Disturbance and resilience of aquatic plant communities in fish ponds after temporary dry periods

Fish pond systems are managed with different practices. Among them, a dry period with one year without water is applied in some cases to promote mineralization of the sediments and control the development of pathogenic bacteria. This dry period induces a drastic disturbance on the plant communities. The objective of this work was to study the influence of a one-year dry period applied every five to seven years on aquatic plant diversity and abundance. For this, we studied the aquatic plant community of 149 fish ponds during the first year after a dried period (Y1), and ponds with a dried period dating back two years (Y2), three years (Y3), four years (Y4) and five to seven years (Ysup5). According to Jackknife index, mean species richness was highest for Y1, with 29 species compared to the other years (24 species for Y2; 19 for Y3; 15 for Y4 and 17 for Ysup5). A total of 15 species were identified as species unique to Y1 and were competitive, fast colonizer and disturbance-tolerant species. Most of these Y1 species developed during the dry year and remain only one year after refilling. After Y1, the evolution of communities was linked to the phenomenon of nestedness based on a loss of several species but not on a complete turnover, with most of species present independently of time. We conclude that a periodic dry period maintains a cycle in plant succession and accommodates highest species richness at the beginning of the cycle.