Wildfires burn vegetation and leave the resultant organic and inorganic ash into the soil surface. Depending on the temperatures and burn durations, the quantity and type of ash can vary widely. Ash mobilization following wildfire is a topic of major concern, since it may result in contamination of surface water bodies within and downstream of the burnt areas. The present study aims to analyse the influence of black and white ash on surface runoff, leachate and total erosion and erosion of organic matter by running a field experiment along 6 weeks, using three replicate lysimeters with control soil, soil with addition of black ash and soil with addition of white ash. There was some suggestion but no statistical evidence that black ash reduced overland flow generation during the initial rainfall events, while black ash was found to increase sediment and organic matter losses by overland flow in a statistically significant manner. This was not during the initial rainfall events and, therefore, not directly related to the presence of a homogenous cover of a well-defined ash layer on the soil surface.

<p>In recent decades, the establishment of monospecific tree plantations has increased markedly. Such changes in land use may have important implications for soil properties and functions. At present, the most common monospecific tree plantations worldwide are those of eucalypt, and they have been reported to negatively affect soil functions such as carbon sequestration and soil biodiversity (macroinvertebrates). This has been attributed, at least in part, to the practice of soil mobilization prior to tree planting. Arguably, the construction of bench terraces for installing eucalypt plantation is an extreme form of soil mobilization and has become increasingly common in Central Portugal, including to facilitate forestry operations on steep slopes such as the planting itself, the application of agrichemicals for fertilization and weed control, mechanical control of the understory fuel load, and the logging and extraction of wood. While bench terracing is a technique that aims at soil and water conservation on steep slopes that are otherwise very hard to cultivate, its effectiveness has been poorly studied. Considerable rates of splash erosion have been reported on the terraces themselves during the initial period after their construction, and so have elevates rates of water erosion on steep tracks.  Slope-scale soil losses, however, are difficult to quantify, even using erosion survey methods due to the fast growth of the eucalypts. While the same is true for the associated fertility losses, the main impact of bench terracing on topsoil fertility may results from the - massive -redistribution and inversion of the soil layers up to depths of 30 cm and more. This study aimed to quantify this direct effect of bench terracing on soil nutrient status. To this end, a 10 ha forest land property was sampled before and immediately after bench terracing during summer 2019. Before bench terracing, on 4th of April 2019, soil sampling was carried out at 5 points along a transect of 100 m centred on the middle section of a South-East facing slope; after bench terracing, on 23rd July 2019, soil sampling was carried out on 5 terraces on the same slope section, separated from each other by 1 terrace. Before bench terracing, the O layer, and the 0-10 cm (A horizon) and 15-20 (B horizon) mineral soil depths were sampled at each transect point; after terracing, the 0-20 cm of mixed mineral soil depths were sampled at each terrace. The mineral soil samples were analysed with respect to PMN and HCW as well as total C, N and P. The results showed clear differences between the nutrient status of the mineral soils before and after bench terracing. The construction of bench terraces diminished all soil nutrient analysed, this not only affected the stock of soil major nutrients, but also strongly affect the labile and plant available fractions. Therefore, terracing has immediately implications in soil fertility and may impose important limitations in the kye ecological functions of forest soil such as nutrient cycling, storage and turnover.</p>

<p>Eucalypt trees are the most planted tree in the world, and in Portugal these plantations occupy 26% of the forested area. The area of Eucalypt monoculture is growing since the 50’s due to the importance of this tree for the pulp and paste industry. With short rotation cycles, it is important to facilitate the cut and transport of the logged trees. In this sense, many forested areas in mountainous regions are being terraced with bulldozers.</p><p>Terracing is a well know soil conservation practice, reducing runoff peak flows, increasing water infiltration and subsequent low soil erosion rates. Nevertheless, the impacts of terracing for eucalypt plantations are still unknown, especially in terms of biodiversity of soil fauna. Hence, to address this research gap, the present study aimed to assess the impacts of terracing on the ground dwelling arthropods in eucalypt plantations.</p><p>This study took place in a mountain slope with old eucalypt trees that were logged (May 2019) and then terraced (July) as ground preparation to receive a new eucalypt plantation. The community of ground dwelling arthropods were accessed using pitfall traps.  The arthropods were collected before the terracing process, in Spring 2019, and then seasonally after terracing until the Spring of 2020Total abundance and richness at order level, as well as, abundance, richness, Shannon-Wiener diversity and Pielou’s Evenness indexes, at Family level of Coleoptera, Araneae and Hymenoptera, were used to depict differences between pre- and post-terracing. The results showed that although terracing did not reduce the total abundance or richness, it changed the community structure. In particular, it was observed an increase in opportunist and generalist families after terracing such as Staphylinidae and Myrmicinae. The spider community also changed, with more hunter families captured after the terrace construction. In overall, the results of our study reveal that although the total abundance and richness of arthropods was not altered by the construction of terraces, their structure was modified.</p>

