Correlation and Community Stability Analysis of Herbaceous Plants in Dashiwei Tiankeng Group, China

Studying the interspecific association and stability of herbaceous communities in different developmental stages of tiankeng is helpful to understand the relationship between tiankeng vegetation and the environment, and can provide an important theoretical basis for the protection and restoration of the karst tiankeng ecosystem. In this study, the herbaceous community of the Dashiwei Tiankeng Group in Guangxi was studied to analyze the interspecific relationships and community stability of herbaceous plants in four different habitats (the earlier stage, middle stage, late stage and the external forest of tiankeng), and to explore whether the herbaceous community structure gradually stabilized with the development of tiankeng. The variance ratio (VR), X2 test, association coefficient (JI) and the Spearman rank correlation coefficient test were used to analyze the interspecific association of the main herbaceous plants in different developmental stages of tiankeng. The stability of the herbaceous community was analyzed by the stability measurement method of M. Godron. The results showed that: (1) the logarithm of the middle stage of tiankeng negatively correlated species was the highest (56.7%), and the logarithm of the later stage of tiankeng positively correlated species was the highest (57.2%). The positive and negative correlation ratio of main herbs decreased first and then increased, indicating that the middle stage of development was the period of high competition among herbs and the biggest difference in resource utilization. The ecological habits of herbaceous plants will be changed from sciophiles to hygrophytes to heliophiles and drought-enduring plants. (2) The earlier stage and middle stage of tiankeng overall relevance had a significant negative correlation, the later stage and external forest of tiankeng overall correlation were not significant positive correlation, and the X2 test and the Spearman rank correlation coefficient of different developmental stages of tiankeng most major herbaceous species were not significant correlation, suggesting that the major herbs in tiankengs had weak association and strong independence. (3) The distance from the intersection point to the stable point (20, 80) was 19.799, 17.867, 18.922 and 17.706, respectively, of the four regression models of tiankengs herb community, which further indicated that the forest herb layers were in an unstable state. The forest outside is relatively more stable than the herbaceous community inside the tiankeng.