Short-term microbial response after laboratory heating and ground mulching adition.

Fire alters soil organic matter inducing quantitative and qualitative changes that presumably will affect post-fire soil microbial recolonisation. Several studies have evidenced marked soil organic carbon reduction after moderate and high intensity fire, which limit the total recovery of microbial biomass during years. In order to evaluate the role of soil organic matter alteration in short-term microbial colonization process, we perform a preliminary experiment where unaltered soil from Sierra Nevada Natural Park was heated at 300 ºC during 20 minutes in a muffle furnace (H300) to simulate a medium-high intensity fire. After heating, soil samples were inoculated with unaltered fresh soil, rewetted at 55-65% of water holding capacity and incubated during 3 weeks. At the same time, unheated soil samples were incubated under the same conditions as control (UH). In addition, trying to partially alleviate soil organic matter fire-induced alterations effects on microbial colonization, we include an organic amendment treatment (M+). So, part of heated and unheated samples were amended with a mix of ground alfalfa:straw (1:1) and soil microbial abundance and activity were monitored together with soil organic matter changes. Heating process reduces total organic carbon content. After one week of incubation carbon content in heated samples was lower than the control one, in both, amended and un-amended samples. Microbial biomass and respiration were negatively affected by heating. Ground mulching addition increase microbial biomass and respiration but was not enough to reach control values during the whole study. Nevertheless, viable and cultivable fungi and bacteria showed different pattern. After two weeks of incubation both, fungi and bacteria were higher in heated samples. Ground mulching addition appears to stimulate fungal response in both, heated and unheated samples. Preliminary results of this experiment evidence the transcendence of soil organic matter fire-induced changes on microbial colonization process and the importance to determine several microbial parameters to obtain a more faithful conclusion about microbial response. The organic amendment appears to alleviate partially heated-induced damage, highlighting the positive stimulation on fungal abundance in both, heated and unheated samples.This research has been funded by the Spanish Ministry of Economy and Competitiveness, through research projects POSTFIRE (CGL2013-47862-C2-1-R) and GEOFIRE (CGL2012-38655-C04-01)Peer Reviewe

Effect of Ph and vegetation cover in soil organic matter structure at a high-mountain ecosystem (Sierra Nevada National Park, Granada, Spain)

Poster nº 8246 en EGU General Assembly 2020, Online, 4–8 May 2020During the last decade, soil organic matter dynamics and its determining factors have received increased attention, mainly due to the evident implication of these parameters in climate change understanding, predictions and possible management. High-mountain soil could be considered as hotspot of climate change dynamic since its high carbon accumulation and low organic matter degradation rates could be seriously altered by slight changes in temperature and rainfall regimes associated to climate change effects. In the particular case of Sierra Nevada National Park, this threat could be even stronger due to its Southern character, although its elevated biodiversity could shed some light on how could we predict and manage climate change in the future. In this study, a quantitative and qualitative organic matter characterization was performed and soil microbial activity measured to evaluate the implication of pH and vegetation in soil organic matter dynamics. The sampling areas were selected according to vegetation and soil pH; with distinct soil pH (area A with pH7) and vegetation (high-mountain shrubs and pine reforested area). Soil samples were collected under the influence of several plant species representatives of each vegetation series. Six samples were finally obtained (five replicates each); three were collected in area A under Juniperus communis ssp. Nana (ENE), Genista versicolor (PIO) and Pinus sylvestris (PSI) and other three were collected in area B under Juniperus Sabina (SAB), Astragalus nevadensis (AST) and Pinus sylvestris (PCA). Qualitative and quantitative analyses of soil organic matter were made to establish a possible relationship with microbial activity estimated by respiration rate (alkali trap) and fungi-to-bacteria ratio using a plate count method. Soil easily oxidizable organic carbon content was determined by the Walkley-Black method (SOC %) and organic matter amount was estimated by weight loss on ignition (LOI %). Analytical pyrolysis (Py-GC/MS) was used to analyse in detail the soil organic carbon composition. Our results showed that the microbial and therefore the dynamics of organic matter is influenced by both, soil pH and soil of organic matter. So that the pH in acidic media prevail as a determining factor of microbial growth over soil organic matter composition conditioned by vegetation.Ministerio de Ciencia Innovación y Universidades (MICIU) for INTERCARBON project (CGL2016-78937-R). N.T. Jiménez-Morillo and L. San Emeterio also thanks MICIU for funding FPI research grants (BES-2013-062573 and Ref. BES-2017-07968). Mrs Desiré Monis is acknowledged for technical assistance

