Turning unproductive soil into profits


Preeti Roychand

La Trobe University
AgriBio Centre for AgriBioscience
Melbourne, VIC, Australia

Sandy soils in Western Australia are bad soils for growing plants due to their poor nutrients and water holding capacity (see an example in Figure 1). In general, these soils are water repellent, which leads to land degradation by increasing soil erosion risk and run-off rates. Nevertheless, these soils may be improved by clay addition, which leads to increase soil organic carbon content (Franzluebbers et al. 1996). Several ways have been used to increase soil organic carbon content in soils: i) no-tillage systems, ii) addition of bio char , iii) organic amendments or fertilizer addition and iv) switch to perennial plants. But there is another potential method for enhancing soil organic carbon storage in soils which has received little attention: mixing of isolated clay with sandy soils. Continue reading

Monday paper: Short-term changes in soil Munsell colour value, organic matter content and soil water repellency after a spring grassland fire in Lithuania


Pereira P, Úbeda X, Mataix-Solera J, Oliva M, Novara A: Short-term changes in soil Munsell colour value, organic matter content and soil water repellency after a spring grassland fire in Lithuania. Solid Earth, 5, 209-225. DOI: 10.5194/se-5-209-2014.

Evidence of earthworm activity (indicated with a red circle) in the burned plot 17 days after the fire.
Evidence of earthworm activity in the burned plot 17 days after the fire.

Abstract

Fire is a natural phenomenon with important implications on soil properties. The degree of this impact depends upon fire severity, the ecosystem affected, topography of the burned area and post-fire meteorological conditions. The study of fire effects on soil properties is fundamental to understand the impacts of this disturbance on ecosystems. The aim of this work was to study the short-term effects immediately after the fire (IAF), 2, 5, 7 and 9 months after a low-severity spring boreal grassland fire on soil colour value (assessed with the Munsell colour chart), soil organic matter content (SOM) and soil water repellency (SWR) in Lithuania. Four days after the fire a 400 m2 plot was delineated in an unburned and burned area with the same topographical characteristics. Soil samples were collected at 0–5 cm depth in a 20 m × 20 m grid, with 5 m space between sampling points. In each plot 25 samples were collected (50 each sampling date) for a total of 250 samples for the whole study. SWR was assessed in fine earth (< 2 mm) and sieve fractions of 2–1, 1–0.5, 0.5–0.25 and < 0.25 mm from the 250 soil samples using the water drop penetration time (WDPT) method. The results showed that significant differences were only identified in the burned area. Fire darkened the soil significantly during the entire study period due to the incorporation of ash/charcoal into the topsoil (significant differences were found among plots for all sampling dates). SOM was only significantly different among samples from the unburned area. The comparison between plots revealed that SOM was significantly higher in the first 2 months after the fire in the burned plot, compared to the unburned plot. SWR of the fine earth was significantly different in the burned and unburned plot among all sampling dates. SWR was significantly more severe only IAF and 2 months after the fire. In the unburned area SWR was significantly higher IAF, 2, 5 and 7 months later after than 9 months later. The comparison between plots showed that SWR was more severe in the burned plot during the first 2 months after the fire in relation to the unburned plot. Considering the different sieve fractions studied, in the burned plot SWR was significantly more severe in the first 7 months after the fire in the coarser fractions (2–1 and 1–0.5 mm) and 9 months after in the finer fractions (0.5–0.25 and < 0.25 mm). In relation to the unburned plot, SWR was significantly more severe in the size fractions 2–1 and < 0.25 mm, IAF, 5 and 7 months after the fire than 2 and 9 months later. In the 1–0.5- and 0.5–0.25 mm-size fractions, SWR was significantly higher IAF, 2, 5 and 7 months after the fire than in the last sampling date. Significant differences in SWR were observed among the different sieve fractions in each plot, with exception of 2 and 9 months after the fire in the unburned plot. In most cases the finer fraction (< 0.25 mm) was more water repellent than the others. The comparison between plots for each sieve fraction showed significant differences in all cases IAF, 2 and 5 months after the fire. Seven months after the fire significant differences were only observed in the finer fractions (0.5–0.25 and < 0.25 mm) and after 9 months no significant differences were identified. The correlations between soil Munsell colour value and SOM were negatively significant in the burned and unburned areas. The correlations between Munsell colour value and SWR were only significant in the burned plot IAF, 2 and 7 months after the fire. In the case of the correlations between SOM and SWR, significant differences were only identified IAF and 2 months after the fire. The partial correlations (controlling for the effect of SOM) revealed that SOM had an important influence on the correlation between soil Munsell colour value and SWR in the burned plot IAF, 2 and 7 months after the fire.

Solid Earth

Solid Earth (SE) is an international scientific journal dedicated to the publication and discussion of multidisciplinary research on the composition, structure and dynamics of the Earth from the surface to the deep interior at all spatial and temporal scales. More at Solid Earth homepage.

