Study On Neighborhood Interference And Competition Characters Of Larix Chinensis

Larix chinensis is one of typical endemic species in China, only distributed in alpine and sub-alpine belt in Mt. Qinling, Shaanxi Province of China. It is also one of endangered species in Chinese Plant red Data Book. It is the only tree that forms the pure forest which has special functions to conserve water, firm mountain stone and maintain water and soil at the timberline area, an altitude 2 600 m-3 600 m. Competition has been considered of one of the major forces that shape the morphology and life history of plants and affect the structure and dynamics of plant communities. Competition among plants exists when resource availability falls below the sum requirement of the community for optimal growth. Competition between both aboveground and belowground resources takes place in different size zones. A competition ecological character is the theoretical basic of population ecology. However, very few researches on this field can be found in L. chinensis, and a systematic investigation was made in this paper.Data on this study were collected in Taibai Mountain Natural Reserve of Shaanxi Province in China. Twelve samples of 40 m X 40 m were investigated, and every plot was stem-mapped, and species, DBH, total height, and crown length were recorded for each tree that had reached a diameter of 5 cm at breast height. In order to study the neighborhood competition effect, the morphological characteristics, in terms of the branching angle, total branch-number, current-year branch length, average branch length, and living branch number of main stem in per-stratum were investigated for L. chinensis in different neighborhood competition intensity.1 By using the method of increasing the range gradually, the average and total competition intensity of objective tree was studied. The results show that: (1) the average competition intensity decreases with the increasing of zone, and in a certain zone, it decreases very quickly while it has a little decrease beyond the zone, by which we can ascertain the zone of neighborhood. (2) the plants with different diameter scale have different neighborhood zone. And the neighborhood zone is 6 m, when we ignore the diameter scale of the subjective tree. (3) the relationship between the total competition intensity and the interference zone follows closely the following equation CI-A\nC+B. That suggests the method of increasing the range gradually can provideefficiently the zone of neighborhood. This study provides a new approach to ascertain the neighborhood zone on studying the plant competition.2 As most researches show, there is no competition index for every plant. An appropriate competition index was only chosen according to investigated object. The results show that: (1) There lie some relations in different competition index. (2) Through analysis and simulation the plot data, a competitive index reflects objectively the competition and growth pattern in L. chinensis, which was selected. As a result, Zhang's competition index was the best.3 By using the method of increasing the range gradually and Zhang's competition index model for individual tree to study the intraspecific and interspecific of L. chinensis. The results show that: with the increase of the size of objective tree and the distance between plants, the intraspecific competition intensity decreases, because of the population density regulation during self-thinning. In the community, there are few other species and their diameter at breast height is less than that of L. chinensis, as a result, the competition intensity of intraspecific was more excessive than that of interspecific. The order of competition intensity is L. chinensis - L. chinensis > Abies fargesii - L. chinensis > Betula utilis - L. chinensis > other species - L. chinensis. The relationship between competition intensity and the diameter of objective tree follows closely the following equation CI=AD , and the changing of competition intensity is very small when the diameter of the objective tree grows to 35 cm. The model can simulate and predict the intraspecific and interspecific competition efficiently.4 The intraspecific and interspecific in Abies fargesii was studied by using Zhang's competition index model for individual tree. The results show that: with the increase of the size of objective tree, the intraspecific competition intensity decreases. The order of competition intensity is L. chinensis - A. fargesii >A. fargesii -A. fargesii > Betula utilis -A. fargesii > other species -A. fargesii. The changing of competition intensity is very small when the diameter of the objective tree grows to 25 cm.5 The intraspecific and interspecific of L. chinensis and A. fargesii was studied by using Zhang's competition index model for individual tree. The results show that: the competition intensity of intraspecific in L chinensis was more intensive than that of interspecific (to A. fargesii), while the competition intensity of intraspecific in A. fargesii was weaker than that of interspecific (to L chinensis). Comparing with A. fargesii, L chinensis has much worse regeneration, higher mortality rate, slower growth...