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| Titel |
Multi-decadal carbon and water relations of African tropical humid forests: a tree-ring stable isotope analysis |
| VerfasserIn |
Koen Hufkens, Gerd Helle, Hans Beeckman, Thales de Haulleville, Elizabeth Kearsley, Pascal Boeckx |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250080066
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| Zusammenfassung |
| Little is known about the temporal dynamics of the carbon sequestering capacity and
dynamics of African tropical humid forest ecosystems in response to various environmental
drivers. This lack of knowledge is mainly due to the absence of ecosystem scale
flux measurements of gas exchange. However, tree growth often displays itself as
alternating pattern of visible rings due to the seasonally varying growth speed of the
vascular cambium. Consequently, analysis of tree growth through tree-ring analysis
provides us with insights into past responses of the carbon sequestering capacity
of key species to abrupt ecosystem disturbances and, while slower, a changing
climate.
Not only does the width and density of growth rings reflect annual growth but their
isotopic composition of 13C/12C and 18O/16O isotopes also reveal the environmental
conditions in which the trees were growing. In particular, stable isotope ratios in tree-rings of
carbon are influenced by fractionation through carboxylation during photosynthesis and
changes in leaf stomatal conductance. Similarly, fractionation of oxygen isotopes of soil
water occurs at the leaf level through evapo-transipiration. As a consequence, 18O/16O (δ18O)
values in wood cores will reflect both the signal of the source water as well as that of for
example summer humidity. Therefore, both C and O stable isotopes might not only
be valuable as proxy data for past climatic conditions but they also serve as an
important tool in understanding carbon and water relations within a tropical forest
ecosystems.
To this end we correlate long term climate records (1961 – present) with tree ring
measurement of incremental growth and high resolution analysis of tree-core stable isotope
composition(δ13C , δ18O) at a tropical humid forests in the DR Congo. The Yangambi Man
And Biosphere (MAB) reserve is located in the north-eastern part of DR Congo, with a
distinct tropical rainforest climate. In addition to the tree-core data records and
extensive meteorological records collected at both sites, observations on green leaf
phenology of key species will provide us with additional information on potential
carbon sequestration dynamics. Because, phenology is a first order control on plant
productivity. In this unique study, using detailed tree-ring analyses together with
auxiliary data, we explore the temporal dynamics of carbon and water relations and the
influence on carbon sequestration of key tree species in African tropical humid forests. |
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