Andrés P., Rosell-Melé A., Colomer-Ventura F., Denef K., Cotrufo M.F., Riba M., Alcañiz J.M. (2019) Belowground biota responses to maize biochar addition to the soil of a Mediterranean vineyard. Science of the Total Environment. 660: 1522-1532.LinkDoi: 10.1016/j.scitotenv.2019.01.101
Biochar is a high carbon material resulting from biomass pyrolysis that, when applied to croplands, can increase soil carbon and soil water retention. Both effects are of critical importance in semi-arid regions, where carbon decline and desertification are the main drivers of soil degradation. Since most environmental services provided by soil are mediated by belowground biota, effects of biochar on soil microbial and invertebrate communities must be evaluated under field conditions before its agricultural application can be recommended. We tested maize biochar for its mid-term effect on soil microbes and micro-arthropods of a Mediterranean vineyard. We applied biochar to three field plots with neutral sandy loam soils at a dose of 5 Mg ha−1. During two years, we monitored the abundance of functional groups of soil micro-arthropods and estimated the biomass of soil microbial groups. We also analyzed the δ13C value of microbial PLFA biomarkers to determine biochar-C utilization by each microbial group taking advantage of the δ13C natural abundance differences between the applied biochar and the soil. Biochar addition significantly reduced soil microbial biomass but did not alter the functional microbial diversity nor the abundance or biodiversity of soil micro-arthropods. The contribution of biochar-C to the diet of most microbial groups was very low through the monitoring period. However, two gram-negative bacterial groups increased their biochar-derived carbon uptake under extreme soil dryness, which suggests that biochar-C might help soil microbes to overcome the food shortage caused by drought. The decrease in microbial biomass observed in our experiment and the concomitant decrease of SOM mineralization could contribute to the carbon sequestration potential of Mediterranean soils after biochar addition. © 2019 Elsevier B.V.
Carabassa V., Ortiz O., Alcañiz J.M. (2019) RESTOQUARRY: Indicators for self-evaluation of ecological restoration in open-pit mines. Ecological Indicators. 102: 437-445.LinkDoi: 10.1016/j.ecolind.2019.03.001
Several methods and criteria to evaluate and assess quarry restoration are available in the scientific literature, but they are very specialized and time consuming. Furthermore, there is a lack of evaluation tools appropriate for technicians involved in these types of activities, such as quarry engineers, restoration managers and quality control supervisors in public administration. The work presented attempts to bridge the gap between scientific knowledge and practical needs by proposing a simplified methodology (RESTOQUARRY protocol), which enables the non-scientific public to evaluate restored areas. This procedure focused on five groups of parameters for zone (homogeneous portions within the whole restored area) evaluation: geotechnical risk, drainage network, erosion and physical degradation, soil quality and vegetation status and functionality. Moreover, three groups of parameters are proposed for area (whole restoration) evaluation: landscape integration, ecological connectivity and fauna, and anthropic impacts. This protocol has been tested in 55 open-pit mines located throughout Catalonia (NE Iberian Peninsula), covering a wide range of Mediterranean climatic conditions and geological substrates. Results indicate that the proposed methodology is suitable for detecting critical parameters that can determine the success of the restoration. © 2019 Elsevier Ltd
Funes I., Savé R., Rovira P., Molowny-Horas R., Alcañiz J.M., Ascaso E., Herms I., Herrero C., Boixadera J., Vayreda J. (2019) Agricultural soil organic carbon stocks in the north-eastern Iberian Peninsula: Drivers and spatial variability. Science of the Total Environment. 668: 283-294.LinkDoi: 10.1016/j.scitotenv.2019.02.317
Estimating soil organic carbon (SOC) stocks under agriculture, assessing the importance of their drivers and understanding the spatial distribution of SOC stocks are crucial to predicting possible future SOC stocks scenarios under climate change conditions and to designing appropriate mitigation and adaptation strategies. This study characterized and modelled SOC stocks at two soil depth intervals, topsoil (0–30 cm) and subsoil (30–100 cm), based on both legacy and recent data from 7245 agricultural soil profiles and using environmental drivers (climate, agricultural practices and soil properties) for agricultural soils in Catalonia (NE Spain). Generalized Least Square (GLS) and Geographical Weighted Regression (GWR) were used as modelling approaches to: (i) assess the main SOC stock drivers and their effects on SOC stocks; (ii) analyse spatial variability of SOC stocks and their relationships with the main drivers; and (iii) predict and map SOC stocks at the regional scale. While topsoil variation of SOC stocks depended mainly on climate, soil texture and agricultural variables, subsoil SOC stocks changes depended mainly on soil attributes such us soil texture, clay content, soil type or depth to bedrock. The GWR model revealed that the relationship between SOC stocks and drivers varied spatially. Finally, the study was only able to predict and map topsoil SOC stocks at the regional scale, because controlling factors of SOC stocks at the subsoil level were largely unavailable for digital mapping. According to the resulting map, the mean SOC stock value for Catalan agriculture at the topsoil level was 4.88 ± 0.89 kg/m 2 and the total magnitude of the carbon pool in agricultural soils of Catalonia up to 30 cm reached 47.9 Tg. The present study findings are useful for defining carbon sequestration strategies at the regional scale related with agricultural land use changes and agricultural management practices in a context of climate change. © 2019 Elsevier B.V.
