Abstract

Myricaria laxiflora, distributed along the riverside of the Yangtze River in the Three Gorges area, lost its habitats and became an endangered species in 2003 due to the water storage of the Three Gorges Project. In order to understand whether density plays an important role in population self-modulation, we conducted an outdoor experiment which included five density treatments in the Center for Ecological and Environmental Research of China Three Gorges University. The changes of seedling death, below-ground seedling biomass, above-ground seedling biomass, total seedling biomass, number of branches, root depth, and length of first grade branch in different density treatments were examined in our experiment. The results showed that seedling survival rate decreased with increase of seedling density, and was reduced significantly when seedling density was greater than 250 ind./m2. Total seedling biomass, above-ground seedling biomass and below-ground seedling biomass differed noticably between density treatments. The correlation coefficient between above-ground biomass and density was bigger than that between below-ground biomass and density. Also, the number of branches, root depth and length of first grade branch decreased significantly with in-creases of seedling density, but number of branches responded more sensitively to density than length of branch and root depth. These results indicated that seedling density significantly stressed seedling survival and growth in Myricaria laxiflora, especially the growth of above-ground parts, and that density played an important role in population self-modulation and stability maintenance. The relationship of total biomass and below-ground biomass with other parts of seedlings were also explored with regression to understand theimpact of density on the growth of different parts of seedlings and to find proper density for population re-construction and management. We suggest that the density of 250 ind./m2 was the limit for population recon-struction.