Search

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.

Special thanks to our field assistants in Indonesia (Basri, Bayu and Darwis) and to Frank Tiedemann, Edgar Tunsch, Dietmar Fellert and Malte Puhan for technical assistance. We thank PTPN VI and the owner of the plantation at Pompa Air for allowing us to conduct our research at their plantation. We would also like to thank the Spanish national project GEISpain (CGL2014-52838-C2-1-R) and the DAAD (scholarship from the programme ‘Research Stays for University Academics and Scientist 2018, ref. no. 91687130)' for partly financing A. Meijide during the preparation of this paper., The potential of palm-oil biofuels to reduce greenhouse gas (GHG) emissions compared with fossil fuels is increasingly questioned. So far, no measurement-based GHG budgets were available, and plantation age was ignored in Life Cycle Analyses (LCA). Here, we conduct LCA based on measured CO2, CH4 and N2O fluxes in young and mature Indonesian oil palm plantations. CO2 dominates the on-site GHG budgets. The young plantation is a carbon source (1012 ± 51 gC m−2 yr−1), the mature plantation a sink (−754 ± 38 gC m−2 yr−1). LCA considering the measured fluxes shows higher GHG emissions for palm-oil biodiesel than traditional LCA assuming carbon neutrality. Plantation rotation-cycle extension and earlier-yielding varieties potentially decrease GHG emissions. Due to the high emissions associated with forest conversion to oil palm, our results indicate that only biodiesel from second rotation-cycle plantations or plantations established on degraded land has the potential for pronounced GHG emission savings., This study was financed by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)— Project-ID 192626868—in the framework of the collaborative German-Indonesian research project CRC990 (subprojects A03, A04 and A05)., Spanish national project GEISpain (CGL2014-52838-C2-1-R) and the DAAD (scholarship from the programme ‘Research Stays for University Academics and Scientist 2018, ref. no. 91687130)

Oil palm (Elaeis guineensis) is the most important oil crop in the world, with more than 85% of the global production coming from Indonesia and Malaysia. However, knowledge of country-wide past, current and likely future greenhouse gas (GHG) footprints from palm oil production remains largely incomplete. Over the past year, first studies reporting measurements of net ecosystem carbon dioxide (CO2) fluxes in oil palm plantations of different ages and on different soil types became available. Combining the recent CO2 flux estimates with existing measurements on methane and nitrous oxide fluxes allows for a refined quantification of the GHG footprint of palm oil production over the whole plantation life cycle.To derive country-wide GHG emissions from palm oil production for both Indonesia and Malaysia, we applied the refined GHG footprint estimates to oil palm area extents. Therein, we differentiated between mineral and peat soils, second- and first-generation plantations and within the latter category also among previous land-use systems from which conversion to oil palm likely occurred. For deriving the current (2020) proportions for each category, we combined FAO data with existing remotely sensed maps on oil palm extent and tree density as well as peatland and intact forest layers. These area proportions were then applied to available historic (1970 – 2010) and future (2030 – 2050) oil palm extent estimates as a business-as-usual scenario (BAU), complemented by alternative scenarios. GHG footprint estimates comprise all GHG emissions from palm oil production, i.e. from land-use change, cultivation, milling and use.Our refined approach estimates the 2020 GHG emissions from palm oil production at 1011 Tg CO2-eq. yr-1 for Indonesia and at 261 Tg CO2-eq. yr-1 for Malaysia. Our results show that while plantations on peatland only represented 17% and 15% of the total plantation area in 2020 for Indonesia and Malaysia, they accounted for 73% and 72% of the total GHG emissions from palm oil production. Emissions in 1980 and 2000 were estimated to be only 1% and 14% of the 2020 palm oil emissions for Indonesia, but already 24% and 96% for Malaysia due to the earlier oil palm expansion. Projected emissions for 2050, assuming further oil palm expansion on suitable land and constant yields from 2020 on, represent 64% of the 2020 value for Indonesia and 97% for Malaysia under a BAU expansion scenario. These lower or constant GHG emissions for future scenarios despite assumed increases in cultivated area are the consequence of lower GHG emissions in second and subsequent rotation cycles. For both countries, the 2050 BAU emissions could be reduced by more than 50% by halting all conversion of peatlands and forests to oil palm from 2020 on, and by more than 75% when additionally restoring all peatlands currently under oil palm to forest until 2050. Closing yield gaps could potentially lead to further emissions savings.

