How does replacing natural forests with rubber and oil palm plantations affect soil respiration and methane fluxes?

This research was conducted under the REDD-ALERT project (Grant Agreement # 226310) with financial support from the European Commission Seventh Framework Programme [FP7/2007-2013]. It was also generously funded by the Australian Agency for International Development (AusAID) (Grant Agreement # 46167) and the Norwegian Agency for Development Cooperation (NORAD) (Grant Agreement #QZA-10/0468). This work is part of the Consultative Group on International Agricultural Research (CGIAR) programs on Trees, Forests and Agroforestry (FTA) and Climate Change, Agriculture and Food Security (CCAFS). Authors extend their gratitude to staff from Brawijaya University in Malang, the Indonesian Soil Research Institute (ISRI) in Bogor, and Balai Lingkungan Pertanian in Jakenan for laboratory support. We also thank Robbin Matthews and John Hillier, whose insights, feedbacks and recommendations contributed to improve the quality of the manuscript and to the modeling team of the School of Biological and Environmental Science from the University of Aberdeen for constructive discussions. Furthermore, we are very thankful to all assistants and to the REDD-ALERT Indonesia team who supported field work in Jambi. Finally, we are very grateful to the two anonymous reviewers for their constructive comments which contributed to improve this manuscript.Peer reviewedPublisher PD

Characterizing degradation of palm swamp peatlands from space and on the ground: an exploratory study in the Peruvian Amazon

Peru has the fourth largest area of peatlands in the Tropics. Its most representative land cover on peat is a Mauritia flexuosa dominated palm swamp (thereafter called dense PS), which has been under human pressure over decades due to the high demand for the M. flexuosa fruit often collected by cutting down the entire palm. Degradation of these carbon dense forests can substantially affect emissions of greenhouse gases and contribute to climate change. The first objective of this research was to assess the impact of dense PS degradation on forest structure and biomass carbon stocks. The second one was to explore the potential of mapping the distribution of dense PS with different degradation levels using remote sensing data and methods. Biomass stocks were measured in 0.25 ha plots established in areas of dense PS with low (n = 2 plots), medium (n = 2) and high degradation (n = 4). We combined field and remote sensing data from the satellites Landsat TM and ALOS/PALSAR to discriminate between areas typifying dense PS with low, medium and high degradation and terra firme, restinga and mixed PS (not M. flexuosa dominated) forests. For this we used a Random Forest machine learning classification algorithm. Results suggest a shift in forest composition from palm to woody tree dominated forest following degradation. We also found that human intervention in dense PS translates into significant reductions in tree carbon stocks with initial (above and below-ground) biomass stocks (135.4 ± 4.8 Mg C ha−1) decreased by 11 and 17% following medium and high degradation. The remote sensing analysis indicates a high separability between dense PS with low degradation from all other categories. Dense PS with medium and high degradation were highly separable from most categories except for restinga forests and mixed PS. Results also showed that data from both active and passive remote sensing sensors are important for the mapping of dense PS degradation. Overall land cover classification accuracy was high (91%). Results from this pilot analysis are encouraging to further explore the use of remote sensing data and methods for monitoring dense PS degradation at broader scales in the Peruvian Amazon. Providing precise estimates on the spatial extent of dense PS degradation and on biomass and peat derived emissions is required for assessing national emissions from forest degradation in Peru and is essential for supporting initiatives aiming at reducing degradation activities

Emissions de gaz à effet de serre par le sol et stockage de carbone en caféiculture conduite sur des Andosols en climat tropical

