and immediately afterwards, especially on peat soils. To variable degrees, specific plantation management measures can prevent or reduce losses of some ecosystem functions (e.g. avoid illegal land clearing via fire, avoid draining of peat, use of integrated pest management, use of cover crops, mulch, and compost) and we highlight synergistic mitigation measures that can improve multiple ecosystem functions simultaneously. The only ecosystem function which increases in oil palm plantations is, unsurprisingly, the production of marketable goods. Our review highlights numerous research gaps. In particular, there are significant gaps with respect to socio-cultural information functions. Further, there is a need for more empirical data on the importance of spatial and temporal scales, such as differences among plantations in different environments, of different sizes, and of different ages, as our review has identified examples where ecosystem functions vary spatially and temporally. Finally, more research is needed on developing management practices that can offset the losses of ecosystem functions. Our findings should stimulate research to address the identified gaps, and provide a foundation for more systematic research and discussion on ways to minimize the negative impacts and maximize the positive impacts of oil palm cultivation.

Land-use change has a strong impact on carbon, energy and water fluxes and its effect is particularly pronounced in tropical regions. Uncertainties exist in the prediction of future land-use change impacts on these fluxes by land surface models due to scarcity of suitable measured data for parametrization and poor representation of key biogeochemical processes associated with tropical vegetation types. Rubber plantations (Havea brasilliensis) are a crucial land-use type across tropical landscapes that has greatly expanded in recent decades. Here, we first synthesize the relevant data for describing the biogeochemical processes of rubber from our past measurement campaigns in Jambi province, Indonesia. We then use these data-sets to develop a rubber plant functional type (PFT) for the Community Land Model (CLM4.5). Field measured data from small-holder plantations on leaf litterfall, soil respiration, latex harvest, leaf area index, transpiration, net primary productivity, and above-ground and fine root biomass were used to develop and calibrate a new PFT-based model (CLM4.5-rubber). CLM-rubber predictions adequately captured the annual net primary productivity and above-ground biomass as well as the seasonal dynamics of leaf litterfall, soil respiration, soil moisture and leaf area index. All of the predicted water fluxes of CLM-rubber were very similar to a site-specific calibrated soil water model. Including temporal variations in leaf life span enabled CLM-rubber to better capture the seasonality of leaf litterfall. Increased sensitivity of stomata to soil water stress and the enhancement of growth and maintenance respiration of fine roots in response to soil nutrient limitation enabled CLM-rubber to capture the magnitude of transpiration and leaf area index. Since CLM-rubber predicted reasonably well the carbon and water use, we think that the current model can be used for larger-scale simulations within Jambi province because more than 99 % of the rubber plantations are smallholder owned in Jambi province and have low soil fertility.

Oil palm (Elaeis guineensis Jacq.) plantations cover large and continuously increasing areas of humid tropical lowlands. Landscapes dominated by oil palms usually consist of a mosaic of mono-cultural, homogeneous stands of varying age, which may be heterogeneous in their water use characteristics. However, studies on the water use characteristics of oil palms are still at an early stage and there is a lack of knowledge on how oil palm expansion will affect the major components of the hydrological cycle. To provide first insights into hydrological landscape-level consequences of oil palm cultivation, we derived transpiration rates of oil palms in stands of varying age, estimated the contribution of palm transpiration to evapotranspiration, and analyzed the influence of fluctuations in environmental variables on oil palm water use. We studied 15 two- to 25-year old stands in the lowlands of Jambi, Indonesia. A sap flux technique with an oil palm specific calibration and sampling scheme was used to derive leaf-, palm- and stand-level water use rates in all stands under comparable environmental conditions. Additionally, in a two- and a 12-year old stand, eddy covariance measurements were conducted to derive evapotranspiration rates. Water use rates per leaf and palm increased 5-fold from an age of 2 years to a stand age of approx. 10 years and then remained relatively constant. A similar trend was visible, but less pronounced, for estimated stand transpiration rates of oil palms; they varied 12-fold, from 0.2 mm day−1 in a 2-year old to 2.5 mm day−1 in a 12-year old stand, showing particularly high variability in transpiration rates among medium-aged stands. Comparing sap flux and eddy-covariance derived water fluxes suggests that transpiration contributed 8 % to evapotranspiration in the 2-year old stand and 53 % in the 12-year old stand, indicating variable and substantial additional sources of evaporation, e.g., from the soil, the ground vegetation and from trunk epiphytes. Diurnally, oil palm transpiration rates were characterized by an early peak between 10 and 11 a.m.; there was a pronounced hysteresis in the leaf water use response to changes in vapor pressure deficit for all palms of advanced age. On the day-to-day basis this resulted in a relatively low variability of oil palm water use regardless of fluctuations in vapor pressure deficit and radiation. We conclude that oil palm dominated landscapes show some spatial variations in (evapo)transpiration rates, e.g., due to varying age-structures, but that the temporal variability of oil palm transpiration is rather low. The stand transpiration of some of the studied oil palm stands was as high or even higher than values reported for different tropical forests, indicating a high water use of oil palms under yet to be explained site or management conditions. Our study provides first insights into the eco-hydrological characteristics of oil palms as well as a first estimate of oil palm water use across a gradient of plantation age. It sheds first light on some of the hydrological consequences of the continuing expansion of oil palm plantations.

