[Interspecific relationships of dominant species in the grassland community of moderately degraded tiankeng of Yunnan, China.]

Karst tiankeng is a special grand negative landform. The environment of tiankeng inside are independent of that outside, showing a unique characteristics of plant community. Taking a moderately degraded tiankeng with good accessibility, Bajiaxiantang as the focus, the dominant species with importance value >1 were selected to clarify the interspecific association of 11 dominant species by the multi-disciplinary approach including the variance ratio (VR) of overall association, Φ2 test, association coefficient (AC) and Spearman rank correlation coefficient. The results showed that VR of overall association in this grassland community was 1.377 (which was larger than 1), indicating that this community had overall significantly positive interspecific association. Given the great difference between the positive and negative association and significantly negative correlation between heliophiles and sciophiles, the community had independent distribution. The number of positive pairs of species (26) was less than that with negative correlation (29) in Spearman correlation analysis. Combined with the difference of tiankeng's micro-environment, dominant plant species of degraded tiankeng could be divided into three ecological groups. The grassland community in tiankeng showed circle distribution pattern.