Herbarium collections and photographic images: Alternative data sources for phenological research

Abstract

Irrefutable evidence is emerging from the scientific literature of universal shifts in phenology as a consequence of climate change. The intimate relationship which exists between seasonal flowering and climatic conditions, coupled with ease of observation, makes the monitoring of flowering events a reliable and cost effective method for the early detection of change in biological systems and an important tool in global change research. However, the long-term data sets required to determine the nature and magnitude of climatic impacts are very limited in Australia, and current research incorporates an interrogation of archival records to redress this important issue. Herbarium collections and photographic images have been found to provide robust estimates broadly in keeping with those published in the literature. This chapter is specifically focussed on accessing long term phenological data from the alternative data sources residing in herbarium and photographic collections. We outline the constraints to be considered when linking phenological changes with climatic fluctuations and long-term trends, offer some cautionary principles for analysis and interpretation and finally offer two case studies where phenological data have been successfully extracted from herbarium records. We investigate the value of less traditional methods such as Generalised Additive Models for Location, Scale and Shape (GAMLSS) adapted for time series data to accommodate possible non-linearities between herbarium records and year and/or climate; and suggest a model-free method of change-point detection. How best, if possible, to infer first flowering dates and actual stage of flowering from snap records is also an issue for inference and interpretation.