Project info Using the forest fires of the China Muerta National Reserve (CMNR) as a natural laboratory for assessing their ecological impacts. FONDECYT Initiation into Research N°11150487. Investigator: Dr. Andres Fuentes Ramirez. Period: 2015-2018
Concluding remarks The effect of fire was indeed strong for the vegetation, especially within the HS and MS areas, where plant richness and abundance were drastically reduced one year after fire. In LS areas, though, species richness and plant abundance were very similar to the unburned forest, but with a higher proportion of exotic species, which seem to be related to the effect of cattle browsing (i.e., as mediators for the establishment of exotic species). Over time, species richness and plant composition in the HS and MS areas tend to get similar to the unburned forest, suggesting the recovery of vegetation in the following years after fire if no further disturbances affect the ecosystem. Interestingly, when cattle is excluded from the system, we observed an increased rate of plant recovery, with higher species richness and plant abundance compared to areas exposed to grazing and browsing. This results highlight the need for better management of burned areas that can promote the recovery of the plant community (i.e., exclusion of cattle from highly fire affected areas). We also looked closer into the post-fire response of A. araucana and Nothofagus pumilio (the two dominant tree species in the forest). Individuals of A. araucana damaged by fire showed a high capacity for vegetative resprouting after fire, especially from canopy and root buds, which tended to increase over time. Nevertheless, N. pumilio showed no survival after fire in the most fire-affected areas (not even at the third year of the study). These results suggest the need for implementing restoration plans within the unit, aiming at recovering the cover and structure of the forest (mainly focused on the active plantation of N. pumilio). Here, novel techniques (such as group planting and the use of biological legacies) could be beneficial for better survival and growth of tree species. Fire not only affected vegetation, but also the forest soil.
Our research also showed that fire increased the availability of soil nutrients in the short-term (i.e., one year after fire), but then, nitrogen (N) greatly decreased in the following years (2017 and 2018) across all fire severities. This response could be related to a positive input of nutrients that occurs shortly after fire due to the burn of vegetation and the consequent feedback of nutrients into the soil, but a decrease of nutrients in the following years due to plant uptake and soil erosion within areas lacking plant cover. Potassium (K) showed an increasing trend over time and higher availability in the most fire-affected areas, which is explained by the elevated deposition of ash in the soil (in HS and MS) that contributes to increase K. Phosphorus (P) and soil organic matter (SOM) did not vary with time-since-fire nor through the fire severity gradient. Lastly, we found an increased abundance of bacteria and fungi within areas affected by fire, which suggests that the biological activity in burned soils can contribute to cycling nutrients and prompt the build-up of organic matter so that it can stimulate the recovery of vegetation after fire. In summary, the ecological impacts of severe fires on forest ecosystems are notorious, especially because of the rapid reduction of plant richness and vegetation cover shortly after fire. Fire can interact with other disturbances, such as cattle browsing, and suppress vegetation even more (i.e., slow recovery of trees and increased risk of plant invasions by exotic species). Soil characteristics are also affected by fire. Nutrients and SOM showed high variability after fire, which can imply numerous cascading effects (at mid-to-long term) on vegetation and the entire ecosystem. Despite the fact that the forest seems to be recovering in the National Reserve China Muerta, further research is needed to deeply understand the dynamics of the ecosystem (i.e., forest structure in the long-term). This project unveiled crucial findings and provides insightful clues to delve into more applied research aimed at the restoration of the endemic, long-lived Araucaria araucana forests in south-central Chile.
Research team Marcia Barrientos Nayadeth Muñoz Andrea Del Fierro Franco Perez Francisco Manquehual Paola Arroyo Jonathan Urrutia Pablo Santibañez Alfredo Zúñiga