Soil Respiration in European Grasslands in Relation to Climate and Assimilate Supply (original) (raw)
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Soil respiration of terrestrial ecosystems, a major component in the global carbon cycle is affected by elevated atmospheric CO2 concentrations. However, seasonal differences of feedback effects of elevated CO2 have rarely been studied. At the Gießen Free-Air CO2 Enrichment (GiFACE) site, the effects of +20% above ambient CO2 concentration have been investigated since 1998 in a temperate grassland ecosystem. We defined five distinct annual seasons, with respect to management practices and phenological cycles. For a period of 3 years (2008–2010), weekly measurements of soil respiration were carried out with a survey chamber on vegetation-free subplots. The results revealed a pronounced and repeated increase of soil respiration under elevated CO2 during late autumn and winter dormancy. Increased CO2 losses during the autumn season (September–October) were 15.7% higher and during the winter season (November–March) were 17.4% higher compared to respiration from ambient CO2 plots. However, during spring time and summer, which are characterized by strong above- and below-ground plant growth, no significant change in soil respiration was observed at the GiFACE site under elevated CO2. This suggests (1) that soil respiration measurements, carried out only during the growing season under elevated CO2 may underestimate the true soil-respiratory CO2 loss (i.e. overestimate the C sequestered), and (2) that additional C assimilated by plants during the growing season and transferred below-ground will quickly be lost via enhanced heterotrophic respiration outside the main growing season.
Soil Carbon Dioxide Emission: Soil Respiration Measurement in Temperate Grassland, Nepal
Journal of Environmental Protection, 2019
Soil carbon dioxide emission: soil respiration is representing a major contributor of accumulating carbon dioxide in the atmosphere that aids to accelerate global warming and altering the climate. Soil temperature, soil water content, sun light and vegetation are considered most common regulators of soil respiration variations in ecosystem. The soil respiration was measured in grassland intended to examine how the soil respiration changed with varying climatic factors, for two years (2015 and 2016) in temperate grassland of Annapurna Conservation Area (ACA), Nepal. In the study, soil temperature accounted exponential function of soil respiration variation at 42.9%, 19.1% and 23.3%, and temperature sensitivity of the soil respiration (Q 10) was obtained at 6.2, 1.4 and 1.8 in October 2015 and April 2016 and both the measurements were combined, respectively. Significant negative (R 2 = 0.50, p < 0.05, October 2015) and positive (R 2 = 0.084, p < 0.05, April 2016) exponential function of soil respiration and soil water content were determined, where high soil respiration values were always measured between 30% and 35% of the soil water content. However, linear significant relationship was determined (R 2 = 0.376, p < 0.05) between soil respiration and photosynthetic photon flux density (PPFD). Soil respiration value averaged in October 2015 was 357 mg CO 2 m −2 h −1 and in April 2016 it was 444.6 mg CO 2 m −2 h −1. Above-and below-ground plant biomasses were obtained at 231.1 g d w m −2 and 1538.8 g d w m −2 in October, and at 449.9 g d w m −2 and 349.0 g d w m −2 in April, respectively. This study showed variation of soil respiration in relation to the factors such as soil temperature, soil water content and photosynthetic photon flux density signifying their importance in governing ecosystem function and carbon balance of the temperate grassland ecosystem.
Soil respiration at forest sites in Saxony (Central Europe)
Environmental Earth Sciences, 2015
Soil respiration is the second largest CO 2-exchange process between terrestrial ecosystems and the atmosphere. Yet, high-quality experimental data are still in demand. During the vegetation period of 2013 we measured soil and ecosystem respiration with a closed dynamic flux chamber at six Saxon ICP-Forests Level II monitoring sites, representative for Central Europe. Each site comprises a closed canopy (UC) and an open field (OF) plot. Apart from CO 2 fluxes, meteorological parameters were recorded, assuring that the chosen measurement period was representative for longer time frames. Additional soil samples delivered current chemical conditions. Carbon dioxide fluxes at the open field plots were 30-250 % higher than under canopy-due to different plant cover. Under canopy, 2.7-5.8 lmol CO 2 m-2 s-1 were determined (median 3.5 lmol CO 2 m-2 s-1), while the open field showed a range of 3.2-15.5 lmol CO 2 m-2 s-1 (median 7.6 lmol CO 2 m-2 s-1). The key drivers for soil metabolism, soil temperature, humidity and nutrient budget, showed distinct plot and site differences. Surmising that the determined fluxes are representative for Saxony and its temperate forests, and calculating with winter half year data from the literature, it can be deduced that 3.85 Mt C of carbon would be released annually from Saxon forest soils. Keywords CO 2-degassing Á CO 2-emissions Á Closed dynamic flux chamber Á Vegetation period Á Saxony Á Level-II sites Á Soil samples Á European forests Á Temperate forests Á LULUCF
Agriculture
Reduction of soil greenhouse gas emissions is crucial to control increases in atmospheric CO2 concentrations. Permanent grasslands are of considerable importance in climate change mitigation strategies as they cover about 13% of the global agricultural area. However, uncertainties remain for the effects of management practices on soil respiration, especially over the short term. This study investigated the influence of different mowing intensities on soil respiration over the short term for Bromus erectus-dominated grasslands in the central Apennines. From 2016 to 2018, soil respiration, temperature, and moisture were measured under three different management systems: customary management, intensive use, and abandonment. Both soil water content and temperature changed over time, however mowing did not affect soil water content while occasionally altered soil temperature. The intensive use promoted higher seasonal mean soil respiration compared to the abandonment only during the 2016...
