Monday paper: Thermal shock and splash effects on burned gypseous soils from the Ebro Basin (NE Spain)


León J, Seeger M, Badía D, Peters P, Echevarría T: Thermal shock and splash effects on burned gypseous soils from the Ebro Basin (NE Spain). Solid Earth, 5, 131-140. DOI: 10.5194/se-5-131-2014.

Extraction of soil blocks for this study.
Extraction of soil blocks for this study.

Abstract

Fire is a natural factor of landscape evolution in Mediterranean ecosystems. The middle Ebro Valley has extreme aridity, which results in a low plant cover and high soil erodibility, especially on gypseous substrates. The aim of this research is to analyze the effects of moderate heating on physical and chemical soil properties, mineralogical composition and susceptibility to splash erosion. Topsoil samples (15 cm depth) were taken in the Remolinos mountain slopes (Ebro Valley, NE Spain) from two soil types: Leptic Gypsisol (LP) in a convex slope and Haplic Gypsisol (GY) in a concave slope. To assess the heating effects on the mineralogy we burned the soils at 105 and 205 °C in an oven and to assess the splash effects we used a rainfall simulator under laboratory conditions using undisturbed topsoil subsamples (0–5 cm depth of Ah horizon). LP soil has lower soil organic matter (SOM) and soil aggregate stability (SAS) and higher gypsum content than GY soil. Gypsum and dolomite are the main minerals (>80%) in the LP soil, while gypsum, dolomite, calcite and quartz have similar proportions in GY soil. Clay minerals (kaolinite and illite) are scarce in both soils. Heating at 105 °C has no effect on soil mineralogy. However, heating to 205 °C transforms gypsum to bassanite, increases significantly the soil salinity (EC) in both soil units (LP and GY) and decreases pH only in GY soil. Despite differences in the content of organic matter and structural stability, both soils show no significant differences (P < 0.01) in the splash erosion rates. The size of pores is reduced by heating, as derived from variations in soil water retention capacity.

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: Soil carbon stocks and their variability across the forests, shrublands and grasslands of peninsular Spain


Doblas-Miranda, E., Rovira, P., Brotons, L., Martínez-Vilalta, J., Retana, J., Pla, M., and Vayreda, J. 2013. Soil carbon stocks and their variability across the forests, shrublands and grasslands of peninsular Spain. Biogeosciences, 10, 8353-8361. DOI: 10.5194/bg-10-8353-2013.

Abstract

Accurate estimates of C stocks and fluxes of soil organic carbon (SOC) are needed to assess the impact of climate and land use change on soil C uptake and soil C emissions to the atmosphere. Here, we present an assessment of SOC stocks in forests, shrublands and grasslands of peninsular Spain based on field measurements in more than 900 soil profiles. SOC to a depth of 1 m was modelled as a function of vegetation cover, mean annual temperature, total annual precipitation, elevation and the interaction between temperature and elevation, while latitude and longitude were used to model the correlation structure of the errors. The resulting statistical model was used to estimate SOC in the ∼8 million pixels of the Spanish Forest Map (29.3 × 106 ha). We present what we believe is the most reliable estimation of current SOC in forests, shrublands and grasslands of peninsular Spain thus far, based on the use of spatial modelling, the high number of profiles and the validity and refinement of the data layers employed. Mean concentration of SOC was 8.7 kg m−2, ranging from 2.3 kg m−2 in dry Mediterranean areas to 20.4 kg m−2 in wetter northern locations. This value corresponds to a total stock of 2.544 Tg SOC, which is four times the amount of C estimated to be stored in the biomass of Spanish forests. Climate and vegetation cover were the main variables influencing SOC, with important ecological implications for peninsular Spanish ecosystems in the face of global change. The fact that SOC was positively related to annual precipitation and negatively related to mean annual temperature suggests that future climate change predictions of increased temperature and reduced precipitation may strongly reduce the potential of Spanish soils as C sinks. However, this may be mediated by changes in vegetation cover (e.g. by favouring the development of forests associated to higher SOC values) and exacerbated by perturbations such as fire. The estimations presented here provide a baseline to estimate future changes in soil C stocks and to assess their vulnerability to key global change drivers, and should inform future actions aimed at the conservation and management of C stocks.

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Biogeosciences (BG) is an international scientific journal dedicated to the publication and discussion of research articles, short communications and review papers on all aspects of the interactions between the biological, chemical and physical processes in terrestrial or extraterrestrial life with the geosphere, hydrosphere and atmosphere. The objective of the journal is to cut across the boundaries of established sciences and achieve an interdisciplinary view of these interactions. Experimental, conceptual and modelling approaches are welcome. More at Biogeosciences homepage.

Monday paper: Modelling soil organic carbon stocks in global change scenarios: a CarboSOIL application


Muñoz-Rojas, M., Jordán, A., Zavala, L. M., González-Peñaloza, F. A., De la Rosa, D., Pino-Mejias, R., and Anaya-Romero, M. 2013. Modelling soil organic carbon stocks in global change scenarios: a CarboSOIL application. Biogeosciences, 10, 8253-8268, DOI: 10.5194/bg-10-8253-2013.

