苔藓植物群落在重庆小寨天坑垂直梯度上的分布规律

Distribution of bryophyte communities along the vertical gradient of oversize sinkhole of Xiaozhai Tiankeng of Chongqing city,China

小寨天坑是目前世界上已发现的规模最大的天坑(坑口直径626 m,最大深度662 m),对天坑生物多样性的研究具有代表意义。将其在垂直深度上等距划分为5个梯度,分析各个梯度苔藓植物群落多样性特征与其环境因子的关系,探讨苔藓植物群落在特大型天坑垂直梯度上分布规律,探索特大型天坑在物种多样性保持的特性。结果表明:(1)小寨天坑苔藓群落共含有苔藓植物39科82属133种:各个梯度苔藓植物群落多样性指数表现为:坑底>中部>中下部>中上部>坑顶,均匀度为:坑底>中部>中下部>中上部>坑顶;(2)β多样性指数分析表明,底部与中下部的Jaccard系数介于(0.25-0.5)之间,说明各个梯度微环境中等不相似,其余各个梯度介于(0-0.25)间,说明极不相似;(3)CCA分析表明:光照对苔藓植物分布的影响最大,其次为湿度,而温度和人为干扰相对较小。天坑底部地处地下河旁,水分充足,加上距地面最深,受人为干扰较少,所以其苔藓植物群落物种多样性最高,是生物避难所的中心,对生物多样性的保持具有更加重要的意义。

Xiaozhai Tiankeng is the largest sinkhole(the diameter of the pit mouth is 626 m;maximum depth is 662 m)discovered in the world at present,which is of representative significance for the study of biological diversity in sinkhole.It was divided into 5 gradients in vertical depth,and the relationship between the diversity characteristics of bryophyte communities and their environmental factors was analyzed,so as to explore the distribution rules of bryophyte communities on the vertical gradient of oversize sinkhole and explore the characteristics of species diversity maintenance in oversize sinkholes.The results showed that:(1)There were 133 bryophyte taxa from 36 genera and 23 families in Xiaozhai tiankeng;diversity index showed the trend of bottom〉middle〉below the average〉above the average〉top.Evenness index showed the trend of bottom〈middle〈below the average〈above the average〈top.(2)The analysis of the β diversity index indicated that the Jaccard coefficients at the bottom and the middle bottom were between(0.25-0.5),indicating that their microenvironment was moderately similar,and the other gradients were between(0-0.25),indicating that they were extremely different.(3)CCA analysis showed that light had the greatest influence on the distribution of bryophytes,followed by humidity,while temperature and human disturbance were relatively small.The bottom of sinkhole located beside the underground river,with sufficient moisture and the deepest distance from the ground,which was less disturbed by human beings.Therefore,The bottom of sinkhole with the highest species diversity was the center of biological refuge,which had more important significance for the conservation of biological diversity.