Microbiological characterization of a semi-arid meadow soil seeded with different proportions of orchard grass and alfalfa

1 póster donde se muestran los resultados de su investigación.-- Póster presentado al XV Congress of the Spanish Society of Nitrogen Fixation, and the IV Portuguese-Spanish Congress on Nitrogen Fixation. En León (España). 16, 17 y 18 de junio de 2015Soil is a pivotal component of the environment and the maintenance of soil quality is critical for ensuring the sustainability of the biosphere. The use of fertilizers has increased at a faster rate than global food production. Modern agriculture is dependent on phosphorus derived from phosphate rock, which is a non‐renewable resource. It is needed to improve P acquisition efficiency for both low input and intensive agroecosystems. However, few studies have focused on cereal‐legume interactions with regard to soil P. The objective of this work was to study the effects of grass‐legume mixtures and phosphorus fertilization on soil microbial community structure and biomass [determined by fatty acid methyl ester (FAME) profiling] as well as on the soil nitrogen (N) mineralisation rate.Peer reviewe

Impacto de tratamentos térmicos en solos florestais afetados por incêndios de diferente severidade e recorrência

Thermal treatments in the laboratory were conducted using unburned and burned samples of two soils affected by low- or high severity fires in order to study their impact on forests ecosystems with different fire regimes (severity, recurrence). Soils samples were heated in a furnace for 15 minutes at 50 ºC, 75 ºC, 100 ºC, 125 ºC, 150 ºC, 175 ºC, 200 ºC and 300 ºC to simulate different fire intensities; the process was repeated after a 1 month incubation of the burned, rewetted samples in order to simulate fire recurrence. The soil temperature was measured with thermocouples at the surface and 1 cm depth. The maximum temperature reached (Tmax) and the amount of heat supplied to the samples (degree-hour, DH) were calculated from the temperature-time curves. A total of 128 temperature-time curves (4 soil field samples x 8 heating temperatures x 2 depths x 2 successive heat treatments) were analyzed and the estimation of several soil physical and chemical properties (color, moisture content, pH, total C, total N, soluble C) was carried out in the different soil treatments. High-severity burning provoked significant changes on these physical and chemical properties, whereas slight modifications or even no changes were due to low-severity burning or soil heating under laboratory conditions. The thermal properties exhibited a higher sensitivity for the detection of the fire regime impact than the physical and chemical properties. The results showed that the temperature-time curves and derived parameters (slope, Tmax, DH) can be successfully used to quantify the impact of thermal shocks at low and high temperatures and to evaluate the effect of fire/heating recurrence on forests ecosystems.Se realizaron, en condiciones de laboratorio, diversos tratamientos térmicos con muestras no quemadas y quemadas de dos suelos afectados por incendios de alta y baja severidad con el fin de determinar su impacto sobre ecosistemas forestales con diferente régimen del fuego (severidad y recurrencia). Las muestras se quemaron en una mufla durante 15 minutos a 50 ºC, 75 ºC, 100 ºC, 125 ºC, 150 ºC, 175 ºC, 200 ºC y 300 ºC para simular diferentes intensidades del fuego; tras un mes de incubación de las muestras quemadas e humectadas, se procedió a una segunda quema para simular la recurrencia del fuego. Se midió la temperatura del suelo con termopares en la superficie y a 1 cm de profundidad y, a partir de las curvas de temperatura-tiempo, se calcularon la temperatura máxima alcanzada (Tmax) y la cantidad de calor suministrada a la muestra (grados-hora, GH). Se analizaron un total de 128 curvas de temperatura-tiempo (4 muestras de suelo x 8 temperaturas de calentamiento x 2 profundidades x 2 tratamientos térmicos consecutivos) y se realizó la caracterización física y química (color, humedad, pH, C total, N total, C soluble en agua) de las muestras de suelo sometidas a los diferentes tratamientos térmicos. Las propiedades físicas y químicas experimentaron cambios significativos como consecuencia del incendio de alta intensidad y no se detectaron variaciones tras el impacto del incendio de baja severidad y del quemado del suelo en condiciones de laboratorio. Las propiedades térmicas mostraron una mayor sensibilidad que las propiedades físicas y químicas para detectar el impacto del régimen del fuego. Los resultados obtenidos demostraron que las curvas de temperatura-tiempo y los parámetros derivados (pendiente, Tmax, GH) pueden usarse satisfactoriamente para cuantificar el impacto del tratamiento térmico a bajas y altas temperaturas y para evaluar el efecto de la recurrencia del fuego/calentamiento en los ecosistemas forestales.Realizaram-se ensaios de laboratório com diferentes tratamentos térmicos em amostras queimadas e não queimadas de dois solos afetados por incêndios de alta e baixa severidade, para determinar o seu impacto em ecossitemas florestais sob diferente regime de fogo (severidade e recorrência). As amostras queimaram-se na mufla durante 15 minutos a 50 º C, 75 º C, 100 º C, 125 º C, 150 º C, 175 º C, 200 º C e 300 º C com o objectivo de simular diferentes intensidades de queima; após de um mês de incubação das amostras queimadas e umedecidas, foi feita uma segunda queima para simular a recorrência do fogo. A temperatura do solo foi medida com termopares na camada superior e a 1 cm de profundidade. A partir das curvas de temperatura-tempo, foi calculada a temperatura máxima alcançada (Tmax) e a quantidade de calor fornecida (graus-hora, DH). Analisaram-se um total de 128 curvas de temperatura-tempo (4 amostras de solo x 8 temperaturas de aquecimento x 2 profundidades x 2 tratamentos térmicos subsecutivos) e caracterizaram-se as propriedades físicas e químicas (color, umidade, pH, C total, N total, C solúvel em agua) das amostras de solo submetidas aos diferentes tratamentos térmicos. As propriedades físicas e químicas apresentaram alterações significativas com respeito à queima de alta intensidade e não foram detectadas variações após o impacto da queima de baixa severidade e também não no que diz respeito ao aquecimento do solo em condições de laboratório. As propriedades térmicas mostraram uma maior sensibilidade que as propriedades físicas e químicas para a deteccão do impacto do regime do fogo. Os resultados obtidos mostram que as curvas de temperatura-tempo e os parâmetros derivados (pendente, Tmax, DH) podem ser utilizados satisfatoriamente para a quantifição do impacto do tratamento térmico a baixas e altas temperaturas, e para avaliar o efeito da recorrência do fogo/aquecimento nos ecossistemas florestais.This study was supported by the Ministerio Español de Economía y Competitividad (AGL2012-39686-C02-01) and by Fundación MAPFRES