The need to sustain global food demand while mitigating greenhouse gases (GHG) emissions is a challenge for agricultural production systems. Since the reduction of GHGs has never been a breeding target, it is still unclear to which extend different crop varieties will affect GHG emissions. The objective of this study was to evaluate the impact of N-fertilization and of the use of growth regulators applied to three historical and three modern varieties of winter wheat on the emissions of the three most important anthropogenic GHGs, i.e. carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). Furthermore, we aimed at identifying which combination of cultivars and management practises could mitigate GHG emissions in agricultural systems without compromising the yield. GHG measurements were performed using the closed chamber method in a field experiment located in Göttingen (Germany) evaluating three historical and three modern winter wheat varieties, with or without growth regulators under two fertilization levels (120 and 240 kg nitrogen ha-1). GHG measurements were carried out for 2 weeks following the third nitrogen fertilizer application (where one third of the total nitrogen was applied), together with studies on the evolution of mineral nitrogen and dissolved organic carbon in the soil. Modern varieties showed significantly higher CO2 emissions (i.e. soil and plant respiration; +23 %) than historical varieties. The soils were found to be a sink for CH4, but CH4 fluxes were not affected by the different treatments. N2O emissions were not significantly influenced by the variety age or by the growth regulators, and emissions increased with increasing fertilization level. The global warming potential (GWP) for the modern varieties was 7284.0 ± 266.9 kg CO2-eq ha-1. Even though the GWP was lower for the historic varieties (5939.5 ± 238.2 kg CO2-eq ha-1), their greenhouse gas intensity (GHGI), which relates GHG and crop yield, was larger (1.5 ± 0.3 g CO2-eq g-1 grain), compared to the GHGI of modern varieties (0.9 ± 0.0 g CO2-eq g-1 grain), due to the much lower grain yield in the historic varieties. Our results suggest that in order to mitigate GHG emissions without compromising the grain yield, the best management practise is to use modern high yielding varieties with growth regulators and a fertilization scheme according to the demand of the crop.

The global population growth and changes in human lifestyle and consumption patterns put immense pressure on the limited freshwater resources in the world. Aiming at sustainable use and equitable allocation of the water resources, it becomes crucial to know the water appropriation for the production of different commodities and consumer goods. These days, oil palm (Elaeis guineensis) is one of the highest-demanded crops around the globe since the oil of its fruits and kernel is widely used as biofuel and major ingredients in food and cosmetic industries. Given this massive demand, the areas under oil palm cultivation in the tropics have continuously been expanding in the last decades, particularly in Indonesia. With the oil palm boom, not only biodiversity loss, and carbon dioxide emissions from deforestation have been increasing, but also the consumptions of blue and green water resources are of concern. In this ongoing research, the concept of water footprint (WF) is employed to quantify the green and blue water use of oil palm production in the Bajubang district, Batanghari regency, Jambi province, Sumatra, Indonesia. This is one of the first studies that uses field-measured data of evapotranspiration (ET) from oil palm plantations in different growth stages over seven years for the purpose of WF assessment, compared to the available literature where ET was estimated using modelling approaches. The multi-year measurements were conducted using the eddy covariance technique, which continuously measures water vapor (H2O) fluxes at the ecosystem level over the plantation. Based on these measurements, specifically, the WF assessment is performed on a product basis during the plantation life cycle, per area and time unit, for the oil palm fruit yield and oil palm derived products (palm oil, palm-oil biodiesel). Besides the crop water consumption at the plantation (i.e. ET) as the core element, other water consumptions in the products’ processing chain are included in the WF assessment. Preliminary results indicate a WF of 2440 m3 t-1 for palm oil and 65 m3 GJ-1 for palm-oil biodiesel. This is about 50% lower than the global average estimates. Local WF account of oil palm products has a critical contribution to product transparency while being useful for comparative purposes. Contrasting the WFs of products serving the same function (e.g., palm oil biodiesel, soybean biodiesel) is of essential importance, aiming at conscious product choices in a world of freshwater scarcity.Keywords: water footprint, oil palm, palm oil, Indonesia, eddy covariance, evapotranspiration

Olive groves are one of the most extensive crops in the Mediterranean region, hence, their management practices can result in significant environmental, social, and economic impacts. Given the generalized water stress conditions across the Mediterranean region, irrigation is usually applied to increase olive crop yield. In Spain, the country with the largest olive crop extension, 29% of the olive cultivated area is irrigated. Cover cropping (i.e. the maintenance of annuals and perennials in between tree rows) can be considered as one of the most widespread conservation practices. It is being increasingly adopted as a sustainable strategy to increase soil organic carbon content and mitigate soil degradation problems caused by soil erosion, apart from other benefits such as the increase of microfauna biodiversity. On the other hand, cover crops may also increase evapotranspiration and, consequently, water demand in olive production systems. While the influence of cover crops on carbon sequestration capacity of olive groves has been previously demonstrated to be positive, their effects on evapotranspiration and water use efficiency, defined as the ratio between carbon uptake and evapotranspiration, remain uncertain.In this study, we aim to assess the effect of cover crops on microclimate conditions, carbon sequestration, evapotranspiration and water use efficiency of an irrigated olive grove located in Jaén (SE Spain), where two adjacent areas were subjected to two different treatments: 1) weed-free treatment, in which a glyphosate-based herbicide is applied annually to avoid spontaneous weed growth (generally in early spring), and 2) weed-cover treatment (i.e. cover crop), where spontaneous weed cover was kept from autumn to spring. Both treatments are equipped with a wide range of environmental sensors to characterize short- and long-term variations in ambient conditions (e.g. air temperature, relative humidity, precipitation, incoming/reflected short- and long-wave radiation, soil moisture and temperature, soil heat flux). In addition, two eddy covariance towers allow the direct measurement of atmosphere-ecosystem exchanges of water, heat, carbon dioxide and momentum at a high temporal resolution (Preliminary results, based on data of the first hydrological year (2015-2016), show that cover crops increase ecosystem evapotranspiration. However, the net carbon uptake was higher in the weed-cover treatment compared to the weed-free treatment, leading to a net increase in ecosystem water use efficiency. Further, the Bowen ratio – conceived as the ratio between sensible and latent heat fluxes – was lower in the weed-cover than in the weed-free treatment. Therefore, despite the fact that cover crops increase water loss through evapotranspiration, they mitigate the carbon footprint of the agrosystem, likely having a positive effect on crop water use efficiency by maximizing the ratio of carbon assimilation to water loss.