Factors controlling short-term soil microbial response after laboratory heating. Preliminary results

Diapositiva de la comunicación oral presentada presentado en el EGU General Assembly 2015, 12-17 April 2015, Vienna, AustriaSoil microbial response after fire is controlled by numerous variables which conclude with a mosaic of results depending on organic carbon alterations or pH fire-induced changes. This fact has complicated the studies focused on post-fire microbial response, compiling high variability of opposite result in the bibliography. Soil laboratory heating cannot emulate a real wildfire effect on soil but lead us the possibility to control several variables and it is a valid tool to clarify the relative weight of different factors controlling microbial response after soil heating. In this preliminary study different heated treatments were applied to unaltered forest soil samples, obtaining 4 different heating treatments to simulate a range of fire intensities: unaltered-control (UH), and soil heated at 300, 450 and 500 ºC. In order to isolate possible nutrient availability or pH heating-induced changes, different culture media were prepared using soil:water extract from each heating treatments and adding different supplements to obtain the total of 11 different culture media: unheated soil without supplements (UH-N-), unheated soil with nutrient supplement (UH-N+), soil heated at 300 ºC without supplements (300-N-), soil heated at 300 ºC with nutrient supplement (300-N+), soil heated at 300 ºC with nutrient supplement and pH-buffered (300-N+pH); soil heated at 450 ºC without supplements (450-N-), soil heated at 450 ºC with nutrient supplement (450-N+), soil heated at 450 ºC with nutrient supplement and pH-buffered (450-N+); soil heated at 500 ºC without supplements (500-N-), soil heated at 500 ºC with nutrient supplement (500-N+), soil heated at 500 ºC with nutrient supplement and pH-buffered (500-N+). Each media was inoculated with different dilutions of a microbial suspension from the original unaltered soil, and the abundance of viable and cultivable microorganisms were measured by plate count method. In addition, the analysis of heating-induced soil organic matter alteration by mean of pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) technique was applied to soil samples and soil:water extract in order to obtain a deeper understanding of soil organic matter-microorganisms interaction after fire. Heating effect on soil:water extract media was evident since the number CFU in those media prepared by mean of heated soil was lower than those counted in media prepared with unaltered soil and inoculated with the same dilution. Nutrient addition appear to promote microbial proliferation in unaltered and 300 ºC treatments, while nutrient and pH compensation appear to attenuate heating effect in samples heated at 300 and 450 ºC. While, media prepared with soil:water extract form soil heated at 500ºC showed similar CFU abundance in all supplement treatments. Soil organic matter analyses evidences difference in the pyrogram obtained from each heating treatment sample, with a marked diminution of peaks with increased temperature. This preliminary study shows us the importance of soil organic matter fire-induced alterations in soil microbial response after soil heating process beyond the C content diminution or changes in C availability.N

Vegetation and pH implications on the dynamic of soil organic matter at high-mountain shrubs ecosystems from Sierra Nevada National Park (Granada, Spain)

Comunicación oral presentada en el ISMOM 2019 - 8th International Symposium on Interactions of Soil Minerals with Organic Components and Microorganisms: 23-28 june, Sevilla (Spain)During the last decade soil organic matter dynamic and its determining factors have received an increased attention mainly due to the evident implication of these parameters in climate change understanding predictions and possible management. High-mountain soil could be consider as hotspot of climate change dynamic since its high carbon accumulation and low organic matter degradation rates could be seriously altered by slight changes in temperature and rainfall regimens associated to climate change effects. In the particular case of Sierra Nevada National Park this threat could be even stronger due to its Southern character although its elevated biodiversity could shed some light on how could we predict and manage climate change in the future. In this study we selected different sampling areas with distinct soil pH (area A with pH7) and vegetation (high-mountain shrubs and pine reforested area). Soil samples were collected under the influence of several plant species representatives of each vegetation series. Six different kind of samples were finally obtained (five replicates each); three were collected in area A under Juniperus communis ssp. Nana (ENE) Genista versicolor (PIO) and Pinus sylvestris (PSI) and other three were collected in area B under Juniperus Sabina (SAB) Astragalus nevadensis (AST) and Pinus sylvestris (PCA). Quantitative and qualitative organic matter characterization and soil microbial biomass and activity were measure in order to evaluate the implication of soil pH and vegetation in soil organic dynamic at this particular high-mountain environment at Sierra Nevada National Par