Copper accumulation and fractionation in vineyard soils from temperate humid zone (NW Iberian Peninsula)

The occurrence of total Cu and Cu fractions (exchangeable Cu, Cu bound to organic matter, Cu bound to amorphous inorganic materials, Cu bound to crystalline Fe and Al oxides and residual Cu) was studied in 170 surface layers of soils from seven vineyard regions located in the NW Iberian Peninsula (Rías Baixas, Ribeira Sacra, Ribeiro, Monterrei, Valdeorras, O Bierzo and Vinhos Verdes). The data showed that long-term application of Cu-based fungicides has led to increased concentrations, mainly in superficial vineyard soil layers. Thus, 64% of the samples showed total Cu levels higher than 100 mg kg 1, threshold for soil contamination. Total Cu content in Ribeiro (248 ± 130 mg kg 1) and Ribeira Sacra (259 ± 118 mg kg 1) soils were significantly higher than those observed for the rest of the vineyard regions (169 ± 90, 139 ± 122, 115 ± 42, 103 ± 42 and 100 ± 48 mg kg 1 in Valdeorras, Rías Baixas, O Bierzo, Vinhos Verdes and Monterrei, respectively). Cu distribution among various soil fractions also differed between winegrowing regions; however, in general, Cu in these vineyard soils is present mainly in less mobile fractions (average values were 48 ± 12% for Cu bound to soil organic matter; 15 ± 9% for Cu associated to amorphous inorganic materials; 12 ± 9% for Cu bound to crystalline Fe and Al oxides and 23 ± 12% for residual Cu), whereas exchangeable Cu constituted approximately 3 ± 3% of total Cu. All soil samples were separated in three well differentiated groups according to their physical, chemical and Cu fractionation data (Ribeiro, Ribeira Sacra and Monterrei samples; O Bierzo, Valdeorras and Monterrei samples; Rías Baixas and Vinhos Verdes samples), being soil type, climate and fungicide application as the most determinant factors for soil quality.Xunta de Galici