<p>The establishment of monospecific eucalypt plantations has increased considerably over the last half-century. At present, eucalypts are the tree species that are planted most widely across the world, and the common practice of soil mobilization prior to their planting has been associated with negative effects on soil functions such as nutrient and water cycling, carbon sequestration, soil erosion control and soil biodiversity conservation. In Central Portugal, the construction of bench terraces for eucalypt plantations areas has become increasingly common on steep terrain. Bench terrace construction implies the mobilization of large quantities of topsoil and, hence, elevated installation costs that are justified by the advantages in planting, fertilizer application, mechanical and agrichemical weed control and, ultimately, salvage logging and extraction of wood and logging residues. Although terraces are a traditional soil and water conservation technique, the hydrological impacts of bench terracing for forest plantations have been poorly studied. The use of heavy machinery in forests has been reported to increase soil compaction and bulk density and, thereby, decrease soil infiltration capacity and increase runoff generation. At the same time, the flat sections of bench terraces will increase not only infiltration of rainfall but also re-infiltration of run-on, for example from the adjacent risers or diverted forest tracks. In the case of eucalypt plantations, (re-)infiltration patterns may be strongly affected by soil water repellency (SWR), as eucalypts have been widely associated with strong to extreme SWR, especially during dry periods. This study aimed to quantify the short- to long-term impacts of bench terrace construction on SWR in eucalypt plantations along a chrono-sequence. To this end, SWR was measured in-situ, using the Methanol droplet (MED) test, for four different periods of time-since-terracing, i.e. 0, 5, 10 and 17 years after terracing. For each of these periods, three pairs of nearby terraced and non-terraced eucalypt plantations were studied, giving a total of 24 study sites. The MED measurements were done during the dry summer of 2020 (in plain covid-19 crisis conditions). The results showed clear differences in SWR between terraced and non-terraced eucalypt plantations. The median SWR was extreme in all non-terraced sites (MED classes 7 to 8) as opposed to highly variable at the terraced sites, ranging from wettable to strong (MED classes 0 to 6). In the case of the terraced sites, the time elapsed since terrace construction had a major impact. The median SWR was very wettable immediately as well as 5 years after terracing, while it was moderate and strong water repellent 10 and 17 years after terracing.</p>

<p>Wildfires are documented to affect physical, chemical and biological properties of topsoil. Besides through the direct heating-induced impacts, wildfires can also affect topsoil properties indirectly through the ash layer deposited on the soil surface immediately after fire. These indirect ash effects are less well understood, because of the marked dynamics in ash loads with time-since-fire due to mobilization by wind and water erosion. Therefore, we took advantage of a lysimeter study - a controlled experiment under field conditions - into the mobilization of ashes by overland flow, to address the ash impacts on topsoil nutrient contents. The lysimeter study involved a total of 15 lysimeters with a surface area of 50 cm by 120 cm and at a slope angle of approximately 10°. The lysimeters were equally and randomly distributed over five treatments. Four treatments involved the application of two types of ash at a rate of 500 g.m<sup>-2</sup> on a 2-3cm-thick layer of soil (in fact, sediments from the Mondego river), while the fifth, control treatment did not. One ash type consisted of black ashes collected in a 2020 burnt mature pine plantation in north-central Portugal, while the white ashes were obtained from a paper mill factory. In turn, two treatments per ash type involved the presence vs. absence of a 10cm-wide strip of 1cm-diameter PVC bars with a density of 1000 bars per m<sup>-2</sup>, mimicking a riparian vegetation zone and, assess its effectiveness to retain eroded ashes preventing them from entering streams. The lysimeter experiment ran for 7 weeks, starting on September 6 (ash application) and ending on 22 October 2021, covering the period that typically corresponds to the initial phase of the post-fire window-of-disturbance in the study region. At the end of the experiment, the upper 2cm of the soil were sampled at 3 locations within each lysimeter, in its middle and halfway its upper and lower halves. This was done after removing the remaining ashes on the soil surface. All soil samples were analysed for their contents of available Phosphorus (Pav) and total Nitrogen (TN) but, at this moment, only the Pav analyses have been concluded. The preliminary Pav results revealed a much smaller enrichment by the black than white ashes. The median Pav contents were 4.6 microgram per gram of soil for the control lysimeters as opposed to  5.6 and 9.2  microgram per gram of soil for the lysimeters with black and white ashes, respectively.  This difference in enrichment could be linked to the differences in Pav content of the two ash types, being 1.9 and 1.0 microgram per gram of the white and black ash, respectively. Furthermore, the Pav enrichment was not affected by the presence/absence of the simulated riparian zone at the bottom of the lysimeters, as the differences in Pav contents of the lysimeters with and without these zones amounted to 0.1 microgram Pav per gram of soil in the case of both the black and the white ashes.</p>