Temperature Induced Flowering Phenology of Olea ferruginea Royle: A Climate Change Effect

Studies from different parts of the world have generated pieces of evidence of climate change’s effects on plant phenology as indicators of global climate change. However, datasets or pieces of evidence are lacking for the majority of regions and species, including for the climate-sensitive Himalayan biodiversity hotspot. Realizing this gap in information, and the wide-ranging implications of such datasets, we integrated real-time field observations and long-term herbarium records to investigate the changes in the spring flowering phenology of Olea ferruginea Royle, commonly known as the Indian Olive, in response to the changing climate in the western Himalayas. We attempted to create phenological change model using the herbarium records and field observations after recording the current dates of flowering and overall temperature trends from the study area over the last four decades from the five regional meteorological observatories of the Jammu province managed by Indian Meteorological Department (IMD) in Jammu and Kashmir. When considering current flowering dates along with herbarium information (years 1878–2008) for O. ferruginea , our Generalized Additive Model (GAM) showed 15–21 days-early flowering over the last 100 years significantly ( p < 0.01). Results of the Mann–Kendall test showed increasing trends of T Min for all seasons significantly ( p < 0.05) for Jammu province whereas T Max was only for the spring season. The increasing T Min of spring, summer, and autumn seasons also influenced the flowering phenology of O. ferruginea significantly ( p < 0.01). By demonstrating the integrated use of methodological tools for finding long-term phenological changes in response to climate change, this work bridges knowledge gaps in phenological research from the developing world in general and the Himalayas in particular.