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| Titel |
Spatial variation in tree mortality |
| VerfasserIn |
Nikée Groot, Oliver Phillips, Simon Lewis, Manuel Gloor, Drew Purves |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250056650
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| Zusammenfassung |
| Climate change, consisting of rising atmospheric carbon dioxide (CO2) concentrations and an
increase in global average temperatures, has currently been accepted as one of the most
pressing societal challenges of the 21st century. The increase in atmospheric CO2
concentrations is a result of carbonsources (mainly fossil fuel) emissions being
greater than the uptake by carbon sinks (the oceans and the land). At present the
global terrestrial vegetation is a substantial carbon sink, but it is highly variable and
its responses to a changing climate are uncertain. An increased atmospheric CO2
concentration could be beneficial to plant growth. Increased temperatures and more frequent
occurrences of drought could lead to plants becoming stressed though, which could make
them more vulnerable to for example insect plagues. Whether the global terrestrial
vegetation will continue to function as a carbon sink or whether it might turn into a
carbon source, will thus depend on the response of the vegetation to the changing
climate.
To understand how the global terrestrial vegetation will respond to climate changes,
Dynamic Global Vegetation Models (DGVMs) are created within the models used to predict
global climate change (Earth System Models, ESMs). These DGVMs contain a growth
component (carbon assimilation) and a mortality component. Compared to the growth
component, the mortality component is generally modelled in a relatively simple fashion.
Most DGVMs assume that carbon loss through mortality occurs at a constant rate or only
incorporate some stochastic disturbances to account for e.g. the occurrence of fires. Thus
potential variations in mortality due to tree size, age, species or location are generally not
taken into account. The objective of this study is thus to identify what determines the
variation in tree mortality across vegetation types and environmental gradients in order to
improve DGVM predictions.
Large-scale variations in mortality are derived from tree censuses as recorded for the
permanent sample plots of the Forest Plots Database1 (pan-tropical) and the USDA FIA
Database2 (United States; temperate). Mortality rates have been determined in two manners;
based on the number of stems and as the amount of biomass lost per unit of area. Both have
been compared amongst the world’s different biological biomes and tree-dominated realms.
Using statistical models, the relations between spatial variations in mortality rates and tree
characteristics (e.g. wood density, diameter at breast height and relative growth rate) and
environmental characteristics (e.g. temperature and cumulative water deficit) have been
quantified. These empirical mortality estimates and the identified mechanistic understanding
will be used to improve present DGVM predictions. Through simulating possible future
climatic changes, the impacts on mortality and carbon storage implications will be
explored.
1 Lopez-Gonzalez, G., Lewis, S.L., Phillips, O.L., Burkitt, M. Forest Plots Database.
http://www.forestplots.net/ Date of extraction [15-04-2010]
2 USDA-Forest Service. Forest Inventory and Analysis Database. http://fia.fs.fed.us/ Date
of extraction [28-09-2010] |
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