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The objective was to know the effect of amendments and mulch (pine woodchips) on three planted autochthonous species in two substrates six years after the beginning of the restoration. But because this kind of mulch contained pine cones, pine seedlings appeared after the first year of the restoration; new objectives were added to the initial one: to know if organic amendments influence pine growth among planted vegetation, and if there were competition among planted species, opportunistic species and pines. Essential soil parameters, plant cover and diversity and pine growth were measured and statistically processed with correlation analyses, ANOVA and Detrended Correspondence Analysis. Six years after restoration organic amendments, applied all over the plots contributed significantly to explain the differences on the tested variables. The combined effects of the two substrates and the two organic amendments effectively enhanced soil properties recovery, but they also facilitated the establishment and entry of new species in addition to planted vegetation, driving a differential plant development. The number of pines, as well as their coverage, depended on the interaction between the amendment and the substrate: a) only one amendment favoured the pines and b) the way the amendment works depended on the substrate. Planted vegetation cover and total plant cover from amended plots doubled that of control plots. Results indicate the potential suitability of organic amendments, pine chips mulch and derived opportunistic species for restoring post-mining areas.

Many industries and agriculture generate huge amounts of wastes either mineral, organic or both, with environmental impact. Some of these residues have the potential to become Technosols when mixed in proper proportions. Degraded terrestrial ecosystems, especially sloping land, show very shallow or no soil left which makes restoration very difficult. Covering such degraded surfaces with Technosols might be a possible solution. The purpose of this paper is to show how some combinations and proportions of residues, mainly sludge from the ornamental stone industry and compost from green residues, become useful Technosols for landscape restoration. We tested in the laboratory twelve different combinations of that sludge, organic compost and other materials, as experimental Technosols. The three best combinations were tested in the field in (3 × 2 m) experimental plots at the open air on a 30° slope. We planted autochthonous species and survival and growth monitored for 1 year. The essential soil physical and chemical properties were also monitored as well as their hydrological behavior by means of repeated rainfall simulations. Treatments with artificial stone sludge up to 70% and slabs were able to provide substrates with physical and chemical properties relatively similar to those of natural soils in arid-semiarid environments like those from SE Spain. Higher content of organic matter and better physical properties were found in the Technosols. No clear differences between types of treatments were detected. Although runoff was slightly higher in Technosols than in natural soils, the treatment with the highest compost content (15%), presented the lowest erodibility, similar to natural soils in the area. None of the tested Technosols produced dangerous leachates exceeding the maximum values recommended by the European legislation. Technosols also increased plant growth of Rosmarinus officinalis and Thymus vulgaris. These results confirm that the tested Technosols can be used for the restoration of degraded soils and, in areas affected by earthworks, as road taluses.

The original publication is available at: publicaciones.unirioja.es/revistas/cig, [EN]A combination of high temporal variability and spatial heterogeneity of rainfall, soil surfaces, and plant cover is the cause of the complex hydrological response in arid/semiarid regions. Under these premises, long-term monitoring is necessary to capture drivers controlling the response of these areas and to be able to model and predict their reaction. A succinct, up-to-date review of the databases and results produced by two representative micro-catchments in the most arid extreme of Europe, Almería (SE Spain), is presented with the aim to show how the different precipitation patterns, during a 20-year period, influence the hydrological behavior on different lithologies and soil surfaces. The problems encountered about the functioning of these experimental stations, including the generation and maintenance of long-term databases, is also reviewed., [ES]Una combinación de elevadas variabilidades, espacial y temporal, en precipitación, superficies del suelo y vegetación es la causa de la compleja respuesta hidrológica en las regiones áridas-semiáridas. Bajo esta premisa es necesario un seguimiento a largo plazo para conocer los factores que controlan las respuestas hidrológicas de estas regiones, poder modelizarlas y predecirlas. Se presenta una breve revisión actualizada de las bases de datos y de los resultados obtenidos en dos microcuencas representativas del semiárido almeriense, en el SE peninsular, con la finalidad de mostrar cómo diferentes patrones de precipitación influyen en el comportamiento hidrológico en diferentes litologías y superficies del suelo, en un período de unos 20 años. Además, se repasan los problemas encontrados respecto al funcionamiento y mantenimiento de estas microcuencas y en las bases de datos generadas., field installations, data gathering, and personnel: MEDALUS (contract no. EV5VCT92- 0128), financed by the EEC European Union; PROHIDRADE (AMB95-0986), PROGESED (HID97-0581), EPOHIDRO (HID98-1056), PROHISEM (REN2001- 2268-C02-01), CANOA (CGL2004-04919-C02-01), PROBASE (CGL2006-11619/ HID), BACARCOS (CGL2011-29429), RESUCI (CGL2014-59946-R), DINCOS (CGL2016-78075-P), financed by the Spanish I+D program; COSTRAS (RNM 3614) financed by Junta de Andalucía; and RESEL (network of Spanish field stations measuring soil erosion), supported by the General Directorate for Nature Conservancy of the Spanish Ministry of Agriculture and Environment.

