Title: Spatial structures of soil organic carbon in tropical forests-A case study of Southeastern Tanzania
Authors: Rossi, Joni ×
Govaerts, Annelies
De Vos, Bruno
Verbist, Bruno
Vervoort, André
Poesen, Jean
Muys, Bart
Deckers, Jozef A. #
Issue Date: 2009
Publisher: Elsevier
Series Title: Catena vol:77 issue:1 pages:19-27
Abstract: Southeastern Tanzania serves as a typical example of soil degradation and soil organic carbon (SOC) losses on
the African continent. Although sequestration of SOC through aforestation or reforestation proved favorable,
these measures are restricted by the ability to produce rapid, cost-effective and precise sampling schemes.
The aim of this study is to contribute to a better knowledge of the spatial distribution of soil C in tropical
natural and plantation forest. This paper presents sampling strategies for estimating mean SOC values as well
as for SOC mapping, based on different methods for SOC determination and on different precision levels. To
do so we conducted a carbon variability study in five common forest types of Southeastern Tanzania (coastal
dry forest, Miombo woodland, teak plantation, pine plantation and cashew plantation) using conventional
statistical methods, as well as geostatistics. In the 5 forest types of this study, SOC stocks in the upper 5 cm
ranges between 5 (in the cashew plantation) and 13 (in the coastal forest) t ha−1. The optimal sampling
distance for measuring mean SOC stocks varies between 36 m (in the patchy miombo woodland) and 422 m
(in the homogenized cashew plantation). Sample sizes fluctuate between 6 and 72 (1 t ha−1 precision) for
respectively cashew plantation and coastal forest. A rectangular grid with a sample interval of 25 m can be
used for SOC mapping with a point kriging estimation error of 3.0 t ha−1 in the coastal forest, 2.6 t ha−1 in
miombo woodland, 2.2 t ha−1 in the teak plantation and 1.1 t ha−1 in the cashew plantation. Since the pine
plantation has no spatial structure; samples can be arranged randomly and its best soil map has an average C
content attributed over the whole field. Refining the sampling strategy with a new spatial variability study in
other forest types can be based on a regular grid with sampling distances of half the range identified in this
study. This paper proves that the optimal sampling scheme varies strongly as a result of the different spatial
behavior of SOC in forests and depends on the required precision and research question. Only when the right
strategy is followed, high standards of precision can be met without economic loss or risk of statistical
ISSN: 0341-8162
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Division of Geography & Tourism
Division Forest, Nature and Landscape Research
Division Soil and Water Management
Natural Resources Section
× corresponding author
# (joint) last author

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