Dynamics of soil organic carbon in the steppes of Russia and Kazakhstan under past and future climate and land use

Changes in land use and climate are the main drivers of change in soil organic matter contents. We investigated the impact of the largest policy-induced land conversion to arable land, the Virgin Lands Campaign (VLC), from 1954 to 1963, of the massive cropland abandonment after 1990 and of climate change on soil organic carbon (SOC) stocks in steppes of Russia and Kazakhstan. We simulated carbon budgets from the pre-VLC period (1900) until 2100 using a dynamic vegetation model to assess the impacts of observed land-use change as well as future climate and land-use change scenarios. The simulations suggest for the entire VLC region (266 million hectares) that the historic cropland expansion resulted in emissions of 1.6⋅ 1015 g (= 1.6 Pg) carbon between 1950 and 1965 compared to 0.6 Pg in a scenario without the expansion. From 1990 to 2100, climate change alone is projected to cause emissions of about 1.8 (± 1.1) Pg carbon. Hypothetical recultivation of the cropland that has been abandoned after the fall of the Soviet Union until 2050 may cause emissions of 3.5 (± 0.9) Pg carbon until 2100, whereas the abandonment of all cropland until 2050 would lead to sequestration of 1.8 (± 1.2) Pg carbon. For the climate scenarios based on SRES (Special Report on Emission Scenarios) emission pathways, SOC declined only moderately for constant land use but substantially with further cropland expansion. The variation of SOC in response to the climate scenarios was smaller than that in response to the land-use scenarios. This suggests that the effects of land-use change on SOC dynamics may become as relevant as those of future climate change in the Eurasian steppes

Large greenhouse gas savings due to changes in the post-Soviet food systems

As the global food system contributes significantly to global greenhouse gas (GHG) emissions, understanding the sources of GHG emissions embodied in different components of food systems is important. The collapse of the Soviet Union triggered a massive restructuring of the domestic food systems, namely declining consumption of animal products, cropland abandonment, and a major restructuring of agricultural trade. However, how these complex changes have affected global GHG emissions is uncertain. Here, we quantified the net GHG emissions associated with changes in the former Soviet Union's food systems. Changes in food production, consumption, and trade together resulted in a net emissions reduction of 7.61 Gt carbon dioxide equivalents from 1992 to 2011. For comparison, this corresponds to one quarter of the CO2 emissions from deforestation in Latin America from 1991 to 2011. The key drivers of the emissions reductions were the decreasing beef consumption in the 1990s, increasing beef imports after 2000, mainly from South America, and carbon sequestration in soils on abandoned cropland. Ongoing transformations of the food systems in the former Soviet Union, however, suggest emissions will likely rebound. The results highlight the importance of considering agricultural production, land-use change, trade, and consumption when assessing countries emissions portfolios. Moreover, we demonstrated how emissions reductions that originate from a reduction in the extent and intensity of agricultural production can be compromised by increasing emissions embodied in rising imports of agricultural commodities.Volkswagen Foundation (BALTRAK)the German Federal Ministry of Food and Agriculture (BMEL) (GERUKA)The Swedish Research Council FormasThe Russian Foundation for Basic ResearchRussian Government Program of Competitive Growth of Kazan Federal UniversityEuropean Research Council (ERC)Peer Reviewe

Chronosequenzielle Entwicklung postagrarischer Luvisole der Laubwaldzone Russlands: Vegetation, Bodenentwicklung, C-Sequestrierung, C-Pools.

Postagrarische Veränderungen der Vegetation, Böden, C-Sequestrierung und C-Pools wurden anhand von drei Luvisol-Chronosequenzen entlang des Nord – Mitte – Süden Gradienten der Laubwaldregion Russlands untersucht. Böden und Vegetation entwickelten sich nach der Auflassung in Richtung natürlicher Ausprägung: Luvisol unter Eichenwald mit Krautschicht. Dabei bekam der ehemaligen Ap-Horizont eine neue morphologische und chemische Stratifizierung ähnlich wie in natürlichen Luvisolen. Der Ap-Horizont war nach 120 Jahren durch Farbe, Gefüge und Lagerungsdichte noch erkennbar. C-Vorräte stiegen im Oberboden (5 cm) von 0.8 bis 1.7 kg m-2 (Norden), von 1.3 bis 1.9 kg m-2 (Mitte) und von 1.4 bis 2.3 kg m-2 (Süden). Die C-Akkumulation wurde mit zunehmender Bodentiefe geringer. Die Zunahme des Gesamt-C verlief in signifikant positiver Korrelation mit der C-Akkumulation in aktiven (freie partikuläre organisches Material (POM); POM in Aggregaten) und passiven (C in Tonfraktion) C-Pools (g kg-1). Durch den Einbau des neuen C nahm das 14C-Alter des C in der Tonfraktion und in Aggregaten ab. Das deutet darauf hin, dass beide C-Pools (aktiv und passiv) auf die Umnutzung sensitiv reagieren

Influence of freeze-thaw events on carbon dioxide emission from soils at different moisture and land use

