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To investigate the temporal dynamics of CO2 efflux from the soil surface in a temperate cropland and to quantify the effects of soil temperature, soil water content, N fertilization and plant growth on soil carbon dioxide efflux (Rs) field and lab experiments were performed. The field experiment was conducted in a cropland site with a conventional farming system in Central Hungary. The temporal changes of Rs were estimated using a closed chamber IRGA system about bi-weekly/monthly between November 2017–November 2019 in 10 positions. The measured average soil CO2 efflux values ranged from 0.06 ± 0.007 to 7.04 ± 0.44 µmol CO2 m–2 s–1 Soil respiration model including soil temperature (Ts), soil water content (SWC) and the incorporation of VIgreen (plant growth and functioning) gave a higher goodness-of-fit value (r2 = 0.54) than the simple temperature response. According to our field results, different variables including Ts, SWC and VIgreen play a principal role in the carbon cycle of the investigated cropland. We further investigated the effects of the main drivers in a laboratory experiment with the same soil. Closed chamber technique was used for measuring the emission of carbon dioxide by a Picarro G1101-i gas analyzer. We also introduced a fertilization experiment: three different N treatments were applied (N0, N75 and N150) with different levels of soil water content on the soil planted with maize and bare soil. According to our laboratory results, the cumulative CO2 efflux from soil was found to have a positive correlation with plant growth and with N fertilizer rate: as higher plant biomass and more N added, more CO2 was emitted, whereas, the cumulative emissions values from planted soil were around two times higher than in bare soil in all treatments. Significant positive correlations were found between CO2 efflux and SWC indicating that the soil water content was the main factor limiting the rate of the CO2 emission from soil in both planted and bare soil, in which the cumulative CO2 efflux was increased with the increase in soil water content, and it was almost three times higher in planted soils at higher soil moisture level than in the bare soil. We can conclude that the effects of plant presence and soil moisture on soil respiration had similar magnitude; however, the effect of N addition was small. [ABSTRACT FROM AUTHOR]

Different management practices may change the rate of soil respiration, thus affecting the carbon balance of grasslands. Therefore, we investigated the effect of grazing and mowing on soil respiration along with its driving variables (soil water content, soil temperature, above and below ground biomass, vegetation indices and soil carbon) in adjacent treatments (grazed and mowed) at a semi-arid grassland in Hungary (2011-2013). The average soil respiration over three years was higher in the mown (6.03 ± 4.07 µmol CO m s) than in the grazed treatment (5.29 ± 3.50 µmol CO m s). While soil water content and soil temperature did not differ between treatments, mowing resulted in 20 % higher soil respiration than grazing, possibly due to 17 % higher average above ground biomass in the mowed than in the grazed treatment. Inclusions of vegetation index VIGreen in the soil respiration model in addition to abiotic drivers improved the explained Rs variance by 16 % in the mowed and by 5 % in the grazed site, respectively. VIGreen alone proved to be a simple and fast indicator of soil respiration (r = 0.31 at grazed, r = 0.44 at mowed site). We conclude that soil respiration is responsive to the combined effect soil water content, soil temperature, biomass and soil carbon content as affected by the management (grazing vs. mowing) practice. [ABSTRACT FROM AUTHOR]

Aims: Our aim was to study the effect of potential biotic drivers, including evapotranspiration (ET) and gross primary production (GPP), on the soil CO production and efflux on the diel time scale. Methods: Eddy covariance, soil respiration and soil CO gradient systems were used to measure the CO and HO fluxes in a dry, sandy grassland in Hungary. The contribution of CO production from three soil layers to plot-scale soil respiration was quantified. CO production and efflux residuals after subtracting the effects of the main abiotic and biotic drivers were analysed. Results: Soil CO production showed a strong negative correlation with ET rates with a time lag of 0.5 h in the two upper layers, whereas less strong, but still significant time-lagged and positive correlations were found between GPP and soil CO production. Our results suggest a rapid negative response of soil CO production rates to transpiration changes, and a delayed positive response to GPP. Conclusions: We found evidence for a combined effect of soil temperature and transpiration that influenced the diel changes in soil CO production. A possible explanation for this pattern could be that a significant part of CO produced in the soil may be transported across soil layers via the xylem. [ABSTRACT FROM AUTHOR]

Soil respiration of grasslands is spatio-temporally variable reflecting the changing biological activities of the soil. In our study we analysed how the long-term soil respiration activities of dry grasslands would perform in terms of resistance and resilience. We also investigated how terrain features are responsible for response stability. We conducted a 7-year-long spatial study in a Hungarian dry grassland, measuring soil respiration (Rs), soil temperature (Ts) and soil water content (SWC) along 15 measuring campaigns in 80 × 60 m grids and soil organic carbon content in 6 of the occasions. Two proxy variables were introduced to grasp the overall Rs activity, as well as its temporal stability: average rankRs, the temporal average Rs rank of a measuring position from the campaigns revealed the persistent spatial pattern of Rs, while rangeRs, the range of ranks of the positions from the campaigns described the amplitude of the Rs response in time, referring to the response stability in terms of resistance or resilience. We formulated a hypothetic concept of a two-state equilibrium to describe the performance of the long-term Rs activity: Rs activity with smaller rangeRs, that is both the lower elevation positions with larger rankRs ("state I") and the higher elevation positions with smaller rankRs ("state II") correspond to an equilibrium state with several terrain attributes being responsible for the equilibrium responses. Majority of the measuring positions was belonging to none of these equilibrium states. These positions showed higher rangeRs for medium rankRs, suggesting resilience (not resistance) as a major strategy for this ecosystem. [ABSTRACT FROM AUTHOR]