Individual plant species form so-called resource islands in the barren semiarid landscape, whereby many soil properties are enhanced including soil structure. Within the soil structure, mostly studied as soil aggregates, microaggregates (During two sampling campaigns in spring 2017 and 2018, soil samples were taken over a distance gradient from two major semiarid grassland plant species in Southern Spain, the legume shrub Anthyllis cytisoides and the grass tussock Macrochloa tenacissima, to the surrounding bare soil. While topsoil was sampled in five distances to the plant during the first sampling campaign, the second one focused stronger on the root influence, hence rhizoplane and rhizosphere were sampled. Additionally, two sites with different parent materials were chosen to scale the effect of EPS on soil aggregation in the presence of inorganic binding agents (here carbonates). Total community DNA and EPS were extracted, followed by quantification of EPS-saccharides and bacterial abundance, as well as examination of the prokaryotic community composition by Illumina amplicon sequencing of the 16S rRNA genes. Further, the particle size distribution of (micro)aggregates in water was determined, with and without ultrasound treatment, as a measure of soil aggregate size distribution and stability.Based on the first sampling campaign, we found that the overall prokaryotic community composition differed between the two sites, but not between plant species. Interdependencies between the community composition and EPS content were revealed, whereby soil organic matter (SOM) seems to be a regulating factor as increasing SOM contents resulted in more EPS-saccharides. Soil microaggregation in the topsoil was enhanced by the plant canopy, especially at the edge of Macrochloa tussocks. Contrary to the expectation that increasing inorganic C contents would diminish the importance of EPS, the parent material richest in inorganic C results in a significant effect of EPS-saccharides on microaggregation.First results of the second sampling campaign indicate that even in the rhizoplane and rhizosphere, parent material had a dominating influence on the prokaryotic community composition. As EPS-saccharide contents and soil aggregation followed a similar decreasing trend with distance to the roots and canopy cover, interdependencies are expected.From the outcomes until now, we can conclude that the availability of decomposable OM influences the prokaryotic community composition and thereby triggers EPS production, whereas large contents of polyvalent cations from carbonates promote the stabilizing effect of EPS on microaggregates.

© 2020 by the authors., Arid and semi-arid ecosystems are characterized by patchy vegetation and variable resource availability. The interplant spaces of these ecosystems are very often covered by cyanobacteria-dominated biocrusts, which are the primary colonizers of terrestrial ecosystems and key in facilitating the succession of other biocrust organisms and plants. Cyanobacterial biocrusts regulate the horizontal and vertical fluxes of water, carbon and nutrients into and from the soil and play crucial hydrological, geomorphological and ecological roles in these ecosystems. In this paper, we analyze the influence of cyanobacterial biocrusts on water balance components (infiltration-runoff, evaporation, soil moisture and non-rainfall water inputs (NRWIs)) in representative semiarid ecosystems in southeastern Spain. The influence of cyanobacterial biocrusts, in two stages of their development, on runoff-infiltration was studied by rainfall simulation and in field plots under natural rainfall at different spatial scales. Results showed that cover, exopolysaccharide content, roughness, organic carbon, total nitrogen, available water holding capacity, aggregate stability, and other properties increased with the development of the cyanobacterial biocrust. Due to the effects on these soil properties, runoff generation was lower in well-developed than in incipient-cyanobacterial biocrusts under both simulated and natural rainfall and on different spatial scales. Runoff yield decreased at coarser spatial scales due to re-infiltration along the hillslope, thus decreasing hydrological connectivity. Soil moisture monitoring at 0.03 m depth revealed higher moisture content and slower soil water loss in plots covered by cyanobacterial biocrusts compared to bare soils. Non-rainfall water inputs were also higher under well-developed cyanobacterial biocrusts than in bare soils. Disturbance of cyanobacterial biocrusts seriously affected the water balance by increasing runoff, decreasing soil moisture and accelerating soil water loss, at the same time that led to a very significant increase in sediment yield. The recovery of biocrust cover after disturbance can be relatively fast, but its growth rate is strongly conditioned by microclimate. The results of this paper show the important influence of cyanobacterial biocrust in modulating the different processes supporting the capacity of these ecosystems to provide key services such as water regulation or erosion control, and also the important impacts of their anthropic disturbance., This work has been supported by several research projects: REBIOARID (RTI2018-101921-B-I00), DINCOS (CGL2016-78075-P) projects, founded by the Spanish National Plan for Research and the European Union ERDF and the BIOCOST project Supported by Biodiversity Foundation of the Ministry for the Ecological Transition., Publisher’s version

