The Desertification Research Center (CSIC-UV-GVA) conducts the first global, systematic and quantitative study of the effects on vegetation of changes in the fire regime.
Coniferous and mixed forests are more vulnerable than shrublands and grasslands to the increase in the intensity and frequency of fires.
Due to global change, many ecosystems are experiencing a disruption in their fire regime, with an increase in the frequency and severity of fires. This can substantially alter plant communities, as well as the structure and functioning of ecosystems. Now, a study led by the Desertification Research Center (CIDE), a joint center of the Spanish National Research Council (CSIC), the University of Valencia (UV) and the Generalitat Valenciana (GVA), confirms this perception. After examining more than 2,000 fire data from all over the planet, the study found that the intensification of fire regimes caused by climate change and other human activities reduces the abundance, diversity and good condition of plants, something that affects woody plants such as coniferous forests the most.
“This research provides, for the first time, a global, systematic and quantitative view of the effect of fire intensification,” says Juli G. Pausas, CSIC researcher at CIDE and lead author of the paper, recently published in the journal Global Ecology and Biogeography. To carry out this work, the authors applied a systematic review and meta-analysis methodology that allows them to analyze a large amount of data from very diverse sources. They were able to systematize 2,363 cases collected in 394 studies from all over the world, although with greater representation from the northern hemisphere.
When considering the components of the fire regime, such as frequency, intensity or type, the study shows that the greatest risk to plants is posed by the severity of fires. Thus, “the intensification of fire regimes due to climate change and other human activities, what we generically call global change, generally reduces the abundance, diversity and fitness of plants,” summarizes Bruno Moreira, a CSIC researcher at CIDE who participates in the study.
The negative effects are stronger with increasing fire severity than with increasing fire frequency, and are more pronounced in woody plants than in herbaceous plants, according to the researchers. In addition, they found that certain vegetation types are more resistant to these changes than others. “Coniferous and mixed forests are more susceptible to fire intensification than open ecosystems such as grasslands and shrublands, something related to the possible shift from low intensity surface fires to high intensity crown fires,” says Roger Grau-Andrés, researcher at the Center for Ecological Research and Forestry Applications (CREAF) and lead author of the paper.
According to Pausas, “Mediterranean shrublands are dominated by crown fire regimes that have historically burned with high intensity, and these ecosystems are remarkably resilient to such conditions. But, in this case, an increase in the frequency of disturbances can also lead to a decrease in diversity,” says the CSIC researcher.
Scientific basis for fire management
Another example of threat to changes in the fire regime is offered by the bristlecone pine or Pinus nigra, abundant in the Iberian Peninsula. “This tree is prepared to survive low intensity fires thanks to its thick bark, which insulates it from flames, and its few branches in the lower part, which prevent the transmission of fire to the crown. However, in the case of more intense fires or fires that affect the entire tree, these protections are not sufficient and the plant does not survive,” explains Moreira.
The researchers emphasize that this study “provides a scientific basis for decision making in ecosystem conservation and fire management policies”, as it identifies the general patterns of plant response to intensification of fire regimes and understands the factors that determine them. By understanding changes in fire regimes, strategies adapted to these new fires can be created.
Thus, “more than a single unified policy, it is a matter of understanding which ecosystems may be more susceptible and establishing priorities for action,” says Pausas. Thus, compared to the most resilient ecosystems, in which “the best conservation strategy may be not to act,” coniferous forests would require appropriate management. For example, in Pinus nigra forests, which are resilient to low-intensity fires and are able to survive frequent surface fires, prescribed burning can help maintain a low-intensity fire regime that makes the trees more resilient.
The study was financed by the FocScales project of the Generalitat Valenciana and the FirEUrisk project of the European Commission.
References:
Grau‐Andrés, R., Moreira, B., & Pausas, J. G. Global plant responses to intensified fire regimes. Global Ecology and Biogeography, e13858. DOI: https://doi.org/10.1111/geb.13858
CIDE Communication
