Pinus halepensis M. versus Quercus ilex subsp. Rotundifolia L. runoff and soil erosion at pedon scale under natural rainfall in Eastern Spain three decades after a forest fire

Afforestation aims to recover the vegetation cover, and restore natural ecosystems. The plant species selected for restoration will determine species richness and the fate of the ecosystem. Research focussing on the impact of vegetation recovery on soil quality are abundant, especially on fire affected land and where rehabilitation, afforestation and restoration projects were carried out. However, little is known about how different plants species affect soil erosion and water losses, which are key factors that will impact the fate of the afforested land. Aleppo pine (Pinus halepensis M.) is the species commonly used for afforestation in the Mediterranean and is very successful when natural recovery takes place, however, the original forests were composed of Holm oaks (Quercus ilex subsp. rotundifolia L.). There is little information about the hydrological and erosional impact of this change of vegetation cover stimulated by a millennia old forest use in the Mediterranean, and a century old afforestation policies and natural recovery as a consequence of land abandonment. To get insights in the effect of plant species on runoff generation and soil erosion, individual trees should be selected. Plots of 1 m2 are necessary to identify homogeneous patches, and were installed under Aleppo pine (4 plots) and Holm oaks (4 plots) in a 30 (34)-years old plant cover recovered after a forest fire that took place in 1979. A raingauge was installed in the study site to characterize the rainfall. The soil erosion plots were built with metal borders and each plot drained to a collector (gutter) and a 60 L container to store the surface runoff. Runoff was measured after each rainfall event and sediment concentration was determined by desiccation. Results show that Aleppo pine covered soils yield six times more runoff (232 mm, 8.31%) than Holm oaks (40 mm, 1.4%) during the experimental period of 2010-2014, when rainfall amount 2,721.1 mm. Runoff sediment concentration was higher in the Aleppo pine plots (4.9 g l 1) than in the Holm oaks plots (2.6 g l 1). Soil erosion rate was ten times higher in Aleppo pine (2.6 Mg ha 1 y 1) than in Holm oaks (0.26 Mg ha 1 y 1)

Effects of Skidding Operations after Tree Harvesting and Soil Scarification by Felled Trees on Initial Seedling Emergence of Spanish Black Pine (Pinus nigra Arn. ssp. salzmannii)

Skidding operations are thought to have negative impacts on soil emergence because they may increase soil compaction and reduce vegetation cover and the soil’s organic matter content. We investigated whether and to what extent tree harvesting and subsequent skidding initially altered seedling emergence in two Mediterranean forests of Pinus nigra Arn. ssp. salzmannii (Spanish black pine) in the Cuenca Mountains (Spain). Our main objective was to compare the Spanish black pine seedling emergence rate among skid trails, soil areas scarified by felled trees, and areas undisturbed next to harvest operations. In addition, we selected an unmanaged stand as reference, in order to look for evidence of seedling emergence under natural conditions. We measured Spanish black pine seed fall and seedling emergence immediately after harvest operations in two locations in the Cuenca Mountains (Palancares and Majadas forests), which are typical forests in Cuenca Mountains. The results showed that the Palancares site presented higher seed fall in comparison to the Majadas site. In addition, seed fall was higher in the unmanaged stand, as we recorded a higher tree density in this site in comparison to harvested stands (Palancares and Majadas). Furthermore, our results demonstrated differences in seedling emergence between lower elevation drier Palancares and higher elevation wetter Majadas and relative differences in seedling emergence among skid trail, scarified, and undisturbed harvested areas. Finally, the unmanaged stand presented the highest seedling emergence in comparison to scarified, compacted, and non-disturbed harvested areas. Overall, the results suggest a short-term impact of skidding on seedling emergence, which should be considered for future management guidelines of Spanish black pine in the Mediterranean climat

Impacts of land-use and climate changes on surface runoff in a tropical forest watershed (Brazil)

Surface runoff generation capacity can be modified by land-use and climate changes. Annual runoff volumes have been evaluated in a small watershed of tropical forest (Brazil), using the Soil and Water Assessment Tool (SWAT) model. Firstly, the accuracy of SWAT in runoff predictions has been assessed by default input parameters and improved by automatic calibration, using 20-year observations. Then, the hydrological response under land uses (cropland, pasture and deforested soil) alternative to tropical forest and climate change scenarios has been simulated. SWAT application has showed that, if forest was replaced by crops or pasture, the watershed’s hydrological response would not significantly be affected. Conversely, a complete deforestation would slightly increase its runoff generation capacity. Under forecasted climate scenarios, the runoff generation capacity of the watershed will tend to decrease and will not be noticeably different among the representative concentration pathways. Pasture and bare soil will give the lowest and highest runoff coefficients, respectively.info:eu-repo/semantics/publishedVersio

Post-fire Management Effects on Sediment (Dis)Connectivity in Mediterranean Forest Ecosystems: Channel and Catchment Response

