M. C. Brundrett
Context: The global diversity hotspot in Southwest Australia has >480 orchids facing increasing threats from climate extremes, fire and habitat decline. Aims: To develop effective and consistent tools for measuring climate impacts on productivity in a diverse urban orchid community. Methods: Annual variations in flower and seed production for 17 orchids were determined using thousands of records over a decade with extreme climate variability. Key results: Rainfall deficits and temperatures in autumn, winter and spring increased substantially over 125 years. Seasonal climate anomalies reduced flowering and seed production for orchids, but this varied between species and seasons. These effects were summarised by climate response (CRI) and sensitivity (CSI) indexes. Early or late flowering species were most vulnerable to seasonal drought, but warm dry conditions promoted visually deceptive pollination. CRIs were strongly correlated with orchid pollination syndromes and flowering times. Effects on mycorrhizal fungi and pollinators were also observed. Extrapolating climate trends to 2100 predicted further impacts on orchid productivity (5-40%). Conclusions: Orchid climate responses were substantial, complex and deeply integrated with key traits such as pollination, phenology and fire responses. Implications: Research in an urban climate observatory produced a climate analysis framework potentially relevant to all orchids and other biota.