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Microbial carbon has recently been highlighted to play a key role in the formation and persistence of soil organic carbon, bearing significant implications for regulating ecosystem carbon stocks under global changes. However, microbial carbon distribution and the link between biomass and necromass components are poorly understood in natural soils, especially at depth. Here, we employ various microbial biomarkers, including phospholipid fatty acids (PLFAs), amino sugars and glycerol dialkyl glycerol tetraethers (GDGTs), to investigate the spatial distribution patterns of microbial biomass and necromass components in the top- (0–10 cm) versus subsoils (30–50 cm) across Chinese temperate grasslands along an aridity gradient. We find that bacterial necromass components are better preserved relative to bacterial biomass in the sub- than topsoil, possibly due to a stronger association of microbial necromass with calcium and/or lower nitrogen competition between plants and microbes at depth in these neutral-to-alkaline soils. As a result, there is a stronger link between bacterial necromass components (especially for core lipid branched GDGTs and muramic acid) and their producers (reflected by intact polar lipid-derived branched GDGTs) in the sub- than topsoil, while such a trend is not observed for fungi- or archaea-derived components. Furthermore, using linear mixed effect model analyses, we find that aridity index best explains the concentration variance of most microbial biomarkers in the topsoil, whereas edaphic properties (i.e., pH and macronutrients) also contribute significantly to their variance in the subsoil. These findings highlight different links between microbial necromass and biomass components and distinct preservation mechanisms for microbial carbon at different soil depths, which is crucial for improved understanding of microbial carbon sequestration potentials at different depths in a changing environment.

Carbon and nitrogen from soil microbial biomass (MCB & MNB) are bio-indicators that have the potential to show changes in soil of ecosystems, and are conditioned, by moisture available in the soil. In this work we evaluated how MCB, MNB and heterotrophic respiration (RH) vary, as a function of moisture in soils of the Dry Magallanic Steppe of Santa Cruz, Argentina. The trial consisted in 3 treatments: a) Control, without variations in precipitation, used as reference, b) irrigation, equivalent to a 54% increase in precipitation compared to the annual average, and c) drought, equivalent to a 54% decrease in precipitation compared to the annual average. MBC was estimated by the fumigation-extraction method. Significant differences were found in MCB between treatments, irrigation had the highest value. MCB were: 505.3 (±81.4), 406.7(±39.2) and 380.4 (±98.4) µg C g-1 dry soil for soil under irrigation, drought and control, respectively. No differences were found in the MNB between treatments and values were: 93.3 (±13.5), 82.8 (±68.9) and 80.7 (±31.1) µg N g-1 dry soil for drought, control and irrigation, respectively. In addition, RH values were: 13.04 (±3.32), 11.17 (±1.47) and 10.60 (±1.29) mg CO2Kg-1day-1 for control, irrigation and drought, respectively. Only MCB showed a relevant change when soil was subjected to drought, meanwhile the other variables did not show significant differences. Results indicate that moisture is an important factor for C in MB, so it is important to continue monitoring in order to establish how changes in precipitation can alter the microbial biomass in these southern environments., El carbono y el nitrógeno de la biomasa microbiana (CBM y NBM) del suelo son bioindicadores que tienen el potencial de mostrar cambios en el suelo de los ecosistemas, y están condicionados por la humedad disponible en el suelo. Se evaluó como varían CBM, NBM y la respiración heterotrófica (RH) en función de la cantidad de humedad en suelos de la Estepa Magallánica Seca de Santa Cruz, Argentina. El ensayo consistió en 3 tratamientos: a) Control, conteniendo la precipitación normal caída, como testigo, b) Riego, equivalente a un aumento del 54% en las precipitaciones respecto a la media anual, y c) Sequía, con una disminución del 54% en las precipitaciones respecto a la media anual. Se estimó el CBM mediante el método de fumigación-extracción. Se encontraron diferencias significativas en el CBM entre los tratamientos, el riego obtuvo la mayor cantidad de CBM. Los valores fueron: 505,3 (±81,4), 406,7(±39,2) y 380,4 (±98,4) µg de C g-1 para riego, sequía y control, respectivamente. No se encontraron diferencias en el NBM entre los tratamientos, siendo los valores 93,3 (±13,5), 82,8 (±68,9) y 80,7 (±31,1) µg de N g-1 de suelo seco para sequía, control y riego, respectivamente. La RH diaria por su parte, presentó valores de 13,04 (±3,32), 11,17 (±1,47) y 10,60 (±1,29) mg C-CO2Kg-1 de suelo seco día-1 para el tratamiento control, riego y sequía, respectivamente. Solo el CBM evidenció un cambio relevante frente a la sequía, las demás variables no presentaron diferencias significativas. Los resultados denotan que la humedad es un factor importante para el C en BM, por lo que es importante seguir monitoreando y establecer como cambios en la precipitación alterar la biomasa microbiana en estos ambientes australes.

