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The International Tundra Experiment (ITEX) is a network of scientists from more than 11 countries, studying tundra plants in more than two dozen Arctic locations. The main goal of the ITEX network is to understand the response of tundra plant species to climate changes, especially to a warming in summer air temperatures. Saxifraga oppositifolia © Esther Lévesque

In order to do so, ITEX put together simple protocols that allow scientists to perform similar experiments in different Arctic sites. The advantage of performing similar experiments is that the results can later be compared among sites.

The Bylot Island Ecological Studies and Environmental Monitoring project has been considered as an official ITEX study site since 1999. Four plant species have been monitored since then: female and male Arctic Willow (Salix arctica), Purple Saxifrage (Saxifraga oppositifolia), Northern Wood Rush (Luzula confusa) and Mountain Avens (Dryas integrifolia). Individual plants from these species were marked and their phenological phases (life stage such as flowering, for example) are monitored many times each summer. The number of flowers produced per each plant is also recorded.

male flower Salix arctica fleur male © Esther Lévesque
female flower Salix arctica fleur femelle © Esther Lévesque

Data from the ITEX site gives us information on how plant production, for example the date at which a plant flowers, changes from year to year. Analysis of our weather data can later help us determine which climate factor is the most responsible for these changes in plant production. In a broader perspective, understanding Arctic plant responses to various environmental factors may give an insight on how these plants are likely to react to climate warming.

 

Results

First Flowering Date

Five years of data is still a relatively small time span to evaluate the relation between phenological events and climatic factors. Nevertheless, some tendencies have been observed with our data.

Within each species, the date at which first flowering events were observed showed small intra-annual variability, but large inter-annual variability. This means that during one year, most of the plants of one species tended to produce their first flower around the same date. However, this first flowering date greatly varied from year to year.

For all the studied plant species, the date of first flowering was not influenced by the environmental conditions of the previous growing season (TDD and number of days above 0°C). However, first flowering seems to be influenced by the current season climatic conditions prior to flowering. Indeed, for all plant species except female S. arctica, flowering is related to June thawing degree-days. Therefore, for most of the monitored plant species, flowering is advanced in years with warm temperature in June.

 

Due to missing values during the first years of sampling, it is not possible to evaluate the relation between climate and the number of flowers. In the future, the accumulation of a larger database will allow us to better assess this relation.