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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.

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)

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.

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.

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/.

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.

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.

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.

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.

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