Wetlands are crucial ecosystems modulating climate change due to their great potential to capture carbon dioxide (CO2), emit methane (CH4) and regulate local climate through evapotranspiration (ET). Common reed wetlands are particularly interesting given their high productivity, abundance and highly efficient internal gas-transport mechanism. However, little is known about the interannual behavior and dominant controlling factors of Mediterranean reed wetlands, characterized by seasonal flooding and remarkable weather variability. After 6 years of ecosystem carbon and ET flux measurements by eddy covariance (3 years for CH4 fluxes), this study shows the functional vulnerability of such wetlands to climate variability, switching between carbon (CO2+CH4) sink (660 g CO2-eeq m-2 y -1 , in 2014) and source (360 g CO2-eq m-2 y -1 , in 2016) in short periods of time. According to our analyses, the great interannual variability appeared to mainly depend on the behavior of reed growth dynamics during the transition to senescence period, what is confirmed through the Enhanced Vegetation Index as a proxy of photosynthetic activity. Additionally, a similar behavior of seasonal and daily patterns of carbon fluxes and ET was found compared with other wetlands under different climates.

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.

The conversion of tropical rainforest to agricultural systems such as oil palm alters biodiversity across a large range of interacting taxa and trophic levels. Yet, it remains unclear how direct and cascading effects of land-use change simultaneously drive ecological shifts. Combining data from a multi-taxon research initiative in Sumatra, Indonesia, we show that direct and cascading land-use effects alter biomass and species richness of taxa across trophic levels ranging from microorganisms to birds. Tropical land use resulted in increases in biomass and species richness via bottom-up cascading effects, but reductions via direct effects. When considering direct and cascading effects together, land use was found to reduce biomass and species richness, with increasing magnitude at higher trophic levels. Our analyses disentangle the multifaceted effects of land-use change on tropical ecosystems, revealing that biotic interactions on broad taxonomic scales influence the ecological outcome of anthropogenic perturbations to natural ecosystems.

Oil palm is rapidly expanding, particularly in Indonesia, but there is still very limited information on water and energy fluxes in oil palm plantations, and on how those are affected by varying environmental conditions or plantation age. In our study, we measured turbulent fluxes of sensible (H) and latent (LE) heat and gross primary productivity (GPP) with the eddy covariance technique for 8 months each in a young oil palm plantation (1-year old) and subsequently in a mature plantation (12-year old) in Jambi Province, Sumatra, Indonesia. Simultaneous measurements of transpiration (T) were performed using the sap flux technique. We additionally estimated albedo, the maximum rate of carboxylation (Vc max ), the maximum rate of photosynthetic electron transport (J max ) and water use efficiency (WUE). LE dominated the energy budget in both plantations, particularly in the mature one, where it accounted for up to 70% of the available energy. In the young oil palm plantation, evapotranspiration (ET) was significantly reduced and H fluxes were higher. The Bowen ratio was higher in the 1-year old plantation (0.67 ± 0.33), where it remained constant during the day, than in the mature plantation (0.14 ± 0.09), where it varied considerably over the day, suggesting the existence of water sources inside the canopy which evaporated during the day. Albedo was similar in both plantations (0.16 ± 0.02 and 0.14 ± 0.01 for the 1 and 12-year old plantation, respectively), while WUE differed with plantation age. Annual T estimates for oil palm were 64 ± 3 and 826 ± 34 mm yr −1 for the 1 and 12-year old plantation, respectively. The corresponding annual ET was 918 ± 46 and 1216 ± 34 mm yr −1 , respectively. The Community Land Model (CLM), a process based land surface model that has been adapted to oil palm functional traits (i.e. CLM-Palm), was used to investigate the contribution of different water sources to the measured fluxes. CLM-Palm differentiates leaf and stem surfaces in modelling water interception and thus is able to diagnose the fraction of dry foliage that contributes to T and the wet fraction of all vegetation surfaces (leaf and stem) that contributes to evaporation. The results of the simulations performed are consistent with the storage of water within the canopy in the mature plantation, and suggest that oil palm trunk surfaces including epiphytes provide water reservoirs for intercepted rain which significantly contribute to ET. The decoupling between GPP and T in the morning and the early decreases of both fluxes at midday point to internal water storage mechanisms in oil palms both in the leaves and in the stem, which delayed the detection of water movement at the leaf petioles. Our measured data combined with the model simulations therefore suggest the existence of both external and internal trunk water storage mechanisms in mature oil palms contributing to ecosystem water fluxes. Oil palm plantations can lead to surface warming at early stages of development, but further assessments should be performed at landscape level. Our study provides data relevant for the parametrization of larger-scale models, which can contribute to understanding the climatic feedbacks of oil palm expansion.

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.