Carbon and nitrogen from soil microbial biomass (MCB & MNB) are bio-indicators that have the potential to show changes in soil of ecosystems, and are conditioned, by moisture available in the soil. In this work we evaluated how MCB, MNB and heterotrophic respiration (RH) vary, as a function of moisture in soils of the Dry Magallanic Steppe of Santa Cruz, Argentina. The trial consisted in 3 treatments: a) Control, without variations in precipitation, used as reference, b) irrigation, equivalent to a 54% increase in precipitation compared to the annual average, and c) drought, equivalent to a 54% decrease in precipitation compared to the annual average. MBC was estimated by the fumigation-extraction method. Significant differences were found in MCB between treatments, irrigation had the highest value. MCB were: 505.3 (±81.4), 406.7(±39.2) and 380.4 (±98.4) µg C g-1 dry soil for soil under irrigation, drought and control, respectively. No differences were found in the MNB between treatments and values were: 93.3 (±13.5), 82.8 (±68.9) and 80.7 (±31.1) µg N g-1 dry soil for drought, control and irrigation, respectively. In addition, RH values were: 13.04 (±3.32), 11.17 (±1.47) and 10.60 (±1.29) mg CO2Kg-1day-1 for control, irrigation and drought, respectively. Only MCB showed a relevant change when soil was subjected to drought, meanwhile the other variables did not show significant differences. Results indicate that moisture is an important factor for C in MB, so it is important to continue monitoring in order to establish how changes in precipitation can alter the microbial biomass in these southern environments., El carbono y el nitrógeno de la biomasa microbiana (CBM y NBM) del suelo son bioindicadores que tienen el potencial de mostrar cambios en el suelo de los ecosistemas, y están condicionados por la humedad disponible en el suelo. Se evaluó como varían CBM, NBM y la respiración heterotrófica (RH) en función de la cantidad de humedad en suelos de la Estepa Magallánica Seca de Santa Cruz, Argentina. El ensayo consistió en 3 tratamientos: a) Control, conteniendo la precipitación normal caída, como testigo, b) Riego, equivalente a un aumento del 54% en las precipitaciones respecto a la media anual, y c) Sequía, con una disminución del 54% en las precipitaciones respecto a la media anual. Se estimó el CBM mediante el método de fumigación-extracción. Se encontraron diferencias significativas en el CBM entre los tratamientos, el riego obtuvo la mayor cantidad de CBM. Los valores fueron: 505,3 (±81,4), 406,7(±39,2) y 380,4 (±98,4) µg de C g-1 para riego, sequía y control, respectivamente. No se encontraron diferencias en el NBM entre los tratamientos, siendo los valores 93,3 (±13,5), 82,8 (±68,9) y 80,7 (±31,1) µg de N g-1 de suelo seco para sequía, control y riego, respectivamente. La RH diaria por su parte, presentó valores de 13,04 (±3,32), 11,17 (±1,47) y 10,60 (±1,29) mg C-CO2Kg-1 de suelo seco día-1 para el tratamiento control, riego y sequía, respectivamente. Solo el CBM evidenció un cambio relevante frente a la sequía, las demás variables no presentaron diferencias significativas. Los resultados denotan que la humedad es un factor importante para el C en BM, por lo que es importante seguir monitoreando y establecer como cambios en la precipitación alterar la biomasa microbiana en estos ambientes australes.

