Changement De Couverture Forestière Dans Le Département De La Likouala (République Du Congo) Durant La Période De 1986 À 2015

A study on the change of forest cover was carried out in the Department of Likouala, Republic of Congo for the period from 1986 to 2015. It was intended to calculate the areas of the different land conversions in the study period, but also to identify the causes of deforestation and forest land Landsat TM (1986), Etm + (2001), and Oli (2015) images were treated with the method of supervised classification "Maximum Likelihood" was applied to obtain the different maps of land type. The results revealed the lost of forest, with 133.624 hectares of intact forests in1986, 126980.89 ha of intact forests in 2001 and 114.166 ha of intact forests in 2015. There were also increases and regressions in areas of other types of land tenure. This study shows that agriculture is the main driving force for the conversion of forest land to non-forest land. Given the importance of the coverage of lost forests, it appears urgent to strengthen the sustainable management of these ecosystems with a view to combating climate change

Stock de carbone dans les gros débris ligneux végétaux : cas des forêts tropicales pluvieuses de la Likouala, République du Congo

In order to improve the knowledge of the functioning of tropical rainfall forests in the Congo basin ,a study on the quantification of the stocks of carbon in coarse woody debris was done in Likouala’s area, in Republic of Congo. To achieve this goal,14 squares plots of 50mx50m had installed on the whole study area, including ten plots in primary forest and four in secondary forests. The method used was to make an inventory of woody debris lying on the ground or Log and snags in the different study plots. There sults of this study revealed average stocks of 603.45kg MS.ha -1 in primary forests, 468.64 kg MS.ha-1 in secondaryforestsand392.68 kgMS.ha- 1 in agroforestry, with no significant differences between stocks in primary forests and secondary forests (P = 0.05). In addition this study revealed that carbon stocks varied from one locality to another in all the study area, as well as between the experimental plots (p = 0.005). This study helps to understand that the Chablis played a key role in the production of large woody debris

Dynamique du carbone organique du sol et de l’azote dans une chronoséquence de plantation de Acacia auriculiformis A. Cunn. ex Benth. (Fabaceae), à Bambou-Mingali (République du Congo)

Dans le contexte international de réchauffement global, plusieurs initiatives sont prises par les pays, les organismes internationaux pour apporter une réponse appropriée qui permettrait de limiter la hausse de la température à 1,5° C, comme le recommande le rapport 1,5° du GIEC. La République du Congo est un pays fortement engagé dans les questions de lutte contre les changements climatiques à travers la gestion durable de ses forêts, la mise en place des plantations domaniales et industrielles, à base d’espèces endogènes et exotiques à croissance rapide dont de Acacia auriculiformis A. Cunn. ex Benth. Pour évaluer l’impact des plantations de Acacia auriculiformis A. Cunn. ex Benth sur la restitution du carbone et de l’azote au sol, une étude portant sur la dynamique du carbone et de l’azote organique du sol dans les plantations de la réserve foncière de Bambou-Mingali a été réalisée. Des échantillons de sol ont été prélevés sur les horizons 0-15 cm et 15-30 cm, d’une chronoséquence de 2, 3, 4, 5, 6, 7, et 8 ans de celles-ci ainsi que sur une savane pure, conformément aux directives du GIEC qui encouragent de collecter les échantillons sol entre 0 et 30 cm de profondeur. L’objectif général de ce travail a été d’évaluer le stock de carbone organique du sol sur une chronoséquence de sept âges de plantations de Acacia auriculiformis A. Cunn. ex Benth.  In the international context of global warming, several initiatives are taken by countries, international organizations to provide an appropriate response that would limit the rise in temperature to 1.5 ° C, as recommended by the 1.5 report of the IPCC. The Republic of the Congo is a country strongly committed to issues of the fight against climate change through the sustainable management of its forests, the establishment of state and industrial plantations, based on endogenous and exotic species with rapid growth, including Acacia auriculiformis A. Cunn. ex Benth. To assess the impact of Acacia auriculiformis A. Cunn plantations. ex Benth on the return of carbon and nitrogen to the soil, a study on the dynamics of carbon and organic nitrogen in the soil in the plantations of the Bambou-Mingali land reserve was carried out. Soil samples were taken on the 0-15 cm and 15-30 cm horizons, with a chronosequence of 2, 3, 4, 5, 6, 7, and 8 years of these as well as on a pure savanna, in accordance with IPCC guidelines which encourage collecting soil samples between 0 and 30 cm depth. The general objective of this work was to assess the stock of organic carbon in the soil over a chronosequence of seven planting ages of Acacia auriculiformis A. Cunn. ex Benth.. The soil samples collected by horizon and by plot were sieved, dried and conditioned in plastic bags for laboratory determination of carbon and total nitrogen by the Walkey and Black and Kjeldahl methods, respectively. The results obtained revealed an age effect on the nitrogen (P = 0.07619), carbon (P = 0.0050) and carbon stock (P = 0.0067) contents. The nitrogen and carbon contents as well as the soil organic carbon stocks were higher in the 8-year-old plantation with averages of 1.25 ± 0.33 mgN respectively. g-1; 15.87 ± 6.08 mgC.g-1 and 28.70 ± 9.48 t.ha-1 and lower in the 6-year-old plot respectively at 0.93 ± 0.05 mgN.g-1; 7.87 ± 0.58 mgC.g-1 and 15.57 ± 1.31 t.ha-1. The study also revealed a horizon effect on carbon and nitrogen contents with respective P-values of 0.0019 and 0.00015. The H0 horizon (0-15 cm) presented the highest stocks whatever the age of the plantation with an average of 32.98 ± 6.56 t.ha-1 in the 8-year-old plot against 16, 46 ± 1.13 t.ha-1 in the 6-year-old plot and on the H1 horizon (15-30 cm) an average of 24.42 ± 11.26 t.ha-1 in the 8-year-old plot against 14 , 69 ± 0.83 t.ha-1 in the 6-year-old plot. Also the C / N ratio is influenced by the age (P-value = 0.008) of the plantation and not by the horizon (P-value = 0.1243). Whatever the parameter considered, it emerges that age influences the return of carbon and nitrogen to the soil. Thus, there is an accumulation of carbon in the plantations of the Acacia auriculiformis chronosequence