Padró J.-C., Carabassa V., Balagué J., Brotons L., Alcañiz J.M., Pons X. (2019) Monitoring opencast mine restorations using Unmanned Aerial System (UAS) imagery. Science of the Total Environment. 657: 1602-1614.LinkDoi: 10.1016/j.scitotenv.2018.12.156
Open-pit mine is still an unavoidable activity but can become unsustainable without the restoration of degraded sites. Monitoring the restoration after extractive activities is a legal requirement for mine companies and public administrations in many countries, involving financial provisions for environmental liabilities. The objective of this contribution is to present a rigorous, low-cost and easy-to-use application of Unmanned Aerial Systems (UAS) for supporting opencast mining and restoration monitoring, complementing the inspections with very high (
Carabassa V., Ortiz O., Alcañiz J.M. (2018) Sewage sludge as an organic amendment for quarry restoration: Effects on soil and vegetation. Land Degradation and Development. 29: 2568-2574.LinkDoi: 10.1002/ldr.3071
Quarry restoration in Mediterranean environments usually needs organic amendments to improve the substrates used for technosol construction. Digested sewage sludges from municipal wastewater treatment plants are rich in organic matter, N, and P and constitute an available and economically interesting alternative for substrate amendment. However, their pollutant burden and labile organic matter content involve an environmental risk that must be controlled. Moreover, ecological succession in restored areas can be influenced by the use of sludge and should be assessed. To minimize these risks, a new sewage sludge dose criterion relating to its labile organic matter and heavy metal content has been established. Sewage sludge doses currently range between 10 and 50 Mg ha−1. In order to verify the suitability of this dose criterion, 16 areas rehabilitated using sewage sludge located in limestone quarries in a Mediterranean climate in Catalonia (NE Spain) have been assessed. These evaluations focused on physicochemical properties of rehabilitated soils, land degradation processes, and ecological succession. In the short term, 6 months after sludge application, an increment of organic matter content in the restored soils was observed, without significant increases in electrical conductivity or heavy metals content, and with a dense plant cover that contributes to effective soil erosion control. Two years after, ruderal plants were still present but later successional species colonized the restored zones in different degrees. These results suggest that sewage sludge, used as a soil amendment according to the proposed methodology, can safely improve technosol quality without constraints that compromise ecological succession. © 2018 John Wiley & Sons, Ltd.
