Emilia Urbanek

Swansea University | SWAN · Department of Geography

Savannah fires are the largest contributor to global carbon (C) emissions from vegetation fires as a result of their high frequency and the large area burnt each year. Fires not only emit CO2 during the combustion process, they can also lead to enhanced CO2 fluxes from affected soils and vegetation, especially during the initial post-fire recovery...

The spike in carbon dioxide (CO2) observed after rewetting of dry soils, known as the ‘Birch effect’, can contribute substantially to total soil carbon (C) emissions, however, the exact mechanisms and timings underlying this sudden CO2 release remain unclear. The amount of applied water and duration of the previous dry period are considered the mai...

Carbon dioxide (CO2) efflux from soil represents one of the biggest ecosystem carbon (C) fluxes and high-magnitude pulses caused by rainfall make a substantial contribution to the overall C emissions. It is widely accepted that the drier the soil, the larger the CO2 pulses will be, but this notion has never been tested for water-repellent soils. So...

Rewetting of dry soil results in a well-known short-term pulse of CO 2 from soil to the atmosphere known as the 'Birch effect'. The displacement of CO 2 in air-filled pores with water during wetting has been recognised as one of the sources of this pulse. The Birch effect has been extensively reported under wettable soil conditions, but some studie...

Forest fires are known to induce changes in soil water-repellency (SWR), often increasing its severity and persistence. SWR restricts infiltration into soils affecting water distribution patterns. This may result in increased overland flow and runoff after the fire, maintaining soil water content low even after substantial rainfall. Rewetting of dr...

Soil water repellency (i.e. hydrophobicity, SWR) is a common soil phenomenon inhibiting water infiltration and water movement in the soil. SWR has significant hydrological implications for enhanced overland and preferential water flows and erosion. Several methods are used to determine the degree of SWR. The methods are typically chosen based on th...

Soil carbon dioxide (CO2) emissions are strongly dependent on pore water distribution, which in turn can be modified by reduced wettability. Many soils around the world are affected by soil water repellency (SWR), which reduces infiltration and results in diverse moisture distribution. SWR is temporally variable and soils can change from wettable t...

Soil CO2 emissions are strongly dependent on water distribution in soil pores, which in turn can be affected by soil water repellency (SWR; hydrophobicity). SWR restricts infiltration and movement of water, affecting soil hydrology as well as biological and chemical processes. Effects of SWR on soil carbon dynamics and specifically on soil respirat...

Prescribed (controlled) fire has recently been adopted as an important wildfire-fighting strategy in the Mediterranean. Relatively little research, however, has assessed its impacts on soil erosion and soil quality. This paper investigates hillslope-scale losses of soil, organic matter and selected nutrients before and after a 'worst-case scenario'...

Laboratory experiments were used to investigate the influence of simulated cracks and roots on soil water repellency (SWR) dynamics with and without basal drainage impedance in wetting–drying cycles. Observations and measurements were taken following water application equivalent to 9.2‐mm rainfall and then periodically during 80 h of drying. In tot...

Reduced soil tillage practices are claimed to improve soil health, fertility and productivity through improved soil structure and higher soil organic matter contents. This study compares soil structure stability of soil aggregates under three different tillage practices: conventional, reduced and no tillage. The erosive strength of soil aggregates...

Current climatic predictions include altered rainfall patterns and increased temperatures which in consequence can enhance the development of soil water repellency (SWR; i.e. hydrophobicity). Soils may become more severely water-repellent or SWR may spread into the environments where it has not been observed before. As the soil moisture dynamics, i...

Methane (CH4) is an important element of the biogeochemical carbon cycle. Methanogenic Archaea are strict anaerobes able to survive in dry and oxic soils, but not in liquid or agar slurry. Little is known about the mechanisms of their survival. The aim of this paper is to study the methanogenic potential of mineral soils stored as air-dry over 20 y...

The actual denitrification to N2O and denitrification capacity to N2O after flooding of different soil samples stored for over 25 years in air-dry conditions and fresh, air dried samples were compared in our study. Zero N2O release was observed from the stored soils but the fresh soil samples had very low actual denitrification to N2O. NO3- additio...

The influence which soil hydrophobicity may have on hillslope hydrology and erosion in any location will depend on the proportion of storm events in which it is spatially contiguous. This in turn is dependent upon (a) the speed and three-dimensional pattern with which it disappears in wet weather and (b) the speed, three-dimensional pattern and deg...

Prescribed (controlled) fire has become an important strategy primarily to limit the likelihood of more devastating wildfire. The considerable increase in wildfire activity in recent decades throughout the Mediterranean, and in Portugal in particular, has meant that this strategy has become increasingly popular despite inherent fears of people abou...

Prescribed fire is increasingly used as a management tool to pre-empt the occurrence of wildfires. Whether their use will lead to an increase in erosion and storm runoff will depend upon the magnitude and duration of impact of single prescribed fires and the frequency they are used. In areas affected by soil water-repellency, the hydrological and...

