喀斯特原生天坑垂直梯度上植物多样性特征——以云南沾益天坑为例

摘要

规模宏大的地表负地形——喀斯特天坑具有巨大的容积和陡峭圈闭的岩壁,在坑底形成异于坑外的独特微生境,是研究物种组成和多样性的理想场所,但目前鲜少对喀斯特天坑植物群落的生态过程及其空间变化特征进行探讨.本研究以云南沾益大毛寺原生天坑植物群落为研究对象,通过游动分割窗技术以及边缘效应值、边缘效应强度和β多样性指数的计算,对原生天坑“坑边缘—坑壁—坑底”的生态交错带进行定量判定,探讨垂直环境梯度上植物群落物种多样性变化特征及天坑内外物种多样性边缘效应特征.研究结果表明,原生天坑“坑边缘—坑壁—坑底”垂直梯度上的生态交错带出现在坑壁中域位置,宽度大约为40 m,是连接天坑内外生态系统的一个特殊生态过渡带;天坑内外植物群落在坑壁出现“断裂”,存在不同于一般生态交错带的“边缘负效应”;基于β多样性指数,垂直环境梯度上植物物种更替率总体呈上升趋势,坑底与坑边缘的植物群落物种组成存在较大差异,坑底拥有更高的物种丰富度和多样性,具有重要的物种多样性保护库价值.%As a kind of grand negative landform,karst tiankeng,termed in the early 21st century,is characterized by huge internal space,steep and enclosed cliff,and unique microhabitat.Its intrazonal habitat conditions are suitable for animal and plant growth and reproduction.Recently,with the exploration of the scientific and aesthetic values of tiankengs,it appears to be an ideal target to study plant species composition and diversity of karst tiankeng,but current researches on the ecological process and its spatial variation are less.Damaosi tiankeng is of a typically natural tiankeng in Zhanyi Tiankeng Group in Yunnan,where it has low accessibility and high intrazonality.It is scientifically necessary to take Damaosi as case study to quantitatively determine the ecotone along the vertical gradient by calculation of the SED value,edge effect value,intensity and β diversity index,and then discuss the community composition,species diversity variation and the edge effect value based on the plant diversity inside and outside tiankeng.The results showed that along the vertical gradient of "pithead-cliff-bottom",the ecotone (its width was 40 m around) of inside and outside of the tiankeng was found in the middle of the tiankeng cliff,and the tiankeng cliff served as a special ecological transition zone connecting its inside and outside ecosystem.The species diversity of plant community inside and outside the tiankeng exhibited interruption in the cliff,a marginal negative effect different from the other ecotone.Based on β diversity index,overall plant species turnover rate presented a rising trend along the vertical gradient,and the plant community species composition in the bottom and pithead of the tiankeng had large difference.There was high species richness and diversity in the bottom of the tiankeng with a valuable species diversity protection pool.Besides,there was no significant relationship between the species diversity and the vertical gradient variation.The finding can improve existing theoretical knowledge system and provide important reference for ecological restoration of the karst area.