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Scientia Silvae Sinicae ›› 2010, Vol. 46 ›› Issue (7): 16-21.doi: 10.11707/j.1001-7488.20100703

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Density-Dependent Sex Ratios for Dioecious Tree Species Populus davidiana and Fraxinus mandshurica

Zhang Chunyu1;Wang Desheng2;Wei Yanbo1，2;Zhao Xiuhai1;Jia Yuzhen1;Zhou Haicheng3   

  1. 1.Key Laboratory for Silviculture and Conservation of Ministry of Education, Beijing Forestry UniversityBeijing 100083; 2. Management Center of Natural Forest Protection Project in Jilin Province Jilin 133613;3.Administration of Changbai Mountain National Nature Reserve in Jilin Province Jilin 133613
  • Received:2009-03-16 Revised:2010-05-25 Online:2010-07-25 Published:2010-07-25

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Abstract:

A 5.2 hm2-plot was respectively established in a secondaryPopulus davidiana-Betula platyphylla forest and secondary conifer and broadleaved mixed forest in Changbai Mountains. The gender of all reproductive individuals of Fraxinus mandshurica andPopulus davidiana in the plots were determined by observing reproductive organs (flowers and/or seeds) through binoculars within the study plots from April to October in 2006, 2007 and 2008.The relationships between sex ratios (male to females) and population density and local stand density were studied for the dioecious tree species, Fraxinus mandshurica andPopulus davidiana. The relationships between sex ratio and sample area, population density and stand density were studied using random-quadrat method. The density-dependent sex ratio was tested by GLM model. The results showed that, the numbers of males and females increased as increasing sample areas for the dioecious tree species, F. mandshurica and P. davidiana. Sex ratios exhibited significant density-dependent for the two dioecious species (P<0.001). Sex ratios decreased with increasing local stand density for F. mandshurica and P. davidiana. Sex ratios showed different responses to density of reproductive individuals and population density in different forest types. The sex ratios of P. davidiana decreased as increasing stem density of reproductive individuals and population density, and those of F. mandshurica increased as increasing stem density of reproductive individuals and population density in secondary P. davidiana-B. platyphylla forests. But contrary results were found in secondary conifer and broadleaved mixed forest. Thus, we concluded that density-dependent sex ratios depended on the species group of studied tree populations in the forests. The response of sex ratios for P. davidiana and F. mandshurica to density of reproductive individuals and population density was different in different forest types.

Key words: dioecy, density-dependent, sex ratios, Fraxinus mandshurica, Populus davidiana