Could original pH and vegetation condition fungal role after fire?

Different fungal and bacterial response after fire is one of the first evidences that were reported in the literature. Divergent heat-resistance, different competitive capacities or even variable sensitivity grade to toxics substances have been proposed as the key factors determining these changes. In the last years, original soil pH and pH fire-induced changes have started to gain importance in the fungal and bacterial behaviour after fire, in both, wildfire and laboratory heating researches (Bárcenas-Moreno et al., 2011; Bárcenas-Moreno et al., 2016a; Bárcenas-Moreno et al., in press). Fungal proliferation is associated to low original pH (pH < 7, or acid conditions), owing to fungi appears to be more competitive than bacteria at this pH, although fungi can proliferate without problem at pH above 7. Therefore, bacteria proliferation after fire is related to pH fire-induced increment associate to ash deposition. Bárcenas-Moreno et al. (2011) found evidences of fungal facilitation to bacterial recovery when pre- and post-fire soil pH is below 7. One possible explanation suggested is related to fungal enzymatic capacities, which could allow fungi to be more competitive against fire-induced organic toxics compound, being releasedby partial combustion of organic matter. Fungal detoxification of soil in the first post-fire moment could facilitate subsequent bacterial colonization. In addition, we should take into account that vegetation plays an important role determining microbial community composition and function, since, plant species composition conditions organic matter quantity and quality (Bárcenas-Moreno et al., 2014). Thus, the establishment of fungal community associated to different plant community and soil pH, could allow us predict the potential response of microbial community after fire conditioned by pH fire-induced changes. In this preliminary study to deepen the fungal role in soil ecology after fire, we isolate soil fungi from, different forest unaltered areas with different pH and original vegetation, and fungal abundance. Diversity and enzymatic capacity to degrade Polycyclic Aromatic Hydrocarbons (PAHs) of viable and cultivable fungi were analysed. In addition, in one of the forest areas selected, we include an area that was burnt 6 years before and compare with the unburnt one. Soil samples were collected under the influence of pine, holm oak, kermes oak, cork oak, rockrose and high mountain shrubs from different geographical areas in the South of Spain. Soil samples collected under cork oak showed the highest viable and cultivable fungal abundance of all samples studied, while soil from high mountain shrubs displayed the lowest one. Nevertheless the number of different fungi isolated was more variable. The average percentage of fungi with laccase activity among all isolates was around 20%, with the highest percentage found under high mountain shrubs and the lowest one under pine on basic conditions (pH < 7) where no isolate was found with this activity. The results obtained in this preliminary study can help us to design new project in order to determine the potential role of fungi in different forest environment susceptible to suffer a wildfire in the future.Peer Reviewe

Efecto del pH y la vegetación en la dinámica de la materia orgánica en suelos de alta montaña

4 páginas.- 3 figuras.- 2 tablas.- 3 referencias.- Póster presentado en el Congreso El suelo: clave para una gestión ambiental sostenible en un escenario de cambio global. IX Simposio sobre Control de la Degradación y Recuperación de Suelos CONDEGRES 2021, celebrado entre los días 24 y 25 de mayo de 2021Conocer mejor la dinámica de la materia orgánica del suelo se ha convertido en objetivo de numerosos estudios, ya que el suelo es uno de los mayores reservorios de carbono que existen. En concreto, este estudio preliminar, se centra en los suelos de alta montaña situados en Sierra Nevada (Granada) ya que la amenaza de pequeñas variaciones en el régimen de temperatura y humedad derivadas del cambio climático podrían conllevar a una liberación importante del carbono almacenado en ellos. Con objetivo de establecer la influencia del pH y la vegetación en la dinámica de la materia orgánica en este escenario, se recolectaron muestras de suelo de dos zonas cercanas, pero con diferencias en su litología, principalmente en relación a los valores de pH. Para cada zona se muestrearon suelos bajo una vegetación de matorral de alta montaña y área reforestada con pino albar. Se ha realizado una caracterización cualitativa y cuantitativa de la materia orgánica del suelo, estudiando de forma paralela la abundancia y actividad microbianas.N

