Investigating phenological trends in the summer flowering perennial Scorzoneroides autumnalis (Asteraceae) using herbarium specimens

Abstract

As the climate warms, the timing of plant phenology around the world is changing in response. Herbarium records offer a wealth of data that can be used to analyze phenological trends over time. While much research has been done on early spring flowering species, there is still a dearth of knowledge of climate change effects on summer and autumn flowering species. This study uses herbarium data to study phenological trends in Scorzoneroides autumnalis, a summer flowering perennial, to begin to address this knowledge gap. A flowering index was introduced as a quantitative combination of collection date and the phenological state of each specimen at the time of collection. Based on analysis of collection date, the flowering time of S. autumnalis was found to advance by 5 days per century and by 2.6 days for each degree Celsius increase in summer temperature. The data also suggest that increasing temperatures increase the length of the flowering period.

Popular Abstract

Historical data sheds light on the timing of summer flowering

Throughout the last century, temperatures have continued to rise, altering ecosystems around the globe. Nearly every natural process is affected by changes in temperature, and all of these processes are interconnected in many complicated ways. One of the most important of these processes is plant reproduction, which has far reaching consequences for the availability of resources necessary for human life. Phenology refers to the cycle of recurring phases that happen in the lives of plants and animals, such as the wave of newly open buds that many view as the first sign of spring.
As the climate becomes more unpredictable, this natural calendar will also change in unforeseen ways. When trying to predict the planet’s response to climate change, taking a close look at how plants have rescheduled their yearly flower debut along with rising temperatures is an important piece of the puzzle. But how can we compare the flowering times of modern plants with that of plants from decades, or even centuries, earlier? Herbarium collections are one answer to this scientific dilemma. In an herbarium, pressed specimens of plants are stored for centuries like botanical time capsules.
Until recently, most research in phenology has focused on spring events. In this study, I have examined Scorzoneroides autumnalis or autumn hawkbit. This plant’s small yellow flowers emerge during the mid and late summer, a relatively unexplored time of year. Because the flowers on each S. autumnalis plant open in a fairly predetermined order, it was possible to combine the flowering progress of each plant with the day it was collected into a value, which I termed “flowering index.” I analyzed the flowering index as well as the collection date of S. autumnalis plants from all over Sweden and as far back as 1860. I found that the plant has started flowering 5 days earlier for every 100 years and 2.6 days earlier for every degree Celsius increase in summer temperature. There is also evidence to suggest that the period of flowering could be getting longer. Considered in the context of ecosystems in which S. autumnalis is abundant, this information can help predict what species interactions, such as availability to pollinators and competition for resources, will look like throughout the year, as the climate warms.



Master’s degree project in Biology 45 credits 2018
Department of Biology, Lund University
Supervisor: Stefan Andersson

• author: Geyer, Elizabeth
• supervisor: Stefan Andersson
• organization: Degree Projects in Biology
• course: BION02 20172
• year: 2018
• type: H2 - Master's Degree (Two Years)
• subject: Biology and Life Sciences
• language: English
• id: 8958538
• date added to LUP: 2018-09-12 13:51:29
• date last changed: 2018-09-12 13:51:29