Landscape evolution and climate in Madagascar: lavakization in the light of archive precipitation data

Szabó, Amanda Imola; Raveloson, Andrea; Székely, Balázs

doi:10.18172/cig.2646

Cited by 9 publications

(10 citation statements)

References 14 publications

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“…The species has been collected in flower from April to May, just after the rainy season, and in fruit in June and from September to October, during the dry season. A single record of young fruit in March 2004 at the start of the dry season is probably due to exceptionally dry weather in February of that year (Szabó et al, 2015).…”

Section: Dalbergia Antsirananae Phillipson Crameri and N Wilding Differs From D Madagascariensis Vatke By Its Smaller Flowersmentioning

confidence: 98%

“…For example, between 2004 and 2015, rosewood accounted for 35 % of the value of all wildlife seizures, more than that of elephants, pangolins, rhinoceros and big cats combined (UNODC, 2016). The problem has been particularly acute in Madagascar (Mason et al, 2016), the origin of more than 50 % of the approximately 10,000 metric tons of rosewood seized globally during the period -2015(UNODC, 2016.…”

Section: Introductionmentioning

confidence: 99%

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Taxonomic studies on Malagasy Dalbergia (Fabaceae). I. Two new species from northern Madagascar, and an emended description for D. manongarivensis

Wilding¹,

Phillipson²,

Crameri³

et al. 2021

Candollea

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Two new species of Dalbergia L. f. (Fabaceae: Dalbergieae) are described from northern Madagascar: Dalbergia antsirananae Phillipson, Crameri & N. Wilding and Dalbergia obcordata N. Wilding, Phillipson & Crameri, and an emended description is provided for a third species, Dalbergia manongarivensis Bosser & R. Rabev. All three species are illustrated with line drawings and photographs, and each is provided with a risk of extinction assessment using the IUCN Red List criteria: all three species are assessed as "Endangered". Dalbergia antsirananae and Dalbergia manongarivensis are closely related, and both appear to be a source of valuable wood, while Dalbergia obcordata is only known as a shrub and is assumed not to produce wood of commercial value.

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Section: Dalbergia Antsirananae Phillipson Crameri and N Wilding Differs From D Madagascariensis Vatke By Its Smaller Flowersmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Taxonomic studies on Malagasy Dalbergia (Fabaceae). I. Two new species from northern Madagascar, and an emended description for D. manongarivensis

Wilding¹,

Phillipson²,

Crameri³

et al. 2021

Candollea

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“…Madagascar is the world's fourth largest island with an area of about 592,000 km 2 [73], and is separated from Mozambique on the main African continent by about 400 km [73]. The climate on the island is subtropical and is characterized by a dry season from May to October and rainy season from November to April [74,75]. Table 1 summarizes the characteristics of the Madagascar image data used in our study, which was extracted from the original FLDAS data.…”

Section: Data and Area Of Interestmentioning

confidence: 99%

Basic Statistical Estimation Outperforms Machine Learning in Monthly Prediction of Seasonal Climatic Parameters

et al. 2021

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Machine learning (ML) has been utilized to predict climatic parameters, and many successes have been reported in the literature. In this paper, we scrutinize the effectiveness of five widely used ML algorithms in the monthly prediction of seasonal climatic parameters using monthly image data. Specifically, we quantify the predictive performance of these algorithms applied to five climatic parameters using various combinations of features. We compare the predictive accuracy of the resulting trained ML models to that of basic statistical estimators that are computed directly from the training data. Our results show that ML never significantly outperforms the statistical baseline, and underperforms for most feature sets. Unlike previous similar studies, we provide error bars for the relative performance of different predictors based on jackknife estimates applied to differences in predictive error magnitudes. We also show that the practice of shuffling data sequences which was employed in some previous references leads to data leakage, resulting in over-estimated performance. Ultimately, the paper demonstrates the importance of using well-grounded statistical techniques when producing and analyzing the results of ML predictive models.

