N2O and CH4 fluxes in Undisturbed and Burned Holm oak, Scots pine and Pyrenean oak forests in Central Spain

We investigated N2O and CH4 fluxes from soils of Quercus ilex, Quercus pyrenaica and Pinus sylvestris stands located in the surrounding area of Madrid (Spain). The fluxes were measured for 18 months from both mature stands and post fire stands using the static chamber technique. Simultaneously with gas fluxes, soil temperature, soil water content, soil C and soil N were measured in the stands. Nitrous oxide fluxes ranged from −11.43 to 8.34 μg N2O–N m−2 h−1 in Q.ilex, −7.74 to 13.52 μg N2O–N m−2 h−1 in Q. pyrenaica and −28.17 to 21.89 μg N2O–N m−2 h−1 in P. sylvestris. Fluxes of CH4 ranged from −8.12 to 4.11 μg CH4–C m−2 h−1 in Q.ilex, −7.74 to 3.0 μg CH4–C m−2 h−1 in Q. pyrenaica and −24.46 to 6.07 μg CH4–C m−2 h−1 in P. sylvestris. Seasonal differences were detected; N2O fluxes being higher in wet months whereas N2O fluxes declined in dry months. Net consumption of N2O was related to low N availability, high soil C contents, high soil temperatures and low moisture content. Fire decreased N2O fluxes in spring. N2O emissions were closely correlated with previous day’s rainfall and soil moisture. Our ecosystems generally were a sink for methane in the dry season and a source of CH4 during wet months. The available water in the soil influenced the observed seasonal trend. The burned sites showed higher CH4 oxidation rates in Q. ilex, and lower rates in P. sylvestris. Overall, the data suggest that fire alters both N2O and CH4 fluxes. However, the magnitude of such variation depends on the site, soil characteristics and seasonal climatic conditions

Local and regional characterisation of the diurnal mountain wind systems in the Guadarrama mountain range (Spain)

Póster presentado en: EGU General Assembly celebrada del 23 al 28 de abril de 2017 en Viena, Austria.This research has been partially funded by the Spanish Government (MINECO projects CGL2015-65627-C3-3-R and CGL2012-37416-C04-02) and by the GR3/14 program (supported by UCM and Banco Santander) through the Research Group “Micrometeorology and Climate Variability” (No.910437)

Grazing, tiling and canopy effects on carbon dioxide fluxes in a Spanish dehesa

There is increasing interest in carbon sequestering capacity of agroforestry systems especially in relation to climate change. Appropriate implementation of silvopastoral practices in dehesa systems may contribute to their sustainability; improve soil carbon (C) and nitrogen (N) storage capacity while reducing the carbon dioxide (CO2) flux from the soil to the atmosphere. The response of soil respiration (Rs) to grazing and tilling practices and trees canopy influence were studied in a dehesa ecosystem in the center of Spain from July 2008 to February 2010. Four different treatments were established: non grazed-non tilled; non grazed-tilled; grazed-non tilled and grazed and tilled. In all the treatments Rs, soil temperature (Ts), soil moisture (Ms), soil C and N stocks were measured. Grazing reduced Rs by 12 % across all experiment. Increments of 3 Mg/ha in C stocks and 0.3 Mg/ha in N stocks in grazing soils were observed. Although, no clear tilling effect on Rs was found, a decrease of 3.5 Mg/ha in soil C stocks and 0.3 Mg/ha in N stocks was detected in tilled soils. Presence of tree canopy induced increases in Rs, soil C and N stocks; while decreases in Ts were observed, but grazing decreased the tree canopy influence on annual C losses by Rs. The Ms constrained the temperature response of Rsduring the experiment, and meaningful Q10 values were only obtainable during the wettest time, ranging from 2.5 to 5.7. Grazing and tree canopy had a positive influence in the ability of soils to store soil C and N, while tilling had a negative effect on soil C and N store capacity in this study. Maintaining the beneficial practices and improving tillage management in this area may have important consequences in carbon sequestration capacity in this dehesa system

Carbon isotope composition, macronutrient concentrations, and carboxylating enzymes in relation to the growth of Pinus halepensis Mill. when subject to ozone stress

12 páginas, 4 figuras.We present here the effects of ambient ozone (O3)-induced decline in carbon availability, accelerated foliar senescence, and a decrease in aboveground biomass accumulation in the Aleppo pine (Pinus halepensis Mill.). Aleppo pine seedlings were continuously exposed in open-top chambers for 39 months to three different types of O3 treatments, which are as follows: charcoal-filtered air, nonfiltered air (NFA), and nonfiltered air supplemented with 40 ppb O3 (NFA+). Stable carbon isotope discrimination (Δ) and derived time-integrated ci /ca ratios were reduced after an accumulated ozone exposure over a threshold of 40 ppb (AOT40) value from April to September of around 20,000 ppb·h. An AOT40 of above 67,000 ppb·h induced reductions in ribulose-1, 5-biphosphate carboxylase/oxygenase activity, aboveground C and needle N and K concentrations, the C/N ratio, Ca concentrations in twigs under 3 mm, and the aerial biomass, as well as increases in needle P concentrations and phosphoenolpyruvate carboxylase (PEPC) activity and the N and K concentrations in twigs under 3 mm. Macronutrients losses, the limitations placed on carbon uptake, and increases in catabolic processes may be the causes of carbon gain diminution in leaves which was reflected as a reduction in aboveground biomass at tree level. Stimulation of PEPC activity, the consequent decreased Δ, and compensation processes in nutrient distribution may increase O3 tolerance and might be interpreted as part of Aleppo pine acclimation response to O3 .This research was funded by the EU EV5V-CT93-0263 project. We are also grateful for the partial funding from Spanish Government projects CGL2006-02922/ CLI, CGL2009-07031/CLI, CGL2006-04025/BOS and Consolider Montes (CSD2008-00040) and Catalan Government project SGR 2009-458.Peer reviewe