Carbon and nitrogen from soil microbial biomass (MCB & MNB) are bio-indicators that have the potential to show changes in soil of ecosystems, and are conditioned, by moisture available in the soil. In this work we evaluated how MCB, MNB and heterotrophic respiration (RH) vary, as a function of moisture in soils of the Dry Magallanic Steppe of Santa Cruz, Argentina. The trial consisted in 3 treatments: a) Control, without variations in precipitation, used as reference, b) irrigation, equivalent to a 54% increase in precipitation compared to the annual average, and c) drought, equivalent to a 54% decrease in precipitation compared to the annual average. MBC was estimated by the fumigation-extraction method. Significant differences were found in MCB between treatments, irrigation had the highest value. MCB were: 505.3 (±81.4), 406.7(±39.2) and 380.4 (±98.4) µg C g-1 dry soil for soil under irrigation, drought and control, respectively. No differences were found in the MNB between treatments and values were: 93.3 (±13.5), 82.8 (±68.9) and 80.7 (±31.1) µg N g-1 dry soil for drought, control and irrigation, respectively. In addition, RH values were: 13.04 (±3.32), 11.17 (±1.47) and 10.60 (±1.29) mg CO2Kg-1day-1 for control, irrigation and drought, respectively. Only MCB showed a relevant change when soil was subjected to drought, meanwhile the other variables did not show significant differences. Results indicate that moisture is an important factor for C in MB, so it is important to continue monitoring in order to establish how changes in precipitation can alter the microbial biomass in these southern environments., El carbono y el nitrógeno de la biomasa microbiana (CBM y NBM) del suelo son bioindicadores que tienen el potencial de mostrar cambios en el suelo de los ecosistemas, y están condicionados por la humedad disponible en el suelo. Se evaluó como varían CBM, NBM y la respiración heterotrófica (RH) en función de la cantidad de humedad en suelos de la Estepa Magallánica Seca de Santa Cruz, Argentina. El ensayo consistió en 3 tratamientos: a) Control, conteniendo la precipitación normal caída, como testigo, b) Riego, equivalente a un aumento del 54% en las precipitaciones respecto a la media anual, y c) Sequía, con una disminución del 54% en las precipitaciones respecto a la media anual. Se estimó el CBM mediante el método de fumigación-extracción. Se encontraron diferencias significativas en el CBM entre los tratamientos, el riego obtuvo la mayor cantidad de CBM. Los valores fueron: 505,3 (±81,4), 406,7(±39,2) y 380,4 (±98,4) µg de C g-1 para riego, sequía y control, respectivamente. No se encontraron diferencias en el NBM entre los tratamientos, siendo los valores 93,3 (±13,5), 82,8 (±68,9) y 80,7 (±31,1) µg de N g-1 de suelo seco para sequía, control y riego, respectivamente. La RH diaria por su parte, presentó valores de 13,04 (±3,32), 11,17 (±1,47) y 10,60 (±1,29) mg C-CO2Kg-1 de suelo seco día-1 para el tratamiento control, riego y sequía, respectivamente. Solo el CBM evidenció un cambio relevante frente a la sequía, las demás variables no presentaron diferencias significativas. Los resultados denotan que la humedad es un factor importante para el C en BM, por lo que es importante seguir monitoreando y establecer como cambios en la precipitación alterar la biomasa microbiana en estos ambientes australes.

Carbon and nitrogen from soil microbial biomass (MCB & MNB) are bio-indicators that have the potential to show changes in soil of ecosystems, and are conditioned, by moisture available in the soil. In this work we evaluated how MCB, MNB and heterotrophic respiration (RH) vary, as a function of moisture in soils of the Dry Magallanic Steppe of Santa Cruz, Argentina. The trial consisted in 3 treatments: a) Control, without variations in precipitation, used as reference, b) irrigation, equivalent to a 54% increase in precipitation compared to the annual average, and c) drought, equivalent to a 54% decrease in precipitation compared to the annual average. MBC was estimated by the fumigation-extraction method. Significant differences were found in MCB between treatments, irrigation had the highest value. MCB were: 505.3 (±81.4), 406.7(±39.2) and 380.4 (±98.4) µg C g-1 dry soil for soil under irrigation, drought and control, respectively. No differences were found in the MNB between treatments and values were: 93.3 (±13.5), 82.8 (±68.9) and 80.7 (±31.1) µg N g-1 dry soil for drought, control and irrigation, respectively. In addition, RH values were: 13.04 (±3.32), 11.17 (±1.47) and 10.60 (±1.29) mg CO2Kg-1day-1 for control, irrigation and drought, respectively. Only MCB showed a relevant change when soil was subjected to drought, meanwhile the other variables did not show significant differences. Results indicate that moisture is an important factor for C in MB, so it is important to continue monitoring in order to establish how changes in precipitation can alter the microbial biomass in these southern environments., El carbono y el nitrógeno de la biomasa microbiana (CBM y NBM) del suelo son bioindicadores que tienen el potencial de mostrar cambios en el suelo de los ecosistemas, y están condicionados por la humedad disponible en el suelo. Se evaluó como varían CBM, NBM y la respiración heterotrófica (RH) en función de la cantidad de humedad en suelos de la Estepa Magallánica Seca de Santa Cruz, Argentina. El ensayo consistió en 3 tratamientos: a) Control, conteniendo la precipitación normal caída, como testigo, b) Riego, equivalente a un aumento del 54% en las precipitaciones respecto a la media anual, y c) Sequía, con una disminución del 54% en las precipitaciones respecto a la media anual. Se estimó el CBM mediante el método de fumigación-extracción. Se encontraron diferencias significativas en el CBM entre los tratamientos, el riego obtuvo la mayor cantidad de CBM. Los valores fueron: 505,3 (±81,4), 406,7(±39,2) y 380,4 (±98,4) µg de C g-1 para riego, sequía y control, respectivamente. No se encontraron diferencias en el NBM entre los tratamientos, siendo los valores 93,3 (±13,5), 82,8 (±68,9) y 80,7 (±31,1) µg de N g-1 de suelo seco para sequía, control y riego, respectivamente. La RH diaria por su parte, presentó valores de 13,04 (±3,32), 11,17 (±1,47) y 10,60 (±1,29) mg C-CO2Kg-1 de suelo seco día-1 para el tratamiento control, riego y sequía, respectivamente. Solo el CBM evidenció un cambio relevante frente a la sequía, las demás variables no presentaron diferencias significativas. Los resultados denotan que la humedad es un factor importante para el C en BM, por lo que es importante seguir monitoreando y establecer como cambios en la precipitación alterar la biomasa microbiana en estos ambientes australes.