Although much is known about soil hydrophobicity, assessments of the overall hydrological and erosional significance of the soil property in areas affected by it are greatly hampered by a lack of knowledge on switching between hydrophobic and hydrophilic states. This arises mainly because of (1) the destructive nature of methods of assessing hydrop...

Mediterranean wildfire activity has increased markedly in recent decades, leading to enhanced runoff and erosion. Limiting post-fire on-site soil degradation and off-site flooding and sedimentation, however, often has a low priority because of the high costs of materials and labour needed to implement many recognised techniques (e.g. seeding, hydro...

Soil structure is often severely affected during high intensity burning, while low intensity prescribed burning has often been thought to have a low or neutral effect on soil aggregation. In this issue of Plant and Soil, (Albalasmeh et al. 2012) report a novel mechanism of aggregate disruption during low intensity burning that may explain some cont...

Soil structure is known to stabilise organic carbon (Corg), as it acts as physical barrier between the decomposing microorganisms and the substrates. It is, however, not fully understood how the organic carbon (Corg) and especially fresh material from plants is distributed within the soil structure. The aim of the current study is to investigate th...

Autoclaving is a commonly used practice to destroy microbial activity in soils but is thought to have a limited effect on other soil properties. Small changes in chemical composition have been reported, but there have been no previous reports of any alteration of physical properties. Th is study, however, showed that autoclaving can cause a major c...

Soil water repellency is a common phenomenon affecting a wide range of soil and land use types in different climates and is considered "the norm rather than the exception with its degree being variable". In all but the most severe cases, soil water repellency is transient with soils wetting eventually after prolonged wet weather and returning, when...

The rapid increase in fire activity in parts of the Mediterranean from the 1960s onwards led to a rise in interest in the application of prescribed fire as a method of reducing fuel loads and thereby limiting the likelihood of the occurrence of severe wildfires and the size of the areas affected. The `windows of opportunity' for carrying out contro...

Fire-induced erosion has been observed in many regions, in both wildfire and controlled fire settings. Erosion rates have in many cases been found to be scale-dependent, with erosion rates decreasing with increasing plot size. Most studies, however, have investigated fire-induced erosion at plot and hillslope scales, leaving the catchment scale lar...

Studies of soil water repellency have often attempted to isolate its hydrological impact by comparing responses of wettable and water repellent soils. It is, however, almost impossible to identify natural wettable and water repellent soils that are otherwise fully comparable. Furthermore no established methodology exists that allows changing a soil...

The Mediterranean region is highly susceptible to wildfires, which can lead to serious soil degradation as a result of physico-chemical soil property changes. Soil reacts in a complex way to changes brought about by fire, but removal of much or all of the vegetation cover and heating effects on the soil usually cause increased overland flow and inc...

Soils are commonly stony, especially in steep upland or heavily degraded sites. The hydrological effect of large stone contents has been previously investigated in wettable but not in water-repellent soils. For the latter, the focus has instead been on the impact of other soil characteristics (e.g. cracks and macropores) likely to promote water per...

This poster presents the research approaches and early results of a programme of field and laboratory investigation to assess three-dimensional patterns of switching of soils between hydrophobic and hydrophilic states. It focuses on soils on terrain of burnt and unburnt eucalyptus, pine and scrub land-use in north-central Portugal. Although much is...

This paper argues that the influence which hydrophobicity may have on overland flow and erosion in areas where it occurs will vary with its three-dimensional character (notably its vertical extent and position and local spatial variability), the frequency and vertical connectivity of any routeways through the hydrophobic layer and the spatiotempora...

Prescribed fire (or a controlled burn) is a management tool used in wildfire-prone areas to reduce the fuel load of living and dead biomass, while attempting to keep disturbance of the ground surface and soil to a minimum. We know that wildfire, particularly of moderate or extreme severity, can cause important changes to the chemical and physical p...

The protective impact of aggregation on microbial degradation through separation has been described frequently, especially for biotically formed aggregates. However, to date little information exists on the effects of organic-matter (OM) quantity and OM quality on physical protection, i.e., reduced degradability by microorganisms caused by physical...

Water repellency properties of individual soil aggregates offer increased reduction of carbon (C) mineralization within soils. These studies explore the spatial distributions of C and groupings of C-H and C = O compounds at multiple soil depths, on surfaces and within multiple sized soil aggregates. Measurements were conducted on soil aggregates, s...

Structured soils are characterized by the presence of inter- and intra-aggregate pore systems and aggregates, which show varying chemical, physical, and biological properties depending on the aggregate type and land use system. How far these aspects also affect the ion exchange processes and to what extent the interaction between the carbon distrib...

The type of tillage in arable soils affects porosity of the soil and in consequence the hydraulic conductivity. The accessibility and mobility of organic carbon in arable soils can differ depending on the type of tillage. The highest differences between conventional or conservation tillage are found in the top-soil layer of the A horizon in pore si...