Alava Provincial Council is researching the resilience of the Legaire beech forest four years after the Entzia tornado

09/02/2023

The study, which is part of the LIFE IP Urban Klima 2050 project, will determine the extent of the forest's recovery after the tornado that devastated 40 hectares, and will also be used to research the evolution of biodiversity after extreme events.

For the last four years, Alava Provincial Council has been researching the resilience of the Legaire beech forest in the Entzia Special Area of Conservation (SAC) in the Zadorra river basin. The aim of this work, which is in its first phase of development, is to determine the extent of the impact and recovery of the ecosystem that was affected after the Entzia tornado in July 2018, which caused trees over an area of approximately 40 hectares to be torn down en masse.

The study, which was commissioned to the University of the Basque Country, is part of the set of actions included as part of the LIFE IP Urban Klima 2050 project and, more specifically, of action C.5.1 Nature-based solutions (NBS) in river basins.

The work team is analysing the adaptive capacity of the Legaire beech forest by comparing two forest management options: a stand with the removal of fallen trees compared to a stand retaining fallen timber. The project is focused on assessing and comparing aspects in four stands of 2 hectares each such as:

• recruitment from new young trees
• soil fertility
• the vigour and growth of adult survivors as key drivers of forest resilience

In this regard, the study has drawn a few conclusions based on the results obtained three years after the tornado. On the one hand, it can be seen that the young beech trees present after the disruption are able to play an important role in natural regeneration given their abundance and size; and, on the other, that the surviving adult trees have a high capacity for growth recovery, which enhances their reproductive potential. Consequently, they become a source of seeds in the areas that were most exposed by the tornado and help the tree canopy to recover.

In terms of tree management implications, the research proposes leaving no-logging zones in places affected by extreme winds and, as far as possible, spatially distributed in a heterogeneous manner over the whole of the affected area. The study also points to preserving surviving trees as another recommendation to be taken into account