[Abstract] Forest fires and post-fire practices influence sediment connectivity (SC). In this study, we use the ‘aggregated index of connectivity’ (AIC) to assess SC in five Mediterranean catchments (198–1090 ha) affected by a wildfire in 2012 in south-eastern Spain. Two temporal scenarios were considered, immediately after the fire and before post-fire management, and 2 years after the fire including all practices (hillslope barriers, check-dams, afforestation, salvage logging and skid trails). One LiDAR (light detection and ranging)-derived digital elevation model (DEM, 2 m × 2 m resolution) was generated, per scenario. The five catchment outlets were established as the computation target (AICоᴜᴛ), and structural and functional SC were calculated. Index outputs were normalized to make the results of the non-nested catchments comparable (AICɴ₋оᴜᴛ). The output analysis includes the SC distribution along the catchments and at local scale (929 sub-catchments, 677 in the burned area), the hillslope and channel measures' effect on SC, and a sedimentological analysis using observed area-specific sediment yield (SSY) at 10 new (built after post-fire practices) concrete check-dams located in the catchments (SSY = 1.94 Mg ha⁻¹ yr⁻¹; σ = 1.22). The catchments with more circular shapes and steeper slopes were those with higher AICɴ₋оᴜᴛ. The structural SC maps – removing the rainfall erosivity influence – allowed evaluating the actual role played by the post-fire practices that reduced SC (x̅ = − 1.19%; σ = 0.41); while functional SC was linked to the actual change of SC (x̅ = + 5.32%; σ = 0.62). Hillslope treatments resulted in significant changes on AICɴ₋оᴜᴛ at sub-catchment scale with certain disconnectivity. A good and positive correlation was found between the SSY and the changes of AICɴ₋оᴜᴛ. However, the coarse DEM resolution explained the lack of effect of the rock check-dams – located on the secondary channels – on AICɴ₋оᴜᴛ. AICɴ₋оᴜᴛ proved to be a useful tool for decision making in post-fire restoration, but an optimal input data is still necessary to refine calculations.European Cooperation in Science and Technology; CA18135Gobierno de Castilla-la Mancha; Sbply/16/180501/ 000109This study was supported by funds provided to the VIS4FIRE Spanish R&D project (RTA2017-00042-C05-00) co-funded by the “Instituto Nacional de Investigación y Tecnología Agraria” (INIA) and FEDER programme. This study was done in the frame of the European Cooperation in Science and Technology (COST) action CA18135 ‘FIRElinks’ (Fire in the Earth System:Science & Society). J. González-Romero holds a scholarship (Sbply/16/180501/000109) from the Regional Government of Castilla-La Mancha/European Social Fund (ESF, EU)

Ex-situ genetic conservation of Pinus nigra salzmannii endangered populations from the Spanish Central Range: abstract

Publishe

Exploring the influence of vegetation cover, sediment storage capacity and channel dimensions on stone check dam conditions and effectiveness in a large regulated river in México

Check dams are widely used for soil conservation at the watershed scale. When structurally sound, these engineering control works retain sediment as planned. However, there is limited information describing the influence of site characteristics on post-construction condition including structural stability and sediment retention capacity. More specifically, the effects of channel morphology, check dam geometry and vegetation characteristics as potentially influencing factors on sediment retention capacity at the watershed level are poorly understood. Thus, an investigation applying field and remotely sensed measurements, multi-regression models, redundancy and sensitivity analysis, and correlation analysis was conducted in a Mexican watershed where the characteristics of 273 check dams were evaluated 3-5 years after construction. Vegetation cover and dimensions of the channel were found to be the most important factors influencing check dam fate. Taller structures experienced the greatest failure risk, in contrast to lower and wider structures and associated vegetation cover that retained long and wide sediment wedges, which helped to stabilise the check dams. The potential sediment storage capacity of the check dams mainly depends on the downstream height of the structure, but also on the vegetation cover near the structure walls; check dams constructed across a range of channel dimensions are able to effectively store sediment. Overall, this study provides a quantitative evaluation of the dominant factors influencing the post-construction conditions of check dams and their ability to store sediment, and thus provides land managers insights into the best strategies for soil conservation at the watershed scale using check dams

Post-fire Management Effects on Hillslope-Stream Sediment Connectivity in a Mediterranean Forest Ecosystem

[Abstract] 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.The authors thank the Regional Government of Castilla-La Mancha (Junta de Comunidades de Castilla-La Mancha) for supporting the study and providing information about the undertaken measures in the burned area. This study was supported by funds provided to the VIS4FIRE Spanish R&D project (RTA 2017-00042-C05-00) co-funded by the “Instituto Nacional de Investigación y Tecnología Agraria” (INIA) and FEDER programme. This study was done in the frame of the European Cooperation in Science and Technology (COST) action CA18135 ‘FIRElinks’ (Fire in the Earth System: Science & Society). J. González-Romero holds a postdoctoral contract supported by the European Social Fund (ESF, EU). The authors declare no conflict of interest. E. Peña holds a scholarship (2020-PREUCLM-16032) from the UCLM and the European Social Fund (FSE). Pedro Antonio Plaza Álvarez holds a predoctoral fellowship from the Spanish Ministry of Education, Culture and Sport (FPU16/03296)Universidad de Castilla-La Mancha; 2020-PREUCLM-1603

Short-term changes in infiltration between straw mulched and non-mulched soils after wildfire in Mediterranean forest ecosystems

Water infiltration is a basic parameter to understand the hydrological response of semi-arid or arid soils - where runoff generation is dominated by infiltration-excess - subjected to wildfire. To evaluate the hydrological effects of straw application on a sandy loam soil after wildfire, the unsaturated hydraulic conductivity, water content and temperature of mulched and nonmulched (considered as control) soils were monitored throughout eight months. Compared to untreated soils, straw maintained higher temperatures and water contents in mulched plots, but reduced their unsaturated hydraulic conductivity, particularly in the drier season. These results suggest that straw release may lead to a decrease of water infiltration capacity of soils subjected to wildfire, with particular evidence in summer in the case of heavy storm occurrence