Living (and reproducing) on the edge: reproductive phenology is impacted by rainfall and canopy decline in a Mediterranean eucalypt

Abstract

Many of the worlds’ forests and woodlands are currently showing symptoms of declining condition due to a range of factors, including changing climatic conditions, drought and insect herbivory. Altered abiotic and biotic conditions can influence the condition of trees that can, in turn, affect tree reproductive cycles. However, the potential impact of tree decline on reproductive cycles has rarely been examined. This study investigated the influence of canopy condition on the reproductive cycle of Eucalyptus wandoo Blakely in south-western Australia. Canopy and seed trap monitoring were used to assess bud production, flowering, fruiting and seed fall over 12 months at 24 sites across two locations (Dryandra Woodland and Wandoo Conservation Park). Time since last fire, rainfall, ambient temperatures and the condition of individual trees were recorded. We found that bud production, flowering and fruiting was correlated with tree condition: healthier trees were generally associated with higher reproductive effort. Time since last fire was also strongly related to the reproductive efforts at both locations. Declining annual rainfall and increased temperatures also impact on reproduction, made evident by the aborted flowering in Dryandra Woodland. Decline in tree condition, coupled with changes in climate, have major implications for flowering phenology of this species and have the potential to alter reproductive effort, recruitment and future population dynamics. Consideration of these issues should be incorporated into the conservation management of E. wandoo and similar Eucalypt species.