Efecto del pH y la vegetación en la dinámica de la materia orgánica en suelos de alta montaña (Póster-Presentación oral)

Presentación oral del póster por Gael Bárcenas-Moreno en el IX Simposio sobre Control de la Degradación y Recuperación de Suelos CONDEGRES 2021, celebrado entre los días 24 y 25 de mayo de 2021.- enlace al video https://youtu.be/fVxmT6Mg7w8Peer reviewe

Influencia de la vegetación y el pH en la dinámica de la materia orgánica en suelos de alta montaña del P.N. de Sierra Nevada

Póster presentado en la XXXII Reunión Nacional de Suelos (RENS2019) 10-13 de septiembre de 2019 en SevillaDurante la última década, los factores relacionados con la dinámica de la materia orgánica del suelo han recibido gran atención debido, principalmente, a su implicación en la evolución del cambio climático, la predicción de sus efectos y posibles alternativas de gestión. Los suelos de alta montaña pueden considerarse puntos críticos ya que mantienen altas tasas de acumulación de carbono y bajas de degradación de materia orgánica, balance que podría alterarse por leves cambios en los regímenes de temperatura y precipitación asociados con el cambio climático. En el caso particular del Parque Nacional de Sierra Nevada, esta amenaza podría ser aún más marcada debido a su localización en el sur de Europa justo en el ecotono mediterráneo, dónde se refleja cualquier cambio ambiental de forma más temprana, aunque su elevada biodiversidad podría tener efectos regulatorios y arrojar alguna luz sobre cómo podríamos predecir y gestionar en el futuro los efectos del cambio climático. Para evaluar la implicación del pH y la vegetación sobre la dinámica de la materia orgánica del suelo, se seleccionaron dos áreas cercanas sobre diferente sustrato que condicionaban diferentes valores de pH: área A, sobre materiales ácidos y con pH 7. Para cada área se muestrearon suelos bajo una vegetación equivalente de arbustos de alta montaña y área reforestada de pino albar. Finalmente se obtuvieron seis tipos diferentes de muestras con cinco repeticiones cada una; tres fueron recolectados en el área A bajo Juniperus communis ssp. nana (ENE), Genista versicolor (PIO) y Pinus sylvestris (PSI) y otros tres se recolectaron en el área B bajo Juniperus sabina (SAB), Astragalus nevadensis (AST) y Pinus sylvestris (PCA). Se realizó una caracterización cuantitativa y cualitativa de la materia orgánica del suelo y se estudió su actividad microbiana. El estudio incluyó el análisis detallado de la estructura molecular mediante pirolisis analítica (Py-GC/MS). Los resultados se discutirán en relación con la influencia del sustrato y la vegetación sobre la dinámica de la materia orgánica del suelo y particularmente de la degradación de ligninas, en este entorno particular de alta montaña del Parque Nacional Sierra Nevada.Proyecto INTERCARBON (CGL2016-78937-R) cofinanciado con fondos de cohesión EU-FEDER. L.M.S.E. agradece su contrato FPI (BES-2017-07968). Desiré Monis por su asistencia técnicaN

Biological and chemical factors controlling the patchy distribution of soil water repellency among plant species in a Mediterranean semiarid forest