Carbon and nitrogen from soil microbial biomass (MCB & MNB) are bio-indicators that have the potential to show changes in soil of ecosystems, and are conditioned, by moisture available in the soil. In this work we evaluated how MCB, MNB and heterotrophic respiration (RH) vary, as a function of moisture in soils of the Dry Magallanic Steppe of Santa Cruz, Argentina. The trial consisted in 3 treatments: a) Control, without variations in precipitation, used as reference, b) irrigation, equivalent to a 54% increase in precipitation compared to the annual average, and c) drought, equivalent to a 54% decrease in precipitation compared to the annual average. MBC was estimated by the fumigation-extraction method. Significant differences were found in MCB between treatments, irrigation had the highest value. MCB were: 505.3 (±81.4), 406.7(±39.2) and 380.4 (±98.4) µg C g-1 dry soil for soil under irrigation, drought and control, respectively. No differences were found in the MNB between treatments and values were: 93.3 (±13.5), 82.8 (±68.9) and 80.7 (±31.1) µg N g-1 dry soil for drought, control and irrigation, respectively. In addition, RH values were: 13.04 (±3.32), 11.17 (±1.47) and 10.60 (±1.29) mg CO2Kg-1day-1 for control, irrigation and drought, respectively. Only MCB showed a relevant change when soil was subjected to drought, meanwhile the other variables did not show significant differences. Results indicate that moisture is an important factor for C in MB, so it is important to continue monitoring in order to establish how changes in precipitation can alter the microbial biomass in these southern environments., El carbono y el nitrógeno de la biomasa microbiana (CBM y NBM) del suelo son bioindicadores que tienen el potencial de mostrar cambios en el suelo de los ecosistemas, y están condicionados por la humedad disponible en el suelo. Se evaluó como varían CBM, NBM y la respiración heterotrófica (RH) en función de la cantidad de humedad en suelos de la Estepa Magallánica Seca de Santa Cruz, Argentina. El ensayo consistió en 3 tratamientos: a) Control, conteniendo la precipitación normal caída, como testigo, b) Riego, equivalente a un aumento del 54% en las precipitaciones respecto a la media anual, y c) Sequía, con una disminución del 54% en las precipitaciones respecto a la media anual. Se estimó el CBM mediante el método de fumigación-extracción. Se encontraron diferencias significativas en el CBM entre los tratamientos, el riego obtuvo la mayor cantidad de CBM. Los valores fueron: 505,3 (±81,4), 406,7(±39,2) y 380,4 (±98,4) µg de C g-1 para riego, sequía y control, respectivamente. No se encontraron diferencias en el NBM entre los tratamientos, siendo los valores 93,3 (±13,5), 82,8 (±68,9) y 80,7 (±31,1) µg de N g-1 de suelo seco para sequía, control y riego, respectivamente. La RH diaria por su parte, presentó valores de 13,04 (±3,32), 11,17 (±1,47) y 10,60 (±1,29) mg C-CO2Kg-1 de suelo seco día-1 para el tratamiento control, riego y sequía, respectivamente. Solo el CBM evidenció un cambio relevante frente a la sequía, las demás variables no presentaron diferencias significativas. Los resultados denotan que la humedad es un factor importante para el C en BM, por lo que es importante seguir monitoreando y establecer como cambios en la precipitación alterar la biomasa microbiana en estos ambientes australes.

