Climate Change Effects on Long-Term Leafing Activity of a Tropical Rainforest Tree Species, Davidsonia pruriens

Leafing activity is a crucial part of the tree life cycle and is tightly linked to photosynthesis, gas exchange and biomass accumulation, among other processes. Despite this, many aspects of leafing phenology, such as climate drivers of community and species-level temporal patterns, are poorly understood in tropical rainforest species. Here, we present 18 years of above-canopy phenological observations of leafing phenology for Davidsonia pruriens, an important endemic species in the Wet Tropics, from January 1997 to December 2014. We assessed changes in leafing patterns through time and how they are being affected by climate drivers. We found that, while the tropical rainforest region is considered to have low seasonality in leaf production, leafing in this species was seasonal with a peak in the wet season. Analysis of climate drivers showed that increased leaf production was correlated with increased daily rainfall and decreased solar radiation. Interannual activity responded similarly to changes in annual rainfall and solar radiation but was also significantly impacted by cyclones and El Niño events. Our results show that Davidsonia pruriens has seasonal leafing patterns which are strongly influenced by climate drivers. Our study is the first to present field-based measurements of long-term leafing phenology in Australia, which clearly demonstrate climate change sensitivity of leafing in an endemic plant, a plant that is a significant bush tucker species to Aboriginal traditional custodians of the rainforest region of Northern Australia.