In the barren semiarid landscape individual plant species improve soil structure, reducing the erosion risks, whereby microaggregates form the most fundamental soil structural components. Extracellular polymeric substances (EPS) are considered an important glue determining aggregation in addition to inorganic binding agents such as carbonates. However, the role of the prokaryotic community in EPS formation and consequently for microaggregation in natural environments is not substantially clarified yet. EPS should be particularly important under semiarid conditions as it forms a protection mechanism of the prokaryotes against desiccation. Therefore, we examined the influence of the prokaryotic community on soil EPS content and subsequently on soil microaggregation in semiarid grasslands, depending on the parent material, common plant species and the distance to the plant. Soil samples were taken over a distance gradient from two major semiarid grassland plant species in Southern Spain, the legume shrub Anthyllis cytisoides and the grass tussock Macrochloa tenacissima, to the surrounding bare soil at two sites, rich and poor in carbonates. Total community DNA and EPS were extracted, followed by quantification of EPS-saccharide, bacterial abundance and examination of the prokaryotic community composition. Further, the particle size distribution of the microaggregate fraction was determined as an indication of microaggregation. We found that the overall prokaryotic community composition differed between the two sites, but not between plant species. Nonetheless, a link between the community composition and EPS content was established, whereby soil organic matter (OM) seems to be a regulating factor as increasing soil OM contents resulted in more EPS-saccharide. Furthermore, microaggregation was enhanced by the canopy, especially at the edge of Macrochloa tussocks. Contrary to the expectation that increasing inorganic C contents would diminish importance of EPS, the parent material richest in inorganic C resulted in a significant effect of EPS-saccharide contents on microaggregation according to the structural equation model. For the inorganic C poor site, EPS-saccharide had no observed direct effect on microaggregation. Based on our results we conclude that the availability of decomposable OM influences the prokaryotic community composition and thereby triggers EPS production whereas large contents of polyvalent cations promote the stabilizing effect of EPS on microaggregates.

Catchment asymmetry is a fairly frequent phenomenon on a global scale but the main causes leading to its formation are still not well understood. Where the intervention of structural or tectonic causes is not relevant, asymmetry seems to result from differential erosion between opposite slopes that flow into the same channel, which is frequently associated with contrasted biocrust and/or vegetation covers. Biocrusts are known to be important surface stabilizing agents. However, their geomorphological consequences at the landscape scale are little known. In this study we combined field measurements with digital elevation models and image analysis to determine whether catchment asymmetry in the Tabernas Desert (semi-arid SE of Spain) is a local or general phenomenon, and to explore the main factors determining asymmetry occurrence, magnitude and direction. We pay special attention to the role of biocrusts. We found that catchment asymmetry is a very common phenomenon in the area; only 25% of the catchments are symmetrical, while approximately 40% present asymmetry with the relatively shady hillslope having a lower gradient, and 35% with that hillslope being the steeper. Solar radiation reaching the soil, surface area and channel gradient in the considered catchment stretch, as well as the total catchment area upstream from the lower point of the considered stretch were the main abiotic factors controlling the formation of the asymmetry. Microclimatic differentiation due to differences in radiation input caused by the uneven topography favoured the relative stabilization of the shadier hillslope and its colonization by biocrusts and later by plants. The effect of the biocrusts and vegetation protection against water erosion on shadier hillslopes is often stronger than that of the set of abiotic factors and gives rise to asymmetries with lower gradients in the shady hillslope by promoting lateral displacement of the channel. We hypothesised that the opposite pattern, with the sunnier hillslope having a lower gradient, occurs when abiotic factors control the development of asymmetry formation. In these conditions, the effect of biocrusts and plants would act in the opposite direction. We propose a conceptual model of feedbacks generating catchment asymmetry, with biocrust playing a crucial role.