The El Niño–Southern Oscillation (ENSO) in 2015 was one of the strongest observed in almost 20 years and set the stage for a severe drought and the emergence of widespread fires and related smoke emission over large parts of Southeast Asia. In the tropical lowlands of Sumatra, which were heavily affected by the drought and haze, large areas of tropical rainforest have been converted into oil palm (Elaeis guineensis Jacq.) plantations during the past decades. In this study, we investigate the impact of drought and smoke haze on the CO2 exchange, evapotranspiration and surface energy budget in a commercial oil palm plantation in Jambi province (Sumatra, Indonesia) by using micrometeorological measurements, the eddy covariance method and a multi linear regression model (MLRM). With the MLRM we identify the contribution of meteorological and environmental parameters to net ecosystem CO2 exchange. During the initial part of the drought, when incoming shortwave radiation was elevated, CO2 uptake increased by 50 % despite a decrease in upper-layer soil moisture by 35 %, an increase in air temperature by 10 % and a tripling of atmospheric vapor pressure deficit. Emerging smoke haze decreased incoming solar radiation by 35 % compared to non-drought conditions and diffuse radiation became almost the sole shortwave radiation flux for two months resulting in a strong decrease in CO2 uptake by 86 %. Haze conditions resulted in a complete pause of oil palm carbon uptake for about 1.5 months and contributed to a decline in oil palm yield by 35 %. With respect to climate change and a pronounced drying trend over the western Pacific during El Niño, our model showed that an increase in drought may stimulate CO2 uptake while more severe smoke haze, in combination with drought, can lead to pronounced losses in productivity and CO2 uptake highlighting the importance of fire prevention.

Forest fires can cause great changes in the composition, structure and functioning of forest ecosystems. We studied the effects of a fire that occurred >50 years ago in a temperate rainforest that caused flooding conditions in a Placic Andosol to evaluate how long these effects last; we hypothesized that the effects of fire on the soil greenhouse gas (GHG) balance could last for many years. We made monthly measurements of fluxes of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) during two years of soils in an unburned forest (UF) and a nearby site that burned >50 years ago (BS). Our results show that CO2 emissions from soils were higher in the UF than in the BS, and positively correlated with temperature and negatively with soil water content at both sites. Both sites were net CH4 sinks (higher in the UF) and fluxes correlated positively with soil water content and negatively with temperature (stronger relation in the BS). Emissions of N2O were low at both sites and showed correlation with friction velocity at the UF site. The soil GHG balance showed that the UF emitted about 80% more than the BS (5079 ± 1772 and 2815 ± 1447 g CO2-eq m−2 y−1, respectively). Combining our measured fluxes with data of CO2 net ecosystem exchange, we estimated that at the ecosystem level, the UF was a GHG sink while the BS was a source, showing a long-lasting effect of the fire and the importance of preserving these forest ecosystems.

Land-use change is the main driver of biodiversity loss in the tropics worldwide. Lowland rainforest regions in Southeast Asia are experiencing particularly high rates of large-scale conversion of forests and agroforests into monocultural tree plantations including oil palm and rubber with devastating effects on forest-dependent species. Canopy-dwelling organisms such as epiphytes are expected to be particularly susceptible to changes in land use, vegetation structure, and microclimate but the consequences of these changes are only poorly known for this plant group in Southeast Asia. We investigated the diversity of vascular epiphytes in four major land-use systems in Jambi Province (Sumatra, Indonesia). Epiphyte communities were sampled in 120 20 × 20 m plots in Bukit Duabelas National Park (lowland rainforest) and in surrounding jungle rubber agroforests as well as in rubber and oil palm plantations owned by smallholders. At plot level, lowland rainforest, jungle rubber, and oil palm were statistically indistinguishable in terms of richness, diversity, and evenness but had significantly higher values than rubber. Oil palm plantations had the highest epiphyte abundance, but lowest total species number of all systems. Furthermore, oil palm had distinct, fern-dominated epiphyte communities that differed significantly from the other systems. In conclusion, the value of monocultural tree plantations of oil palms and rubber trees for epiphyte conservation is very low. Jungle rubber, an extensively managed yet vanishing system, represents a refuge for epiphytes and could play a vital role in conserving epiphyte diversity, especially of ferns and orchids. Non-orchid angiosperms, however, mainly occurred in forest and are thus most threatened by forest conversion.

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.

Oil palm (Elaeis guineensis Jacq.) water use was assessed by sap flux density measurements with the aim to establish the method and derive water-use characteristics. Thermal dissipation probes were inserted into leaf petioles of mature oil palms. In the laboratory, we tested our set-up against gravimetric measurements and derived new parameters for the original calibration equation that are specific to oil palm petioles. In the lowlands of Jambi, Indonesia, in a 12-year-old monoculture plantation, 56 leaves on 10 palms were equipped with one sensor per leaf. A 10-fold variation in individual leaf water use among leaves was observed, but we did not find significant correlations to the variables trunk height and diameter, leaf azimuthal orientation, leaf inclination or estimated horizontal leaf shading. We thus took an un-stratified approach to determine an appropriate sampling design to estimate stand transpiration (Es, mm day(-1)) rates of oil palm. We used the relative standard error of the mean (SEn, %) as a measure for the potential estimation error of Es associated with sample size. It was 14% for a sample size of 13 leaves to determine the average leaf water use and four palms to determine the average number of leaves per palm. Increasing these sample sizes only led to minor further decreases of the SEn of Es. The observed 90-day average of Es was 1.1 mm day(-1) (error margin ± 0.2 mm day(-1)), which seems relatively low, but does not contradict Penman-Monteith-derived estimates of evapotranspiration. Examining the environmental drivers of Es on an intra-daily scale indicates an early, pre-noon maximum of Es rates (11 am) due to a very sensitive reaction of Es to increasing vapor pressure deficit in the morning. This early peak is followed by a steady decline of Es rates for the rest of the day, despite further rising levels of vapor pressure deficit and radiation; this results in pronounced hysteresis, particularly between Es and vapor pressure deficit.

