The importance of tree allometry for local-scale variation in aboveground biomass

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https://soctropecol.eu/

ISBN 978-3-00-059300-0

CHALLENGES IN

TROPICAL ECOLOGY AND CONSERVATION -

GLOBAL PERSPECTIVES

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Challenges in tropical ecology and conservation - global perspectives

IMPRINT

Editors

Pierre-Michel Forget – Muséum National d’Histoire Naturelle Catherine Reeb – Sorbonne Université

Jérémy Migliore – Université Libre de Bruxelles Heike Kuhlmann – KCS Kuhlmann Convention Service

Concept, Layout and Cover

[email protected]

This book is available at www.gtoe.de ISBN: 978-3-00-059300-0

The respective authors are solely responsible for the contents of their contributions in this book.

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Society for Tropical Ecology | Gesellschaft für Tropenökologie e.V. Challenges in tropical ecology and conservation - global perspectives

S13-P01 – TROPICAL TREE ALLOMETRY

THE IMPORTANCE OF TREE ALLOMETRY FOR LOCAL-SCALE

VARIATION IN ABOVEGROUND BIOMASS

Grace Jopaul Loubota Panzou1_{, Ted Feldpausch}2_{, Sylvie Gourlet-Fleury}3_{, Eric Forni}3_{, Jean-Louis}

Doucet1_{, Joël Loumeto}4_{, Adeline Fayolle (speaker)}1

1_{Gembloux Agro-Bio Tech, Gembloux, BE, [email protected]}

2_{University of Exter, Exeter, UK} 3_{CIRAD, Montpellier, FR}

4_{University of Marien Ngouabi, Brazzaville, CG}

Aboveground biomass (AGB) plays a critical role in determining the long-term dynamics of carbon in tropical forests. Consequently, understanding what factors are important in controlling AGB in tropical forests has major implications for projecting the terrestrial carbon stocks, in the context of an increasingly uncertain future. In this study, we aimed to explore the local-scale AGB variation in two forest sites in northern Congo, representative of contrasted forest types under the same climate but growing on vastly different soils and parent material (quartzite substrate for CIB and sandstone substrate for Mokabi). Tree diameter was measured in 36 permanent forest plots of 1-ha in each site, and tree allometry (total tree height, height of the first branch and crown dimensions) was measured on a subsample of 18 plots of 1-ha in each site. Allometric data were available for a total of 2202 trees (1040 for CIB and 1162 for Mokabi) covering a large range of diameters (10-200 cm). We first developed site-specific allometric models that were used to estimate AGB at plot level. We then explore the determinants of AGB variation at plot level using multiple regressions and mixed linear models.

For a given diameter, trees tended to be taller and to have deeper crown in the Celtis forest of the CIB (rich soils), while they tended to have larger crown in the Manilkara forest of the Mokabi (sandy soils). Similar trends were reported within species for the sixteen species shared by both sites, suggesting an environmental control of tree allometry. We found that AGB strongly varied between the two forest sites, with greater AGB per hectare in the Celtis forest of the CIB site. Within-site AGB variation was positively related to basal area, though between-site AGB variation was determined by tree allometry (height-diameter and crown allometries). These results have strong implications for forest biomass and carbon monitoring.

S13-P02 – TROPICAL TREE ALLOMETRY

EVOLUTION OF ABOVEGROUND BIOMASS OF DRY TROPICAL

FOREST IN THE NORTH-WEST COAST OF MADAGASCAR IN

RELATION WITH HUMAIN ACTIVITIES

Tian Li1,2_{, Lantotiana Michel Eric Randriamanana}3_{, Harimalalanirina Fabriella Camélias}

Rasoamanantenaniaina3_{, Nomenjanahary Zo Tahina}3_{, Roger Edmond}3_{, Faramalala Miadana}3_,

Hary Jeannoda Vololoniaina3_{, Annette Hladik}4_{, Riera Bernard}1,2

1_{Mécanismes adaptatifs & évolution, Paris, FR, [email protected]}

2_{Muséum National d’Histoire Naturelle, Paris, FR}

3_{Université d’Antananarivo, Département Biologie et Ecologie Végétale, Antananarivo, MG}

4_{UMR 7206. Éco-Anthropologie et Ethnobiologie, MNHN, CNRS et Université Paris-7., Paris, FR}

The dynamics of tropical dry forest woody plants was studied in the protected area of Antrema, North-west Madagascar. Stem density, basal area, and above-ground biomass were estimated from two large permanent censuses of 3 plots, in the forests of Badrala, Ankoririaka and Ambanjabe. They were established on contrasting locations and censused three times at Badrala, first in 2014, then again in 2016 and another time in 2017 together with Ankoririka and Ambanjabe forest.

Mean stem density was 462 stems ha-1_{in 2014, 460 stems ha}-1_{in 2016, 466 stems ha}-1_{in 2017}

in Badrala forest, with the basal area 11.9 m2_{in 2014, 12.2 m}2_{in 2016, 13.3 m}2_{in 2017. Stem}

mortality rate ranged between 0.65 % and 1.25 % y-1. In this plot, stem density increases slightly over the study period, on the contrary, the cut of stem has increased over the years.

In Ankoririka and Ambanjabe forests, stems density was 392 per ha-1_{and 420 per ha}-1_{, with}

the basal area 6.73 m2_{and 11,26 m}2_{in 2017, and in recent years 7 trees were cut in Ankoririka}

and 28 trees in Ambanjabe, which represent 10 % of total basal area. The difference in stem density, basal area and stem cut is consistent with the hypothesis of different typologies of pedology and the distance between villages and Doany (sacred place for local people). Even though in a protected area, the dynamic of forest suffers still a strong influence by the ethnic people.