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Scientia Silvae Sinicae ›› 2015, Vol. 51 ›› Issue (2): 1-10.doi: 10.11707/j.1001-7488.20150201

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Population Structure and Dynamics of Juniperus rigida in Different Regions of Loess Plateau

Zhang Yafang1, Li Dengwu1,2, Wang Mei1,3, Liu Pan1   

  1. 1. College of Forestry, Northwest A & F University Yangling 712100;
    2. Ningxia Helan Mountain Forest Ecosystem Orientational Research Station Yinchuan 750000;
    3. Tibet Vocational Technical College Lhasa 850000
  • Received:2013-12-31 Revised:2014-04-30 Online:2015-02-25 Published:2015-03-11

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Abstract:

【Objective】Population structure and dynamics of plant can reflect the survival of the population and display the interaction between plant and environment. It is an important content of population ecology, and it has significant implications to protection and utilization of plant resources. Juniperus rigida is a wild tree species with priority for protection in Loess Plateau, a comparative study on structure and dynamics of Juniperus rigida populations in different regions of Loess Plateau was carried out to analyze population survival and dynamics of Juniperus rigida in Loess Plateau, in order to reveal the trend of population development. This study would have important theoretical and practical significance for developing strategies of rehabilitating Juniperus rigida population.【Method】A field survey was carried out on 5 populations of Juniperus rigida selected in 5 different regions in Loess Plateau (Wuchuan, Inner Mongolia; Zhuolu, Hebei; Hunyuan, Shanxi; Fugu, Shaanxi; Helanshan, Ningxia) by using sample plots. According to the characteristics of life history of the species and considering results from previous studies, diameter, height and crown width were divided into classes and population structure was constructed using the classes. Static life table, survival curve, mortality curve, disappearance rate curve were produced using space to replace time, i.e. diameter structure instead of age structure. 4 functions (survival, accumulative mortality, mortality density, and hazard rate) of survival analysis were used to analyze population dynamics of Juniperus rigida.【Result】 Different extents of absence of some diameter classes was found in diameter structure of 5 populations; Height structures of Zhuolu and Hunyuan populations were relatively complete; Certain extent of absence of crown-width classes were found in the 5 populations, the crown coverage of Wuchuan, Zhuolu and Hunyuan populations were mostly within 2 m2, while Helanshan population was mostly larger than 3 m2. The static life table showed that there were large differences of number of survival trees among different age classes, the number of survival trees decreases with age; the highest rate of mortality and disappearance rate were both in age class IV; and the highest life expectancy was in age class I. Two types of the survival curves of 5 populations were found, Wuchuan fitted Deevey-III while the others tended fit Deevey-II. The changes of mortality and disappearance rate were in similar trends for the 5 populations. Four survival curves of 5 populations showed that, the populations Wuchuan and Fugu reduced at young ages, grew stably at middle ages and declined at old ages, and Fugu showed a sharper reduction, while the populations Zhuolu and Hunyuan had a steep reduction in early growth and a late recession, and the population Helanshan reduced slightly at young ages and recessed late.【Conclusion】There were some differences among 5 populations of different regions in the structures of diameter class, height class and crown width class. Populations of Zhuolu and Hunyuan showed regeneration potential as the population density of them were relatively large and they also had a certain number of young plants; Fugu population had a considerable number of aging plant; the diameter class structures of Fugu, Wuchuan and Helanshan were relatively complete, while the population density were smaller and young plants were comparatively rare. There were environmental screenings and competitive pressures in the process of young trees growing up into big trees, and the survival ability of the big trees were stronger. The populations Zhuolu and Hunyuan could be restored and updated if the ecological environment could be improved as there were some young trees in Zhuolu and Hunyuan populations; the regeneration and development of Fugu population lacking young trees would be limited without the supplementation of young trees. In order to protect the populations of Juniperus rigida, attentions should be paid to protecting the young trees; and measures should be taken to promote germination as it was low under natural conditions; For populations with serious aging such as Fugu population, supplementary plantings should be used to ensure regeneration and development of the populations.

Key words: Juniperus rigida, population structure, static life table, survival curve, survival analysis

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