Indonesia is currently one of the regions with the highest transformation rate of the land surface worldwide due to the expansion of oil palm plantations and other cash crops replacing forests on large scales. Land cover changes, which modify land surface properties, have a direct effect on the land surface temperature (LST), a key driver for many ecological functions. Despite the large historic land transformation in Indonesia toward oil palm and other cash crops and governmental plans for future expansion, this is the first study so far to quantify the impact of land transformation in Indonesia on LST. We analyse LST from the thermal band of a Landsat image and produce a high resolution surface temperature map (30 m) for the lowlands of the Jambi province on Sumatra (Indonesia), a region of large land transformation towards oil palm and other cash crops over the past decades. We compare LST, albedo, Normalized Differenced Vegetation Index (NDVI), and evapotranspiration (ET) of seven different land cover types (forest, urban areas, clear cut land, young and mature oil palm plantations, acacia and rubber plantations) and show that forests have lower surface temperatures than these land cover types indicating a local warming effect after forest conversion with LST differences up to 10.09 ± 2.6 ºC (mean ± SD) between forest and clear cut land. The differences in surface temperatures are explained by an evaporative cooling effect offsetting an albedo warming effect. Our analysis of the LST trend of the past 16 years based on MODIS data shows that the average daytime surface temperature of the Jambi province increased by 1.05 ºC, which followed the trend of observed land cover changes and exceed the effects of climate warming. Our study provides evidence that the expansion of oil palm plantations and other cash crops leads to changes in biophysical variables, warming the land surface and thus enhancing the increase in air temperature due to climate change.

Tropical lowland rainforests are increasingly threatened by the expansion of agriculture and the extraction of natural resources. In Jambi Province, Indonesia, the interdisciplinary EFForTS project focuses on the ecological and socio-economic dimensions of rainforest conversion to jungle rubber agroforests and monoculture plantations of rubber and oil palm. Our data confirm that rainforest transformation and land use intensification lead to substantial losses in biodiversity and related ecosystem functions, such as decreased above- and below-ground carbon stocks. Owing to rapid step-wise transformation from forests to agroforests to monoculture plantations and renewal of each plantation type every few decades, the converted land use systems are continuously dynamic, thus hampering the adaptation of animal and plant communities. On the other hand, agricultural rainforest transformation systems provide increased income and access to education, especially for migrant smallholders. Jungle rubber and rubber monocultures are associated with higher financial land productivity but lower financial labour productivity compared to oil palm, which influences crop choice: smallholders that are labour-scarce would prefer oil palm while land-scarce smallholders would prefer rubber. Collecting long-term data in an interdisciplinary context enables us to provide decision-makers and stakeholders with scientific insights to facilitate the reconciliation between economic interests and ecological sustainability in tropical agricultural landscapes.