Carbon and nitrogen from soil microbial biomass (MCB & MNB) are bio-indicators that have the potential to show changes in soil of ecosystems, and are conditioned, by moisture available in the soil. In this work we evaluated how MCB, MNB and heterotrophic respiration (RH) vary, as a function of moisture in soils of the Dry Magallanic Steppe of Santa Cruz, Argentina. The trial consisted in 3 treatments: a) Control, without variations in precipitation, used as reference, b) irrigation, equivalent to a 54% increase in precipitation compared to the annual average, and c) drought, equivalent to a 54% decrease in precipitation compared to the annual average. MBC was estimated by the fumigation-extraction method. Significant differences were found in MCB between treatments, irrigation had the highest value. MCB were: 505.3 (±81.4), 406.7(±39.2) and 380.4 (±98.4) µg C g-1 dry soil for soil under irrigation, drought and control, respectively. No differences were found in the MNB between treatments and values were: 93.3 (±13.5), 82.8 (±68.9) and 80.7 (±31.1) µg N g-1 dry soil for drought, control and irrigation, respectively. In addition, RH values were: 13.04 (±3.32), 11.17 (±1.47) and 10.60 (±1.29) mg CO2Kg-1day-1 for control, irrigation and drought, respectively. Only MCB showed a relevant change when soil was subjected to drought, meanwhile the other variables did not show significant differences. Results indicate that moisture is an important factor for C in MB, so it is important to continue monitoring in order to establish how changes in precipitation can alter the microbial biomass in these southern environments., El carbono y el nitrógeno de la biomasa microbiana (CBM y NBM) del suelo son bioindicadores que tienen el potencial de mostrar cambios en el suelo de los ecosistemas, y están condicionados por la humedad disponible en el suelo. Se evaluó como varían CBM, NBM y la respiración heterotrófica (RH) en función de la cantidad de humedad en suelos de la Estepa Magallánica Seca de Santa Cruz, Argentina. El ensayo consistió en 3 tratamientos: a) Control, conteniendo la precipitación normal caída, como testigo, b) Riego, equivalente a un aumento del 54% en las precipitaciones respecto a la media anual, y c) Sequía, con una disminución del 54% en las precipitaciones respecto a la media anual. Se estimó el CBM mediante el método de fumigación-extracción. Se encontraron diferencias significativas en el CBM entre los tratamientos, el riego obtuvo la mayor cantidad de CBM. Los valores fueron: 505,3 (±81,4), 406,7(±39,2) y 380,4 (±98,4) µg de C g-1 para riego, sequía y control, respectivamente. No se encontraron diferencias en el NBM entre los tratamientos, siendo los valores 93,3 (±13,5), 82,8 (±68,9) y 80,7 (±31,1) µg de N g-1 de suelo seco para sequía, control y riego, respectivamente. La RH diaria por su parte, presentó valores de 13,04 (±3,32), 11,17 (±1,47) y 10,60 (±1,29) mg C-CO2Kg-1 de suelo seco día-1 para el tratamiento control, riego y sequía, respectivamente. Solo el CBM evidenció un cambio relevante frente a la sequía, las demás variables no presentaron diferencias significativas. Los resultados denotan que la humedad es un factor importante para el C en BM, por lo que es importante seguir monitoreando y establecer como cambios en la precipitación alterar la biomasa microbiana en estos ambientes australes.

