Abstract:

Six plots were investigated and field data were obtained with the contiguous grid quadrate method in a natural Populus euphratica forest in the upper reaches of the Tarim river. We developed a static life table and a survival function of Populus pruinosa population based on the population life table and a theory of survival analysis. Survivorship curves，and the mortality rate were determined，and population dynamics were analyzed by using the spectral analysis. The results showed that： 1)Survival numbers of P.pruinosa populations were decreased with the increasing of age, and the expecting life of individuals with DBH larger than 40 cm declined obviously. 2)The Survivorship curve of the populations was Deevey Ⅲ. Four survival functions showed that the P.pruinosa population declined in young age and stabilized in old age. 3)There were two peaks of mortality rate existed in the lifespan：respectively occarred at the first and 11th age class periods. Seedling shortage was the restricting factor of development. 4) The spectral analysis of the populations showed that there was a marked periodic fluctuation in the process of natural regeneration. 5)The higher mortality rate of P. pruinosa seedlings might be integrated by the interplay of biological characteristics of P.pruinosa and deteriorating habitat（groundwater level decreasing）.

Key words: Tarim River, Populus pruinosa, population demography, survival function, spectral analysis