In Situ Rainwater Conservation Through Half-Moon Terraces for Sustaining C. registanense in the Indian Thar Desert

Abstract

Cynanchum registanense Jayanthi is a rare threatened species of the arid region which needs conservation efforts. We report here its diversity in nature and efficacy of traditional rainwater conservation structure, i.e., half-moon terrace (HMT) in accelerating plant regeneration and population buildup as well as in situ conservation. Two biotypes of C. registanense found in nature are (i) common on rocky crevices having crisped margin leaves with light yellow flowers, and (ii) growing on sand deposition having leaf margin entire and dark yellow flowers. Ecologically, it is a subdominant species with relative importance values ranging from 8.71 to 49. Monitoring plant population and growth parameters for 3 years showed that the HMT conserving sufficient rainwater quantities successfully regenerated plants of C. registanense. Box-whisker plots revealed relatively high annual variability of the plant populations and high median values in four quadrats situated closer to the embankment of HMT as compared to those located away from the embankment. Comparing mean plant populations between adjacent pairs of quadrats using a t-test revealed that C. registanense regenerating within 5 m of HMT embankment flourished better than those growing farther away. Plant population showed a moderately positive linear relationship (R² = 0.30), significant at p > 0.10. It was further revealed that a minimum of 27 mm rainfall spread over 6-day period is essential for conserving C. registanense. Overall, findings of this study proved existence of variability in habitat-specific C. registanense in arid region of western Rajasthan, which could be conserved in situ and enhanced in its density by a traditional rainwater conservation method.