Preliminary Study On The Population & Community Characteristics Of Picea Schrenkiana Var. Tianschanica And Its Geographic Variation

Main forest in Tianshan Mountains is the montane forest dominated by Picea schrenkiana var. tianschanica, and the altitudinal range of the forest varies with the change of longitude and relevant environmental conditions. The growth status of P. schrenkiana var. tianschanica as well as the species and number of companion plants in the community varies regularly along the vertical gradient in the different longitudes. P. schrenkiana var. tianschanica forest in Zhaosu, Gongliu, Wusu, Urumqi and Hami which covered about 12 longitudes(81°05′-93°41.5′E)along the Tianshan Mountains was investigated using vertical transects to study the structure, dynamics, distribution pattern, and cone & needle size characters of the spruce population, and to analyze characteristics of stands, species diversity and biomass of the communities dominated by the spruce population. A preliminarily analysis was given to the geographical variations of the population & community characteristics along the longitudinal and altitudinal gradients. The main results are as follows:(1)In order to explore the population structure of P. schrenkiana var. tianschanica in the different sites, the percentage of trees in the different sizes, the diameter distribution, and the fitted equations for accumulated percentage of P. schrenkiana var.tianschanica were analyzed. From the percentage of seedling & sampling and the small trees, the order is Hami, Urumqi, Gongliu, Zhaosu and Wusu.The structure of diameter class in Zhaosu, Gongliu, Wusu, Urumqi and Hami took on inversed"J"Shape. The index curve correlation coefficient is highest in Zhaosu and Urumqi, while the logarithm curve correlation coefficient is highest in Gongliu, Wusu and Hami.(2)Based on the methods of"the space-for-time substitution"and stem size structure in place of age structure, the population static life tables were made, and the population curves of survivorship, mortality rate, killing power value and hazard rate function were drawn in order to explore the population dynamics of P. schrenkiana var. tianschanica in the different sites. The results showed that the survivorship curve of the population generally trended to the type of DeeveyⅡ, suggesting that the population was stable. There were two mortality peaks for each population in the different sites. The mortality rate and the time when mortality peaked were significantly different among different sites. (3)The distribution pattern of P. schrenkiana var. tianschanica population was studied on the basis of theoretical distribution model and aggregation intensity indeces. The results are as follows: The population distribution pattern is influenced by the age stages and altitudinal ranges. The clustering intensity increased with the increasing of the DBH or the age stages. The clustering intensity was strongest in the upper altitude.(4)Two methods were used to analyze the change of cone size characters along the altitudinal gradient. Three altitudinal ranges (low, middle and high)were divided for each site and the differences of cone size characters within each altitudinal range were analyzed, and the variation of cone size characters along altitudinal gradient at 50 m intervals was explored. The results showed that the cone size characters varied with different range of altitude in each site. The cone length and the ratio of cone length to width decreased along the altitudinal gradient, while the cone width didn't change significantly along the altitudinal gradient. The variation of cone width was lower than that of cone length. The cone size characters varied with the altitude, slope and longitude. The variation of cone length was mainly influenced by the altitude and slope, the variation of cone width was mainly influenced by the longitude, however, the ratio of cone length to width showed a negative correlation to altitude, slope and longitude.(5)Regression analysis was used in studying the variation of needle characters in the different altitudinal gradient. Anova analysis and variation coefficient were used in the needle morphological variation in the different sites. The results showed that the needle length and the ratio of needle length to width decreased with the increasing altitude. The needle width increased with the increasing altitude. The variation coefficients of needle length were smallest in the needle morphological variation.(6)Average and maximum DBH showed no significant variation while average and maximum tree height, mean stand density, total basal area and stand volume of the forest generally showed hump-shaped curves with the increasing of the altitude. In spite of the variation of the altitudinal range in the different sites, the changes of average and maximum tree height, mean stand density, total basal area and stand volume along the altitudinal gradient of the forest could be described by the quadratic curve equations;The stand density and the density of seedling & saplings in the mid-east [0]were higher than those in the west, while in other aspects[0] including the average DBH, the maximum DBH, average tree height, maximum tree height, total basal area, stand volume, crown width and the height beneath the branch all took on the general trend is that the west is higher than the mid-east.(7)At most longitudinal positions, P. schrenkiana var. tianschanica forest was basically of pure forest, with P. schrenkiana var. tianschanica as the dominant species, very few of other arbor and shrub speices, and the species of herbs being controlled by the growth of P. schrenkiana var. tianschanica. This forest had the widest distribution, highest canopy, best growth, and highest stand volume at middle altitudes, resulting in the lowest species richness of herbs. In spite of the variation of the altitudinal range in the different sites, the herb species richness in P. schrenkiana var. tianschanica forest in Tianshan Mountains showed an inversed hump-shaped variation along the altitude, which could be described by the quadratic equation.(8)The biomass of P. schrenkiana var. tianschanica was estimated with the regression equation based on the date of community investigation. The results showed that the biomass in the different sites ranged from 88.695 to 436.915 t·hm-2. The western biomass was higher than the mid-east; Variation of biomass along the altitudinal gradient and in the different DBH class all took on the unimodal pattern.