What is the persistence capacity of a forest?
A research group at the Forest Science Centre of Catalonia (CTFC) has defined an index to measure the capacity of a forest to cope with natural disturbances, such as fires, droughts or windthrows. The index is based on the diversity and abundance of response traits present in species to respond to these threats.
By applying this index in different types of forests in the Iberian Peninsula, they found that mixed forests and those formed by non-native species resist better than other forest formations.
Solsona, June 13th, 2016. The Persistence Index is based on the presence of certain features, called “response traits”, which help the species to resist or recover after a disturbance. Resprouting ability, deep roots and hard downy leaves are key traits for the forest species to withstand and recover after a disturbance.
This study not only helps to better understand the response of ecosystems, but it can become a very useful tool for decision making in forest management, especially in climate change context. The study, which also involved members of CREAF, has been published in Ecological Indicators.
The persistence of Iberian forests
To assess the index on a real dataset, the research group calculated it for the Iberian Peninsula and the Balearic Islands forests, from the Third National Forest Inventory data. Authors noted that the persistence capacity of the Iberian forests varies according to different forest formations.
Forests composed of non-native species, such as eucalyptus plantations, showed a very high index – therefore higher resistance and resilience – compared to other forests, especially coniferous. Mixed forests also had quite high index values, since greater species richness is related to a greater variety of response traits. However, according to the main author, Martina Sanchez-Pinillos, “there is a threshold beyond which adding more species does not mean a big difference in the number of traits and the response capacity saturates”.
Calculated in successive forest inventories, the Persistence Index can be used to assess past management activities, and would report on the change in the resistance and recovery capacity of forests over time. Similarly, it could also be used to assess the consequences that current management strategies could have in the future.
Flexible and adaptable to any natural community
The index can be calculated to forests, but also to any other type of natural communities, for example, a fish community affected by pollutants dissolved in water. Besides being easy to calculate, it has a great flexibility, allowing to choose response traits based on the perturbation considered. Thus, it can be used to compare the persistence capacity of forests in southern Europe, whose most important threats are drought and fire, with the ones in central Europe, threatened mainly by windstorms.
In any case, to have a more precise idea of the vulnerability of forests, the information that the index provides should be combined with other environmental and management data, such as forest structure, size of trees or biomass accumulation in the understory. In addition, according to the authors, future research should be directed to find, for each type of community, the minimum value of the index to ensure enough persistence capacity against disturbances threatening them.
Martina Sánchez-Pinillos, Lluís Coll, Miquel De Cáceres, Aitor Ameztegui (2016). Assessing the persistence capacity of communities facing natural disturbances on the basis of species response traits. Ecological Indicators. DOI:10.1016/j.ecolind.2016.01.024