TY - JOUR
T1 - Simulating structural forest patterns with a forest gap model
T2 - A model evaluation
AU - Risch, Anita C.
AU - Heiri, Caroline
AU - Bugmann, Harald
N1 - Funding Information:
We thank Peter Biber, Forest Yield Science at the Technological University in Munich, for letting us use Strugen, Stéphanie Schmid for helping with the stand initialization in Strugen and Manuel Bleichenbacher for providing several programs for data conversion. We are grateful to several volunteers for their help during data collection. This study was funded by the Swiss Federal Institute of Technology, Zurich (grant No. TH-1’/01-1). We also would like to express our gratitude to the Swiss National Park Service for the administrative and logistic support of our research in the SNP, and to two reviewers for useful comments on an earlier version of this manuscript.
PY - 2005/1/20
Y1 - 2005/1/20
N2 - Ecological models can be characterized by their degree of generality, reality and precision. Any model, being a deliberate simplification of reality, cannot excel in all three aspects. Forest gap models have been widely used for studying tree population dynamics, but their predictions have not often been tested for their local precision, but rather for their broad agreement with descriptions of near-natural vegetation. The objectives of our study were (1) to evaluate the performance of the forest gap model ForClim, which had been developed striving for generality and realism, in simulating the long-term development of structural features in Swiss mountain forests; and (2) to examine whether and how the model needs to be changed to improve its precision for a specific site. We used long-term forest data (45 years) from three different forest types in the Swiss National Park. Initial simulation runs for the most dominant forest type in the study area failed to reproduce the observed structural patterns. A detailed analysis of the growth performance of individual trees led to the conclusion that a modified height-diameter function was required, which presumably increases the generality of the model. The new model structure led to simulated stand features that were broadly consistent with observations. After, in addition, taking local variations of model parameters (on mortality, browsing, and seedling establishment rates) into account, we were able to considerably improve the performance of ForClim in simulating the structural features of the different mountain forest stands. We suggest that from the point of view of its revised structure, the ForClim model is principally suitable for site-specific applications, but local precision can only be achieved by site-specific parameter estimation procedures. We conclude that model evaluation and validation as conducted in this study could be quite useful for increasing the reliability of simulations performed with this class of models.
AB - Ecological models can be characterized by their degree of generality, reality and precision. Any model, being a deliberate simplification of reality, cannot excel in all three aspects. Forest gap models have been widely used for studying tree population dynamics, but their predictions have not often been tested for their local precision, but rather for their broad agreement with descriptions of near-natural vegetation. The objectives of our study were (1) to evaluate the performance of the forest gap model ForClim, which had been developed striving for generality and realism, in simulating the long-term development of structural features in Swiss mountain forests; and (2) to examine whether and how the model needs to be changed to improve its precision for a specific site. We used long-term forest data (45 years) from three different forest types in the Swiss National Park. Initial simulation runs for the most dominant forest type in the study area failed to reproduce the observed structural patterns. A detailed analysis of the growth performance of individual trees led to the conclusion that a modified height-diameter function was required, which presumably increases the generality of the model. The new model structure led to simulated stand features that were broadly consistent with observations. After, in addition, taking local variations of model parameters (on mortality, browsing, and seedling establishment rates) into account, we were able to considerably improve the performance of ForClim in simulating the structural features of the different mountain forest stands. We suggest that from the point of view of its revised structure, the ForClim model is principally suitable for site-specific applications, but local precision can only be achieved by site-specific parameter estimation procedures. We conclude that model evaluation and validation as conducted in this study could be quite useful for increasing the reliability of simulations performed with this class of models.
KW - ForClim
KW - Forest succession
KW - Growth function
KW - Long-term forest data
KW - Validation
UR - http://www.scopus.com/inward/record.url?scp=7444250887&partnerID=8YFLogxK
U2 - 10.1016/j.ecolmodel.2004.06.029
DO - 10.1016/j.ecolmodel.2004.06.029
M3 - Article
AN - SCOPUS:7444250887
SN - 0304-3800
VL - 181
SP - 161
EP - 172
JO - Ecological Modelling
JF - Ecological Modelling
IS - 2-3
ER -