Study On Larix Principis-rupprechtii Population Natural Regeneration Pattern In Clearing Strip

Larix principis-rupprechtii is one of main constructive tree species of conifer forest which is distributed in semi-humid region, north China. Shannxi Province is the fittest area for growth and development of Larix principis-rupprechtii, that constituting the main body of Chinese Larix principis-rupprechtii resource. Presently, studies on Larix principis-rupprechtii population and community are rather insufficient. The population structure, spatial pattern of different age-classes and their correlation were studied in a natural regenerating stand which lies in a clear-cut strip. 5 plots of 20mx20m were set totally. The location of every tree was mapped by "Interpoint method", and the DBH and height of each individual were recorded. To analysis Larix principis-rupprechtii population structure and dynamic, we adopted the method of size class substituting for age class. Trees were divided into five size classes, viz. age I DBH<2.5, age II 2.5 cm < DBH<7.5 cm, ageIII 7.5 cm < DBH<12.5 cm, ageIV 12.5 cm < DBH<17.5 cm and ageV DBH > 17.5 cm. The spatial pattern of Larix principis-rupprechtiiwas analyzed using five independent methods, the Morisita index ( I_δ ) ,variance to mean ratio( V/ X ) ,the congregation index ( m/m ) , negative binomial distribution parameter ( K)and spatial point pattern analysis( SPPA). The results revealed that Larix principis-rupprechtii population trends decline for the shortage of seedling and sapling. But the population has the potential to be stable. The size class reflected the past disturbance history of population at a certain extent. Forest edge regeneration in shady slope is an important mode for Larix principis-rupprechtii, which could be used as basis of zonal cutting regeneration design. The trees of age I and age II were clumped under most spatial scales studied whereas the others were randomly and uniform distributed. We concluded that the current distribution pattern of Larix principis-rupprechtii was related to itself biological characteristics and disturbance. It also reflected the pattern and mechanism of population natural regeneration. The intensity of assemblage (IA ) varied with scale. The first two methods indicated that IA decreased with increasing scale, but the SPPA method showed that the IA first increased with increasing scale and then declined at greater scales. The relationship between saplings and big trees was significantly positive correlative with the scale less than 1.5m. However, the relationship between individuals of older trees is significantly negative correlative with small scale. The relationships between individuals in different age-classes are almost all irrelative with larger scale. The relationship between Larix principis-rupprechtii and Picea spp. is almost all irrelative, but it trends to be negative correlative. The big trees of Larix principis-rupprechtiipromote growth of Picea spp. seedlings. The Morisita index ( I_δ ) and variance to mean ratio ( V/ X ) wre good for determining the spatial pattern type of population, but SPPA was...