Variation in Pollination Systems of Australian Subtropical Rainforests: The Implications for Climate Change

Abstract

The goal of this study was to contribute to the understanding of subtropical rainforest pollination systems and their natural variability in order to predict the likely impact of climate change on pollination in these systems. Pollination is a pivotal process within all forest ecosystems and the sustainability of any given plant species is dependent on its success. Climate change and associated changes in environmental cues to phenology and ontology of both plants and their pollinators has the potential to decouple pollinator mutualisms, decreasing reproductive success. Two approaches were used to investigate potential pollination variability: 1. To understand broadly the characteristics of the elements that interact in pollination – that is the physical environment, flower morphology and phenology, and the flower-visiting insect fauna – at a community level. 2. To estimate the natural variability of these elements along an altitudinal gradient as a surrogate for climate change. A profile of flower morphology and phenology for the rainforest plants of Lamington National Park demonstrated the predominance of small white flowers, seasonal flowering and the strong influence of El Niño on flowering patterns among this subtropical rainforest flora. A global comparison of morphological characteristics demonstrated that there was no “typical” rainforest flower morphology. An altitudinal gradient was established as part of the collaborative IBISCA Queensland project, the core of which was the establishment of a permanent set of 20 reference plots, four at each of five altitudes in Lamington National Park, southeast Queensland. Effectively this allowed the examination of adjacent climates which differed in overall mean temperature by about 4.8°C organised into five 1.2°C stages. Along the environmental gradient temperature decreased and moisture increased with increased altitude. The higher altitudes showed less variability in temperature and daily relative humidity. High and constant atmospheric moisture was experienced at the two highest altitudes (900 m and 1100 m) and was considered the result of frequent cloud cover at these higher altitudes. Changes in soil physical characteristics accompanied changes in moisture availability.