The physical and mechanical properties of wood affect the growth and development of trees, and also act as the main criteria when determining wood usage. Our understanding on patterns and controls of wood physical and...The physical and mechanical properties of wood affect the growth and development of trees, and also act as the main criteria when determining wood usage. Our understanding on patterns and controls of wood physical and mechanical properties could provide benefits for forestry management and bases for wood application and forest tree breeding. However, current studies on wood properties mainly focus on wood density and ignore other wood physical properties. In this study, we established a comprehensive database of wood physical properties across major tree species in China. Based on this database, we explored spatial patterns and driving factors of wood properties across major tree species in China. Our results showed that(i) compared with wood density, air-dried density, tangential shrinkage coefficient and resilience provide more accuracy and higher explanation power when used as the evaluation index of wood physical properties.(ii) Among life form, climatic and edaphic variables, life form is the dominant factor shaping spatial patterns of wood physical properties, climatic factors the next, and edaphic factors have the least effects, suggesting that the effects of climatic factors on spatial variations of wood properties are indirectly induced by their effects on species distribution.展开更多
This paper proposes the Nonnegative Garrote(NG)estimator for linear model with heteroscedastic errors.On the other hand,under some regularity conditions,the authors show the asymptotic optimality of the NG estimator b...This paper proposes the Nonnegative Garrote(NG)estimator for linear model with heteroscedastic errors.On the other hand,under some regularity conditions,the authors show the asymptotic optimality of the NG estimator by referring to the idea of the asymptotic optimality of the model average estimator.Simulation results and a real data analysis are reported for testing the results obtained previously.These results provide a stronger theoretical basis for the use of NG estimator by strengthening existing findings.展开更多
基金supported by Creative Research Groups of National Natural Science Foundation of China(31321061)National Natural Science Foundation of China(30370419 and 31300450)
文摘The physical and mechanical properties of wood affect the growth and development of trees, and also act as the main criteria when determining wood usage. Our understanding on patterns and controls of wood physical and mechanical properties could provide benefits for forestry management and bases for wood application and forest tree breeding. However, current studies on wood properties mainly focus on wood density and ignore other wood physical properties. In this study, we established a comprehensive database of wood physical properties across major tree species in China. Based on this database, we explored spatial patterns and driving factors of wood properties across major tree species in China. Our results showed that(i) compared with wood density, air-dried density, tangential shrinkage coefficient and resilience provide more accuracy and higher explanation power when used as the evaluation index of wood physical properties.(ii) Among life form, climatic and edaphic variables, life form is the dominant factor shaping spatial patterns of wood physical properties, climatic factors the next, and edaphic factors have the least effects, suggesting that the effects of climatic factors on spatial variations of wood properties are indirectly induced by their effects on species distribution.
基金supported by the National Natural Science Foundation of China under Grant No.61501331the Natural Science Foundation of Zhejiang Province under Grant No.LY14F010002。
文摘This paper proposes the Nonnegative Garrote(NG)estimator for linear model with heteroscedastic errors.On the other hand,under some regularity conditions,the authors show the asymptotic optimality of the NG estimator by referring to the idea of the asymptotic optimality of the model average estimator.Simulation results and a real data analysis are reported for testing the results obtained previously.These results provide a stronger theoretical basis for the use of NG estimator by strengthening existing findings.