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.

88 Pags.- 4 Figs.- 3 Tabls. The definitive version is available at: http://www.sciencedirect.com/science/journal/01678809 This article belongs to a special issue "Quantification and mitigation of greenhouse gas emissions in Mediterranean cropping systems" / Edited By Alberto Sanz-Cobena, Luis Lassaletta, Josette Garnier and Pete Smith, available at http://www.sciencedirect.com/science/journal/01678809/238/supp/C, An integrated assessment of the potential of different management practices for mitigating specific components of the total GHG budget (N2O and CH4 emissions and C sequestration) of Mediterranean agrosystems was performed in this study. Their suitability regarding both yield and environmental (e.g. nitrate leaching and ammonia volatilization) sustainability, and regional barriers and opportunities for their implementation were also considered. Based on its results best strategies to abate GHG emissions in Mediterranean agro-systems were proposed. Adjusting N fertilization to crop needs in both irrigated and rain-fed systems could reduce N2O emissions up to 50% compared with a non-adjusted practice. Substitution of N synthetic fertilizers by solid manure can be also implemented in those systems, and may abate N2O emissions by about 20% under Mediterranean conditions, with additional indirect benefits associated to energy savings and positive effects in crop yields. The use of urease and nitrification inhibitors enhances N use efficiency of the cropping systems and may mitigate N2O emissions up to 80% and 50%, respectively. The type of irrigation may also have a great mitigation potential in the Mediterranean region. Drip-irrigated systems have on average 80% lower N2O emissions than sprinkler systems and drip-irrigation combined with optimized fertilization showed a reduction in direct N2O emissions up to 50%. Methane fluxes have a relatively small contribution to the total GHG budget of Mediterranean crops, which can mostly be controlled by careful management of the water table and organic inputs in paddies. Reduced soil tillage, improved management of crop residues and agro-industry by-products, and cover cropping in orchards, are the most suitable interventions to enhance organic C stocks in Mediterranean agricultural soils. The adoption of the proposed agricultural practices will require farmers training. The global analysis of life cycle emissions associated to irrigation type (drip, sprinkle and furrow) and N fertilization rate (100 and 300 kg N ha−1 yr−1) revealed that these factors may outweigh the reduction in GHG emissions beyond the plot scale. The analysis of the impact of some structural changes on top-down mitigation of GHG emissions revealed that 3–15% of N2O emissions could be suppressed by avoiding food waste at the end-consumer level. A 40% reduction in meat and dairy consumption could reduce GHG emissions by 20–30%. Reintroducing the Mediterranean diet (i.e. ∼35% intake of animal protein) would therefore result in a significant decrease of GHG emissions from agricultural production systems under Mediterranean conditions., The authors would like to thank the Spanish National R+D+i Plan (AGL2012-37815-C05-01, AGL2012-37815-C05-04) and very specifically the workshop held in December 2016 in Butrón (Bizkaia) to synthesize the most promising measures to reduce N2O emissions from Spanish agricultural soils. BC3 is sponsored by the Basque Government. M. L. Cayuela thanks Fundación Seneca for financing the project 19281/PI/14. This paper has been produced within the context of the REMEDIA network: http://redremedia.wordpress.com/.

Drip-fertigated systems have variable distributions of water and nutrients in the soil, which influence soil microbial activity. Because there is a lack of data on greenhouse gas (GHG) fluxes for these systems, a field experiment comparing drip irrigation systems (fertigated and non-fertigated) was carried out in a melon crop. For the fertigated treatment, nitrogen (N) as NH4NO3 was dissolved in irrigation water and split into six applications (Fertigation treatment). In the non-fertigated soil (ANS treatment), granular NH4NO3 was incorporated homogeneously into the upper part of soil surface at planting. A control treatment without N fertilizer was also included. In order to evaluate the pattern of nitrous oxide (N2O) and methane (CH4), measurements were made at six different distances from the irrigation distributor point (dripper). An additional field experiment with N-15-labelled N fertilizer was carried out in parallel, with the aim of evaluating the contribution of nitrification and denitrification to the total N2O flux. Two different sources of N-15 were applied: (NH4NO3)-N-15 (20 at% excess N-15) ((NH4+)-N-15 treatment, TR1) and (NH4NO3)-N-15 (20 at% excess(15)N) ((NO3-)-N-15 treatment, TR2). Results indicated that both treatments (ANS and Fertigation) had small emission fluxes of N2O (< 0.1% of N applied). However, Fertigation produced larger emissions (175.3 g N2O-N ha(-1)) than ANS (90.1 g N2O N ha(-1)), with the pattern of N2O emission being strongly influenced by nitrification in both systems. Denitrification also contributed to emissions of (N2O)-N-15 but mainly on the day after fertilizer application in the Fertigation treatment. Methane fluxes were also affected by N fertilizer, with a decrease in the sink effect for CH4 when NH4+ was present in the soil.