Amount of Soil Carbon Stock within Primary and Secondary Forest in the North of the Republic of Congo

The amount of carbon stock under different land type’s cover was studied in the north east of Republic of Congo. Samples of soil from the surface 0-15 cm horizon were collected under 12 land types classes. Results showed that the lowest soil C was noted in flooded primary forests of Lophira alata Banks ex Gaertu. With an amount of 17.21 t C ha-1, and the highest values were noted in the savanna of Jardinea congoensis with an amount of 117.6 t C ha-1 and the primary forest of Guibourtia demeusei (Harms) Léon. With 116.16 t C ha-1 (p < 0.05).Our study revealed the importance of carbon stock in different type of land in tropical area to reduce the emission of CO2 from the conversion of forestland to another type of land

Diversité floristique et dynamique de reconstitution de la forêt du Parc Zoologique sous plantations à eucalyptus à Brazzaville, Congo

La forêt du Parc Zoologique est l’une des forêts naturelles reliques intra urbaines de la ville de Brazzaville. Cet écosystème subit une pression anthropique due aux besoins croissants en bois énergie, en bois d’artisanat et en plantes utilisées en phytothérapie. Les zones les plus dégradées ont été reboisées en eucalyptus. Il a été constaté que dans le sous bois des forêts à eucalyptus, se réalise la reconstitution de la forêt naturelle. Une étude diachronique a été effectuée pour suivre cette reconstitution. Des placettes de 600 m² d’âges différents ont été délimitées dans ces plantations, dans lesquelles ont été notées toutes espèces de forêt naturelle existantes, leurs diamètres à la hauteur de la poitrine et leur nombre d’individus. Les résultats obtenus montrent que les types morphologiques des ligneux augmentent avec l’âge de la plantation d’eucalyptus tandis que les formes herbacées décroissent avec l’augmentation de l’âge. De même, le nombre de types biologiques varient avec l’âge de la plantation à eucalyptus. En suivant les trois espèces dominantes de cette forêt naturelle (Millettia laurentii et Markhamia tomentosa et Bosqueiopsis gillettii), on constate qu’elles possèdent plusieurs plantules dans le sous-bois des plantations d’eucalyptus, mais très peu de celles-ci n’arrivent au stage macrophanérophytes du fait du taux de mortalité élevé. Un schéma de reconstitution forestière a été proposé à partir des observations faites de cette forêt.© 2016 International Formulae Group. All rights reserved.Mots clés: Diversité floristique, dynamique de reconstitution, forêt naturelle, plantations à Eucalyptus, BrazzavilleEnglish Title:  Floristic diversity and reconstitution dynamics of the Zoological Park Forest under eucalyptus cultivation in Brazzaville, CongoEnglish AbstractThe Zoological Park forest is a natural relic’s forest established at the center of Brazzaville’s city. This ecosystem is undergoing anthropogenic pressure due to the growing needs in wood energy, wooden crafts and plants used in herbal medicine. The more degraded areas were reforested with eucalyptus. It was found in the undergrowth of eucalyptus forests, the replenishment of natural forest. A diachronic study was made to follow this reconstruction. Plots of 600 m2 of different ages have been delineated in these plantations, in which all species of existing natural forest, DBH and the number of individuals were recorded. The results obtained show that morphological types of woody increase with age of the eucalyptus plantation while herbaceous forms decrease with increasing age. Similarly, the numbers of biological types vary with the age of the eucalyptus plantation. By following the three dominant species of this natural forest (Millettia laurentii) and Markhamia tomentosa and Bosqueiopsis gillettii, there they have several plants in the understory of eucalyptus plantations, but very few of these seedlings reach stage macrophanerophytes by virtue of the high mortality rate. A forest recovery scheme has been proposed from the observations of this forest.© 2016 International Formulae Group. All rights reserved.Keywords: Diversity floristic, dynamic of recovery, natural forest, plantations with Eucalyptus, Brazzavill