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“…The eastern part of the island is humid and covered by tropical rainforest while the southern and western regions are drier and dominated by (wooded) grasslands including shrubby bushlands and arborescent species of Euphorbia. Madagascar is often considered to experience very high erosion rates (Szabó et al, 2015). The most spectacular erosion-forms on the island are large inverse-teardrops shaped gullies or 'lavaka' meaning 'hole' in Malagasy language.…”

Section: Introductionmentioning

confidence: 99%

“…The most spectacular erosion-forms on the island are large inverse-teardrops shaped gullies or 'lavaka' meaning 'hole' in Malagasy language. Lavaka are omnipresent in the central highlands of Madagascar (Brosens et al, 2022;Cox et al, 2010;Szabó et al, 2015;Voarintsoa and Cox, 2012;Wells and Andriamihaja, 1993) and frequently initiate on convex slopes covered by grassland vegetation and patches of shrubs (Brosens et al, 2022;Wells and Andriamihaja, 1993). Active lavaka are absent under forest vegetation (Aubréville and Bossanyi, 2015).…”

Section: Introductionmentioning

confidence: 99%

Stable isotope profiles of soil organic carbon in forested and grassland landscapes in the Lake Alaotra basin (Madagascar): insights in past vegetation changes

Razanamahandry

Dewaele

Govers

et al. 2022

Preprint

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Abstract. The extent to which the central highlands of Madagascar were once covered by forests is still a matter of debate: while reconstructing past environments is inherently difficult, the debate is further hampered by the fact that the evidence documenting land cover changes and their effects on carbon and sediment dynamics in Madagascar has hitherto mainly been derived from lake coring studies. Such studies provide an integrated view over relatively large areas but do not provide information on how land use change affects hillslopes in terms of carbon and sediment dynamics. Such information would not only be complementary to lake inventories but may also help to correctly interpret lake sediment data. Carbon stable isotope ratios (δ13C) are particularly useful tracers to study the past dynamics of soil carbon over timespans ranging from years to centuries and thus to understand the consequences of land-use change over such timespans. We analyzed soil profiles down to a depth of 2 m from pristine forests and grasslands in the Lake Alaotra region in central Madagascar. Along grassland hillslopes, SOC content was extremely low, from 0.4 to 1.8 % in the top layer, and decreased rapidly to ca. 0.2 % below 100 cm depth. The current vegetation predominantly consists of C4 grasses (δ13C ~−13 ‰), yet soil δ13C-OC range between −25.9 and −16.6 ‰, and most profiles show a decrease in δ13C-OC with depth. This contrasts with our observations in the C3-dominated forest profiles, which show a typical enrichment in 13C with depth. Moreover, the SOC stock of grasslands was ~55.6 % lower than along the forested hillslopes for the upper 0–30 cm layer. δ13C values in grassland and forest profiles converge to similar values (within 2.0 ± 1.8 ‰) at depths below ~80 cm, suggesting that the grasslands in the Lake Alaotra region have indeed developed on soils formerly covered by a tree vegetation dominated by C3 plants. We also observed that the percent of modern carbon (pMC) of the bulk OC in the top, middle and lower middle positions of grasslands was less than 85 % near the surface. This could reflect a combination of (i) the long residence time of forest OC in the soil, (ii) the slow replacement rate of grassland-derived OC, (iii) and the substantial erosion of the top positions towards the valley position of grasslands. In the valley positions of our grassland hillslopes, the topsoil OC has a higher δ13C value and consists of younger carbon (pMC > 100 %), suggesting a recent expansion of grass vegetation. Our approach, based on the large difference in δ13C values between the two major photosynthetic pathways (C3 and C4) in (sub)tropical terrestrial environments, provides a relatively straightforward method to quantitatively determine changing vegetation cover. We advocate for its broader application across Madagascar to better understand the islands’ vegetation history.

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Landscape evolution and climate in Madagascar: lavakization in the light of archive precipitation data

Cited by 9 publications

References 14 publications

Taxonomic studies on Malagasy Dalbergia (Fabaceae). I. Two new species from northern Madagascar, and an emended description for D. manongarivensis

Taxonomic studies on Malagasy Dalbergia (Fabaceae). I. Two new species from northern Madagascar, and an emended description for D. manongarivensis

Basic Statistical Estimation Outperforms Machine Learning in Monthly Prediction of Seasonal Climatic Parameters

Stable isotope profiles of soil organic carbon in forested and grassland landscapes in the Lake Alaotra basin (Madagascar): insights in past vegetation changes

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