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Keywords:

  • ant–plant interaction;
  • floral nectar;
  • honeydew;
  • planting density;
  • plant sugar;
  • revegetation

Abstract

Ecological restoration aims to re-establish both biodiversity and ecological function in damaged ecosystems. Ants are important drivers of ecological functions and are early colonizers of restored ecosystems. Rates at which ants perform functions are thought to be fuelled by access to plant sugars. In revegetated farmland in south-eastern Australia, I tested if ant activity on trees, which reflects use of arboreal sugars, follows a predictable trajectory of recovery towards a remnant-like state. Additionally, I examined whether planting method alters this trajectory by comparing tube stock (TS), which results in low Eucalyptus densities, with direct seeding (DS), which results in high Eucalyptus densities. Replicate sites (n = 5) of young (planted between 1998 and 2001) and old (planted between 1989 and 1994) TS and DS revegetation, pastures and remnants were compared. Activity on trunks was significantly positively correlated with ant tending of Hemiptera in young and old revegetation. In DS plantings, activity and estimated liquid loads on Eucalyptus trees were low and rapidly approached that in remnants, while TS sites remained similar to high values observed in pastures with trees. Patterns for Acacia were less clear, reflecting consistent densities for this species between TS and DS. At the whole-of-field scale, planting methods did not differ. Importantly, although trajectories differed, neither TS nor DS sites approached the low activity or estimated liquid loads observed in remnants. Rates of ant use of arboreal sugars and associated sugar-fuelled processes may thus take considerably longer to recover than the period covered by this study. This finding suggests planting method may affect the trajectory and outcome of revegetation for plant health, as well as sugar-fuelled ecosystem functions performed by ants.