Monday paper: Seasonal changes in the soil hydrological and erosive response depending on aspect, vegetation type and soil water repellency in different Mediterranean microenvironments


Gabarrón-Galeote, M.A., Martínez-Murillo, J.F., Quesada, M.A., Ruiz-Sinoga, J.D. 2013. Seasonal changes in the soil hydrological and erosive response depending on aspect, vegetation type and soil water repellency in different Mediterranean microenvironments. Solid Earth, 4, 497-509. DOI: 10.5194/se-4-497-2013.

Abstract

Mediterranean areas are characterized by a strong spatial variability that makes the soil hydrological response highly complex. Moreover, Mediterranean climate has marked seasons that provoke dramatic changes on soil properties determining the runoff rates, such as soil water content or soil water repellency (SWR). Thus, soil hydrological and erosive response in Mediterranean areas can be highly time- as well as space-dependant. This study shows SWR, aspect and vegetation as factors of the soil hydrological and erosive response. Erosion plots were set up in the north- and the south-facing hillslope and rainfall, runoff, sediments and SWR were monitored. Soil water repellency showed a seasonal behaviour and it was presented in three out of four microenvironments after the summer, disappearing in the wet season. In general, runoff rate was higher in shrubs patches (0.47 ± 0.67 mm) than in inter-shrub soils (1.54 ± 2.14 mm), but it changed seasonally in different ways, depending on the aspect considered, decreasing in the north-facing hillslope and increasing in the south-facing one. The main factor determining the hydrological and erosive response was the rainfall intensity, regardless of the rainfall depth of the event. This response was modulated mainly by SWR in the north-facing hillslope and the vegetation pattern in the south-facing one.

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Solid Earth (SE) is an international scientific journal dedicated to the publication and discussion of multidisciplinary research on the composition, structure and dynamics of the Earth from the surface to the deep interior at all spatial and temporal scales. More at Solid Earth hompage.

Impact of fires on soil properties, runoff generation and sediment transport


Notes on session Session SSS 9.6/GM 6.7/HS 12.6 (EGU2013)

Conveners: Lee MacDonald; Jonay Neris; Stefan Doerr; Artemi Cerdà; J. Jacob Keizer

Wildfires are increasingly recognized as the primary cause of geomorphic change in forests and brush lands, and climate change is expected to further increase both the amount and severity of wildfires. Recent studies have provided an increasing amount of data on how fires can affect runoff and erosion rates, but there is still much to be done on the underlying causes of the observed increases, and how fire affects vary across vegetation types, climates, and spatial scale.

Post-wildfire landscape.
Post-wildfire landscape.

Dr. Scott Woods at the University of Montana was taking a leading role in this process-based research until his career was tragically ended by lung cancer. The Soil System Science sponsored a session in his honor during the 2013 EGU meeting, and this was entitled Impact of fires on soil properties, runoff generation and sediment transport.  The main aim of this session was to discuss the recent studies on the effects of fires on soil properties, the resultant changes in runoff and erosion rates, and the effectiveness of different post-fire treatments to mitigate these effects.

Impact of fires on soil properties, runoff generation and sediment transport oral session.
Impact of fires on soil properties, runoff generation and sediment transport oral session.

Twenty-four papers were submitted to this session.  The morning oral session in the morning began with a brief summary of Scott’s career, and this was followed by eight talks.  The session then shifted to a different room where a series of short presentations summarized many of the 16 poster papers.    The afternoon poster session then provided a lively venue for further discussions, and in the evening many of the presenters attended the special dinner for all those working on topics related to soil erosion.  Discussions are being held regarding the possible publication of the papers in a special issue of a peer-reviewed journal.

Ash and soil water repellency effects on soil hydrology in fire-affected Mediterranean ecosystems


Merche B. Bodí
merche.bodi@uv.es
SEDER-Soil Erosion and Degradation Research Group, Departament de Geografia. Universitat de València. Valencia, Spain
GEA-Grupo de Edafología Ambiental, Departamento de Agroquímica y Medio Ambiente, Universidad Miguel Hernández, Elche, Spain

Cover.
Cover. Click to enlarge.

After a wildfire, changes in the vegetation, micro and macro fauna, biochemical cycles, soil properties, and hydrological and geomorphological processes may occur. The most studied cause of these changes is the heat input, but the environmental conditions after the fire and the new ash cover also play an important role. Continue reading

Stefan Doerr: meet the expert in (soil water) repellency


Rob Bryant
College of Engineering, Swansea University

Rick Shakesby
College of Science, Swansea University

Stefan Doerr achieved a Diplom from Tübingen University (1993) and at that stage his main interests lay in limestone geomorphology. His interests in research into soil began at Swansea University where his PhD (awarded 1997) concerned soil water repellency relating to burned and unburned eucalypt and pine forests in north-central Portugal.

Research in Australia (downunder!) in 2009 (Stefan on the right).

Continue reading