Temporal Changes in the Inequality of Early Growth of Cunninghamia lanceolata (Lamb.) Hook.: A Novel Application of the Gini Coefficient and Lorenz Asymmetry |
| |
Authors: | Zhong Ma Jisen Shi Guang Wang Zhenxiang He |
| |
Institution: | (1) Department of Biology, University of Louisiana at Lafayette, Lafayette, LA 70503, USA;(2) Biology Department, Division of Science, Truman State University, Kirksville, MO 63501, USA;(3) Forest Genetics and Gene Engineering Lab, Nanjing Forestry University, 210037 Nanjing, P.R. China;(4) College of Life Sciences, Nanjing University, 210093 Nanjing, P.R. China |
| |
Abstract: | Growth within tree populations varies among individuals due to changes in biotic and abiotic factors. The degree of such variation,
defined as growth inequality, serves as a useful indicator of the uniformity of growth within a population in response to
the prevalent environmental conditions. By application of the Gini coefficient (G), an index for inequality, we characterized
the early growth inequality of ninety crosses of Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) and their open-pollinated parental lines. Tree cumulative height was measured annually for 8 consecutive years. Both
the crosses and parental lines exhibited temporal changes in growth inequality. The inequality of total height among the crosses
decreased logarithmically with age by nearly 3-fold after 13 growing seasons, suggesting that tree height became less variable
among the crosses as trees grew larger. Interestingly, the Lorenz asymmetry, an index reflecting the shape of the Lorenze
curve from which G is derived, revealed that the inequality of annual height increment among the crosses resulted from an
alternate contribution of the fast-growing and slow-growing trees. Among parental lines, two provenances with the smallest
and the largest overall inequality in total height showed a similar pattern of changes in annual growth inequality, and the
provenance differences were consistent over time. Compared to the other provinces, a local provenance exhibited less variation
in total height among individual trees as reflected by a smaller value of inequality, and was better adapted to the field
conditions. Our results demonstrated the sensitivity and usefulness of the Gini coefficient and Lorenz asymmetry for the analysis
of growth inequality in non-natural populations. Growth inequality is a potentially useful evaluation criterion for early
selection. Given comparable initial growth, provenances/families with lower growth inequality values would likely outperform
those with higher growth inequality, and eventually tree size of the latter would be more variable due to greater variations
among individual trees. Assessment of growth inequality at early ages will advance our understanding of variability of tree
growth within a population, facilitate forest genetics improvement programs, and enhance the efficiency of tree breeding. |
| |
Keywords: | Cunninghamia lanceolata (Lamb ) Gini coefficient Lorenz asymmetry Lorenz curve quantitative trait |
本文献已被 PubMed SpringerLink 等数据库收录! |
|