Carbon sequestration and environmental effects of afforestation with Pinus radiata D. Don in the Western Cape, South Africa |
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| Authors: | Juan F García-Quijano Jan Peters Liesbet Cockx Gerrit van Wyk Andrei Rosanov Gaby Deckmyn Reinhart Ceulemans Shane M Ward Nicholas M Holden Jos Van Orshoven Bart Muys |
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| Institution: | (1) Division Forest, Nature and Landscape, Katholieke Universiteit Leuven, Celestijnenlaan 200E, 3001 Leuven, Belgium;(2) Laboratory of Hydrology and Water Management, Ghent University, Coupure links 653, 9000 Ghent, Belgium;(3) Department of Soil Management and Soil Care, Ghent University, Coupure links 653, 9000 Ghent, Belgium;(4) Department of Forest and Wood Science, Faculty of Agricultural and Forestry Sciences, Stellenbosch University, Private Bag X1, 7602 Matieland, South Africa;(5) Department of Soil Science, University of Stellenbosch, Private Bag X1, 7602 Matieland, South Africa;(6) Department of Biology, University of Antwerp, 2610 Wilrijk, Belgium;(7) Department of Biosystems Engineering, Faculty of Engineering and Architecture, University College Dublin, Belfield, Dublin 4, Ireland;(8) Department of Agricultural and Food Engineering, University College Dublin, Belfield, Dublin 4, Ireland |
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| Abstract: | A three-step methodology to assess the carbon sequestration and the environmental impact of afforestation projects in the
framework of the Flexible Mechanisms of the Kyoto Protocol (Joint Implementation and Clean Development Mechanism) was developed
and tested using a dataset collected from the Jonkershoek forest plantation, Western Cape, South Africa, which was established
with Pinus radiata in former native fynbos vegetation and indigenous forest. The impact of a change in land use was evaluated for a multifunctional,
a production and a non-conversion scenario. First, the carbon balance was modelled with GORCAM and was expressed as (1) C
sequestration in tC ha−1 year−1 in soil, litter, and living biomass according to the rules of the first commitment period of the Kyoto Protocol, and (2)
CO2 emission reductions in tC ha−1 year−1, which includes carbon sequestered in the above-mentioned pools and additionally in wood products, as well as emission reductions
due to fossil fuel substitution. To estimate forest growth, three data sources were used: (1) inventory data, (2) growth simulation
with a process-based model, and (3) yield tables. Second, the effects of land use change were assessed for different project
scenarios using a method related to Life Cycle Assessment (LCA). The method uses 17 quantitative indicators to describe the
impact of project activities on water, soil, vegetation cover and biodiversity. Indicator scores were calculated by comparing
indicator values with reference values, estimated for the climax vegetation. The climax vegetation is the site-specific ecosystem
phase with the highest exergy content and the highest exergy flow dissipation capacity. Third, the land use impact per functional
unit of 1 tC sequestered was calculated by combining the results of step 1 and step 2. The average baselines to obtain carbon
additionality are 476 tC ha−1 for indigenous forest and 32 tC ha−1 for fynbos. Results show that the influence of the growth assessment method on the magnitude of C sequestration and hence
on the environmental impact per functional unit is large. When growth rate is assessed with the mechanistic model and with
the yield table, it is overestimated in the early years and underestimated in the long term. The main conclusion of the scenario
analysis is that the production forest scenario causes higher impacts per functional unit than the multifunctional scenario,
but with the latter being less efficient in avoiding CO2 emissions. The proposed method to assess impacts on diverse components of the ecosystem is able to estimate the general tendency
of the adverse and positive effects of each scenario. However, some indicators, more specifically about biodiversity and water
balance, could be improved or reinterpreted in light of specific local data about threat to biodiversity and water status. |
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