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| 1 | Incorporating shape constraints in generalized additive modelling of the height-diameter relationship for Norway spruce显示文摘Background:Measurements of tree heights and diameters are essential in forest assessment and modelling.Tree heights are used for estimating timber volume,site index and other important variables related to forest growth and yield,succession and carbon budget models.However,the diameter at breast height(dbh) can be more accurately obtained and at lower cost,than total tree height.Hence,generalized height-diameter(h-d) models that predict tree height from dbh,age and other covariates are needed.For a more flexible but biologically plausible estimation of covariate effects we use shape constrained generalized additive models as an extension of existing h-d model approaches.We use causal site parameters such as index of aridity to enhance the generality and causality of the models and to enable predictions under projected changeable climatic conditions.Methods:We develop unconstrained generalized additive models(GAM) and shape constrained generalized additive models(SCAM) for investigating the possible effects of tree-specific parameters such as tree age,relative diameter at breast height,and site-specific parameters such as index of aridity and sum of daily mean temperature during vegetation period,on the h-d relationship of forests in Lower Saxony,Germany.Results:Some of the derived effects,e.g.effects of age,index of aridity and sum of daily mean temperature have significantly non-linear pattern.The need for using SCAM results from the fact that some of the model effects show partially implausible patterns especially at the boundaries of data ranges.The derived model predicts monotonically increasing levels of tree height with increasing age and temperature sum and decreasing aridity and social rank of a tree within a stand.The definition of constraints leads only to marginal or minor decline in the model statistics like AlC.An observed structured spatial trend in tree height is modelled via 2-dimensional surface fitting.Conclusions:We demonstrate that the SCAM approach allows optimal regression modelling flexibility similar to the standard GAM but with the additional possibility of defining specific constraints for the model effects.The longitudinal character of the model allows for tree height imputation for the current status of forests but also for future tree height prediction. | Natalya Pya Matthias Schmidt | 2016 | Forest Ecosystems2016，3，2： | 3 |
| 2 | Multicriteria analysis in decision making under information uncertainty显示文摘 | Pya ekel Martini J S C Palhares R M | | 0，，02： | 1 |
| 3 | Changes in the probability of heavy precipitation:important indicators of climatic change显示文摘 | Karl T R Easterling D R | 1999 | Climatic Change1999，42，： | 1 |
| 4 | Preparation of a nanocomposite of polypropylene and smectite显示文摘 | Kurokawa Y Yasuda H Pya A | 1996 | Journal of Materials Science Letters1996，15，： | 1 |
| 5 | Evaporation losing its strength显示文摘 | Peterson T C Golubev V S Grolsman Pya | 1995 | Nature1995，377，： | 1 |
| 6 | Evaporation losing its strength显示文摘 | Peterson T C Golubev V S Groisman PYa | 1995 | Nature1995，377，： | 1 |
| 7 | Variations in low cloud cover over the United States during the second half of the 20th century显示文摘 | Sun B PYa Groisman | 2004 | Journal of Climate2004，17，： | 1 |
| 8 | Empirical data on contemporary global climate changes (temperature and precipitation) 显示文摘 | Vinnikov K Y Groisman PYA Lugina K M | 1990 | Cli- mate1990，3，： | 1 |
| 9 | Cytogenetic variation in Vitis vinifera in relation to polyploidy and hvbridization显示文摘 | GOLODRIGA PYA DIREEVA LK | 1975 | Trudy PO Prikladnoi Botanike Genetike I Selektsii1975，57，2： | 1 |
| 10 | Evaporation losing its strength显示文摘 | Peterson T C Golubev V S Grolsman Pya | 1995 | Nature1995，377，： | 1 |
| 11 | Cytogenetic variation in vitis vinifera in relation to polyploidy and hybridization显示文摘 | Golodriga PYA Direeva LK | 1975 | Trudy po Prikladnoi Botanike Genetike i Selektsii1975，57，2： | 1 |
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