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Atoll forest dynamics before and after rat control

Tobias counting plantlets of Pisonia grandis
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  3. Atoll forest dynamics before and after rat control

Atoll forest dynamics before and after rat control

Ce projet se concentre sur l’effet de l’éradication des rats sur les dynamiques forestières . Un suivi annuel des semis, du recrutement des espèces ligneuses indigènes et du pourcentage de couverture végétale herbacée a été mis en place sur les Motu Reiono et Motu Ahuroa en 2018 et 2021. Les résultats préliminaires de 2023 montrent que la réponse de la végétation à la dératisation peut varier en fonction des caractéristiques écologiques et de la composition végétale initiale du motu, et soulignent l’importance d’un suivi à long terme.

Chercheurs principaux : Jean-Yves Meyer
Affiliations : Délégation à la Recherche and UMR SECOPOL
Dates du projet : anuary 2018-long term

Update : 2023

In 2023, five new 25 m long transects were set up on Motu ‘A’ie and surveyed to assess the effects of the Yellow Crazy Ant Anoplolepis gracilipes eradication. This will continue in 2024 to record any changes in vegetation dynamics.

The preliminary results show that vegetation response to rat eradication may vary according to the ecological characteristics of motus, especially their initial plant composition (e.g. no coconut plantation in Ahuroa) and the importance of long term monitoring.

  • Asplenium nidus Asplenium nidus
  • Guettarda speciosa Guettarda speciosa
  • Microsorum grossum Microsorum grossum
  • Portulaca lutea Portulaca lutea
  • Pandanus tectorius Pandanus tectorius

Sampling is conducted along twenty 25 m long transects representing 1,000 one square meter quadrats.

This work has revealed:

  1. a slow decrease of Pisonia grandis seedlings with time in both motus;
  2. an increase of Cocos nucifera seedlings in Reiono but not in Ahuroa ;
  3. a strong increase of Pandanus tectorius and Guettarda speciosa seedlings, especially in Ahuroa ;
  4. an increase of the cover of herbaceous plant (Boerhavia tetrandra in Reiono, Portulaca oleracea in Ahuroa), and native ferns (Asplenius nidus and Microsorum grossum);
  5. the role and importance of natural disturbances (high swells, tree fall gaps caused by strong winds) in seed germination and seedlings survival during several years of monitoring.

 

Image
Jean Yves Meyer on Tetiaroa