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| Titel |
Investigating the controls on Gross Primary Productivity of a high elevation tropical montane cloud forest |
| VerfasserIn |
M. J. van de Weg, P. Meir, Y. Malhi, M. Williams, J. Silva-Espejo, J. Grace |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250063489
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| Zusammenfassung |
| Tropical montane cloud forests (TMCF) are a unique, but little understood ecosystem that can
be found in tropical mountainous areas around the world. In recent years, the interest in the
carbon (C) cycle of TMCFs has increased, especially with regard to possibilities for carbon
sequestration and storage practices. Compared with tropical lowland rainforests, these forests
have a low aboveground net primary productivity (ANPP), a small standing biomass and a
small leaf area index (LAI), while the forests are characterized by the stunted growth form of
the trees.
However, estimates of gross primary productivity (GPP) of TMCFs are scarce, and
there are uncertainties in what factors are most important in controlling TMCF
productivity.
We investigated the controlling factors on GPP in a TMCF in the Andes in
south east Peru (13º11’28”S / 71º35’24”W). First, we measured physiological and
structural parameters of the vegetation. On a leaf level, the carboxylation efficiency of
Rubisco (V cmax) and the electron transport capacity (Jmax) were as high as those
found in tropical lowland forests, but as expected the LAI was smaller. Therefore, in
terms of the capacity for TMCF C uptake, the total leaf area is more important in
explaining the difference between TMCF GPP and tropical lowland forest GPP, than
photosynthetic capacity of the leaf tissue. Furthermore, we used the vegetation parameters,
together with meteorological data from the site with a process based simulator (the
SPA model) to simulate TMCF GPP and to evaluate the relative importance of the
environmental controls on GPP. To our knowledge, this is the first estimate of TMCF
GPP that uses parameters and drivers that are derived from the site simulated in the
model.
Simulated annual GPP was 16.2 ± SE 1.6 t C ha-1 yr-1, which is about half of the GPP
commonly observed in neotropical lowland rainforests. Temperature and, to a lesser extent
photosynthetic active radiation (PAR), were the strongest environmental controls on GPP.
In contrast, simulated GPP was relatively insensitive to changes in the hydraulic
parameters, or observed changes in soil water content. This results is consistent with
the observation that (periodic) drought stress is a very unlikely explanation for
the lower GPP and NPP of TMCF with respect to lowland tropical rain forests. |
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