Can random components explain differences in the height-diameter relationship in mixed uneven-aged stands?
• Context Tree height prediction is an important issue in forest management since tree heights are usually measured only in a sample of trees. Although numerous model approaches have been used for this purpose, no agreement on which one is more appropriate has been achieved. • Aims To analyse the random effects of basic and generalised height-diameter (h-d) models fitted to multi-species uneven-aged forest stands, and to establish their ability to explain differences between ecoregions, plots and species. • Methods Height and diameter measurements for 29,084 trees from 187 sample plots located in the state of Durango (Mexico) were used. Basic and generalised h-d models were fitted in a mixed-models framework. The variability between ecoregions, plots and species was considered in the random effects definition. Model calibration for different height sampling designs and sampling sizes was also analysed. • Results Random components performed well in explaining the differences in the h-d relationship between the different plots and species; however, no significant variance for the random effects was found for the different ecoregions. A calibrated basic h-d model produced similar results to a fixed-effects generalised h-d model when a sufficiently large number of trees was used in the calibration process. • Conclusion From a practical point of view, if no calibration is carried out, different models should be used for the different species, so that at least the variation among species is captured. © 2013 INRA and Springer-Verlag France.
| Main Authors: | , , , |
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| Format: | journal article biblioteca |
| Language: | eng |
| Published: |
2014
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| Online Access: | http://hdl.handle.net/20.500.12792/5976 |
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| Summary: | • Context Tree height prediction is an important issue in forest management since tree heights are usually measured only in a sample of trees. Although numerous model approaches have been used for this purpose, no agreement on which one is more appropriate has been achieved. • Aims To analyse the random effects of basic and generalised height-diameter (h-d) models fitted to multi-species uneven-aged forest stands, and to establish their ability to explain differences between ecoregions, plots and species. • Methods Height and diameter measurements for 29,084 trees from 187 sample plots located in the state of Durango (Mexico) were used. Basic and generalised h-d models were fitted in a mixed-models framework. The variability between ecoregions, plots and species was considered in the random effects definition. Model calibration for different height sampling designs and sampling sizes was also analysed. • Results Random components performed well in explaining the differences in the h-d relationship between the different plots and species; however, no significant variance for the random effects was found for the different ecoregions. A calibrated basic h-d model produced similar results to a fixed-effects generalised h-d model when a sufficiently large number of trees was used in the calibration process. • Conclusion From a practical point of view, if no calibration is carried out, different models should be used for the different species, so that at least the variation among species is captured. © 2013 INRA and Springer-Verlag France. |
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