Spatial Prediction of Soil Organic Carbon Stock in the Moroccan High Atlas Using Machine Learning

Soil organic carbon (SOC) is an essential component, which soil quality depends on. Thus, understanding the spatial distribution and controlling factors of SOC is paramount to achieving sustainable soil management. In this study, SOC prediction for the Ourika watershed in Morocco was done using four machine learning (ML) algorithms: Cubist, random forest (RF), support vector machine (SVM), and gradient boosting machine (GBM). A total of 420 soil samples were collected at three different depths (0-10 cm, 10-20 cm, and 20-30 cm) from which SOC concentration and bulk density (BD) were measured, and consequently SOC stock (SOCS) was determined. Modeling data included 88 variables incorporating environmental covariates, including soil properties, climate, topography, and remote sensing variables used as predictors. The results showed that RF (R-2 = 0.79, RMSE = 1.2%) and Cubist (R-2 = 0.77, RMSE = 1.2%) were the most accurate models for predicting SOC, while none of the models were satisfactory in predicting BD across the watershed. As with SOC, Cubist (R-2 = 0.86, RMSE = 11.62 t/ha) and RF (R-2 = 0.79, RMSE = 13.26 t/ha) exhibited the highest predictive power for SOCS. Land use/land cover (LU/LC) was the most critical factor in predicting SOC and SOCS, followed by soil properties and bioclimatic variables. Both combinations of bioclimatic-topographic variables and soil properties-remote sensing variables were shown to improve prediction performance. Our findings show that ML algorithms can be a viable tool for spatial modeling of SOC in mountainous Mediterranean regions, such as the study area

Éstimation du stock de carbone organique dans les iliçaies du Moyen Atlas marocain

18 páginas, 10 tablas, 8 figuras.[EN] This study was conducted in Quercus ilex Moroccan ecosystem of Middle Atlas, with the aim the determinination of organic carbon stock in the different components (soil, litter and biomass). The best correlations were obtained by allometric regressions of the type : Y (carbomasse) = a[C1.30]b for each fraction of the tree biomass between all stands. The total carbomass of aboveground stands (Quercus ilex, cedar, cedar oxycèdre) varies between 50 and 156 tC.ha-1 respectively for Reggada and Ajdir ; more than 40 % of carbon is sequestered in the cedar forest to Dayat Hachlaf and Ajdir. Thus, It appears from this study that the soil organic carbon stock (SOCS) varies from 52 tC.ha-1 for Reggada to 141 tC.ha-1 for Ajdir. More than 75 % of SOCS is stored in the first 30 centimeters. The correlative approach shows that SOCS are strongly dependent on the soil depth fof the different forest stands. They decreased following an exponential curve with a negative exponent in all stands. The litter organic carbon stock (LCS) varies from 3.5 tC.ha-1 for Reggada to 14.3 tC.ha-1 for Ajdir. The stock of total organic carbon soil (SOCS + LCS + root carbomass) is between 50 and 69 % of the total organic carbon stock in the Quercus ilex ecosystems of Middle Atlas. The stock of total organic carbon (soil, litter and biomass (aboveground and root) in the forest ecosystems studied varied among 116 tC.ha-1 in Reggada to 273 tC.ha-1 in Ajdir.Thus, the STOC vary considerably with the total basal area of the stands.[FR]La présente étude a été réalisée dans l’écosystème de la chênaie verte du Moyen Atlas marocain, avec pour objectif la détermination du stock de carbone organique dans les différentes compartiments (sols, litière et biomasse). Les meilleurs corrélations ont été obtenues avec des régressions allométriques de type : Y(carbomasse) = a[C1,30]b pour les différentes composantes épigée des iliçaies du Moyen. La carbomasse totale de la partie aérienne des peuplements (chêne vert, cèdre et oxycèdre) varie entre 50 et 156 tC.ha-1 respectivement pour Reggada et Ajdir ; dont plus de 40 % du carbone est séquestrée dans la cédraie pour Dayat Hachlaf et Ajdir. Ainsi, Il en ressort de cette étude que le stock de carbone des sols (SCOS) varie de 52 tC.ha-1 pour Reggada à 141 tC.ha-1 pour Ajdir. Plus de 75 % du SCOS est emmagasiné dans les 30 premiers centimètres. L’approche corrélative montre que les SCOS sont fortement dépendants de la profondeur pour les différents sites d’études. Les SCOS diminuent avec la profondeur en suivant une courbe exponentielle à exposant négatif pour toutes les parcelles. Le stock de carbone organique dans la litière au sol (SCL) varie de 3,5 tC.ha-1 pour Reggada à 14,3 tC.ha-1 pour Ajdir. Le stock du carbone organique total des sols (SCOS + SCL + carbomasse racinaire) représente entre 50 et 69 % du stock de carbone organique total des écosystèmes d’iliçaies du Moyen Atlas. Le stock de carbone organique total (sol, litière et biomasse (aérienne et racinaire)) dans les écosystèmes étudiés varie entre 116 tC.ha-1 pour Reggada et 273 tC.ha-1 pour Ajdir. Ainsi, il augmente linéairement avec la surface terrière totale des peuplements.Peer reviewe

Organic Carbon Storage in Evergreen Oak Forest Ecosystems of the Middle and High Moroccan Atlas Areas

