| Populus wenxianica Z. C. Feng et J. L. Guo belongs to the genus of populus, family of salicaceae. It grows in Wen county and it is an endemic species of Gansu. Professor Feng Zicheng published it as a new species of populus and named it as polulus wenxianica in the 1990's. There has been no report about the growth rules and adaptability of this species by far since it was named. This paper, in order to show its growth rules, systematically investigated the growth dynamic of annual seedlings, the tree growth process and the biomass distribution. The impacts of environment changes on the growth of this species were preliminarily discussed by using the basic principles of dendroecology. All these will provide the scientific basis for the exploitation and protection of this species. The main results are as follows: (1)Based on the investigation of height and diameter growth of annual seedlings, the growth pattern and growth parameters in seedling stage were studied. The results indicated that the growth of populus wenxianica annual seedlings can be modeled by logistic curve, and can be divided into 3 stages: first slow growth stage, fast growth stage, second slow growth stage. The annual growth parameters of 100 seedlings are the beginning date of fast growth (DB), the middle date of fast growth(DM), the ending date of fast growth (DE), the length of fast growth(LG),the maximum average rate of growth(XRG), and the maximum value of height(KH) and diameter(KD) of populus wenxianica. The annual growth parameters of height are listed as follows: DB June 5, DM July 8, XRG 4.4886 cm·d-1, DE August 13, LG 70 days, KH 221.03 cm. The annual growth parameters of seedlings diameter are as follows: DB June13, DM July 13, XRG 0.193 mm·d-1, DE August 8, LG 59 days, KD 16.605 mm. The diameter and height of total annual growth are distinctively correlative with XRG and LG respectively. (2) With the stem analysis data of populus wenxianica collected in Wenxian, Gansu, the individual growing process of DBH(diameter at breast high), H(height),V(timber volume) were analyzed, the results showed that: the height growth of this species began at first while the DBH and V growth began later. The DBH, H and V increment process can be modeled by logistic curve while the annual increment and the mean increment equations of each factor varied, and the annual increment and the mean increment process can be modeled by polynominal functions. Multivariate quantitative study on single tree growth stage of natural populus wenxianica was made by using optimization method to classify ordered samples. The growth process was divided into 4 stages, they were sapling stage (1~4a), fast growing stage (5~11a), diameter growing stage (12~19a) and mature stage (20~27a). And according to the growth stages division, some management measures were suggested. The populus wenxianica achieved its quantitative maturity at 24 years old, its total timber volume increment was 0.8068 m3 while the mean increment was 0.0336 m3 at this time. (3)Investigation of biomass percentage of different organs of up-ground parts showed the trunk of 56.12%, the bark of 13%, the leaves of 9.5% and the branches of 21.4%. Some regression models were founded between the biomass of different organs and the height and diameter at breast high, which showed that the biomass of different organs was positively correlated with the height and the diameter at breast high of the tree. Meanwhile, the systematic deviation of these models were tested, the results indicated that the estimation accuracy of these models were high. The biomass tables of different organs of up-ground parts of populus wenxianica were established, which can be a reference to biomass investigation of populus wenxianica. (4)A 52-year tree-ring standardized chronology ranging from 1953 to 2004 was developed according to some basic principles of dendroecology. Statistical analysis of the chronology indicated a mean series inter-correlation of 0.431, a signal-to-noise ratio of 14.03, and a mean sensitivity of 0.1964. Correlation analysis between the tree-ring index and the meterological data showed that radial growth was positively correlated with rainfall in April, May of the current year, and in October of the previous year, which proved the rainfall had a significant impact on the growth of populus wenxianica. On the whole, the correlation between the temperature and the growth of the tree is small, The radial growth was negatively correlated with monthly average temperature in growth seasons (from May to August in current year), and it was significantly correlated with monthly average temperature in May. All these suggested that the growth of populus wenxianica was influenced by rainfall and temperature together. The regression model between tree-ring indexes and the monthly rainfall and monthly average temperature were founded, the optimal equation is:...
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