Given their ability to provide food, raw material and alleviate poverty, oil palm (OP) plantations are driving significant losses of biodiversity-rich tropical forests, fuelling a heated debate on ecosystem degradation and conservation. However, while OP-induced carbon emissions and biodiversity losses have received significant attention, OP water requirements have been marginalized and little is known on the ecohydrological changes (water and surface energy fluxes) occurring from forest clearing to plantation maturity. Numerical simulations supported by field observations from seven sites in Southeast Asia (five OP plantations and two tropical forests) are used here to illustrate the temporal evolution of OP actual evapotranspiration (ET), infiltration/runoff, gross primary productivity (GPP) and surface temperature as well as their changes relative to tropical forests. Model results from large-scale commercial plantations show that young OP plantations decrease ecosystem ET, causing hotter and drier climatic conditions, but mature plantations (age > 8−9 yr) have higher GPP and transpire more water (up to +7.7%) than the forests they have replaced. This is the result of physiological constraints on water use efficiency and the extremely high yield of OP (six to ten times higher than other oil crops). Hence, the land use efficiency of mature OP, i.e. the high productivity per unit of land area, comes at the expense of water consumption in a trade of water for carbon that may jeopardize local water resources. Sequential replanting and herbaceous ground cover can reduce the severity of such ecohydrological changes and support local water/climate regulation.

Among the mitigation strategies to prevent nitrogen (N) losses from ureic fertilizers, urease inhibitors (UIs) have been demonstrated to promote high N use efficiency by reducing ammonia (NH3) volatilization. In the last few years, some field experiments have also shown its effectiveness in reducing nitrous oxide (N2O) losses from fertilized soils under conditions of low soil moisture. An incubation experiment was carried out with the aim of assessing the main biotic mechanisms behind N2O emissions once that the UIs N-(n-butyl) thiophosphoric triamid (NBPT) and phenil phosphorodiamidate (PPDA) were applied with Urea (U) under different soil moisture conditions (40, 60 and 80 % water-filled pore space, WFPS). In the same study we tried to analyze to what extent soil WFPS regulates the effect of these inhibitors on N2O emissions. The use of PPDA in our study allowed us to compare the effect of NBPT with that of another commercially available urease inhibitor, aiming to see if the results were inhibitor-specific or not. Based on the results from this experiment, a WFPS (i.e. 60 %) was chosen for a second study (i.e. mesocosm experiment) aiming to assess the efficiency of the UIs to indirectly affect N2O emissions through influencing the pool of soil mineral N. The N2O emissions at 40 % WFPS were almost negligible, being significantly lower from all fertilized treatments than that produced at 60 and 80 % WFPS. When compared to U alone, NBPT+U reduced the N2O emissions at 60 % WFPS but had no effect at 80 % WFPS. The application of PPDA significantly increased the emissions with respect to U at 80 % WFPS whereas no significant effect was found at 60 %. At 80 % WFPS, denitrification was the main source of N2O emissions for all treatments. In the mesocosm study, the application of NBPT+U was an effective strategy to reduce N2O emissions (75 % reduction compared to U alone), due to a lower soil ammonium (NH4 +) content induced by the inhibitor. These results suggest that adequate management of the UI NBPT could provide, under certain soil conditions, an opportunity for mitigation of N2O emissions from fertilized soils.

The aim of our research was to obtain information on the isotopic fingerprint of nitrous oxide (N2O) associated with its production and consumption during denitrification. An arable soil was preincubated at high moisture content and subsequently amended with glucose (400 kg C ha−1) and KNO3 (80 kg N ha−1) and kept at 85% water-filled pore space. Twelve replicate samples of the soil were incubated for 13 days under a helium-oxygen atmosphere, simultaneously measuring gas fluxes (N2O, N2 and CO2) and isotope signatures (δ18O-N2O, δ15Nbulk-N2O, δ15Nα, δ15Nβ and 15N site preference) of emitted N2O. The maximum N2O flux (6.9 ± 1.8 kg N ha−1 day−1) occurred 3 days after amendment application, followed by the maximum N2 flux on day 4 (6.6 ± 3.0 kg N ha−1 day−1). The δ15Nbulk was initially −34.4‰ and increased to +4.5‰ during the periods of maximum N2 flux, demonstrating fractionation during N2O reduction, and then decreased. The δ18O-N2O also increased, peaking with the maximum N2 flux and remaining stable afterwards. The site preference (SP) decreased from the initial +7.5 to −2.1‰ when the N2O flux peaked, and then simultaneously increased with the appearance of the N2 peak to +8.6‰ and remained stable thereafter, even when the O2 supply was removed. We suggest that this results from a non-homogenous distribution of NO in the soil, possibly linked to the KNO3 amendments to the soil, causing the creation of several NO pools, which affected differently the isotopic signature of N2O and the N2O and N2 fluxes during the various stages of the process. The N2O isotopologue values reflected the temporal patterns observed in N2O and N2 fluxes. A concurrent increase in 15N site preference and δ18O of N2O was found to be indicative of N2O reduction to N2.

