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Li Z.C.,Hainan University | Luo W.,Chinese Academy of Sciences | Chen Y.F.,Chinese Academy of Forestry | Hong X.J.,Hainan Bawangling National Natural Reserve | And 2 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2015

Dacrydium pectinatum is the only Dacrydium genus of Podocarpaceae family in China. It is one of the symbolic species in tropical mountain rain forest in Hainan Island and one of the key species to maintain the natural communities in that region. Its distribution range is very narrow and it can only be found in the forest region of Bawang Mountain, Jianfengling Mountain and Diaoluoshan Mountain. From the beginning of 1960s, the natural forest of D. pectinatum has been severely damaged because of people's massive logging of tropical forests in Hainan. As a result the distribution area of D. pectinatum has become ever smaller, the quality of D. pectinatum forest has gotten ever worse, and it has become ever harder for the D. pectinatum to naturally regenerate themselves. What's worse, there has emerged a decline in tree-age structure. Based on this situation, D. pectinatum was listed in China Rare and Endangered Plants Red Data Book as the third degree of endangered plants in 1992. The paper first defines the three stages of D. pectinatum growth based on its diameter at breast height and tree height. Specifically seedling is defined as the tree with a height under 50 cm, sapling refers to the tree with a DBH lower than 10 cm and a height over 50 cm, and matured trees are those whose DBH are larger than 10 cm. The paper used geostatistics and constrained ordination analysis method to analyze the space distribution characteristics of D. pectinatum in three life stages from the perspective that there is relevance between its space distribution in different life stages and microhabitats factors. Also, the spatial autocorrelation of 11 microhabitats is analyzed. The results showed that: 1) there was an obvious difference in the spatial distribution of D. pectinatum in its different life stages. The seedlings were in aggregating distribution and lived with significant spatial autocorrelation. However, the aggregating intensity gradually weakened with the seedlings growing into sapling and then to matured trees; 2) RDA analysis showed that there were significant differences in the relationship between the distribution patterns and microhabitat factors in different life stages of D. pectinatum, and the effect of habitat filtering varied with the change in its life stages. 3) The effect of microhabitat variables on the spatial variability of the seedling, the sapling, and the mature trees were 78.4%, 41.2%, and 33.6%, respectively. In the whole life stage, the period from the seedling to the sapling is the key to successful plant colonization. And seedlings have got stronger environmental sensitivity than the adult tree. It follows that the restrictive effect of microhabitat factors on D. pectinatum's distribution mainly occurred in its seedling stage; 4) In sound conditions, 22.2% variation can be interpreted by PCNM variables and microhabitat variables in common. And a typical 'induced spatial variation' phenomenon was found, which means that the spatial variation of microhabitat variables can result in the spatial variation of D. pectinatum throughout its seedling, sapling stage and matured stage. The results confirmed the relevance between microhabitats and the distribution of D. pectinatum in different life stages. And the paper provided a scientific foundation for better understanding of the relationship between the mechanisms of population maintenance, the spatial distribution pattern of D. pectinatum, and its regeneration dynamics. If there will be any further research on this topic, it is suggested that the monitoring and the study be carried out during a longer time span, and larger size of sample be studied, for a more accurate analysis of the influence of microhabitat factors on seedling regeneration and its survival pattern. © 2015, Ecological Society of China. All rights reserved.

Li Z.-C.,Chinese Academy of Forestry | Chen Y.-F.,Chinese Academy of Forestry | Hong X.-J.,Hainan Bawangling National Natural Reserve | Han W.-T.,Hainan Bawangling National Natural Reserve | Li X.-C.,Hainan Bawangling National Natural Reserve
Chinese Journal of Ecology | Year: 2015

Dacrydium pectinatum is one of the symbolic species in tropical mountain rain forest in Hainan Island and one of the key species to maintain the natural communities in that region. Based on the survival theory and point pattern analysis, we analyzed the demographic structure, spatial distribution characteristics and inter-species relationships of D. pectinatum. The results showed that: 1) The tree number for each age class of the D. pectinatum population showsed that the mortality in the first period of life stage is high, and the population is relatively stable in the middle period, after which the mortality increases gradually. 2) The survival curve of D. pectinatum population changes greatly. The population mortality and disappearance rate are higher in I-V age classes, showing the form of Deevey-III; in the VII-XVII age classes, the survival curve shows the form of Deevey- I. 3) In the range of the study scale, there is an obvious difference in the spatial distribution of D. pectinatum at different life stages. The individuals perform aggregation distribution at small and medium scales in the early and middle periods of life stages, however, the aggregation intensity gradually is weakened with the increase of scale and age, from a clumped to a random pattern as trees grow from young to middle-aged to old trees. In the later period of life stage, individuals show random distribution at the entire study scale. 4) The spatial association among different life stages is not significant, and most of them exhibit no correlation. © 2015, editorial Board of Chinese Journal of Ecology. All rights reserved.

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