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Asynchronous xylogenesis among and within tree species in the central Congo Basin
Get PDFBackground Xylogenesis is synchronous among trees in regions with a distinct growing season, leading to a forest wide time lag between growth and carbon uptake. In contrast, little is known about interspecifc or even intraspecifc variability of xylogenesis in tropical forests. Yet an understanding of xylogenesis patterns is key to successfully com bine bottom-up (e.g., from permanent forest inventory plots) and top-down (e.g., from eddy covariance fux towers) carbon fux estimates. Methods Here, we monitor xylogenesis development of 18 trees belonging to 6 abundant species during 8 weeks at the onset of the rainy season from March to April 2022 in a semideciduous rainforest in the Yangambi reserve (cen tral Democratic Republic of the Congo). For each tree, the weekly cambial state (dormant or active) was determined by epifuorescence microscopy. Results We fnd interspecifc variability in the cambial phenology, with two species showing predominant cam bial dormancy and two species showing predominant cambial activity during the monitoring period. We also fnd intraspecifc variability in two species where individuals either display cambial dormancy or cambial activity. All trees kept>60% of their leaves throughout the dry season and the monitoring period, suggesting a weak relationship between the phenology of the cambial and foliar. Our results suggest that individual trees in Yangambi asynchro nously activate their cambial growth throughout the year, regardless of leaf phenology or seasonal rainfall. Conclusion These results are consistent with global analysis of gross primary productivity estimates from eddy covar iance fux towers, showing that tropical biomes lack a synchronous dormant period. However, a longer-term monitor ing experiment, including more species, is necessary to confrm this for the Congo Basin. As Yangambi is equipped with facilities for microscopic wood analysis, a network of inventory plots and a fux tower, further research in this site will reveal how xylogenesis patterns drive annual variability in carbon fuxes and how ground-based and top-down measurements can be combined for robust upscaling analysis of Congo basin carbon budgets. Keywords Cambial phenology, Tropical forest, Yangambi, Carbon storage, Congo Basi
Living with landslides: land use on unstable hillslopes in a rural tropical mountainous environment in DR Congo
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Is morphological-based taxonomy still effective in modern times? A response to Parrinha <i>et al.</i> (2025)
No full textWe reevaluate the recent species description of Holaspis ngalangi from Angola by Parrinha et al. (2025), which was based solely on variable morphological characters, through comparative analysis of specimens across the genus' range, including material previously examined but not reported by the original authors. Our analysis demonstrates that the proposed diagnostic traits of this species (precloacal scale morphology and ventral scale arrangement) are hyper-variable within both H. guentheri and H. laevis, showing neither biogeographic nor morphological consistency. Notably, specimens from Angola's Dundo Museum, though examined by Parrinha et al. (2025), were omitted from their analysis despite exhibiting the same variable characteristics, strongly indicating these represent intraspecific variation rather than diagnostic species-lineage features. Consequently, we formally place Holaspis ngalangi Parrinha, Marques, Gon-çalves, Tuitenko, Bauer & Ceríaco, 2025 as a junior synonym of Holaspis guentheri Gray, 1863, representing the second recent case of an Angolan reptile species description based solely on morphological data being synonymised within the last decade. These repeated cases highlight the inherent risks of morphology-only taxonomy, particularly when: (1) diagnostic characters show extensive overlap among taxa, and (2) multiple lines of evidence are not incorporated. Our findings also emphasize the critical need for robust, integrative species delimitation approaches in understudied regions like Angola, where high levels of cryptic diversity and phenotypic plasticity are likely to complicate taxonomic assessments
République Démocratique du Congo, Carte administrative , Province de Lualaba, Territoire de Kapanga
No full textCross-Validation of GEMS Total Ozone from Ozone Profile and Total Column Products Using Pandora and Satellite Observations
Get PDFThis study presents a comprehensive validation of total ozone columns from ozone profile (O3P) and total ozone column (O3T) products measured by the Geostationary Environment Monitoring Spectrometer (GEMS), through comparisons with Pandora, Ozone Mapping and Profiler Suite (OMPS) and TROPOspheric Monitoring Instrument (TROPOMI). O3P version 3.0 demonstrates reduced dependence on viewing geometry compared to version 2.0, whereas the O3T product shows a consistent offset between versions (v2.0 vs. v2.1). In comparison with Pandora, O3P exhibits seasonal bias patterns similar to those seen in TROPOMI and OMPS, ranging from −2% in summer to +5% in winter. However, O3T maintains abnormally persistent negative biases across seasons and times of day, along with a long-term degradation of 2–3% from 2021 to 2024. These findings suggest that O3T biases likely result from uncorrected radiometric biases rather than algorithmic limitations. Validation metrics further highlight inconsistencies in O3T, including a lower regression slope (~0.95) in the mid-latitude and higher root mean square errors in the low-latitude (~5%), compared to the other products (near 1.0 and 1–3%, respectively). Overall, O3P outperforms TROPOMI and OMPS across most validation metrics in mid-latitudes and performs similarly at low latitudes
Etude dendrochronologique du Triptyque de Notre-Dame des Sept-Douleurs de Bernard van Orley
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