Carbon and nitrogen from soil microbial biomass (MCB & MNB) are bio-indicators that have the potential to show changes in soil of ecosystems, and are conditioned, by moisture available in the soil. In this work we evaluated how MCB, MNB and heterotrophic respiration (RH) vary, as a function of moisture in soils of the Dry Magallanic Steppe of Santa Cruz, Argentina. The trial consisted in 3 treatments: a) Control, without variations in precipitation, used as reference, b) irrigation, equivalent to a 54% increase in precipitation compared to the annual average, and c) drought, equivalent to a 54% decrease in precipitation compared to the annual average. MBC was estimated by the fumigation-extraction method. Significant differences were found in MCB between treatments, irrigation had the highest value. MCB were: 505.3 (±81.4), 406.7(±39.2) and 380.4 (±98.4) µg C g-1 dry soil for soil under irrigation, drought and control, respectively. No differences were found in the MNB between treatments and values were: 93.3 (±13.5), 82.8 (±68.9) and 80.7 (±31.1) µg N g-1 dry soil for drought, control and irrigation, respectively. In addition, RH values were: 13.04 (±3.32), 11.17 (±1.47) and 10.60 (±1.29) mg CO2Kg-1day-1 for control, irrigation and drought, respectively. Only MCB showed a relevant change when soil was subjected to drought, meanwhile the other variables did not show significant differences. Results indicate that moisture is an important factor for C in MB, so it is important to continue monitoring in order to establish how changes in precipitation can alter the microbial biomass in these southern environments., El carbono y el nitrógeno de la biomasa microbiana (CBM y NBM) del suelo son bioindicadores que tienen el potencial de mostrar cambios en el suelo de los ecosistemas, y están condicionados por la humedad disponible en el suelo. Se evaluó como varían CBM, NBM y la respiración heterotrófica (RH) en función de la cantidad de humedad en suelos de la Estepa Magallánica Seca de Santa Cruz, Argentina. El ensayo consistió en 3 tratamientos: a) Control, conteniendo la precipitación normal caída, como testigo, b) Riego, equivalente a un aumento del 54% en las precipitaciones respecto a la media anual, y c) Sequía, con una disminución del 54% en las precipitaciones respecto a la media anual. Se estimó el CBM mediante el método de fumigación-extracción. Se encontraron diferencias significativas en el CBM entre los tratamientos, el riego obtuvo la mayor cantidad de CBM. Los valores fueron: 505,3 (±81,4), 406,7(±39,2) y 380,4 (±98,4) µg de C g-1 para riego, sequía y control, respectivamente. No se encontraron diferencias en el NBM entre los tratamientos, siendo los valores 93,3 (±13,5), 82,8 (±68,9) y 80,7 (±31,1) µg de N g-1 de suelo seco para sequía, control y riego, respectivamente. La RH diaria por su parte, presentó valores de 13,04 (±3,32), 11,17 (±1,47) y 10,60 (±1,29) mg C-CO2Kg-1 de suelo seco día-1 para el tratamiento control, riego y sequía, respectivamente. Solo el CBM evidenció un cambio relevante frente a la sequía, las demás variables no presentaron diferencias significativas. Los resultados denotan que la humedad es un factor importante para el C en BM, por lo que es importante seguir monitoreando y establecer como cambios en la precipitación alterar la biomasa microbiana en estos ambientes australes.

Carbon and nitrogen from soil microbial biomass (MCB & MNB) are bio-indicators that have the potential to show changes in soil of ecosystems, and are conditioned, by moisture available in the soil. In this work we evaluated how MCB, MNB and heterotrophic respiration (RH) vary, as a function of moisture in soils of the Dry Magallanic Steppe of Santa Cruz, Argentina. The trial consisted in 3 treatments: a) Control, without variations in precipitation, used as reference, b) irrigation, equivalent to a 54% increase in precipitation compared to the annual average, and c) drought, equivalent to a 54% decrease in precipitation compared to the annual average. MBC was estimated by the fumigation-extraction method. Significant differences were found in MCB between treatments, irrigation had the highest value. MCB were: 505.3 (±81.4), 406.7(±39.2) and 380.4 (±98.4) µg C g-1 dry soil for soil under irrigation, drought and control, respectively. No differences were found in the MNB between treatments and values were: 93.3 (±13.5), 82.8 (±68.9) and 80.7 (±31.1) µg N g-1 dry soil for drought, control and irrigation, respectively. In addition, RH values were: 13.04 (±3.32), 11.17 (±1.47) and 10.60 (±1.29) mg CO2Kg-1day-1 for control, irrigation and drought, respectively. Only MCB showed a relevant change when soil was subjected to drought, meanwhile the other variables did not show significant differences. Results indicate that moisture is an important factor for C in MB, so it is important to continue monitoring in order to establish how changes in precipitation can alter the microbial biomass in these southern environments., El carbono y el nitrógeno de la biomasa microbiana (CBM y NBM) del suelo son bioindicadores que tienen el potencial de mostrar cambios en el suelo de los ecosistemas, y están condicionados por la humedad disponible en el suelo. Se evaluó como varían CBM, NBM y la respiración heterotrófica (RH) en función de la cantidad de humedad en suelos de la Estepa Magallánica Seca de Santa Cruz, Argentina. El ensayo consistió en 3 tratamientos: a) Control, conteniendo la precipitación normal caída, como testigo, b) Riego, equivalente a un aumento del 54% en las precipitaciones respecto a la media anual, y c) Sequía, con una disminución del 54% en las precipitaciones respecto a la media anual. Se estimó el CBM mediante el método de fumigación-extracción. Se encontraron diferencias significativas en el CBM entre los tratamientos, el riego obtuvo la mayor cantidad de CBM. Los valores fueron: 505,3 (±81,4), 406,7(±39,2) y 380,4 (±98,4) µg de C g-1 para riego, sequía y control, respectivamente. No se encontraron diferencias en el NBM entre los tratamientos, siendo los valores 93,3 (±13,5), 82,8 (±68,9) y 80,7 (±31,1) µg de N g-1 de suelo seco para sequía, control y riego, respectivamente. La RH diaria por su parte, presentó valores de 13,04 (±3,32), 11,17 (±1,47) y 10,60 (±1,29) mg C-CO2Kg-1 de suelo seco día-1 para el tratamiento control, riego y sequía, respectivamente. Solo el CBM evidenció un cambio relevante frente a la sequía, las demás variables no presentaron diferencias significativas. Los resultados denotan que la humedad es un factor importante para el C en BM, por lo que es importante seguir monitoreando y establecer como cambios en la precipitación alterar la biomasa microbiana en estos ambientes australes.

