The flowers that bloom in the spring
by
Malcolm Clark
Monash University
Coauthors: Roy Thompson (University of Edinburgh)

We report on an analysis of data from the Royal Botanical Gardens, Edinburgh, on the first flowering dates of 153 species of flowering plants over 26 years, related to monthly rainfall and daily mean temperatures in Edinburgh for the corresponding years.

We develop a model, derived from botanical considerations, in which the temperature sensitivity of a given species is measured in terms of "growth degree days" above a threshold temperature. This model raises some interesting issues of statistical inference, including estimation in non-linear models subject to constraints on the parameters, and hypothesis-testing of non-hierarchical models.

The fitted model enables us to predict the change in the expected first flowering dates under various global warming scenarios for those species with significant temperature sensitivity. Our prediction is that under our fitted model and a likely scenario of increased temperatures in Edinburgh, most of these species will come into flower about 50 days earlier than at present.

Date received: March 26, 2002