14 páginas, con 7 figuras y 5 tablasWe report carbon stock in biomass, litter and soil estimated for six locations in natural Quercus ilex L. stands of the Middle and High Moroccan Atlas. Twenty trees at each location were selected according to their diameter classes and felled to measure the biomass of trunk, branches, twigs and leaves and determine allometric relationships. Soil was sampled in five depths (0 - 15, 15 - 30, 30 - 50, 50 - 70 and 70 - 100 cm) and litterfall production measured in all tree stands. The total carbon stock in above-ground biomass ranged between 17 Mg∙ha−1 in Aït Aamar stand (High Atlas) and 91 Mg∙ha−1 in Ksiba stand (Middle Atlas). Perennial organs (trunk, branches and twigs) stored over 95% of the tree carbon stock. Soil organic carbon concentrations ranged from 0.01% (in 70 - 100 cm in all stands) to 8.1% (in 0 - 15 cm in the Ajdir stand in Middle Atlas). The total organic carbon stock in the soil ranged between 141.4 t∙ha−1 in Ajdir and 24.6 t∙ha−1 in Asloul. The litter contained 0.2 Mg C ha−1 in the clearing (C2) stand of High Atlas and 14.3 Mg C ha−1 in (Ajdir) of carbon. The best fitted model for predicting carbon stock in tree biomass was obtained by applying the allometric equation Y = aXb for each biomass fraction and stand, where Y is the aboveground biomass (dry weight) and X is the DBH (Mean diameter at breast height, 1.30 m). These previous data obtained in the present study confirm the important function of these natural forests as longterm C sinks, in forest biomass, litter and soil. The potential long term C storage of these systems is moderately high, especially in less-intensively managed forests that include large trees. The established relationship between DBH and carbon stock in different tree organs can be used for forest carbon accounting, and also synthesize available information on oak forest as a sink for atmospheric CO2, and identify the management options that may enhance the capacity for C capture/ storage in forest soils.Peer reviewe

Carbon storage in degraded cork oak (Quercus suber) forests on flat lowlands in Morocco

The present study aims to quantify the carbon stored in a degraded cork oak (Quercus suber L.) ecosystem in the north west of Morocco, in view of potential management implications. To this end, carbon stocks were evaluated in the first 100 cm of the soil, the cork oak trees, and the understorey species (both above- and belowground). Results show that the total carbon stocks in the cork oak ecosystem ranges from 65 to 237 Mg ha-1 with a mean value of 121 Mg ha-1. The first 100 cm of the soil (including the forest floor) represents the largest carbon pool (~51% of the total organic carbon) of the ecosystem. Tree biomass (above- and belowground tissues of cork oak) represents the second largest pool (47%), whereas the contribution of the understorey is less than 2%. Within the first 100 cm of the soil, over 87% of all the soil organic carbon is situated in the first 40 cm of the soil depth. The amount of carbon stored here ranges from 30 to 110 Mg ha-1and these organic carbon stocks vary considerably with the stand basal area of the cork oak (R2 = 0.82). In practice, the carbon stocks of the different pools considered are strongly correlated with the stand density of the cork oak stands. In the semi-arid forest ecosystems of our study, management prescriptions aiming at increasing the standing biomass of the cork oak should thus considerably contribute, both directly through tree biomass and indirectly through increased soil organic matter, to efficient carbon sequestration

The potential of Eucalyptus plantations to restore degraded soils in semi-arid Morocco (NW Africa)

Key message Short-rotation forestry using eucalyptus in degraded oak forests in the semi-arid area of NW Morocco can be a useful strategy to avoid further degradation and carbon loss from this ecosystem, but it might be constrained by nutrient and water supply in the long term.[br/] Context Land degradation and deforestation of natural forests are serious issues worldwide, potentially leading to altered land use and carbon storage capacity.[br/] Aims Our objectives were to investigate if short-rotation plantations can restore carbon pools of degraded soils, without altering soil fertility.[br/] Methods Carbon and nutrient pools in above- and below-ground biomass and soils were assessed using stand inventories, harvested biomass values, allometric relationships and selective sampling for chemical analyses.[br/] Results Carbon pools in the total ecosystem were low in the degraded land and in croplands (6–13 Mg ha−1) and high in forests (66–94 in eucalyptus plantations; 86–126 in native forests). The soil nutrient status of eucalyptus stands was intermediate between degraded land and native forests and increased over time after eucalyptus introduction. All harvest scenarios for eucalyptus are likely to impoverish the soil but, for the moment, the soil nutrient status has not been affected.[br/] Conclusion Afforestation of degraded land with eucalyptus can be a useful restoration tool relative to carbon storage and soil fertility, provided that non-intensive forestry is applied

Rare images of an intense 18F-FDG PET-scan uptake in an incidentally discovered thyroid lesion: A case report

Thyroid carcinoma is a type of cancer that starts in the cells of the thyroid gland, which plays a crucial role in regulating the body's metabolism. Thyroid cancer can manifest in various forms. We report the case of an 89 year-old patient presenting an incidental intense Fluorine-18-fluorodeoxyglucose (18F-FDG) PET-computed tomography (PET-CT) uptake within a thyroid lesion and the role of 18F-FDG PET-CT guiding the anatomopathological examination. The prevalence of FDG-avid thyroid incidentaloma ranges between 0.2% and 8.9%. Higher risks of cancer seems to be related to focal or unilateral uptake of 18F-FDG. Lesions with higher standardized uptake values or suspicious CT are more likely to be cancers. The diagnosis is clinically challenging. Nuclear and radiological images can guide practitioners