Abstract

Global climate change, as a consequence of the increasing levels of atmospheric CO2 concentration, may significantly affect both soil organic C storage and soil capacity for C sequestration. CarboSOIL is an empirical model based on regression techniques and developed as a geographical information system tool to predict soil organic carbon (SOC) contents at different depths. This model is a new component of the agro-ecological decision support system for land evaluation MicroLEIS, which assists decision-makers in facing specific agro-ecological problems, particularly in Mediterranean regions. In this study, the CarboSOIL model was used to study the effects of climate change on SOC dynamics in a Mediterranean region (Andalusia, S Spain). Different downscaled climate models were applied based on BCCR-BCM2, CNRMCM3, and ECHAM5 and driven by SRES scenarios (A1B, A2 and B2). Output data were linked to spatial data sets (soil and land use) to quantify SOC stocks. The CarboSOIL model has proved its ability to predict the short-, medium- and long-term trends (2040s, 2070s and 2100s) of SOC dynamics and sequestration under projected future scenarios of climate change. Results have shown an overall trend towards decreasing of SOC stocks in the upper soil sections (0–25 cm and 25–50 cm) for most soil types and land uses, but predicted SOC stocks tend to increase in the deeper soil section (0–75 cm). Soil types as Arenosols, Planosols and Solonchaks and land uses as “permanent crops” and “open spaces with little or no vegetation” would be severely affected by climate change with large decreases of SOC stocks, in particular under the medium–high emission scenario A2 by 2100. The information developed in this study might support decision-making in land management and climate adaptation strategies in Mediterranean regions, and the methodology could be applied to other Mediterranean areas with available soil, land use and climate data.

Biogeosciences (BG) is an international scientific journal dedicated to the publication and discussion of research articles, short communications and review papers on all aspects of the interactions between the biological, chemical and physical processes in terrestrial or extraterrestrial life with the geosphere, hydrosphere and atmosphere. The objective of the journal is to cut across the boundaries of established sciences and achieve an interdisciplinary view of these interactions. Experimental, conceptual and modelling approaches are welcome. More at Biogeosciences homepage.

Solid Earth: Organic carbon stocks in Mediterranean soil types under different land uses (Southern Spain)


M. Muñoz-Rojas, A. Jordán, L. M. Zavala, D. De la Rosa, S. K. Abd-Elmabod, and M. Anaya-Romero. 2012. Organic carbon stocks in Mediterranean soil types under different land uses (Southern Spain). Solid Earth, 3, 375-386.

Abstract

Soil C sequestration through changes in land use and management is one of the sustainable and long-term strategies to mitigate climate change. This research explores and quantifies the role of soil and land use as determinants of the ability of soils to store C along Mediterranean systems. Detailed studies of soil organic C (SOC) dynamics are necessary in order to identify factors determining fluctuations and intensity of changes. In this study, SOC contents from different soil and land use types have been investigated in Andalusia (Southern Spain). We have used soil information from different databases, as well as land use digital maps, climate databases and digital elevation models. The average SOC content for each soil control section (0–25, 25–50 and 50–75 cm) was determined and SOC stocks were calculated for each combination of soil and land use type, using soil and land cover maps. The total organic C stocks in soils of Andalusia is 415 Tg for the upper 75 cm, with average values ranging from 15.9 Mg C ha−1 (Solonchaks under “arable land”) to 107.6 Mg C ha−1 (Fluvisols from “wetlands”). Up to 55% of SOC accumulates in the top 25 cm of soil (229.7 Tg). This research constitutes a preliminary assessment for modelling SOC stock under scenarios of land use and climate change.

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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.

Soils at Imaggeo: ‘Lithic Rhodoxeralf’, by Jorge Mataix-Solera


This soil profile is a Lithic Rhodoxeralf (Soil taxonomy), Chromic Luvisol (World Reference Base for Soil Resources), commonly called Terra rossa. The picture was shot in Located in Alicante (SE Spain).

Click the picture for more information, contact data and full resolution.

Lithic Rhodoxeralf, by Jorge Mataix-Solera. Click to see the original picture at Imaggeo.

Imaggeo is the online open access geosciences image repository of the European Geosciences Union.

The impact of citrus production. An approach from the soil system


Artemi Cerdà
artemio.cerda@uv.es
http://www.uv.es/~acerda
Soil Erosion and Degradation Research Group (SEDER).
Departament de Geografia. Universitat de València. Blasco Ibàñez, 28, 46010, Valencia, Spain

Soil conservation and orchard production

Soil conservation is the key to maintaining the food production, soil sustainability, and the functionality of terrestrial ecosystems. However, chemical agriculture, based on synthetic chemical fertilizers, herbicides and pesticides, has led to soil degradation where soil quality became secondary to other agricultural factors, such as water, microclimate, and the variety of the crop. In too many instances soils are not properly managed, despite their key role in the functioning of terrestrial biogeochemical cycles, plant and animal nutrition, and the success of human societies. And one of those instances is chemically farming orchards.

Although soil erosion problems have been present in Spain since the Neolithic period due to human impact and enviromental conditions (droughts, high rainfall intensities, steep slopes), farmers developed agricultural systems to control the soil and water losses by means of terracing (García Ruiz, 2010).

Nave-lane-late oranges production in Valencia. The oranges are an icon of Valencia.
Nave-lane-late oranges production in Valencia. The oranges are an icon of Valencia. Click to enlarge.

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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