Structure Of Natural Coniferous Forest Community In The Kanas Reserve, Xinjiang

The natural coniferous forest in Xinjiang Kanas Nature Reserve is a typical representative of the Southern tagia of west Siberia in China, and research on it had a very high scientific value. Based on the investigation on forest community in the longer-time research plot which was 25 hectare area, the species diversity of communities, population structure, stand spatial structure, the main population niche and interspecific association were analysed. The purpose was to provide a theoretical basis for sustainable forest management. The richness index, evenness index and diversity index were used in the analysis of species diversity. The size structure and height structure of main forest type were used in the analysis of population structure. Three typical stand structure parameters such as neighborhood pattern, mingling degree, and neighborhood comparison were used to analyze the stand spatial structure. Niche analyzed with formula of Levins niche breadth and formula of Pinaka niche overlap basing 2x2 contingency table, and adopting x1-test were used to analyze the interspecific association. The results were as follows:(1) Community of natural coniferous forest consisting of 18 families,31 genera and 33 species in Kanas Reserve.6 species of them belong to 6 genera and 3 families in the tree layer, and the dominant species were Larix sibirica, Picea obovata and Pinus sibirica. There were 7 species belonging to 6 genera and 4 families in the shrub layer, and the dominant species were Lonicera caerulea var. altaica and Spiraea chameadryfolia. There were 20 species belonging to 20 genera and 15 families in the herb layer, and the dominant species were Poanemoralis, Vaccinium vitis-idaea and Carex polyphylla.(2) The richness index ranking showed that herb layer> shrub layer> tree layer. And the evenness index and diversity index ranking showed the same results that herb layer> tree layer> shrub layer. There was a negative correlation between elevation and four indexes, the slope was also. There was extremely significant correlation among these four indexes. Richness increased with the increasing of the plot area, and no longer increased until a certain degree.(3) Diameter and height of Picea obovata and Pinus sibirica structure showed a reverse J type. The population structure of Larix sibirica and Betula pendula was spindle type.(4) Stand mean neighborhood pattern was 0.509, which indicated that the distribution pattern of the stand was random. With the increasing of tree diameter, its distribution pattern changed from random distribution to cluster distribution, and then to random distribution. The average value of mingling degree was 0.629, which indicated that the content of different tree species mingling intensively. The mingling degree of P. obovata was the lowest. The mingling degree increased with the increasing of diameter classes, gradually. Abies sibirica and L. sibirica had more dominant position in the stand than P. sibirica. Neighborhood comparison decreased with increasing of tree diameter.(5) Picea obovata had a wider niche breadth and the value was 0.9131, while the minimum value of the niche breadth species was Abies sibirica (0.0521) in tree layer. The widest niche breadth species of shrub layer was Lonicera caerulea var. altaica, while narrower niche was Betula nana. Vaccinium vitis-idaea in herb layer had a wider niche breadth and the value was 0.8686, while Lilium martagon Linn var. pilosiusculum Freyn, Radix Paeoniae and Saxifraga punctata had a narrower one and the value was only 0.0400.(6) There were three pairs which niche overlaps were higher than 0.05 in tree layer, accounting for 20%. Five pairs of shrub layer for niche overlap values greater than 0.05, accounting for 23.81%. Fifty-five pairs of herb layer for niche overlap values greater than 0.05, accounting for the total number of 28.95%. The results showed that the degree of niche overlap was not high in the community.(7) The analysis showed that the overall interspecific association of the natural forest community was a significant positive association (VR=2.32>1). The study was conducted on the interspecific among the 561 species pairs in three levels. The test showed that there were 250 species pairs in positive association, accounted for 44.56 %. Among them,4 pairs in extremely significant positive association accounting for 0.71% and 7 pairs in significant positive association accounting for 1.25%. On the other hand, there were 311 species pairs in negative association, accounted for 55.44 %, which 0 pairs and 14 pairs respectively showed extremely significant negative association and significant negative association.