吉首蒲儿根种群土壤养分特征与分布格局

Characteristics of Soil Nutrients and Distribution Pattern of Sinosenecio jishouensis Population

吉首蒲儿根是近年发现的新物种,对其仅有的3个自然样地生境表层土壤养分特征进行分析,并运用相邻格子法研究其种群分布格局。结果显示:(1)吉首蒲儿根生于海拔300～370m的瀑布下或溪沟边,群落为草丛、灌丛或次生灌丛;种群生境土壤含水量较为丰富,约为34.28%,pH值为8.51～8.60,有机质含量为107 500～143 300mg·kg-1,全氮含量为2 800～3 500mg·kg-1;有机质、全氮、全钾的含量显著高于对照样地,铜元素含量显著低于对照样地,而铁、磷、锰、铬、铅和锌含量与对照样地无显著差异。(2)土壤含水量、有机质、氮素的缺乏及铜含量的增加可能是限制该种群扩展的重要因素。(3)仅有的3个吉首蒲儿根种群的分布格局均呈集群分布,但聚集程度有所差异,方差/均值比率分别为6.68、14.39、11.53,t检验差异显著。(4)流沙瀑布种群的斑块聚集尺度为64m2,夯峡瀑布种群为8m2,而雷公洞种群的斑块大小尚无法判定。研究认为,吉首蒲儿根种群的分布格局可能与该物种的繁殖方式、种子传播的有限性及生境异质性有关。

Sinosenecio jishouensis D. G. Zhang,Y. Liu ＆ Q. E. Yang is a new species which is only distributed in Dehang canyon at Wuling mountain areas of northwestern Hunan. According to IUCN Red Species List S. jishouensis ranked as the Critically Endangered Species （CR） for its extremely small and rare popu lations. The content of main nutritional components in surface soil （0- 30 cm） of natural habitat of three plots of S. jishouensis was analyzed and its population distribution pattern was determined by using checkerboard frame method. The results showed that： （1）S. jishouensis were always found in habitat of waterfall and the Stream-ravine with an altitude from 300 m to 370 m,and its communities were always grasses,bushes and secondary bushes. To measure the environment factors in the habitats, we found that water content of soil get to 34.28% ,the pH values varied from 8.51 to 8.60,organic matter changed from 107 500 mg · kg^-1 to 143 300 mg·kg^-1 ,and total nitrogen contents with a variable from 2 800 mg· kg^-1 to 3 500 mg · kg^-1. Compared with the environment factors in plots of S. jishouensis and the control plots showed that,the contents of organic matter,total nitrogen,and total potassium are obviously high （P〈0.05）,and the contents of copper is significantly below the control ones （P〈0.05）,while the contents of iron,phos-phorus,manganese,chromium,lead and zinc in soil were not different from controls. （2）Low contents of water,organic matter, total nitrogen and high content of copper soil are probably the important environment factors to limit development of S. jishouensis population. （3） The distribution patterns of the only three natural S. jishouensis populations are clumped,and the intensity of clustering is different among different populations. The variance/mean ratios of these populations were 6.68,14.39 and 11.53, respectively, t test show remarkably difference. （4）The highest congregation areas are 64 m2 and 8 m2, respectively, at the Liusha population and Hangxia population,but the patch at Leigongdong population can not be demonstrate. Reproductive system, seeds with finite dispersal, and heterogeneity of its habitat conditions, are the major impact factors for the distribution patterns of S. jishouensis.