Raya-Moreno I., Cañizares R., Domene X., Carabassa V., Alcañiz J.M. (2017) Comparing current chemical methods to assess biochar organic carbon in a Mediterranean agricultural soil amended with two different biochars. Science of the Total Environment. 598: 604-618.LinkDoi: 10.1016/j.scitotenv.2017.03.168
Several methods have been proposed to quantify biochar C recalcitrance but their suitability is questionable. The aims of this work are: i) to compare the suitability of thermal or chemical oxidation and acid hydrolysis methods to quantify biochar C-pool in a biochar-amended soil, and ii) to calculate the biochar content in the soil through a mass balance derived from the obtained data. Two contrasted biochars from pine wood and corn cob remains were incorporated at a rate of 5 Mg C ha− 1 to a sandy loam vineyard soil with neutral pH and low organic carbon content, in field conditions. The analytical methods used to determine the oxidability and hydrolyzation of soil and biochar-C were: i) weight loss-on-ignition (LOI) at three temperatures (375 °C, 550 °C and 950 °C) for the assessment of organic matter, and ii) dry-combustion (TOC), strong (sO) and mild (mO) acid potassium dichromate oxidations, acid hydrolysis (AH) and peroxide oxidation (PO) for the assessment of organic C-pools. mO mainly estimated the easy oxidisable organic fraction of soil. Resistant organic carbon (ROC), estimated as non-hydrolysable organic carbon by AH and as non-oxidisable by mO, led to similar values in control soil (5 g C kg− 1 soil), whereas different ROC values were obtained in soils amended with biochar (6–12 g C kg− 1 soil). The suitability of these different methods as proxies to quantify biochar C was verified through a mass balance observing differences between them. PO removes well native soil organic matter, but also attacks partially biochar's fraction, so an underestimation exists. However, mO leaves intact biochar in the amended soil. Summarising, LOI, TOC and mO were the best proxies for biochar-C quantification, especially the last one, somewhat clarifying the debate on this topic. © 2017 Elsevier B.V.
Marks E.A.N., Mattana S., Alcañiz J.M., Pérez-Herrero E., Domene X. (2016) Gasifier biochar effects on nutrient availability, organic matter mineralization, and soil fauna activity in a multi-year Mediterranean trial. Agriculture, Ecosystems and Environment. 215: 30-39.LinkDoi: 10.1016/j.agee.2015.09.004
Gasifier pine biochar is a carbon-rich material which may be useful as a soil amendment. In Europe and elsewhere there may be potential added value of char produced in industrial gasifiers, up to now considered as wastes. Pine gasification biochar was tested as a soil amendment in a multi-year Mediterranean barley crop field trial, applied at 12 and 50tha-1 while applying half the usual N rate at 50kgha-1, contrasted with a full 100kg ha-1 N fertilizer treatment without biochar. Over the 6-30 month period following the application, biochar treatments did not have any significant effect on soil microbial biomass, respiration, or metabolic coefficient. N mineralization as NO3 - was decreased by biochar at 6 and 12 months from experiment start and coincided with ammonium accumulation. Biochar increased overall soil concentrations of K+ and SO4 2-, attributed to a direct additive effect, agreeing with data from other sources. Biochar treatments (with half usual N fertilization) did not have any significant effects on barley crop parameters, and when biochar treatments were contrasted against full N fertilization with no biochar, the usual N dosage was clearly more beneficial to crop development. Finally, soil fauna activity was negatively impacted by gasifier biochar treatments in years two and three, indicating a risk to soil processes mediated by soil invertebrates. Though this gasifier biochar is expected to be highly stable and therefore of interest for carbon sequestration, its utilization therefore risks negative effects on some biologically-mediated soil processes at high application rates. © 2015 Elsevier B.V.
Ojeda G., Mattana S., Avila A., Alcaniz J.M., Volkmann M., Bachmann J. (2015) Are soil-water functions affected by biochar application?. Geoderma. 249-250: 1-11.LinkDoi: 10.1016/j.geoderma.2015.02.014
Today biochar is considered a stable-carbon source that is able to improve soil quality. However, although biochar effects on some soil properties are already becoming well known, its impact on complex soil hydrological functions has yet to be better assessed. The main objectives are: (a) to determine the impact of different biochar amendments on important physical and chemical soil properties and (b) to determine whether the origin (biomass or sewage sludge) and pyrolysis technique can change biochar properties and regulate biochar influence on important soil functions, i.e. nutrient release, water sorption, and carbon storage. Six types of biochar produced from different biomass sources (pine, poplar or sludge) and pyrolysis processes (slow, fast or gasification) were applied to a sandy-loam, low-organic-matter, calcareous soil (mean dose: 18. g/kg) and incubated in a greenhouse without seeding. Two sampling campaigns, one month and one year after biochar amendments, were performed. The overall impact of biochar, analysed by principal response curves (PRCs), indicated that it could improve or deteriorate soil hydrological properties at different intensities. Soil wettability was modified due to sludge biochar addition to soil by increased water penetration dynamics during the capillary rise process of about 18%. In contrast, water storage as a soil function during soil drying was not affected. Because no differences on aggregate stability were observed between treatments, increments on soil organic carbon could not be related to biochar physical protection caused by aggregate formation or by enhanced aggregate stability. As a result, carbon storage, considered as a soil function provided by biochar, was mainly related to its chemical stability. On the other hand, nutrient flux during soil slaking was improved, increasing nutrient release from soil to water. In terms of biochar properties, an increment of surface wettability of biochar during water drop penetration was observed after one year of its addition to soil, where the mean values of contact angle (CA) decreased 69.5%. This important result suggest that initial biochar hydrophobicity (CA. >. 90°) disappeared after 1. year. It was observed that PRC analysis was able to identify important key soil properties that should be monitored when biochar is used as soil amendment. We conclude that the impact of biochar on soil functions depends mainly on biochar feedstock rather than on the pyrolysis technique used during its production. In general, the performance of biochar obtained from sludge and vegetal biomass was markedly different. © 2015 Elsevier B.V.