Natural soil water repellency is a property that has already been observed in forest soils and is characterized by its patchy distribution. There are many factors involved in its development. In this work, we have studied a large number of chemical and biological factors under the influence of different plant species (. Pinus halepensis, Quercus rotundifolia, Cistus albidus and Rosmarinus officinalis) to learn which has the greatest responsibility for its presence and persistence in the top-soil layer. We observed strong and significant correlations between ergosterol, glomalin related soil protein (GRSP), extractable lipids, soil organic matter (SOM) content and water repellency (WR). Our results suggested lipid fraction as the principal factor. Moreover, apart from Pinus, fungal biomass seems to be also related to the SOM content. Soil WR found under Pinus appears to be the most influenced by fungi. Quality of SOM, to be precise, lipid fraction could be responsible for WR and its relationship with fungal activity.Peer Reviewe

Assessment of temperature peaks reached during a wildfire. An approach using X-ray diffraction and differential thermal analysis

1. INTRODUCTION Wildfires may induce important chemical and physical changes in soils, including changes in the soil composition, mineralogical changes, soil water repellency, aggregate stability or textural changes (Bodí et al., 2013; Granged et al., 2011a, 2011b, 2011c; Jordán et al., 2011, 2013; Mataix-Solera et al., 2011). As these changes usually occur after threshold temperature peaks, the assessment of these helps to explain many of the processes occurring during burning and in the postfire (Pereira et al., 2012, 2013; Shakesby, 2011). In July 2011, a wildfire burnt a pine forested area (50 ha) in Gorga (Alicante, SW Spain), approximately at 38◦ 44.3’ N and 0◦ 20.7’ W. Main soil type is Lithic Xerorthent developed from limestone. The study of mineralogical changes in soil after a wildfire should help to assess fire temperature peaks reached during burning. In order to study the impact of fire temperature on mineralogical changes and determine temperature peaks during burning, burnt soil plots under shrubland were randomly collected (0-5 cm deep). Control samples from adjacent unburnt areas were also collected for control. 2. METHODS Soil samples were ground using an agate mortar and then sieved (< 0.002mm) and analyzed by X-ray diffraction (XRD). XRD was conducted on a Bruker (model D8 advance A25) powder θ:θ diffractometer, which uses a Cu anticathode (40KV, 30mA), Ni filter in the diffracted bean and lineal detector. Powder samples were scanned from 3 to 70◦ 2θ, using a step size of 0.015◦ 2θ and a scan speed of 0.15◦ 2θ s−1. Mineralogical phase identification and quantification of minerals was carried out with XPowder. In order to study other possible reaction in burnt soil, unburnt soil samples were exposed to temperatures of 300, 500 and 700 ◦C in a Mufla furnace during 20 minutes. Unburnt control and treated samples were analyzed by differential thermal analysis (DTA) and thermogravimetric analysis (TG). 3. RESULTS Diffractograms show that the blixita peak, found in the control sample, disappears in the diffractograms of burnt samples. Other significant peaks (calcite, quartz and microcline, for example) do not show significant changes between control and burnt samples. After semiquantitative analysis, the proportion of calcite increased in burnt soil samples (76.3%, on average) respect to control unburnt soil samples (62.3%). This increase may be explained by calcium carbonate released by ash after combustion of organic matter. Consequently, quartz proportion decreased in burnt samples (10.7%, on average) respect to control samples (26.1%). After DTA analysis, a valley occurs between 400 and 700 ◦C in the control sample which is not present in 500 and 700 oC heated samples. This loss of energy is attributed to combustion of organic matter approximately between 400 and 500 ◦C, as well as thermal changes in iron oxides (which occurs approximately between 300 and 500 ◦C) and loss of structural water (>420 ◦C). In samples heated at 500 and 700 ◦C, these changes are not appreciated as they occurred during calcination. In the 300 ◦C heated sample, some of these changes partially occurred. Peaks observed approximately at 100 ◦C correspond to release of absorbed water. Peaks at 900 ◦C are a consequence of destruction of calcite. Finally a peak was observed at 680 ◦C in the control sample may be explained as a consequence of the destruction of blixite (Pb8(OH)2Cl4), which was present in control samples (1.1%) but not in burnt samples. This peak is probably masked in heated samples.This research has been funded by the Spanish Ministry of Economy and Competitiveness through the project HYDFIRE (CGL2010-21670-C02-01) and a research contract to Nicasio T. Jiménez-Morillo (BES-2013-062573)N