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Evaluating the ability of LPJ-GUESS to simulate the tree size structures of tropical forests

Knapen, Margot Jeanne LU (2021) In Student thesis series INES NGEK01 20211
Dept of Physical Geography and Ecosystem Science
Abstract
Tropical forests are of great importance to all living-beings due to their high biodiversity and the valu-able resources, such as food and fuel, they provide. In addition, tropical trees sequester a high amount of carbon and consequently over half of the global forest carbon stock can be found in the tropics. Climate change, however, might weaken this carbon sink and possibly result in tropical forests turning into net carbon sources. The tree size structures of forests and growth and mortality processes are strongly related to each other and determine the accumulation of biomass.

LPJ-GUESS is a Dynamic Global Vegetation Model (DGVM), which can be used to simulate tropical forest dynamics. However, it has not been thoroughly evaluated... (More)
Tropical forests are of great importance to all living-beings due to their high biodiversity and the valu-able resources, such as food and fuel, they provide. In addition, tropical trees sequester a high amount of carbon and consequently over half of the global forest carbon stock can be found in the tropics. Climate change, however, might weaken this carbon sink and possibly result in tropical forests turning into net carbon sources. The tree size structures of forests and growth and mortality processes are strongly related to each other and determine the accumulation of biomass.

LPJ-GUESS is a Dynamic Global Vegetation Model (DGVM), which can be used to simulate tropical forest dynamics. However, it has not been thoroughly evaluated against field data of tropical tree size distributions. The aim of this study was therefore to further enhance our understanding of the behaviour of LPJ-GUESS by means of comparing simulated distributions of tree size versus tree density and tree size versus biomass to a validation dataset. Six locations within the tropical rainforest ecozone were chosen across Africa, South America and Southeast-Asia. It was found that LPJ-GUESS generally underestimates the total amount of biomass. A total of eleven parameters were adjusted according to the one-at-a-time principle, which showed large variability between the six sites. The results of the parameter changes are described and are consistent with expectations from the literature. An increase in the disturbance interval, for example, stimulated the accumulation of biomass whilst reducing the tree density. This can be explained by the fact that fewer disturbances cause trees to grow older and consequently store more biomass, whilst their bigger crowns reduce the amount of light passing through the canopy. Recommendations for further studies are presented and stress the importance of exploring parameters interactions. Based on the results from this study it is advised to explore the re-sponse of LPJ-GUESS when altering the disturbance interval, crown area and kallom1 (an allometric constant) simultaneously. (Less)
Please use this url to cite or link to this publication:
author
Knapen, Margot Jeanne LU
supervisor
organization
course
NGEK01 20211
year
type
M2 - Bachelor Degree
subject
keywords
tropical forests, tree size distributions, LPJ-GUESS, carbon, biomass, sensitivity analysis
publication/series
Student thesis series INES
report number
542
language
English
id
9057228
date added to LUP
2021-06-22 08:41:46
date last changed
2021-06-22 08:41:46
@misc{9057228,
  abstract     = {{Tropical forests are of great importance to all living-beings due to their high biodiversity and the valu-able resources, such as food and fuel, they provide. In addition, tropical trees sequester a high amount of carbon and consequently over half of the global forest carbon stock can be found in the tropics. Climate change, however, might weaken this carbon sink and possibly result in tropical forests turning into net carbon sources. The tree size structures of forests and growth and mortality processes are strongly related to each other and determine the accumulation of biomass.

LPJ-GUESS is a Dynamic Global Vegetation Model (DGVM), which can be used to simulate tropical forest dynamics. However, it has not been thoroughly evaluated against field data of tropical tree size distributions. The aim of this study was therefore to further enhance our understanding of the behaviour of LPJ-GUESS by means of comparing simulated distributions of tree size versus tree density and tree size versus biomass to a validation dataset. Six locations within the tropical rainforest ecozone were chosen across Africa, South America and Southeast-Asia. It was found that LPJ-GUESS generally underestimates the total amount of biomass. A total of eleven parameters were adjusted according to the one-at-a-time principle, which showed large variability between the six sites. The results of the parameter changes are described and are consistent with expectations from the literature. An increase in the disturbance interval, for example, stimulated the accumulation of biomass whilst reducing the tree density. This can be explained by the fact that fewer disturbances cause trees to grow older and consequently store more biomass, whilst their bigger crowns reduce the amount of light passing through the canopy. Recommendations for further studies are presented and stress the importance of exploring parameters interactions. Based on the results from this study it is advised to explore the re-sponse of LPJ-GUESS when altering the disturbance interval, crown area and kallom1 (an allometric constant) simultaneously.}},
  author       = {{Knapen, Margot Jeanne}},
  language     = {{eng}},
  note         = {{Student Paper}},
  series       = {{Student thesis series INES}},
  title        = {{Evaluating the ability of LPJ-GUESS to simulate the tree size structures of tropical forests}},
  year         = {{2021}},
}