Ojeda G., Ortiz O., Medina C.R., Perera I., Alcaniz J.M. (2015) Carbon sequestration in a limestone quarry mine soil amended with sewage sludge. Soil Use and Management. : 0-0.LinkDoi: 10.1111/sum.12179
To reclaim a limestone quarry, 200 and 400 Mg/ha of municipal sewage sludge were mixed with an infertile calcareous substrate and spread as mine soil in 1992. Soil samples were taken 1 week later and again after 17 yr of mine soil rehabilitation so as to assess changes in the amount and persistence of soil organic carbon (SOC). Sludge application increased SOC as a function of the sludge rate at both sampling times. Seventeen years after the sludge amendments, the nonhydrolysable carbon was increased in the 400 Mg/ha of sludge treatment. The recalcitrance of SOC was less in sludge-amended soils than in the control treatment at the initial sampling, but 17 yr later this trend had reversed, showing qualitative changes in soil organic carbon. The CO2-C production had not differed between treatments, yet the percentage of mineralized SOC was less in the high sludge dose. When the size of active (Cactive) and slow (Cslow) potentially mineralizable C pools was calculated by curve fitting of a double-exponential equation, the proportion of Cactive was observed to be smaller in the 400 Mg/ha sludge treatment. Soil aggregate stability, represented by the mean weight diameter of water-stable soil aggregates, was significantly greater in mine soil treated with the high dose of sludge (18.5%) and SOC tended to be concentrated in macro-aggregates (5-2 mm). Results suggest that SOC content in sludge-amended plots was preserved due by (i) replacement of the labile organic carbon of sludge by more stable compounds and (ii) protection of SOC in aggregates. © 2015 British Society of Soil Science.
Marks E.A.N., Alcaniz J.M., Domene X. (2014) Unintended effects of biochars on short-term plant growth in a calcareous soil. Plant and Soil. : 0-0.LinkDoi: 10.1007/s11104-014-2198-2
Background and aims Biochar has demonstrably improved crop yields in weathered and acidic soils, but studies in calcareous soils are particularly lacking, so biochar effects on plant growth was investigated under these conditions. Methods Six biochars were obtained from different feedstocks and production technologies. Chemical characterization of fresh biochars included total and extractable nutrients, labile carbon, and Fourier transform infrared spectroscopy. Extractable nutrients were also evaluated in biochar-soil mixtures with a basic (pH >8.2) test soil. Bioassays with lettuce and ryegrass were carried out to relate biochar chemical properties to effects on plant biomass. Results A sewage sludge slow pyrolysis char was stimulatory to plant growth, as was a slow pyrolysis pine wood char at an intermediate concentration, while gasification and fast-pyrolysis pine and poplar wood chars were strongly inhibitory, with reductions in biomass at realistic application rates of 5-19 t ha-1. Conclusions Statistical comparison of plant responses with biochar composition led to the assessment that plant responses were most correlated with volatile matter content and total P content, whose availability was likely regulated by pH and Ca content. Potential effects of phytotoxins were considered, but these were seen to be much less probable than effects due to nutrient availability. © 2014 Springer International Publishing Switzerland.
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