Modelling of carbon flux in grassland ecosystems in Ukraine (original) (raw)
Related papers
Soil Respiration in European Grasslands in Relation to Climate and Assimilate Supply
Ecosystems, 2008
Soil respiration constitutes the second largest flux of carbon (C) between terrestrial ecosystems and the atmosphere. This study provides a synthesis of soil respiration (R s ) in 20 European grasslands across a climatic transect, including ten meadows, eight pastures and two unmanaged grasslands. Maximum rates of R s (R s max ), R s at a reference soil temperature (10°C; R s 10 ) and annual R s (estimated for 13 sites) ranged from 1.9 to 15.9 lmol CO 2 m -2 s -1 , 0.3 to 5.5 lmol CO 2 m -2 s -1 and 58 to 1988 g C m -2 y -1 , respectively. Values obtained for Central European mountain meadows are amongst the highest so far reported for any type of ecosystem. Across all sites R s max was closely related to R s 10 .
Agricultural and Forest Meteorology, 2012
In savannah and tropical grasslands, which account for 60% of grasslands worldwide, a large share of ecosystem carbon is located below ground due to high root:shoot ratios. Temporal variations in soil CO 2 efflux (R S ) were investigated in a grassland of coastal Congo over two years. The objectives were (1) to identify the main factors controlling seasonal variations in R S and (2) to develop a semi-empirical model describing R S and including a heterotrophic component (R H ) and an autotrophic component (R A ). Plant above-ground activity was found to exert strong control over soil respiration since 71% of seasonal R S variability was explained by the quantity of photosynthetically active radiation absorbed (APAR) by the grass canopy. We tested an additive model including a parameter enabling R S partitioning into R A and R H . Assumptions underlying this model were that R A mainly depended on the amount of photosynthates allocated below ground and that microbial and root activity was mostly controlled by soil temperature and soil moisture. The model provided a reasonably good prediction of seasonal variations in R S (R 2 = 0.85) which varied between 5.4 mol m −2 s −1 in the wet season and 0.9 mol m −2 s −1 at the end of the dry season. The model was subsequently used to obtain annual estimates of R S , R A and R H . In accordance with results reported for other tropical grasslands, we estimated that R H accounted for 44% of R S , which represented a flux similar to the amount of carbon brought annually to the soil from below-ground litter production. Overall, this study opens up prospects for simulating the carbon budget of tropical grasslands on a large scale using remotely sensed data.
Global Biogeochemical Cycles, 1993
Century is a model of terrestrial biogeochemistry based on relationships between climate, human management (fire, grazing), soil properties, plant productivity, and decomposition. The grassland version of the Century model was tested using observed data from 11 temperate and tropical grasslands around the world. The results show that soil C and N levels can be simulated to within + 25% of the observed values (100 and 75% of the time, respectively) for a diverse set of soils. Peak live biomass and plant production can be simulated within + 25% of the observed values (57 and 60% of the time, respectively) for burned, fertilized, and irrigated grassland sites where precipitation ranged from 22 to over 150 cm. Live biomass can be generally predicted to within + 50% of the observed values (57% of the time). The model underestimated the live biomass in extremely high plant production years at two of the Russian sites. A comparison of Century model results with statistical models showed that the Century model had slightly higher r • values than the statistical models. Data and calibrated model results from this study are useful for analysis and description of grassland carbon dynamics, and as a reference point for testing more physiologically based models prediction's of net primary production and biomass. Results indicate that prediction of plant and soil organic matter (C and N) dynamics requires knowledge of climate, soil texture, and N inputs. 786 may follow in the form of changes in nutrient availability and the rate of cycling of carbon and nitrogen between the biosphere, atmosphere, and geosphere. The carbon in terrestrial vegetation and soils worldwide outweighs the amount found in the atmosphere and the ocean surface layers. The role of grasslands in global biogeochemical cycles should not be overlooked, especially when the contribution of worldwide grassland burning is considered [Hao et al., 1990; Hall and Scurlock, 1991]. Tropical grasslands occupy 15 million km,., and in terms of both land area and productivity are nearly equal to tropical forests. Together with 9 million kin,. of temperate grasslands, they cover nearly one fifth of the Earth's land surface and are likely to remain constant in area for the near future [Lieth, 1972; Hall and Scurlock, 1991]. Carbon stored in grassland soils, temperate and tropical, has been estimated at 30% of the world total of soil carbon lAnderson, 1991 ]. . The grassland sites used in this study range from temperate grasslands in the United States and Russia and natural and converted grasslands in wet and dry regions of the tropics.
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.
