Carbon sequestration and water-use by eucalypt plantations in Congo and Brazil

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Carbon sequestration and water-use by eucalypt

plantations in Congo and Brazil

Yann Nouvellon, Jose Luis Stape, Jean-Marc Bonnefond, Jean-Pierre Bouillet,

Laurent Saint-André, Olivier Hamel, Daniel Epron

To cite this version:

Yann Nouvellon, Jose Luis Stape, Jean-Marc Bonnefond, Jean-Pierre Bouillet, Laurent Saint-André, et al.. Carbon sequestration and water-use by eucalypt plantations in Congo and Brazil. International Conference Knowledge-based management of tropical rainforests, Nov 2009, Cayenne, France. 1 p. �hal-02821083�

Plantations roles and status Session 5 Rôles et place des plantations

Carbon sequestration and water-use by eucalypt plantations in Congo

and Brazil.

Yann Nouvellon* (yann.nouvellon@cirad.fr), José Luiz Stape** (jlstape@ncsu.edu), JM Bonnefond*** (bonnefon@bordeaux.inra.fr), Jean-Pierre Bouillet****

(Jean-pierre.bouillet@cirad.fr), Laurent Saint-André**** (standre@cirad.fr), Olivier Hamel***** (Olivier.hamel@cirad.fr)

Daniel Epron******* (daniel.epron@scbiol.uhp-nancy.fr)

*CIRAD- Persyst, France and University of São Paulo (USP), Brazil **USP, Brazil, and North Carolina State University, USA

*** UR126,INRA, France ****CIRAD- Persyst, France

*****CIRAD / ES, France

*******

Université de Nancy, France

Tropical plantation forests provide an increasing share of the global wood supply. In Brazil, Eucalyptus plantations cover a large (4 millions ha) and rapidly increasing area. They are managed in short (5-7 years) rotations, mainly for the production of pulpwood for the paper industry, or charcoal for the steel industry. High yields on highly weathered tropical soils and their ability to grow as coppice are the main reasons for their success. In some cases, well managed, and highly productive eucalypt plantations, established on pastures or degraded lands may contribute to alleviate the human pressure on natural resources, e.g. in those countries, including Brazil, where a part of the charcoal fuelling the steel industry or other local needs is still derived from wood collected in natural forests. However, the future of tropical eucalypt plantations will also depend on their ability to sustain high yields and to preserve soil fertility, and on their impact on water-resources, especially in areas where large amounts of water are needed for agriculture or other human activities. Studies on long-term trends in soil fertility, and quantitative assessments of carbon-sequestration and water-use over full eucalyptus rotations, under different climate and for different soil conditions and management practices are therefore needed.

We present the main outcomes of about 10 years of research on carbon and water budgets of eucalypt stands in South-western Congo, and South-eastern Brazil. The dataset includes about 5.5 years of eddy-covariance measurements of water vapour and CO2 flux over three eucalyptus stands

(2 years * 2 clonal eucalypt plantations in Congo, and 1.5 year over one Eucalyptus grandis plantation in Brazil), and data from continuous monitoring of soil moisture, tree growth and net primary production over full rotations in Congo and Brazil. Chronosequence studies were also carried out to investigate trends in soil carbon stocks, and the dynamics of carbon accumulation in the forest floor and in the aboveground biomass as stand ages. We found no change (Congo) or slight increase (Congo and Brazil) in soil carbon stocks after one or several rotations after afforestation of native savannahs (Congo) or Cerrado (Brazil), meaning that the long-term average of carbon amounts in exported wood provides a reasonable approximation of average net ecosystem production (NEP), which varied by more than two-fold between studied eucalypt stands, with the lowest values in Congo (4.5 tC/ha/yr), and the highest values in Brazil (11 tC/ha/yr). Actual evapotranspiration (AET) after canopy closure also varied two fold between less productive stands in Congo (600 mm/yr, about half of annual precipitation) and most productive stands in Brazil (1300 mm/yr, nearly equating the annual rainfall). In Brazil, deep drainage (at depths > 5m) was observed only during the first two years, whereas in Congo, AET was always much lower than rainfall. In Congo, large differences in production and water-use efficiencies were observed between the two studied clones. Differences in production and AET between Congolese and Brazilian stands were mainly explained by sharp differences in global and net radiation, leaf area index, soil water storage capacity and fertilizer inputs, which were all higher in Brazilian stands than in Congolese stands.

International Conference Knowledge-based management of tropical rainforests” - Abstracts