Mulching and seeding treatments for post-fire stabilization techniques in Laza (NW Spain): medium-term effects on soil quality and effectiveness

The impact of fire and different post-fire stabilisation treatments like mulching and seeding on some selected physical, chemical biochemical and microbiological properties as well as the efficacy of these treatments on control of post-fire erosion was evaluated in a burnt area affected by a high severity wildfire located in Laza (NW Spain). Soil samples were collected from the A horizon (0-2 cm) of the burnt soil 8 and 12 months after the wildfire as well as from the unburnt soil located in an adjacent plot used as control; sediments were periodically collected after precipitation events in the burnt soil with and without different post-fire stabilisation treatments. The results clearly showed that a significant medium-term impact of the wildfire on most soil properties analyzed was still observed 12 months after the fire event and that mulching and seeding treatments did not affect the overall soil quality (physical, chemical, biochemical and microbiological properties) of this burned soil. Sediments data indicated that both stabilisation treatments were effective to control post-fire erosion since, compared to the burnt control, soil losses were reduced by 85% in the mulching treatment and by 30% in the seeding treatment

Recovery of a soil under different vegetation one year after a high intensity wildfire

Studies on soil recovery in fragile ecosystems following high intensity wildfires are scarce. The aim of the present investigation is to evaluate the impact of a high intensity wildfire in an ecosystem under different vegetation (shrubland and pinewood) located at Vilardevós (Galicia, NW Spain) and highly susceptible to suffer soil erosion due to the steep relief and high erositivity of the rainfall. Soil samples were collected from the A horizon (0-5 cm) 1 year after the fire and soil quality was evaluated by analysis of several physical, chemical and biochemical properties measured in the fraction < 2 mm. The results showed marked effects of the wildfire on most properties analyzed even 1 year after the fire; however, a different effect both in the trend (positive, negative) and magnitude were observed, depending on the soil property analyzed. In general, the sensitivity to detect fire induced changes followed the order: biochemical properties > chemical properties > physical properties. The data also showed that the fire impact was different depending on the soil vegetation considered (shrubland and pinewood). Moreover, the data confirmed the slow soil recovery in this fragile ecosystem and, therefore, the need of adopting post-fire stabilisation and rehabilitation treatments in order to minimize the post-fire erosion and soil degradation

Microbial community structure of vineyard soils with different pH and copper content

The phospholipid fatty acid (PLFA) pattern of vineyard soils from the Northwest of the Iberian Peninsula was studied to identify soil factors determining the microbial community structure, with special emphasis on effects of Cu pollution and pH. A wide range of soil samples, collected from six winegrowing regions (Rías Baixas, Ribeiro, Ribeira Sacra, Monterrei, Valdeorras and Vinhos Verdes) was analyzed. Physico-chemical properties, including total Cu content, five different Cu fractions and available Cu, were also determined. Total Cu varied between 33 and 1120 mg kg1 and pHwater between 4.3 and 7.3. Soil pH rather than Cu content was most important in determining the composition of the microbial community. An increase in the relative concentrations of the monounsaturated PLFAs 16:1ω5, 16:1ω7c, 17:1ω8 and 18:1ω7 and a decrease of br18:0, i17:0, 17:0 and cy19:0 was correlated to an increase in pH. A significant effect of Cu was also found, with an increase in the branched fatty acids 10Me17:0, i16:0, 10Me18:0, a17:0 and br17:0 as consequence of Cu pollution. This change in the PLFA pattern was correlated to both the total and available fractions of Cu. Although the PLFA pattern was a useful tool to assess factors affecting the microbial composition, it is difficult to differentiate between these factors.Xunta de Galicia | Ref. 09MDS013291P

Soil Heating at High Temperatures and Different Water Content: Effects on the Soil Microorganisms

Soil properties determining the thermal transmissivity, the heat duration and temperatures reached during soil heating are key factors driving the fire-induced changes in soil microbial communities. The aim of the present study is to analyze, under laboratory conditions, the impact of the thermal shock (infrared lamps reaching temperatures of 100 °C, 200 °C and 400 °C) and moisture level (0%, 25% and 50% per soil volume) on the microbial properties of three soil mixtures from different sites. The results demonstrated that the initial water content was a determinant factor in the response of the microbial communities to soil heating treatments. Measures of fire impact included intensity and severity (temperature, duration), using the degree-hours method. Heating temperatures produced varying thermal shock and impacts on biomass, bacterial activity and microbial community structureThis research was funded by Spanish Ministry of Economy and Competitiveness (AGL2012-39686-C02-01) and for the for the MAPFRE foundation. A. Barreiro and A. Lombao are recipients of FPU grant from Spanish Ministry of EducationS

