Short-term Macrochloa tenacissima response understory Pinus halepensis Mill forest after early prescribed burns in a semi-arid landscape.

Climate change has led to altered fire patterns in the Mediterranean basin due to rising temperatures and greenhouse gas emissions, diminishing the resilience of forest ecosystems. To address this threat, forest management increasingly employs preventive measures like controlled burns, aiming to mitigate wildfire damage. However, understanding the impact of prescribed burns on vegetation remains crucial. Our study focuses on assessing the ecological effects of early-season prescribed burns on Macrochloa tenacissima communities within Pinus halepensis Mill forests on the Iberian Peninsula. These forests, with southeast-facing slopes and arid soils, heavily rely on alpha grass for post-fire recovery, acting as a shield against runoff and erosion. Yet, the presence of highly flammable resprouting species can lead to rapid combustible material accumulation. We evaluated parameters like coverage, floral diversity (α-diversity), aboveground plant biomass, photosynthetic activity, and chemical leaf properties of alpha grass, a year after a low-intensity controlled burn. Comparing burnt and unburnt areas revealed significant changes in α-diversity and ecophysiology of Macrochloa tenacissima due to early-season prescribed burns. These short-term shifts underscore the need for further exploration of underlying mechanisms. Our analysis also showed distinct shifts in alpha grass leaf chemical composition between the two plot types, potentially impacting post-fire recovery strategies. Although prescribed burning might not be optimal for reducing fire risk in resprouting species-dominated forests, it conserves native plants and enhances ecosystem diversity, providing valuable ecological benefits. In conclusion, our research deepens our understanding of early-season burning's repercussions on flammable vegetation dynamics and combustible material availability in semi-arid landscapes. It contributes to standardized management protocols, aiding effective forest service administration and wildfire risk reduction.

Short-term recovery of soil and pine tree canopy after late prescribed burning in a semi-arid landscape.

Climate change worsening due to global warming and progressive abandonment in rural areas mean that wildfires are increasing in extent and severity terms, and are one of the major disturbances in the Mediterranean Basin. To mitigate these disturbances, preventive management tools need to be used. Fire employment is being implemented, known as prescribed burnings, as forestry actions to change vegetation lines both vertically and horizontally to eliminate forest fuel load continuity. This study aimed to know the ecological effects of late prescribed burning treatments under mixed trees. Prescribed burns were carried out in October 2019 in the municipality of Ayna, Albacete (SE Spain). To assess the short-term (12-month) fire impact on soil, we measured soil respiration with a CO2 flow chamber and analyzed soil physico-chemical properties. We also used minidisc infiltrometers to analyze soil repellency and soil hydraulic conductivity over a 1-year monitoring period. In addition, we evaluated the effects on tree strata by performing chemical nature analyses of fallen needles in Pinus pinaster after prescribed burning. According to our initial hypotheses, the results did not show significant changes in any parameter evaluated during the study period. However, some variables were affected in the first 3 months, needlefall and in microbiological activity, such as variations in soil physico-chemical properties, which can be due to long dry seasons combined with prescribed burning. This study attempts to observe and make known the effects that low-intensity prescribed burning has on soil and needlefall, which are relevant for updating forest management tools.

Post-fire management effects on hillslope-stream sediment connectivity in a Mediterranean forest ecosystem.

Forest fires intensify sediment transport and aggravate local and off-site consequences of soil erosion. This study evaluates the influence of post-fire measures on structural and functional sediment connectivity (SC) in five fire-affected Mediterranean catchments, which include 929 sub-catchments, by using the "aggregated index of connectivity" (AIC) at two temporal scenarios: I) immediately after the fire and before implementing post-fire practices ('Pre-man'), and II) two years after the fire ('Post-man'). The latter includes all the emergency stabilization practices, that are hillslope barriers, check-dams and afforestation. The stream system was set as the target of the computation (STR), to be representative of intense rainfall-runoff events with effective sediment delivery outside the catchments. Output normalization (AICN) allows comparing the results of the five basins between them. The sedimentological analysis is based on specific sediment yield (SSY) -measured at the check-dams installed after the fire -, and this data is used for output evaluation. Stream density and slope variables were the most influential factors on AICN-STR results at the sub-catchment scale. Post-fire hillslope treatments (barriers when built in high densities and afforestation) significantly reduced AICN-STR in comparison with untreated areas in both structural and functional approaches. Despite the presence of hillslope treatments, the higher erosive rainfall conditions resulted in higher AICN-STR values in the Post-man scenario (functional approach). A positive and good correlation was found between the measured SSY and the AICN-STR changes due to the post-fire practices and vegetation recovery, showing the good correspondence of the computation results and the real sediment dynamics of the studied catchments. Overall, AICN demonstrated to be a useful and versatile tool for post-fire management, which needs further research to optimize its applicability.