Context Since the nineteenth century, rural areas have experienced progressive abandonment mostly due to socioeconomic changes, with direct and indirect effects on forest disturbance regimes occurring in these human-dominated landscapes. The role of land abandonment in modifying disturbance regimes has been highlighted for some types of disturbances, albeit being still somewhat overlooked compared to climate change. Objectives This literature review is aimed at highlighting the most relevant effects of land abandonment and land-use legacy on the regime of different types of forest disturbances, providing insight into land-use change/disturbances interactions. Methods We searched in the Scopus and Web of Science databases for relevant studies at the global scale dealing with eight major natural disturbances: avalanche, flooding, herbivory, insect outbreak, landslide, rockfall, wildfire and windthrow. We classified papers into five relevance classes, with the highest score (4) assigned to studies quantitatively measuring the interactions between abandonment dynamics and disturbance regimes. Results Most papers focused on wildfires in Mediterranean Europe in the twentieth century, where landscape homogenisation and fuel build-up contributed to worsening their frequency, size and severity. Dense forests developed following land abandonment instead exert inhibiting effects toward mass movements such as avalanches, rockfalls and landslides. Regarding the other investigated disturbances, we found only a few studies presenting site-specific and partly contrasting effects. Conclusions Land abandonment triggers ecological processes at the landscape scale, altering land cover patterns and vegetation communities, which in turn affect disturbance regimes. Implications for land and resource management mostly depend on the stage at which post-abandonment secondary succession has developed.

Background The Mediterranean basin is currently facing major changes in fire regimes as a result of climate and land-use changes. These alterations could affect the ability of forests to recover after a fire, hence triggering degradation processes and modifying the provision of fundamental ecosystem services. Examining patterns and drivers of post-fire forest recovery, particularly for obligate seeders without specific fire-adaptive traits, thus becomes a priority for researchers and land managers. We studied the post-fire dynamics of Scots pine (Pinus sylvestris L.) stands affected by a mixed-severity fire in North-Western Italy, aiming to understand the impact of fire on soil properties and assess drivers, spatial distribution, and characteristics of short-term post-fire recovery. Results We observed that fire did not significantly affect soil organic carbon (OC) content, while we detected significantly lower nitrogen (N) content in severely burnt sites. Regeneration density was particularly abundant in medium-severity areas, while it drastically decreased in high-severity patches. The most abundant tree species in the regeneration layer was Scots pine, followed by goat willow (Salix caprea L.), European aspen (Populus tremula L.), and, to a lesser extent, European larch (Larix decidua Mill.). Slope, fire severity, and distance from seed trees emerged as the most important drivers of post-fire forest regeneration patterns. Conclusions Our results highlight the importance of preserving seed trees from salvage logging, even if they are damaged and have a low survival probability. Active post-fire management, such as tree planting, should be limited to large and severely burnt patches, where natural forest regeneration struggles to settle, increasing the risk of ecosystem degradation. These findings could be useful for informing land managers, helping them to enhance potential mitigation strategies in similar ecosystems and plan appropriate restoration approaches.

<p>Applied nucleation (AN) is a nature-based solution alternative to traditional regular plantations. It is a cost-effective technique that integrates artificial seedlings and natural regeneration dynamics to enhance forest recovery, mimicking successional processes. Given the current shift of disturbance regimes caused by global change, this technique will likely be a valuable active restoration approach for many forest ecosystems affected by extreme disturbance events. Indeed, AN is suitable for ecological restoration after stand-replacing events, improving seed availability and microsite conditions supporting natural regeneration. AN has been mostly applied in tropical forests, but its use in Mediterranean forests should be increasingly considered since a higher occurrence of large and severe fires has been observed over the last decades and further increases are expected in the future. These changes are raising concerns about regeneration recruitment, particularly for obligate seeders in mountain ecosystems. In these ecosystems, it is crucial to reconsider current post-fire policies to identify strategies that promote and maintain the ecosystem services of degraded forests, particularly when natural regeneration is ineffective. The main aim of this study was to define the best methodology for implementing AN in a mountain area affected by a large stand-replacing fire that occurred in 2005 in the Aosta Valley Region (North-Western Italy). After the fire salvage logging was performed, increasing ecosystem degradation, and, 16 years later, natural regeneration is still scarce and struggling to settle. Hotspots for AN were identified based on post-fire natural regeneration response to a series of site characteristics, such as topography, fire severity, and distance from seed trees. We assessed the drivers of post-fire regeneration through a machine learning correlative model (Bayesian Regression Tree, BART). The probability of regeneration presence across the landscape was then predicted under the current situation and a set of AN scenarios. Starting from the current scenario, we reclassified the prediction raster into three levels, according to the probability of presence and uncertainty. Polygons with low uncertainty and probability (< 0.3) were included in level one and considered hotspots for AN. From these predictions, it was possible to assess the most efficient active management scenario to speed up the regeneration process. Our results showed that AN could be a promising post-fire management technique for promoting natural regeneration while limiting anthropic interventions and their related economic and ecological costs.  </p>

<p>Wildfires play the role of ecosystem shapers in the majority of terrestrial biomes. Nowadays, their regimes are changing as a consequence of land abandonment and climate change. After-fire dynamics are widely studied in North America and Mediterranean environments. However, soils developed in different biomes might not unequivocally respond to fire-induced heating, and forests of the Western Italian Alps are not unfamiliar to fire occurrence.</p><p>For these reasons, we conducted several experiments (at plot and lab scale) at environmentally realistic conditions to systematically assess the impacts of fire on the physico-chemical properties of soils belonging to the Italian Alpine ecological region.</p><p>A homogenous pine forest (<em>Pinus sylvestris</em> L.) located in a mountain region near Torino experienced the passage of a severe and large wildfire in fall 2017. The field survey carried out in 2020 revealed that lower organic carbon (OC) contents and higher bulk density (BD) values were associated to a greater fire severity. Abundance of pyrogenic carbon was related to the steepness degree, as a consequence of erosion. In the superficial horizons, the naturally high WR expected from soils developed under a conifer stand was not present.</p><p>To elucidate mechanisms regulating WR occurrence and evolution, the thermal transformations borne by Alpine soils were investigated at controlled laboratory conditions. Topsoil samples displayed extremely different wettable behaviors upon increasing temperatures (Ts), with or without WR build-up. This occurred mainly in relation to content and composition of organic matter (OM), particle size distribution and abundance of iron (Fe) oxides. Notwithstanding the initial sample hydrophobicity, WR was dramatically lost above 200 °C due to increasing pH values, inducing OM de-sorption from the negatively charged mineral surfaces.</p><p>In the same T range, the thermal transformation of soil Fe oxides were found to be primarily directed towards oxidative processes (hematite formation). Ts up to 300 °C could have potentially promoted the stabilization of the remaining (non-combusted) OM, with the synthesis of defect-rich Fe oxides and enrichment in condensed and aromatic compounds, and yet OM was highly dispersible at the high pH values resulting from the thermal treatment, such that OC might be weakly retained on mineral phases in an after-fire scenario.</p>