Citizen science in mountain environments
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Altitude

The dates of phenological events for plant species are closely linked to the temperature, which itself varies with altitude. This is why it is essential in a mountain zone to analyse phenological observations by taking into account the altitude.

Gradient d'altitude sous les aiguilles de Chamonix - © CREA Mont-Blanc

For the same species, two individuals can have phenological cycles that are out of sync according to the altitude at which they are living. In the spring, an individual that lives at high altitudes will have phenological events that occur later than an individual that has settled at lower altitudes. In autumn, this same individual at high altitudes will have phenological events that begin earlier. The nicer weather is shorter for living beings that have settled at high altitudes. Living organisms at high altitudes have thus developed adaptations allowing them to complete their reproduction and growth cycle more quickly than those in the lowlands.

Faced with climate variations, the same species reacts differently according to its location (altitude, latitude, mountain range…)?

On the other hand, the analysis for animals is more complex and other parameters must be considered. In fact, the duration of day and night is the principal factor determining the reproduction date.

Example of an altitude difference of 600 m, contrast between 1,300 m and 1,900 m in altitude:

  • Gap among coal tits: 8 days later at 1,900 m
  • Gap among frogs: 38 days
  • Gap among trees: 12 days
  • Difference in temperature: 3.6 °C lower at 1,900 m
  • Gap in the snow melting date: 35 days

 

Zoom in on vegetation: the larch

According to research currently underway at CREA, it has been observed over the last 10 years that trees located at the subalpine level (1,600 to 2,000 m), have a more noticeable budding trend than those located farther down, in montane level (800 to 1600m).   

 

Graphique du debourrement du mélèze


Graph: larch bud

Average annual date of budding for the larch by altitude gradient in the Alps mount range. Trend curve over 10 years.

Montane level (800 - 1,600 m)

Subalpine level (>1,600 m)

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Temperature and altitude

The temperature decreases on average by 0.6°C when increasing in altitude by 100 m. Depending on the altitude, a phenological gap can be observed among the species.