Quantification Des Stocks De Carbone De Trois Pools Clés De Carbone En Afrique Centrale : Cas De La Forêt Marécageuse De La Likouala (Nord Congo)

The data of carbon stock of central African swamps forests are very few. This study carried out an assessment of the carbon stock of living biomass and coarse woody debris of three biotopes (flooded forest, seasonal flooded forest, and terra firm forest) of Likouala swamp forest (North of Congo). The average of the carbon stock are 190.72±98.7 tC/ha, 39.69±21.24 tC/ha, and 9.45±6.6 tC/ha respectively for above ground, billow ground, and coarse woody debris. The carbon stock of our swamp forest tends to increase generally from the flooded forest to the terra firm forest. In addition, the average of the coarse woody debris carbon stock increases with the increasing of the above ground carbon stock

First estimates of fine root production in tropical peat swamp and terra firme forests of the central Congo Basin

Tropical peatlands are carbon-dense ecosystems because they accumulate partially-decomposed plant material. A substantial fraction of this organic matter may derive from fine root production (FRP). However, few FRP estimates exist for tropical peatlands, with none from the world's largest peatland complex in the central Congo Basin. Here we report on FRP using repeat photographs of roots from in situ transparent tubes (minirhizotrons), measured to 1 m depth over three one-month periods (spanning dry to wet seasons), in a palm-dominated peat swamp forest, a hardwood-dominated peat swamp forest, and a terra firme forest. We find FRP of 2.6 ± 0.3 Mg C ha-1 yr-1, 1.9 ± 0.5 Mg C ha-1 yr-1, and 1.7 ± 0.1 Mg C ha-1 yr-1 in the three ecosystem types respectively (mean ± standard error; no significant ecosystem type differences). These estimates fall within the published FRP range worldwide. Furthermore, our hardwood peat swamp estimate is similar to the only other FRP study in tropical peatlands, also hardwood-dominated, from Micronesia. We also found that FRP decreased with depth and was the highest during the dry season. Overall, we show that minirhizotrons can be used as a low-disturbance method to estimate FRP in tropical forests and peatlands

First Evidence of Peat Domes in the Congo Basin using LiDAR from a fixed-wing drone

This work was funded by CongoPeat, a NERC Large Grant (NE/R016860/1) to S.L.L. and E.T.A.M. (UAV data collection, I.J.D. time), a NERC Open CASE Studentship to S.L.L., I.L. and G.D. and a Phillip Leverhulme Prize to S.L.L. (peat depths).The world’s most extensive tropical peatlands occur in the Cuvette Centrale depression in the Congo Basin, which stores 30.6 petagrams of carbon (95% CI, 6.3–46.8). Improving our understanding of the genesis, development and functioning of these under-studied peatlands requires knowledge of their topography and, in particular, whether the peat surface is domed, as this implies a rain-fed system. Here we use a laser altimeter mounted on an unmanned airborne vehicle (UAV) to measure peat surface elevation along two transects at the edges of a peatland, in the northern Republic of Congo, to centimetre accuracy and compare the results with an analysis of nearby satellite LiDAR data (ICESat and ICESat-2). The LiDAR elevations on both transects show an upward slope from the peatland edge, suggesting a surface elevation peak of around 1.8 m over ~20 km. While modest, this domed shape is consistent with the peatland being rainfed. In-situ peat depth measurements and our LiDAR results indicate that this peatland likely formed at least 10,000 years BP in a large shallow basin ~40 km wide and ~3 m deep.Publisher PDFPeer reviewe

Tropical peatlands and their conservation are important in the context of COVID-19 and potential future (zoonotic) disease pandemics.

