The Next Phase Of Carbon Stock And Greenhouse Gas Emission Research For Asb

“Best bet” Land-use Systems

Thematic reports

Carbon Sequestration And Trace Gas Emissions

Unique id: IDAZCB2B

Source file: D:\Projects\ASB\ASB Country and Thematic reports\Climate Change WG Report\phase2final999.xml

Authors: C. A. Palm, P. L. Woomer, J. Alegre, L. Arevalo, C. Castilla, D. G. Cordeiro, B. Feigl, K. Hairiah, J. Kotto-Same, R. Lasco, , A. Mendes, A. Moukam, D. Murdiyarso, R. Njomgang, W. J. Parton, A. Ricse, V. Rodrigues, S. M. Sitompul, M. van Noordwijk

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The following set of hypotheses was developed based on the results from the different benchmark sites in the first two phases of ASB. These hypotheses will guide the next phase of research in order to increase our ability to estimate and predict the effects of land-use change in the tropics on climate change.

C sequestration

Carbon accumulation rates of natural fallow systems are higher than those of agroforestry systems.

Time-averaged carbon stocks of tree-based systems are determined primarily by rotation length and tree planting or regeneration strategy and not by species diversity.

Changes in above-ground C stocks have a greater effect on net radiative forcing impact than do changes in below-ground C stocks, N₂O emissions and CH₄ sink strength.

Nitrous oxide emissions

N₂O fluxes are linked primarily to anaerobic conditions and are thus more related to the soil type, primarily texture, and landscape position, than to land use per se (unless N fertilizers are applied).

On a given soil type and landscape position, N₂O emissions are directly related to above-ground carbon and nitrogen stocks (and cycling), unless nitrogenous fertilizers are applied.

Given equal above-ground carbon stocks, N₂O fluxes are not affected by plant biodiversity.

Methane sinks

CH₄ fluxes are more related to soil type, landscape position, and water balance than to above-ground vegetation of the land use (unless N fertilizers are applied).

Changes in CH₄ sink strength are directly related to changes in bulk density and surplus soil N, as a result of land-use change.

At equal above-ground C stocks, CH₄ fluxes are not affected by above-ground biodiversity.

These hypotheses will be addressed through selective sampling in locations that will allow such comparisons to be made. The teams at the benchmark sites are already trained in the various protocols for measuring C stocks and greenhouse gas emissions and modeling C changes with CENTURY. The capacity building will continue, but the investment during the first two phases of ASB provides the human capital needed to undertake this next phase.