The assessment of crop derived CO2 emissions allows true insights to the contribution of the agriculture to those emissions. This research aimed to establish the quantity of CO2 derived from some crops and the behaviour of microbial biomass associated, as follows: coffee C. Arabica L., cassava M. esculenta, beans P. vulgaris and lettuce L. sativa. In addition it was proposed to know which of the crops brought about the highest CO2 emissions in response to respectively two crop management types, both technical and traditional. In order to measure these emissions in the field, the method proposed by Swisher (1999) was used, and to measure the microbial biomass the estimation method and the fumigation-extraction. The coffee crop caused the highest CO2 emissions. The crop management method did not influence these emissions. Additionally it was found that climate conditions had a direct influence on the respiration rates across the plantations studied, also revealing that coffee crops had higher respiration ratesduring rainy periods than the other crops., La cuantificación del CO2 generado por los cultivos agrícolas permite obtener una mirada real del aporte de la agricultura a dichas emisiones. En esta investigación se buscó establecer la cantidad de CO2 liberada y el comportamiento de la biomasa microbiana en función del manejo de cultivos de café Coffea arabica L. yuca Manihot esculenta Crantz, fríjol Phaseolus vulgaris L. y lechuga Lactuca sativa L. determinar cuál de ellos causó el mayor aporte dependiendo del tipo de manejo, tanto tecnificado o tradicional. Para cuantificar el CO2 producido en campo, se utilizó el método propuesto por para determinar la cantidad de biomasa se utilizó el método de estimación (biomasa microbiana), en función del carbono microbiano y el método fumigación–extracción, empleado por Paz et al. (2006). El cultivo que presentó mayor liberación de CO2 fue el café. La modalidad de manejo del cultivo no tuvo influencia en la liberación de CO2. Por su parte las condiciones climáticas influyeron sobre las tasas de respiración entre cultivos, indicando que el café en época de poca lluvia respiró más que los otros cultivos.

The assessment of crop derived CO2 emissions allows true insights to the contribution of the agriculture to those emissions. This research aimed to establish the quantity of CO2 derived from some crops and the behaviour of microbial biomass associated, as follows: coffee C. Arabica L., cassava M. esculenta, beans P. vulgaris and lettuce L. sativa. In addition it was proposed to know which of the crops brought about the highest CO2 emissions in response to respectively two crop management types, both technical and traditional. In order to measure these emissions in the field, the method proposed by Swisher (1999) was used, and to measure the microbial biomass the estimation method and the fumigation-extraction. The coffee crop caused the highest CO2 emissions. The crop management method did not influence these emissions. Additionally it was found that climate conditions had a direct influence on the respiration rates across the plantations studied, also revealing that coffee crops had higher respiration ratesduring rainy periods than the other crops., La cuantificación del CO2 generado por los cultivos agrícolas permite obtener una mirada real del aporte de la agricultura a dichas emisiones. En esta investigación se buscó establecer la cantidad de CO2 liberada y el comportamiento de la biomasa microbiana en función del manejo de cultivos de café Coffea arabica L. yuca Manihot esculenta Crantz, fríjol Phaseolus vulgaris L. y lechuga Lactuca sativa L. determinar cuál de ellos causó el mayor aporte dependiendo del tipo de manejo, tanto tecnificado o tradicional. Para cuantificar el CO2 producido en campo, se utilizó el método propuesto por para determinar la cantidad de biomasa se utilizó el método de estimación (biomasa microbiana), en función del carbono microbiano y el método fumigación–extracción, empleado por Paz et al. (2006). El cultivo que presentó mayor liberación de CO2 fue el café. La modalidad de manejo del cultivo no tuvo influencia en la liberación de CO2. Por su parte las condiciones climáticas influyeron sobre las tasas de respiración entre cultivos, indicando que el café en época de poca lluvia respiró más que los otros cultivos.