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.

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. peerReviewed

Smallholder-dominated agricultural mosaic landscapes are highlighted as model production systems that deliver both economic and ecological goods in tropical agricultural landscapes, but trade-offs underlying current land-use dynamics are poorly known. Here, using the most comprehensive quantification of land-use change and associated bundles of ecosystem functions, services and economic benefits to date, we show that Indonesian smallholders predominantly choose farm portfolios with high economic productivity but low ecological value. The more profitable oil palm and rubber monocultures replace forests and agroforests critical for maintaining above- and below-ground ecological functions and the diversity of most taxa. Between the monocultures, the higher economic performance of oil palm over rubber comes with the reliance on fertilizer inputs and with increased nutrient leaching losses. Strategies to achieve an ecological-economic balance and a sustainable management of tropical smallholder landscapes must be prioritized to avoid further environmental degradation., Small-scale farmers in Southeast Asia are increasingly turning to monocultures of oil palm and rubber to maximize income. Clough and colleagues demonstrate that this land-use change in Indonesia comes at a cost to a wide array of ecosystem functions and biodiversity.

Oil palm is one important agricultural commodity that has high economic value. Oil palm productivity is significantly influenced by its water use (needs). Measurement and estimation of oil palm evapotranspiration is needed for determination of its water needs. Various methods are available and this study compare three methods, consisting of aerodynamic, Bowen-Ratio and Penman-Monteith methods in analyzing water needs/use of oil palms plantation located in PTPN VI Jambi. Peak of evapotranspiration rate occured in the afternoon around 13.00 and 14.00 local time. Bowen-Ratio method has higher estimation value of evapotranspiration than the other two methods. Ratio between evapotranspiration and global radiation of two and ten-years old oil palm plantations remain similar, around 47%. Penman Monteith method has the nearest estimation value to reference method (aerodynamic method) showed by the smallest RMSE value, 0.087 for two years oil palm and 0.157 for ten-years old oil palm.

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.

Oil palm plantations are expanding vastly in Jambi, resulted in altered surface roughness and turbulence characteristics, which may influence exchange of heat and mass. Micrometeorological measurements above oil palm canopy were conducted for the period 2013–2015. The oil palms were 12.5 years old, canopy height 13 meters and 1.5 years old canopy height 2.5 m. We analyzed the influence of surface roughness and turbulence strenght on heat (sensible and latent) fluxes by investigating the profiles and gradient of wind speed, and temperature, surface roughness (roughness length, zo, and zero plane displacement, d), and friction velocity u*. Fluxes of heat were calculated using profile similarity methods taking into account atmospheric stability calculated using Richardson number Ri and the generalized stability factor ζ. We found that roughness parameters (zo, d, and u*) directly affect turbulence in oil palm canopy and hence heat fluxes; they are affected by canopy height, wind speed and atmospheric stability. There is a negative trend of d towards air temperature above the oil palm canopy, indicating the effect of plant volume and height in lowering air temperature. We propose studying the relation between zero plane displacement d with a remote sensing vegetation index for scaling up this point based analysis.

Fertilizer and irrigation management are two of the most important factors which directly influence nitrification and denitrification processes from agricultural soils and, therefore, emissions of nitrous oxide (N2O) and nitric oxide (NO). To date, the effect of combining organic fertilizer (applied before planting) with a drip irrigation system (DI) on the emissions of these nitrogen (N) oxides has not been evaluated. The different distribution and amount of water applied with this irrigation system should produce less favourable conditions for denitrification than other irrigation systems, such as furrow irrigation (FI), and this could be used to mitigate emissions of N2O, especially following organic fertilizer application. In order to test this hypothesis, a field experiment was carried out to compare the influence of FI and DI on N2O and NO emissions using digested pig slurry (DPS) as organic fertilizer during a melon crop (Cucumis melo L. cv. Sancho) season. Plots without any N fertilizer were used as a control (control). The irrigation system influenced the water distribution pattern, producing significantly higher ammonium-N (NH4+-N) and nitrate-N (NO3−-N) concentrations in the soil under DI than under FI. Moreover, the differences observed in water filled pore space (WFPS) and mineral N also favoured a different pattern of emissions of N oxides. Only one large pulse of N2O (106.9 mg N m−2 d−1) and NO (0.81 mg N m−2 d−1) were observed for FI after the first irrigation event while several pulses were observed for DI during the entire experimental period. As a consequence, nitrous oxide emissions were 75% and 28% lower from control and DPS, respectively under DI than under FI. In contrast, NO emissions were higher for DI on some sampling dates in both treatments, but without significant differences in the cumulative NO emissions between both irrigation systems. In conclusion, this work shows that combining drip irrigation with organic fertilizer for horticultural crops in semiarid climates could be a good management strategy for three reasons: it saves water; it re-uses organic residues and it mitigates N2O emissions.

