We carried out niche monitoring and analysis of plant populations under the forest community in the talus slope ecotone of a typical moderate-degraded Bajiaxiantang tiankeng to provide scientific references for biodiversity conservation and vegetation restoration in degraded tiankeng area. The results showed that soil ammonium, available potassium, and available phosphorus signifi-cantly affected species distribution, which explained 37.4%, 32.8%, 29.3% of the total variation, respectively. With the change of talus slope of tiankeng (pit, uphill, mid-slope, downhill and pit bottom), life form of understory plants changed from evergreen and xerophytes to evergreen and hygro-mesophytes, with the niche overlap of herbs being larger than that of shrubs. Shrubs of Viburnum congestum and Campylotropis polyantha, and herbs of Arisaema erubescens and Arthraxon hispidus had wide ecological amplitude and strong resistance, which occupied the upper layer of the shrub and herb layers. Shrub Cornus oblonga and herb Geranium nepalense, Agrimonia pilosa lost the competitiveness with increasing soil alkalinity. Niche characteristics of understory dominant species in Bajiaxiantang were closely related to the canopy structure of mixed trees, ecological strategies of shrub and herb species, unique habitat of tiankeng, and the importance value of dominant species.
以典型的中度退化天坑——巴家陷塘天坑为例,对其倒石坡生态交错带森林群落优势种种群进行生态位特征分析,以期为喀斯特天坑的生物多样性保护及天坑地表区域植被的生态修复提供科学参考.结果表明:土壤养分铵态氮、速效钾、有效磷相较于土壤水分和温度对天坑物种分布影响最显著,解释量分别为37.4%、32.8%、29.3%.随着天坑倒石坡坡位(坑口-上坡位-中坡位-下坡位-坑底)的变化,其林下植物生活型由常绿旱生向常绿湿中生变化,草本种群生态位重叠程度较灌木种群更大.灌木植物密花荚蒾、小雀花和草本植物一把伞南星、荩草有较宽的生态幅和抗逆性,占据天坑林下灌草层的上层.随着土壤碱性不断加强,灌木植物长圆叶梾木和草本植物尼泊尔老鹳草、黄龙尾失去竞争力.巴家陷塘林下优势种的生态位特征与针阔混交林的冠层结构、林下灌草的生态策略、天坑独特的生境、优势物种的重要值等密切相关.
Keywords: Karst tiankeng; environmental gradient; niche; talus slope.