The COVID-19 pandemic has caused global disruption, with the emergence of this and other pandemics having been linked to habitat encroachment and/or wildlife exploitation. High impacts of COVID-19 are apparent in some countries with large tropical peatland areas, some of which are relatively poorly resourced to tackle disease pandemics. Despite this, no previous investigation has considered tropical peatlands in the context of emerging infectious diseases (EIDs). Here, we review: (i) the potential for future EIDs arising from tropical peatlands; (ii) potential threats to tropical peatland conservation and local communities from COVID-19; and (iii) potential steps to help mitigate these risks. We find that high biodiversity in tropical peat-swamp forests, including presence of many potential vertebrate and invertebrate vectors, combined, in places, with high levels of habitat disruption and wildlife harvesting represent suitable conditions for potential zoonotic EID (re-)emergence. Although impossible to predict precisely, we identify numerous potential threats to tropical peatland conservation and local communities from the COVID-19 pandemic. This includes impacts on public health, with the potential for haze pollution from peatland fires to increase COVID-19 susceptibility a noted concern; and on local economies, livelihoods and food security, where impacts will likely be greater in remote communities with limited/no medical facilities that depend heavily on external trade. Research, training, education, conservation and restoration activities are also being affected, particularly those involving physical groupings and international travel, some of which may result in increased habitat encroachment, wildlife harvesting or fire, and may therefore precipitate longer-term negative impacts, including those relating to disease pandemics. We conclude that sustainable management of tropical peatlands and their wildlife is important for mitigating impacts of the COVID-19 pandemic, and reducing the potential for future zoonotic EID emergence and severity, thus strengthening arguments for their conservation and restoration. To support this, we list seven specific recommendations relating to sustainable management of tropical peatlands in the context of COVID-19/disease pandemics, plus mitigating the current impacts of COVID-19 and reducing potential future zoonotic EID risk in these localities. Our discussion and many of the issues raised should also be relevant for non-tropical peatland areas and in relation to other (pandemic-related) sudden socio-economic shocks that may occur in future

Age, extent and carbon storage of the central Congo Basin peatland complex

Peatlands are carbon-rich ecosystems that cover just three per cent of Earth's land surface, but store one-third of soil carbon. Peat soils are formed by the build-up of partially decomposed organic matter under waterlogged anoxic conditions. Most peat is found in cool climatic regions where unimpeded decomposition is slower, but deposits are also found under some tropical swamp forests. Here we present field measurements from one of the world's most extensive regions of swamp forest, the Cuvette Centrale depression in the central Congo Basin. We find extensive peat deposits beneath the swamp forest vegetation (peat defined as material with an organic matter content of at least 65 per cent to a depth of at least 0.3 metres). Radiocarbon dates indicate that peat began accumulating from about 10,600 years ago, coincident with the onset of more humid conditions in central Africa at the beginning of the Holocene. The peatlands occupy large interfluvial basins, and seem to be largely rain-fed and ombrotrophic-like (of low nutrient status) systems. Although the peat layer is relatively shallow (with a maximum depth of 5.9 metres and a median depth of 2.0 metres), by combining in situ and remotely sensed data, we estimate the area of peat to be approximately 145,500 square kilometres (95 per cent confidence interval of 131,900-156,400 square kilometres), making the Cuvette Centrale the most extensive peatland complex in the tropics. This area is more than five times the maximum possible area reported for the Congo Basin in a recent synthesis of pantropical peat extent. We estimate that the peatlands store approximately 30.6 petagrams (30.6 × 10(15) grams) of carbon belowground (95 per cent confidence interval of 6.3-46.8 petagrams of carbon)-a quantity that is similar to the above-ground carbon stocks of the tropical forests of the entire Congo Basin. Our result for the Cuvette Centrale increases the best estimate of global tropical peatland carbon stocks by 36 per cent, to 104.7 petagrams of carbon (minimum estimate of 69.6 petagrams of carbon; maximum estimate of 129.8 petagrams of carbon). This stored carbon is vulnerable to land-use change and any future reduction in precipitation