The present study determined the influence of initial moisture conditions on the production and consumption of nitrous oxide (N 2 O) during denitrification and on the isotopic fingerprint of soil-emitted N 2 O. Sieved arable soil was pre-incubated at two different moisture contents: pre-wet at 75% and pre-dry at 20% water-filled pore space. After wetting to 90% water-filled pore space the soils were amended with glucose (400 kg C ha −1 ) and KNO 3 (80 kg N ha −1 ) and incubated for 10 days under a He/O 2 -atmosphere. Antecedent moisture conditions affected denitrification. N 2 + N 2 O fluxes and the N 2 O-to-N 2 ratio were higher in soils which were pre-incubated under dry conditions, probably because mobilization of organic C during the pre-treatment enhanced denitrification. Gaseous N fluxes showed similar time patterns of production and reduction of N 2 O in both treatments, where N 2 O fluxes were initially increasing and maximised 3–4 days after fertilizer application, and N 2 fluxes were delayed by 1–2 days. Time courses of δ 15 N bulk –N 2 O and δ 18 O–N 2 O exhibited in both treatments increasing trends until maximum N 2 fluxes occurred, reflecting isotope fractionation during intense NO 3 − reduction. Later this trend slowed down in the pre-dry treatment, while δ 18 O–N 2 O was constant and δ 15 N bulk –N 2 O decreased in the pre-wet treatment. We explain these time patterns by non-homogenous distribution of NO 3 − and denitrification activity, resulting from application of NO 3 − and glucose to the surface of the soil. We assume that several process zones were thus created, which affected differently the isotopic signature of N 2 O and the N 2 O and N 2 fluxes during the different stages of the process. We modelled the δ 15 N bulk –N 2 O using process rates and associated fractionation factors for the pre-treated soils, which confirmed our hypothesis. The site preference (SP) initially decreased while N 2 O reduction was absent, which we could not explain by the N-flux pattern. During the subsequent increase in N 2 flux, SP and δ 18 O–N 2 O increased concurrently, confirming that this isotope pattern is indicative for N 2 O reduction to N 2 . The possible effect of the antecedent moisture conditions of the soil on N 2 O emissions was shown to be important.

n this study, we compare annual fluxes of methane (CH4), nitrous oxide (N2O) and soil respiratory carbon dioxide (CO2) measured at nine European peatlands (n = 4) and shrublands (n = 5). The sites range from northern Sweden to Spain, covering a span in mean annual air temperature from 0 to 16 °C, and in annual precipitation from 300 to 1300 mm yr−1. The effects of climate change, including temperature increase and prolonged drought, were tested at five shrubland sites. At one peatland site, the long-term (>30 yr) effect of drainage was assessed, while increased nitrogen deposition was investigated at three peatland sites. The shrublands were generally sinks for atmospheric CH4 whereas the peatlands were CH4 sources, with fluxes ranging from −519 to +6890 mg CH4-C m−2 yr−1 across the studied ecosystems. At the peatland sites, annual CH4 emission increased with mean annual air temperature, while a negative relationship was found between net CH4 uptake and the soil carbon stock at the shrubland sites. Annual N2O fluxes were generally small ranging from –14 to 42 mg N2O-N m−2 yr−1. Highest N2O emission occurred at the sites that had highest concentration of nitrate (NO3−) in soil water. Furthermore, experimentally increased NO3− deposition led to increased N2O efflux, whereas prolonged drought and long-term drainage reduced the N2O efflux. Soil CO2 emissions in control plots ranged from 310 to 732 g CO2-C m−2 yr−1. Drought and long-term drainage generally reduced the soil CO2 efflux, except at a~hydric shrubland where drought tended to increase soil respiration. When comparing the fractional importance of each greenhouse gas to the total numerical global warming response, the change in CO2 efflux dominated the response in all treatments (ranging 71–96%), except for NO3− addition where 89% was due to change in CH4 emissions. Thus, in European peatlands and shrublands the feedback to global warming induced by the investigated anthropogenic disturbances will be dominated by variations in soil CO2 fluxes., JRC.H.2-Air and Climate