Coffee plantations represent 7.5% of the world's permanent crops and generally use large amounts of N fertilizer (up to 350 kg N ha-1 y-1). Coffee is often grown under the shade of N fixing trees. The contribution of N fixing plants to N2O emissions is a growing concern in the sustainable development framework. To date results in the literature are contradictory. We, therefore, studied the greenhouse gas (GHG) balance in two highly fertilized (250 kg N ha-1 y-1) coffee plantations, in Costa Rica: a monoculture and a plantation shaded by the N2 fixing legume species Inga densiflora. We periodically measured soil fluxes of N2O, CH4 and CO2, their edaphic determinants (gravimetric moisture, water-filled pore space, temperature and mineral nitrogen content) and soil N mineralization rates. In addition, we characterized, in the laboratory, the biological parameters of nitrification-denitrification and their related N2O and N2 production in order to simulate continuous N2O emissions using the models NGAS and NOE for a one year period. We also assessed soil C dynamic and C accumulation in biomass and litter. Our measurements showed a very large contribution of fertilizer induced N2O emissions, on average 77%, to the annual budgets (4.3 ± 0.3 and 5.8 ± 0.5 kg N2O-N ha-1 y-1, in the monoculture and the shaded plantation, respectively). The fertilizations also temporarily increased soil respiration rates. The low values of the biological activities (notably denitrification potentials < 1 kg N ha-1 d-1) explained that the observed N2O fluxes were always smaller than 300 g N ha-1 d-1 in environmental conditions yet favourable to N2O production (high soil temperature, moisture and nitrate content). The similarity of the biological activities measured in both coffee plantations and also the similar annual N2O budgets derived through measurements and modelling suggests only a small magnitude effect of the N2 fixing legume tree species on N2O emissions. The sum of soil non CO2 GHG fluxes and C storage in the shaded culture (11.93 ± 2.17 Mg CO2-equivalent ha-1 y-1) was 4 times larger than the total GHG balance in the monoculture (2.67 ± 1.94 Mg CO2-equivalent ha-1 y-1). Our results therefore confirm that coffee grown in an agroforestry system, on an Andosol, increases the GHG sink and that, for the current context, the use of an N2 fixing legume species as shade tree does not contradict this observation.La caféiculture représente 7,5% des cultures permanentes mondiales et utilise généralement de grandes quantités de fertilisants azotés (jusqu'à 350 kg N ha-1 an-1). La caféiculture est souvent pratiquée sous couvert d'arbres dont certains sont fixateurs d'azote. La contribution des plantes fixatrices d'azote aux émissions de N2O est un sujet prégnant dans le cadre du développement durable, avec des résultats dans la littérature qui peuvent parfois apparaître contradictoires. Dans ce contexte, nous avons étudié le bilan des gaz à effet de serre (GES) dans deux cultures caféières fortement fertilisées (250 kg N ha-1 an-1), au Costa Rica : une monoculture et une culture ombragée par l'espèce légumineuse fixatrice de N2 Inga densiflora. Nous avons mesuré périodiquement les flux de N2O, CH4 et CO2 à l'interface solatmosphère, leurs déterminants édaphiques (humidité gravimétrique, espace poral occupé par l'eau, température et teneur en azote minéral) et les taux de minéralisation de l'azote dans le sol. Par ailleurs, nous avons caractérisé, au laboratoire, les paramètres biologiques de nitrification-dénitrification et leur production associée de N2O et N2 pour simuler en continu les émissions de N2O avec les modèles NGAS et NOE sur une durée d'un an. Enfin, nous avons évalué la dynamique du C du sol et l'accumulation de C dans les biomasses et la litière. Nos mesures ont montré une très forte contribution de la fertilisation azotée aux émissions de N2O, soit une proportion moyenne de 77% des bilans annuels (4,3 ± 0,3 et 5,8 ± 0,5 kg N-N2O ha-1 an-1, respectivement dans la monoculture et la culture ombragée). Les fertilisations ont également augmenté temporairement la respiration du sol. Les valeurs faibles des activités biologiques (notamment des potentiels de dénitrification < 1 kg N ha-1 j-1) ont expliqué les flux toujours inférieurs à 300 g N ha-1 j-1 observés dans des conditions environnementales pourtant favorables à la production de N2O (température, humidité et teneur en nitrate du sol élevées). La similarité entre les activités biologiques mesurées sur les deux cultures de café ainsi que celle entre les bilans annuels de N2O établis à partir de mesures et de modélisation permettent de conclure sur un effet de faible ampleur de l'espèce légumineuse fixatrice de N2 sur les émissions de N2O. Le bilan des flux de GES hors CO2 à l'interface sol-atmosphère et du stockage de C de la culture ombragée (11,93 ± 2,17 Mg CO2-equivalent ha-1 an-1) a été 4 fois supérieur au bilan de la monoculture (2,67 ± 1,94 Mg CO2-equivalent ha-1 an-1). Nos résultats tendent donc à confirmer que la culture de café conduite en agroforesterie, sur un Andosol, augmente le puits de GES et que, dans le contexte présent, l'utilisation d'une légumineuse fixatrice de N2 comme espèce ombragère ne contredit pas cette observation

Greenhouse gas emission factors for land use and land-use change in Southeast Asian peatlands

Tropical peat swamp forests, which are predominantly located in Southeast Asia (SEA) and play a prominent role as a global carbon store, are being intensively degraded and converted to agricultural lands and tree plantations. For national inventories, updated estimates of peat emissions of greenhouse gases (GHG) from land use (LU) and land-use change in the tropics are required. In this context, we reviewed the scientific literature and calculated emission factors of peat net emissions of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) in seven representative LU categories for SEA i.e. intact peat swamp forest, degraded forest (logged, drained and affected by fire), mixed croplands and shrublands, rice fields, oil palm, Acacia crassicarpa and sago palm plantations. Peat net CO2 uptake from or emissions to the atmosphere were assessed using a mass balance approach. The balance included main peat C inputs through litterfall and root mortality and outputs via organic matter mineralization and dissolved organic carbon

Changes in soil CH4fluxes from the conversion of tropical peat swamp forests: a meta-analysis

Cambodia: AngkorGrayscaleForman Safety Negatives, Box

Emissions de gaz à effet de serre par le sol et stockage de carbone en caféiculture conduite sur des andosols en climat tropical

MONTPELLIER-SupAgro La Gaillarde (341722306) / SudocSudocFranceF