News July 2024

Not every plant likes more heat

You can investigate possible responses of woody plants to climate change with temperature tests. We conducted such an experiment on seedlings of three shrub species: hazel, blackthorn and common red dogwood. Groups of plants were subjected to three regimes of elevated temperature:

  1. elevated temperature in spring
  2. elevated temperature in summer/autumn
  3. elevated temperature in spring and summer/autumn

The experiments taught us that not all species respond in the same way.

  • Hazel is a species that can tolerate some shade. The seedlings showed reduced growth when spring temperatures were increased and seemed to experience stress. Blackthorn and common dogwood are more light-loving species, and here the temperature increase acted as a growth stimulus.
  • Hazel showed early leaf discolouration after the warmer summer/autumn. Due to the temperature increase, the growing season was shorter for this species. In contrast, blackthorn and common dogwood just showed delayed leaf discolouration and thus had a longer growing season.
  • Blackthorn only experienced growth promotion the year after the temperature treatments. This seems to indicate that this species produced more reserve substances due to increased photosynthesis at higher temperature, and did not draw on this reserve until the following year. After higher spring temperatures, blackthorn showed more height growth the following year. Presumably, at this temperature regime, this species stores reserve substances preferentially in the twigs. After a regime with higher summer/autumn temperatures, we observed more thickness growth in the trunks the following year, suggesting that in this case the reserve substances were stored more in this location.
  • Common dogwood was able to directly cash in on the increased temperature in summer/autumn into more height growth.

Climate change creates highly variable weather conditions, such as periods of increased temperature. These results teach us that not all species will respond to climate change in the same way. Extrapolating results to other unstudied species is not easily possible.

Kristine Vander Mijnsbrugge

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Image above: INBO


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