Use of Logs Downed by Wildfires as Erosion Barriers to Encourage Forest Auto-Regeneration: A Case Study in Calabria, Italy

Abstract

The easy implementation of ecologically-sound remediation measures for the prompt stabilisation of burned areas may be crucial in Mediterranean forest environments. Manual in situ contour redirection of burned felled logs could aid in soil erosion control and facilitate forest self-regeneration. In this study, a plot-scale runoff/sediment yield survey was conducted in Calabria, Italy, within a Mediterranean pine forest that was affected by an extreme wildfire spanning over 15,000 hectares in the summer of 2021. The hydrological response to 24 rainfall events was analysed after one year of monitoring using nine Wischmeier and Smith 20% sloping plots, which were distributed into three plot-blocks representing different conditions (forested, burned with randomly directed fallen logs, and burned with fallen logs manually redirected along contour lines). The post-fire condition (with felled logs in random positions) exhibited a consistent overall increase (approximately four times) in runoff and sediment yield compared to the pre-fire situation. This degradation effect was mitigated by approximately 30% through the manual redirection of burned logs, which promoted early (three to five weeks) vegetation regeneration (including tree emergence) and enhanced coverage as vegetation spread from the log positions. The results obtained so far provide encouraging insights and warrant further research on steeper slopes and complementary aspects (regulatory, biological, mechanical, economic, etc.).

A Nature-Based Approach Using Felled Burnt Logs to Enhance Forest Recovery Post-Fire and Reduce Erosion Phenomena in the Mediterranean Area

“…A large area of Aspromonte National Park (ANP) was affected by a huge fire season in August 2021: in approximately 10 days more than five thousand hectares of forest was burnt. In the area where our experimental plots are located (see next paragraph Section 2.2), a high fire severity has been recorded, with crown scorch from 80% to 100% (Scheme 1a) [58,64]. More details about severity mapping in Aspromonte Massif area can be found in an already published paper by one of the authors of this manuscript [65].…”

“…Calabria is a peninsula-shaped region located at the southernmost part of Italy, with 90% of territory being mountainous or hilly. The territory, due to its peculiar geo-lithological, morphological and climatic characteristics, is among the most vulnerable and unstable in the Mediterranean basin [58,[61][62][63]. From the climatic point of view, the mountainous areas, located a short distance from the sea, have a typical climate with frequent snow during the winter.…”

“…ex Maire). The mountain area, moreover, was subjected to several reforestation operations over the last 70 years; therefore, it is also characterised by a high density of artificial forest of Pinus nigra to which is added the Pinus radiata D. Don (800-1000 per ha with a height ranging from 14 to 20 m and crown diameters from 4 to 7.5 m), non-native species that have, however, become dominant (photo 1b) [58].…”

“…The experimental site is located in Roccaforte del Greco (970 m a.s.l., 38 • 03 ′ N; 15 • 54 ′ E, Figure 3) characterised by hot Mediterranean climate and semi-arid conditions [73], with mean temperatures of 5 • C in January and 23 • C in August, a mean annual rainfall depth of 1036 mm and monthly rainfall ranging between 13.7 mm in July and 153 mm in December [58].…”

“…However, most studies, by focusing mainly on only one aspect (e.g., soil erosion or vegetation response separately), highlight the need for in-depth multidisciplinary approaches aimed at investigating the effects of measures on the whole ecosystem in order to understand the dynamics that govern ecological functionality and resilience in terms of the self-regeneration capacity. A first attempt was undertaken by Bombino et al [58] in the Aspromonte Massif (southern Calabria), demonstrating a significant reduction in runoff and sediment yield by using in situ collapsed burnt trees, manually redirected along the contour lines immediately after the extreme event; the hydrologic study is also integrated with some preliminary observations on the regeneration capacity of the forest.…”