The Toxicity Exerted by the Antibiotic Sulfadiazine on the Growth of Soil Bacterial Communities May Increase over Time

The toxicity exerted by the antibiotic sulfadiazine on the growth of soil bacterial communities was studied in two agricultural soils for a period of 100 days. In the short-term (2 days of incubation), the effect of sulfadiazine on bacterial growth was low (no inhibition or inhibition <32% for a dose of 2000 mg·kg−1). However, sulfadiazine toxicity increased with time, achieving values of 40% inhibition, affecting bacterial growth in both soils after 100 days of incubation. These results, which were here observed for the first time for any antibiotic in soil samples, suggest that long-term experiments would be required for performing an adequate antibiotics risk assessment, as short-term experiments may underestimate toxicity effectsThis study has been funded by the Spanish Ministry of Economy and Competitiveness through the projects CGL2015-67333-C2-1-R and -2-R (FEDER Funds), and by Xunta de Galicia via CITACA Strategic Partnership (ED431E 2018/07) and BV1 research group (ED431C 2017/62-GRC). David Fernández Calviño holds a Ramón y Cajal contract (RYC-2016-20411) financed by the Spanish Ministry of Economy Industry and Competitiveness. Vanesa Santás Miguel holds a pre-doctoral fellowship founded by the University of VigoS

Enzyme activities in vineyard soils long-term treated with copper-based fungicides

Copper-based fungicides have been applied in vineyard soils for a long time, which has resulted in increasing soil Cu concentration. However, information relating to non-target effects of these fungicides on microorganisms of these soils is scarce. The aim of this study was to determine the potential enzyme activities of vineyard soils in relation to Cu content and evaluate the potential risks of long-term application of Cu-based fungicides. For this purpose, a wide range of soil samples, having different total, exchangeable and bioavailable Cu contents, were collected from six regions of quality wines located in the NW Iberian Peninsula, and the activity of dehydrogenase, b-glucosidase, urease and phosphatase were measured. Overall, the results obtained indicate adverse effects of Cu on dehydrogenase, b-glucosidase and phosphatase activities and an inconsistent effect on urease activity. Threshold Cu concentrations at which changes in the enzyme activities became evident were 150e200 mg total Cu kg 1 and 60e80 mg bioavailable Cu kg-1.Xunta de Galici

Burn severity and land-use legacy influence bird abundance in the Atlantic-Mediterranean biogeographic transition

Fire regimes in mountain landscapes of southern Europe have been shifting from their baselines due to rural abandonment and fire exclusion policies. Understanding the effects of fire on biodiversity is paramount to implement adequate management. Herein, we evaluated the relative role of burn severity and heterogeneity on bird abundance in an abandoned mountain range located in the biogeographic transition between the Eurosiberian and Mediterranean region (the Natural Park ‘Baixa Limia–Serra do Xurés’). We surveyed the bird community in 206 census plots distributed across the Natural Park, both inside and outside areas affected by wildfires over the last 11 years (from 2010 to 2020). We used satellite images of Sentinel 2 and Landsat missions to quantify the burn severity and heterogeneity of each fire within each surveyed plot. We also accounted for the past land use (forestry or agropastoral use) by using a land cover information for year 2010 derived from satellite image classification. We recorded 1735 contacts from 28 bird species. Our models, fitted by using GLMs with Poisson error distribution (pseudo-R2-average of 0.22 ± 0.13), showed that up to 71% of the modeled species were linearly correlated with at least one attribute of the fire regime. The spatiotemporal variation in burnt area and severity were relevant factors for explaining the local abundance of our target species (39% of the species; Akaike weights >0.75). We also found a quadratic effect of at least one fire regime attribute on bird abundance for 60% of the modeled species. The past land use, and its legacy after 10 years, was critical to understand the role of fire (Akaike weights >0.75). Our findings confirm the importance of incorporating remotely sensed indicators of burn severity into the toolkit of decision makers to accurately anticipate the response of birds to fire managementS