Tree roots can penetrate deeply in African semi-deciduous rain forests: evidence from two common soil types

Freycon Vincent, Wonkam Christelle Joëlle, Fayolle Adeline, Laclau Jean-Paul, Lucot Eric, Jourdan Christophe, Cornu Guillaume, Gourlet-Fleury Sylvie. 2015. Tree roots can penetrate deeply in African semi-deciduous rain forests: evidence from two common soil types. Journal of Tropical Ecology, 31 (1) : 13-23.

https://doi.org/10.1017/S0266467414000595

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Quartile : Q4, Sujet : ECOLOGY

Résumé : Despite the important functional role of deep roots in withdrawing water during drought, direct measurements of root distribution are very rare in tropical rain forests. The aim of this study was to investigate the root distribution of Entandrophragma cylindricum, a common tree species in the Central African semi-deciduous rain forest, in Ferralsols and Arenosols. We dug two pits to a depth of 6 m in Ferralsols and two pits to a depth of 3 m in Arenosols, close to E. cylindricum trees. The vertical soil profiles were divided into 10 × 10-cm grid cells and the roots counted were distributed in three diameter classes. We fitted a root distribution model to our dataset. We found that vertical root distribution was shallower in Arenosols than in Ferralsols. Root penetration was not stopped even by a Ferralsol with high gravel content in its subsoil. Overall, our measurements showed that 95% of all roots were distributed to depths of between 258 and 564 cm from the soil surface, which is much deeper than the 95 cm depth previously reported in the literature for tropical rain forests. As sampling depth could explain this discrepancy, we recommend a sampling depth of at least 3¿5 m to accurately estimate root distribution. The drier the dry season, the deeper the sampling depth should be. Our results are consistent with global models of root distribution in forest ecosystems, which are driven by climate variables. We thus suggest that deep rooting could be common in rain forests with a marked dry season.

Mots-clés Agrovoc : forêt tropicale humide, racine, enracinement, profil du sol, écologie forestière, ferralsol, aérosol, saison sèche, sécheresse

Mots-clés géographiques Agrovoc : Afrique centrale

Classification Agris : K01 - Foresterie - Considérations générales
F62 - Physiologie végétale - Croissance et développement
P33 - Chimie et physique du sol

Champ stratégique Cirad : Axe 6 (2014-2018) - Sociétés, natures et territoires

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