A field experiment was carried out in a non-irrigated barley crop (Hordeum vulgare L. cv Bornova) with the aims of evaluating the effects of applying organic and inorganic fertilizers on soil carbon dioxide (CO2) and methane (CH4) fluxes and assessing the residual effect of these fertilizers after the first rainfall events of autumn. Both soil CO2 and CH4 fluxes seemed to be dependent on temperature. The soils were a net sink for CH4 and the application of inorganic fertilizers reduced the sink potential. CO2 emissions increased following the application of fertilizers and after the first rainfall events in the autumn. The use of digested pig slurry caused a reduction of the CO2 equivalents produced per unit of crop yield.

Contradictory findings can be found in the literature regarding the effects of applying organic instead of mineral fertilizers on the associated emissions of nitrous oxide (N2O) and nitric oxide (NO). The main aim of this experiment was to study the effect on these emissions of applying mineral or organic fertilizers to a non-irrigated crop under Mediterranean conditions. A secondary aim was to determine whether application of the fertilizer had a residual effect on the N2O and NO pulses observed after the first rainfall events in autumn, and the magnitude of these fluxes. A field experiment was carried out with a barley crop (Hordeum vulgare L. cv Bornova). Untreated pig slurry (UPS), digested pig slurry (DPS), municipal solid waste (MSW) and composted crop residues mixed with sewage sludge (CCR + S) were applied to the soil. The resulting emissions were compared with those from a mineral fertilizer, urea (U), and a control treatment (C), in which no nitrogen was applied. Very low NO and N2O fluxes were measured during the entire experimental period in all treatments. The accumulated N2O emissions from the organic and inorganic fertilizers ranged from 266 to 345 g N2O-N ha−1 and did not show significant differences. Three of the four organic fertilizers had the positive effect of reducing NO emissions (28.82–44.48 g NO-N ha−1) compared with inorganic fertilizer (61.86 g NO-N ha−1). Nitrous oxide pulses were observed in autumn. Negative N2O fluxes were measured on several occasions. The emission factor relating N2O emissions to the N applied as fertilizer, ranged from 0.06 to 0.17% for MSW and DPS, respectively, which is much lower than the default factor proposed by the IPCC. The emission factor which relates N2O emissions to crop production ranged from 241 to 361 mg N2O-N kg−1 for DPS and U, respectively, suggesting that DPS should be promoted in order to reduce N2O emissions.

Significant climate risks are associated with a positive carbon-temperature feedback in northern latitude carbon-rich ecosystems, making an accurate analysis of human impacts on the net greenhouse gas balance of wetlands a priority. Here, we provide a coherent assessment of the climate footprint of a network of wetland sites based on simultaneous and quasi-continuous ecosystem observations of CO2 and CH4 fluxes. Experimental areas are located both in natural and in managed wetlands and cover a wide range of climatic regions, ecosystem types, and management practices. Based on direct observations we predict that sustained CH4 emissions in natural ecosystems are in the long term (i.e., several centuries) typically offset by CO2 uptake, although with large spatiotemporal variability. Using a space-for-time analogy across ecological and climatic gradients, we represent the chronosequence from natural to managed conditions to quantify the "cost" of CH4 emissions for the benefit of net carbon sequestration. With a sustained pulse-response radiative forcing model, we found a significant increase in atmospheric forcing due to land management, in particular for wetland converted to cropland. Our results quantify the role of human activities on the climate footprint of northern wetlands and call for development of active mitigation strategies for managed wetlands and new guidelines of the Intergovernmental Panel on Climate Change (IPCC) accounting for both sustained CH4 emissions and cumulative CO2 exchange.

The expansion of rubber cultivation in Southeast Asia raises concerns about the integrity of the hydrological cycle. From mainland Asia, high evapotranspiration from rubber plantations was reported. Our study was conducted in the Sumatran lowlands (Indonesia), where rubber is grown by small-holders under maritime climate. We assessed patterns of water use with sap flux methods, focusing on influences of tree age and size. We first tested a field measurement scheme in methodological experiments and subsequently applied it to 10 plots in mono-cultural rubber plantations. Among fully leaved, mature stands, maximum sap flux densities decreased with increasing tree diameter in 14- and 16-year old plantations, but not in 7- and 8-year old ones. Consequentley, tree water use increased more steeply with increasing diameter in the younger than in the older plantations. In contrast to this, among the same five mature plantations, stand-scale transpiration decreased with increasing mean tree diameter and height. This was due to a negative linear relationship between diameter and stand density. Among seven fully leaved plantations, stand age explained 95% of the site-to-site variability in transpiration. Temporally, rubber transpiration showed pronounced seasonality due to leaf shedding. Transpiration in our study was substantially lower than in rubber plantations in mainland Asia; reasons include differences in methods, management and climate. On Sumatra, rubber may be eco-hydrologically less concerning than e.g. oil palm plantations, due to low transpiration and periodical leaf shedding. Our study endorses the importance of considering age, management, climate and species in eco-hydrological assessments of tropical plantation landscapes.