In mountainous areas of Europe, the abandonment of grasslands followed by forest expansion is the dominant land-use change. Labile (i.e. easily decomposable) litter represents the major source for soil microbial products, which promote soil aggregation and long-term C stabilization. Our objective was to investigate changes in the content and origin of soil C components involved into aggregate stabilization (i.e. carbohydrates) following forest expansion on abandoned grassland in the Alps, where only few studies have been conducted. Changes in carbohydrates and thermally labile C were assessed along a land-use gradient in the Southern Alps (Italy) following analysis of carbohydrate monomers and thermal analysis of mineral soil and physical soil fractions. The land-use gradient comprised managed grassland, two transitional phases in which grassland abandonment led to colonization by Picea abies (L.) Karst., and an old forest dominated by Fagus sylvatica L. and P. abies.Grassland abandoned for 10years tended to have higher levels of carbohydrate and thermally labile soil C than managed grassland and old forest, presumably caused by differences in the quality and amount of litter input. Carbohydrates and thermally labile C showed similar patterns in bulk soil, suggesting that thermal analysis can be used to complement chemical analysis although a straightforward relationship could not be established. Following forest expansion on abandoned grassland, ratios of microbially to plant-derived carbohydrates and thermally labile to resistant components decreased in bulk soil and soil fractions. Forest expansion entailed decreasing amounts of microbially derived compounds known to be important for aggregate stability, and corresponded to decreased soil C allocation to stable aggregates. The combination of carbohydrate and thermal analyses revealed a lower abundance of microbially derived C components after forest colonization on abandoned grasslands, thus resulting in lower

Terrestrial ecosystems are exposed to atmospheric and climatic changes including increases in atmospheric CO2 concentration, temperature and alterations of precipitation patterns, which are predicted to continue with consequences for ecosystem services and functioning in the future. In a field scale experiment on temperate heathland, manipulation of precipitation and temperature was performed with retractable curtains, and atmospheric CO2 concentration was increased by FACE. The combination of elevated CO2 and warming was expected to affect belowground processes additively, through increased belowground sequestration of labile carbohydrates due to elevated CO2 in combination with temperature increased process rates. Together, these changes might increase microbial activity and availability of plant nutrients. Two years after the start of the experiment, belowground processes responded significantly to the treatments. In the combined temperature and CO2 treatment the dissolved organic nitrogen concentration decreased and the ammonium concentration increased, but this release of nutrients was not mirrored by plant parameters. Microbial biomass carbon and microbial enrichment with 13C and 15N (1 year after 13C215N-glycine was injected into the soil) increased in warmed plots and in elevated CO2 plots, but not when these treatments were combined. Furthermore, drought led to an increase in Calluna biomass and total plant nitrogen pool. The full combination of warming, elevated CO2 and periodic drought did not unambiguously express the ecosystem responses of single factors additively, which complicates predictions of ecosystem responses to multifactor climate change.

Terrestrial ecosystems are exposed to atmospheric and climatic changes including increases in atmospheric CO2 concentration, temperature and alterations of precipitation patterns, which are predicted to continue with consequences for ecosystem services and functioning in the future. In a field scale experiment on temperate heathland, manipulation of precipitation and temperature was performed with retractable curtains, and atmospheric CO2 concentration was increased by FACE. The combination of elevated CO2 and warming was expected to affect belowground processes additively, through increased belowground sequestration of labile carbohydrates due to elevated CO2 in combination with temperature increased process rates. Together, these changes might increase microbial activity and availability of plant nutrients. Two years after the start of the experiment, belowground processes responded significantly to the treatments. In the combined temperature and CO2 treatment the dissolved organic nitrogen concentration decreased and the ammonium concentration increased, but this release of nutrients was not mirrored by plant parameters. Microbial biomass carbon and microbial enrichment with 13C and 15N (1 year after 13C215N-glycine was injected into the soil) increased in warmed plots and in elevated CO2 plots, but not when these treatments were combined. Furthermore, drought led to an increase in Calluna biomass and total plant nitrogen pool. The full combination of warming, elevated CO2 and periodic drought did not unambiguously express the ecosystem responses of single factors additively, which complicates predictions of ecosystem responses to multifactor climate change.