Global Change Biology, 2007
Responses of soil respiration to atmospheric and climatic change will have profound impacts on ecosystem and global carbon (C) cycling in the future. This study was conducted to examine effects on soil respiration of the concurrent driving factors of elevated atmospheric CO 2 concentration, air warming, and changing precipitation in a constructed old-field grassland in eastern Tennessee, USA. Model ecosystems of seven oldfield species were established in open-top chambers and treated with factorial combinations of ambient or elevated (1300 ppm) CO 2 concentration, ambient or elevated (13 1C) air temperature, and high or low soil moisture content. During the 19-month experimental period from June 2003 to December 2004, higher CO 2 concentration and soil water availability significantly increased mean soil respiration by 35.8% and 15.7%, respectively. The effects of air warming on soil respiration varied seasonally from small reductions to significant increases to no response, and there was no significant main effect. In the wet side of elevated CO 2 chambers, air warming consistently caused increases in soil respiration, whereas in the other three combinations of CO 2 and water treatments, warming tended to decrease soil respiration over the growing season but increase it over the winter. There were no interactive effects on soil respiration among any two or three treatment factors irrespective of time period. Treatment-induced changes in soil temperature and moisture together explained 49%, 44%, and 56% of the seasonal variations of soil respiration responses to elevated CO 2 , air warming, and changing precipitation, respectively. Additional indirect effects of seasonal dynamics and responses of plant growth on C substrate supply were indicated. Given the importance of indirect effects of the forcing factors and plant community dynamics on soil temperature, moisture, and C substrate, soil respiration response to climatic warming should not be represented in models as a simple temperature response function, and a more mechanistic representation including vegetation dynamics and substrate supply is needed.
European Journal of Soil Science, 2007
The fate of carbon (C) in grassland soils is of particular interest since the vast majority in grassland ecosystems is stored below ground and respiratory C-release from soils is a major component of the global C balance. The use of 13 C-depleted CO 2 in a 10-year free-air carbon dioxide enrichment (FACE) experiment, gave a unique opportunity to study the turnover of the C sequestered during this experiment. Soil organic matter (SOM), soil air and plant material were analysed for d 13 C and C contents in the last year of the FACE experiment and in the two following growing seasons. After 10 years of exposure to CO 2 enrichment at 600 ppmv, no significant differences in SOM C content could be detected between fumigated and non-fumigated plots. A 13 C depletion of 3.4& was found in SOM (0-12 cm) of the fumigated soils in comparison with the control soils and a rapid decrease of this difference was observed after the end of fumigation. Within 2 years, 49% of the C in this SOM (0-12 cm) was exchanged with fresh C, with the limitation that this exchange cannot be further dissected into respiratory decay of old C and freshly sequestered new C. By analysing the mechanistic effects of a drought on the plant-soil system it was shown that rhizosphere respiration is the dominant factor in soil respiration. Consideration of ecophysiological factors that drive plant activity is therefore important when soil respiration is to be investigated or modelled.
Carbon cycling and sequestration opportunities in temperate grasslands
2004
Temperate grasslands account for c. 20% of the land area in Europe. Carbon accumulation in grassland ecosystems occurs mostly below ground and changes in soil organic carbon stocks may result from land use changes (e.g. conversion of arable land to grassland) and grassland management. Grasslands also contribute to the biosphere±atmosphere exchange of non-CO 2 radiatively active trace gases, with¯uxes intimately linked to management practices. In this article, we discuss the current knowledge on carbon cycling and carbon sequestration opportunities in temperate grasslands. First, from a simple two-parameter exponential model ®tted to literature data, we assess soil organic carbon¯uxes resulting from land use change (e.g. between arable and grassland) and from grassland management. Second, we discuss carbon¯uxes within the context of farming systems, including crop±grass rotations and farm manure applications. Third, using a grassland ecosystem model (PaSim), we provide estimates of the greenhouse gas balance, in CO 2 equivalents, of pastures for a range of stocking rates and of N fertilizer applications. Finally, we consider carbon sequestration opportunities for France resulting from the restoration of grasslands and from the de-intensi®cation of intensive livestock breeding systems. We emphasize major uncertainties concerning the magnitude and non-linearity of soil carbon stock changes in agricultural grasslands as well as the emissions of N 2 O from soil and of CH 4 from grazing livestock.
Antecedent Conditions Influence Soil Respiration Differences in Shrub and Grass Patches
Quantifying the response of soil respiration to past environmental conditions is critical for predicting how future climate and vegetation change will impact ecosystem carbon balance. Increased shrub dominance in semiarid grasslands has potentially large effects on soil carbon cycling. The goal of this study was to characterize the effect of antecedent moisture and temperature conditions on soil respiration in a grassland now dominated by shrubs. Continuous measurements of soil respiration, soil temperature, and soil moisture were made over the