Aims: Soil respiration (Rs) is a complex process including a wide range of soil biota and pathways of carbon cycling, all being under the control of various drivers. The most important biotic driver is the photosynthetic activity of the vegetation providing supply mainly for the autotrophic component of Rs: roots and their symbiotic partners. The objective of this study was to describe the time-lagged relationship between gross primary production (GPP) and the mycorrhizal Rs component in order to determine the amount of carbon derived from GPP appearing as mycorrhizal respiration (Rmyc).Measurements of Rs were conducted in three treatments - (i) undisturbed, root and arbuscular mycorrhizal fungi (AMF)-included (Rs), (ii) root-excluded (Rhet+myc) and (iii) root- and AMF-excluded (Rhet) plots - for three consecutive years in a Central-Hungarian dry sandy grassland. GPP data were derived from eddy-covariance measurements, while an automated system was used for continuous measurements of Rs. We analysed the relationship between Rmyc and GPP by using cross-correlation and by fitting sine wave models on the diel datasets.GPP was found to be the main driver of Rmyc, responding with an average time lag of 18 h. The greatest lags were detected during periods characterized by minimal photosynthetic activity, while lags were the smallest during active periods.Based on the seasonal changes in the delay, we concluded that GPP and soil temperature had simultaneous effects on the diel pattern of CO2 emission of the different autotrophic components depending on the vegetation activity and environmental conditions.Methods: Soil respiration (Rs) is a complex process including a wide range of soil biota and pathways of carbon cycling, all being under the control of various drivers. The most important biotic driver is the photosynthetic activity of the vegetation providing supply mainly for the autotrophic component of Rs: roots and their symbiotic partners. The objective of this study was to describe the time-lagged relationship between gross primary production (GPP) and the mycorrhizal Rs component in order to determine the amount of carbon derived from GPP appearing as mycorrhizal respiration (Rmyc).Measurements of Rs were conducted in three treatments - (i) undisturbed, root and arbuscular mycorrhizal fungi (AMF)-included (Rs), (ii) root-excluded (Rhet+myc) and (iii) root- and AMF-excluded (Rhet) plots - for three consecutive years in a Central-Hungarian dry sandy grassland. GPP data were derived from eddy-covariance measurements, while an automated system was used for continuous measurements of Rs. We analysed the relationship between Rmyc and GPP by using cross-correlation and by fitting sine wave models on the diel datasets.GPP was found to be the main driver of Rmyc, responding with an average time lag of 18 h. The greatest lags were detected during periods characterized by minimal photosynthetic activity, while lags were the smallest during active periods.Based on the seasonal changes in the delay, we concluded that GPP and soil temperature had simultaneous effects on the diel pattern of CO2 emission of the different autotrophic components depending on the vegetation activity and environmental conditions.Results: Soil respiration (Rs) is a complex process including a wide range of soil biota and pathways of carbon cycling, all being under the control of various drivers. The most important biotic driver is the photosynthetic activity of the vegetation providing supply mainly for the autotrophic component of Rs: roots and their symbiotic partners. The objective of this study was to describe the time-lagged relationship between gross primary production (GPP) and the mycorrhizal Rs component in order to determine the amount of carbon derived from GPP appearing as mycorrhizal respiration (Rmyc).Measurements of Rs were conducted in three treatments - (i) undisturbed, root and arbuscular mycorrhizal fungi (AMF)-included (Rs), (ii) root-excluded (Rhet+myc) and (iii) root- and AMF-excluded (Rhet) plots - for three consecutive years in a Central-Hungarian dry sandy grassland. GPP data were derived from eddy-covariance measurements, while an automated system was used for continuous measurements of Rs. We analysed the relationship between Rmyc and GPP by using cross-correlation and by fitting sine wave models on the diel datasets.GPP was found to be the main driver of Rmyc, responding with an average time lag of 18 h. The greatest lags were detected during periods characterized by minimal photosynthetic activity, while lags were the smallest during active periods.Based on the seasonal changes in the delay, we concluded that GPP and soil temperature had simultaneous effects on the diel pattern of CO2 emission of the different autotrophic components depending on the vegetation activity and environmental conditions.Conclusion: Soil respiration (Rs) is a complex process including a wide range of soil biota and pathways of carbon cycling, all being under the control of various drivers. The most important biotic driver is the photosynthetic activity of the vegetation providing supply mainly for the autotrophic component of Rs: roots and their symbiotic partners. The objective of this study was to describe the time-lagged relationship between gross primary production (GPP) and the mycorrhizal Rs component in order to determine the amount of carbon derived from GPP appearing as mycorrhizal respiration (Rmyc).Measurements of Rs were conducted in three treatments - (i) undisturbed, root and arbuscular mycorrhizal fungi (AMF)-included (Rs), (ii) root-excluded (Rhet+myc) and (iii) root- and AMF-excluded (Rhet) plots - for three consecutive years in a Central-Hungarian dry sandy grassland. GPP data were derived from eddy-covariance measurements, while an automated system was used for continuous measurements of Rs. We analysed the relationship between Rmyc and GPP by using cross-correlation and by fitting sine wave models on the diel datasets.GPP was found to be the main driver of Rmyc, responding with an average time lag of 18 h. The greatest lags were detected during periods characterized by minimal photosynthetic activity, while lags were the smallest during active periods.Based on the seasonal changes in the delay, we concluded that GPP and soil temperature had simultaneous effects on the diel pattern of CO2 emission of the different autotrophic components depending on the vegetation activity and environmental conditions. [ABSTRACT FROM AUTHOR]