Oil Palm (Elaeis guinensis Jacq) has a unique morphological characteristics, in particular it has a uniform canopy. As the plant become older, its canopy coverage will completely cover the surface and influence characteristics of its microclimate. Sensible heat flux estimation of oil palm plantation could be used to identify the contribution of oil palm in reducing or increasing heat to its surrounding environment. Determination of heat flux from oil palm plantation was conducted using two methods, Aerodynamic and Penman-Monteith. The result shows that the two methods have similar diurnal pattern. The sensible heat flux peaks in the afternoon, both for two and twelve years oil palm plantations. Sensible heat flux of young plantation is affected by atmospheric stability (stable, unstable and neutral), and is higher than that of older plantation, with mean values of 0.52 W/m2 (stable), 43.53 W/m2 (unstable), 0.63 W/m2 (neutral), with standard deviation of 0.50, 28.75 and 0.46 respectively. Sensible heat flux estimated by Penman-Monteith method in both young and older plantation was higher than the value determined by Aerodynamic method with respective value of 0.77 W/m2 (stable), 45.13 W/m2 (unstable) and 0.63 W/m2 (neutral) and 0.34 W/m2 (stable), 35.82 W/m2 (unstable) and 0.71 W/m2 (neutral).

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.

Rice paddy fields are one of the greatest anthropogenic sources of methane (CH4), the third most important greenhouse gas after water vapour and carbon dioxide. In agricultural fields, CH4 is usually measured with the closed chamber technique, resulting in discontinuous series of measurements performed over a limited area, that generally do not provide sufficient information on the short-term variation of the fluxes. On the contrary, aerodynamic techniques have been rarely applied for the measurement of CH4 fluxes in rice paddy fields. The eddy covariance (EC) technique provides integrated continuous measurements over a large area and may increase our understanding of the underlying processes and diurnal and seasonal pattern of CH4 emissions in this ecosystem. For this purpose a Fast Methane Analyzer (Los Gatos Research Ltd.) was installed in a rice paddy field in the Po Valley (Northern Italy). Methane fluxes were measured during the rice growing season with both EC and manually operated closed chambers. Methane fluxes were strongly influenced by the height of the water table, with emissions peaking when it was above 10-12 cm. Soil temperature and the developmental stage of rice plants were also responsible of the seasonal variation on the fluxes. The measured EC fluxes showed a diurnal cycle in the emissions, which was more relevant during the vegetative period, and with CH4 emissions being higher in the late evening, possibly associated with higher water temperature. The comparison between the two measurement techniques shows that greater fluxes are measured with the chambers, especially when higher fluxes are being produced, resulting in 30% higher seasonal estimations with the chambers than with the EC (41.1 and 31.8 g CH4 m-2 measured with chambers and EC respectively) and even greater differences are found if shorter periods with high chamber sampling frequency are compared. The differences may be a result of the combined effect of overestimation with the chambers and of the possible underestimation by the EC technique., JRC.H.2-Air and Climate

12 Páginas, 6 figuras y 7 tablas estadísticas, Organic fertilizers may differ greatly in composition and as a result there may also be differences in nitrogen oxides emissions following their application to soils. The aim of this study was to evaluate the influence of mineral and organic N fertilizers on the nitrification and denitrification processes, and consequently on N2O and NO emissions. Therefore, a field experiment was carried out on an irrigated sandy loam soil under Mediterranean conditions during the maize (Zea mays L.) growing season. Untreated pig slurry (UPS) both with and without the nitrification inhibitor dicyandiamide (UPS + DCD), digested thin pig slurry fraction (DTP), composted solid fraction of slurry mixed with urea (CPS + U) and composted municipal solid waste mixed with urea (MSW + U) were applied at a rate of 175 kg available N ha 1. Their emissions were compared with those from urea (U) and a control treatment to which no nitrogen fertilization was administered (Control). Accumulated nitrous oxide losses during the crop season ranged from 6.0 to 9.3 kg N2O-N ha 1 for the Control and CPS + U, respectively, whereas nitric oxide losses ranged from 0.01 to 0.23 kg NO-N ha 1, for the Control and U, respectively. The use of digested slurries mitigated N2O emission by 25% in relation to untreated pig slurry, but NO emissions were similar for both treatments. Dicyandiamide reduced N2O and NO emissions by 64 and 78% with respect to slurry without the inhibitor. An indirect effect of DCD on denitrification was also observed, with a reduction of 32% in denitrification with respect to the slurry without the inhibitor. In this case, the greatest reduction in denitrification losses occurred during the irrigation period. Composts mixed with urea reduced NO emissions by 56% (CPS + U) and 85% (MSW + U) in relation to the urea treatment, but its effect on N2O depended on the type of compost involved: CPS + U increased N2O emission by 27%, whereas MSW + U reduced it by 55% in relation to urea. Denitrification was the most important process responsible for N2O emissions when organic fertilizers were applied to the soil, while nitrification was the most important for the inorganic fertilizer. The C:N ratio of fertilizers was a good predictor of their NO emissions, denitrification losses and N2O/N2 ratio. On the other hand, added soluble N was a good predictor for cumulative N2O emissions during the period before irrigation. This work shows that an appropriate selection of organic fertilizers based on their composition could be used to mitigate emissions of the atmospheric pollutants NO and N2O in comparison with urea.

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.