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Background Mulching and burnt wood treatments are commonly applied to prevent the loss of soil quality and erosion, but their effect on soil multifunctionality remains unexplored. Aims We filled this gap by assessing the medium-term (4 years) effects of these treatments on soil multifunctionality after a large wildfire in NW Spain. Methods Straw mulching (SM) and cut plus lopping (CpL) treatments were applied in high-severity affected areas of heathland plant communities. CpL areas had been afforested with Scots pine 15 years before the fire. We considered four soil functions estimated in treated and burned control plots 4 years after fire: (1) carbon regulation; (2) water regulation; (3) soil fertility; and (4) nutrient cycling. The functions were integrated into a multifunctionality index and linear models were used to evaluate treatments effect. Key results SM had no impact on individual functions and multifunctionality. Conversely, CpL with burnt Scots pine wood was able to sustain higher levels of multiple functions simultaneously than control areas. Consistent trade-offs between soil functions emerged in control areas for both treatments. Conclusions Burnt wood could ensure long-lasting effects to promote soil multifunctionality in Mediterranean ecosystems. Implications We recommend using a multifunctionality approach to avoid biases in treatment success.

We analyse the effects of burn severity on individual soil properties and soil quotients in Mediterranean fire-prone pine forests immediately after a wildfire. Burn severity was measured in the field through the substrate stratum of the Composite Burn Index and soil samples were taken 7–9 days after a wildfire occurred in a Pinus pinaster Ait. ecosystem. In each soil sample, we analysed physical (size of soil aggregates), chemical (pH, organic C, total N and available P) and biological (microbial biomass C, β-glucosidase, urease and acid phosphatase activities) properties. Size of aggregates decreased in the areas affected by high burn severity. Additionally, moderate and high severities were associated with increases in pH and available P concentration and with decreases in organic C concentration. Microbial biomass C showed similar patterns to organic C along the burn severity gradient. The enzymatic activities of phosphatase and β-glucosidase showed the highest sensitivity to burn severity, as they strongly decreased from the low-severity scenarios. Among the studied soil quotients, the C:N ratio, microbial quotient and β-glucosidase:microbial biomass C quotient decreased with burn severity. This work provides valuable information on the impact of burn severity on the functioning of sandy siliceous soils in fire-prone pine ecosystems.

In the present study, we analyse the germination and seedling growth of three Pinus species (P. pinaster, P. sylvestris and P. nigra) under laboratory conditions after thermal shocks simulating the temperature effects of fire. Temperatures up to 150°C and 5 min exposure show negative effects on the percentage germination of P. pinaster seeds. P. sylvestris and P. nigra cannot stand temperatures greater than 110°C and 5 min exposure. In all three species, thermal shocks delay the start of germination. In addition, seeds from P. pinaster germinate over a longer time range. Seedling aerial growth after germination is influenced by high temperatures in P. sylvestris and P. nigra, but not in P. pinaster. Finally, thermal shocks produce a reduction in root growth in comparison with aerial growth in P. sylvestris.

The present study analyses the reproductive behaviour of Pinus pinaster at different ages of the parent trees after subjecting the seeds to variations in environmental factors and inhibitory substances. An experiment was designed in which seeds from mature (43 years old) and young (13 years old) trees were subjected to different environmental factors: darkness, thermal shocks and the presence of inhibitory substances from the needles and the undergrowth humus of P. pinaster. A control treatment was also carried out for the seeds of each age. The results obtained indicate that the age of the parent trees has a significant effect on mean germination time after experimental treatments: shock temperatures, darkness, and leaf and humus exudates. Seeds from young populations have shorter mean germination times than those from adult populations. Similarly, mature P. pinaster populations show more diversity in the length of innate dormancy of their seeds than younger populations. However, age has no significant effect on total percentage germination. Significant reductions in germination were observed when seeds from mature and young trees were exposed to temperatures equal to or above 150°C for 5 min. Increased temperature also produces a delay in the onset of germination in both populations.

Early post-fire structural dynamics in three Quercus pyrenaica communities after intense fires was studied. In the first year there is a marked domination of perennial species (herbaceous or woody); afterwards, herbaceous species tend to decrease in importance and ligneous species increase. Changes in species diversity were analysed as an indicator of recovery and stability in the communities. An increase was observed in the second year, and then diversity was maintained or reduced slightly in the third and fourth years. Spatial heterogeneity tends to diminish with time.