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.
Partitioning of soil CO2 flux components in a temperate grassland ecosystem
European Journal of Soil Science, 2012
We deployed an automated multiplexed soil-respiration (SR) system to monitor partitioned soil CO 2 component fluxes (from roots, mycorrhizal hyphae and heterotrophs) in a UK grassland using a combination of shallow surface (total SR flux), deep (excluding roots and mycorrhizal fungi) and 20-μm pore mesh window soil collars (excluding roots only). Soil CO 2 efflux was monitored during a 3-month period during summer. Repeated cutting of mycorrhizal connections in some of the mycorrhizal treatments enabled assessment of subsequent recovery of mycorrhizal fluxes and a comparison with deep collar fluxes. After soil collar insertion, fluxes in the deep collars were significantly reduced, by approximately 40%. Whereas fluxes in the uncut, mycorrhizal collar treatments remained close to those from the surface collar, cut mycorrhizal treatments showed an immediate reduction after cutting to values close to those from the deep collar with a subsequent recovery of around 4 weeks. Overall, the autotrophic root and mycorrhizal flux was relatively stable throughout. Whereas root fluxes contributed about 10-30% of the total flux during the initial larger flux period, this declined and there was an increased mycorrhizal contribution during the latter part of the measurement period. Moreover, SR flux components differed in their response to key climatic factors, with root fluxes responding equally to temperature and light. Importantly, whereas the heterotrophic flux component responded strongly to temperature and soil moisture, the mycorrhizal component responded much less to those factors, but more to light. We also investigated treatment impacts over time on soil biochemical variables such as microbial biomass C, extractable C, microbial quotient and metabolic quotient, and bacterial community structure, and discussed these in relation to measured SR fluxes and the partitioning technique.
The Science of the total environment, 2017
The North Wyke Farm Platform (NWFP) generates large volumes of temporally-indexed data that provides a valuable test-bed for agricultural mathematical models in temperate grasslands. In our study, we used the primary datasets generated from the NWFP (https://nwfp.rothamsted.ac.uk/) to validate the SPACSYS model in terms of the dynamics of water loss and forage dry matter yield estimated through cutting. The SPACSYS model is capable of simulating soil water, carbon (C) and nitrogen (N) balance in the soil-plant-atmosphere system. The validated model was then used to simulate the responses of soil water, C and N to reseeding grass cultivars with either high sugar (Lolium perenne L. cv. AberMagic) or deep rooting (Festulolium cv. Prior) traits. Simulation results demonstrated that the SPACSYS model could predict reliably soil water, C and N cycling in reseeded grassland. Compared to AberMagic, the Prior grass could fix more C in the second year following reseeding, whereas less C was l...
Geoderma, 2020
Long-term changes in soil organic carbon (SOC) are difficult to quantify experimentally because of measurement errors and high spatial and temporal variability. Modelling can help to provide a more robust assessment by reducing these uncertainties and reproducing greenhouse gas (GHG) and C exchange processes in an ecosystem by identifying key drivers. In this study, the Denitrification-Decomposition (DNDC95) model was used to evaluate SOC density (SOCρ) and its annual changes (ΔSOCρ) in temperate grassland soils, which received different forms of nitrogen (N) (i.e. inorganic and organic) and at different application rates for 45 years. We found that simulated values for SOCρ (0-15 cm depth) in unfertilized (54 t C ha −1) and fertilized soils (55 t C ha −1) were lower than measured values (73 and 77 t C ha −1 , respectively). Despite some variations, measured and simulated SOCρ was higher under cattle (88-99 vs. 66-116 t C ha −1) than pig slurry (75-78 vs. 55-69) applications, and increased with increasing rates of added C. Irrespective of nutrient treatment, overall mean sequestration rates were 0.46 ± 0.06 (observed) and 0.37 ± 0.01 (simulated) t C ha −1 yr −1. Simulated values explained 66% of the variability between years and treatments (slope: 1.41; intercept: −34.58 t C ha −1) with reasonably good prediction efficiency The variations in simulated values could be explained by differences in applied N (63%), which were linked to differences in C (62%), rainfall (15%) and air temperature (11%). The model (R 2 0.77-0.99/-0.99; p < 0.05-< 0.0001) was sensitive to soil variables, and SOCρ increased with increasing clay fraction, bulk density and inherent SOC concentration. Finally, simulated (and measured) values suggest that a new SOC equilibrium was not reached even after 45 years of intensive management. The study demonstrated how DNDC provides reasonably accurate representation of how organic N applications, as well as key soil and climatic variables may affect SOC density changes over time.