密度对濒危物种疏花水柏枝幼苗存活与生长的影响

疏花水柏枝(Myricarialaxiflora)原产于三峡库区长江干流的河滩,三峡水库的蓄水淹没了其所有的野生种群,使之濒临绝灭。通过一系列的密度处理实验,我们研究了不同密度下疏花水柏枝幼苗的存活率、幼苗总生物量、地下生物量、地上生物量、一级枝数、二级枝数、一级枝长度的变化,揭示了密度对一年生幼苗存活与生长的影响。结果显示,随着密度的增加,疏花水柏枝种群内部的竞争加剧,幼苗的死亡率增加,特别是当密度大于250ind./m2时,死亡率显著上升,上述体现植株生长状况的各指标值也随密度的增加而显著减小。表明疏花水柏枝一年生幼苗的存活与生长受到密度的影响。文中还建立了密度影响下疏花水柏枝各构件部分生长发育的回归模型,解释了密度对它们的调节作用。最后对疏花水柏枝种群重建中的相关问题进行了分析讨论,以求为回归引种实践提供参考。

Effects of density on seedling survival and growth of an endangered species Myricaria laxiflora

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 Pro-ject. In order to understand whether density plays an important role in population self-modulation,we con-ducted an outdoor experiment which included five density treatments in the Center for Ecological and Envi-ronmental Research of China Three Gorges University. The changes of seedling death,below-ground seed-ling 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 coeffi-cient 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 increases 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.