BACKGROUND: The repeated freeze-thaw events during cold season, freezing of soils in autumn and thawing in spring are typical for the tundra, boreal, and temperate soils. The thawing of soils during winter-summer transitions induces the release of decomposable organic carbon and acceleration of soil respiration. The winter-spring fluxes of CO(2 )from permanently and seasonally frozen soils are essential part of annual carbon budget varying from 5 to 50%. The mechanisms of the freeze-thaw activation are not absolutely clear and need clarifying. We investigated the effect of repeated freezing-thawing events on CO(2 )emission from intact arable and forest soils (Luvisols, loamy silt; Central Germany) at different moisture (65% and 100% of WHC). RESULTS: Due to the measurement of the CO(2 )flux in two hours intervals, the dynamics of CO(2 )emission during freezing-thawing events was described in a detailed way. At +10°C (initial level) in soils investigated, carbon dioxide emission varied between 7.4 to 43.8 mg C m(-2)h(-1 )depending on land use and moisture. CO(2 )flux from the totally frozen soil never reached zero and amounted to 5 to 20% of the initial level, indicating that microbial community was still active at -5°C. Significant burst of CO(2 )emission (1.2–1.7-fold increase depending on moisture and land use) was observed during thawing. There was close linear correlation between CO(2 )emission and soil temperature (R(2 )= 0.86–0.97, P < 0.001). CONCLUSION: Our investigations showed that soil moisture and land use governed the initial rate of soil respiration, duration of freezing and thawing of soil, pattern of CO(2 )dynamics and extra CO(2 )fluxes. As a rule, the emissions of CO(2 )induced by freezing-thawing were more significant in dry soils and during the first freezing-thawing cycle (FTC). The acceleration of CO(2 )emission was caused by different processes: the liberation of nutrients upon the soil freezing, biological activity occurring in unfrozen water films, and respiration of cold-adapted microflora

Inorganic carbon is overlooked in global soil carbon research: A bibliometric analysis

Soils are a major player in the global carbon (C) cycle and climate change by functioning as a sink or a source of atmospheric carbon dioxide (CO2). The largest terrestrial C reservoir in soils comprises two main pools: organic (SOC) and inorganic C (SIC), each having distinct fates and functions but with a large disparity in global research attention. This study quantified global soil C research trends and the proportional focus on SOC and SIC pools based on a bibliometric analysis and raise the importance of SIC pools fully underrepresented in research, applications, and modeling. Studies on soil C pools started in 1905 and has produced over 47,000 publications (>1.7 million citations). Although the global C stocks down to 2 m depth are nearly the same for SOC and SIC, the research has dominantly examined SOC (>96 % of publications and citations) with a minimal share on SIC (<4%). Approximately 40 % of the soil C research was related to climate change. Despite poor coverage and publications, the climate change-related research impact (citations per document) of SIC studies was higher than that of SOC. Mineral associated organic carbon, machine learning, soil health, and biochar were the recent top trend topics for SOC research (2020–2023), whereas digital soil mapping, soil properties, soil acidification, and calcite were recent top trend topics for SIC. SOC research was contributed by 151 countries compared to 88 for SIC. As assessed by publications, soil C research was mainly concentrated in a few countries, with only 9 countries accounting for 70 % of the research. China and the USA were the major producers (45 %), collaborators (37 %), and funders of soil C research. SIC is a long-lived soil C pool with a turnover rate (leaching and recrystallization) of more than 1000 years in natural ecosystems, but intensive agricultural practices have accelerated SIC losses, making SIC an important player in global C cycle and climate change. The lack of attention and investment towards SIC research could jeopardize the ongoing efforts to mitigate climate change impacts to meet the 1.5–2.0 °C targets under the Paris Climate Agreement of 2015. This bibliographic study calls to expand the research focus on SIC and including SIC fluxes in C budgets and models, without which the representation of the global C cycle is incomplete

Temperature Sensitivity of Soil Respiration in Two Temperate Forest Ecosystems: The Synthesis of a 24-Year Continuous Observation

Soil respiration (SR) is one of the largest fluxes in the global carbon cycle. The temperature sensitivity of SR (often termed as Q10) is a principal parameter for evaluating the feedback intensity between soil carbon efflux and global warming. The present study aimed to estimate the seasonal and interannual dynamics of the temperature sensitivity of SR based on a long-term 24-year series of measurements in two temperate forest ecosystems in European Russia. The study was conducted in a mature mixed forest with sandy Entic Podzol and in a secondary deciduous forest with loamy Haplic Luvisol. The SR rate was measured continuously from December 1997 to November 2021 at 7&ndash;10-day intervals using the closed chamber method. Sandy Entic Podzol demonstrated a higher temperature sensitivity of SR in comparison with loamy Entic Luvisol. The Q10 values for both soils in dry years were 1.3&ndash;1.4 times lower than they were in the years with normal levels of humidity. For both types of soil, we observed a significant positive correlation between the Q10 values and wetness indexes. The interannual variability of Q10 values for SR in forest soils was 18%&ndash;40% depending on the calculation approach and levels of aridity/humidity over the growing season. The heterogeneous Q10 values should be integrated into SR and C balance models for better predictions

Changes in soil carbon stock after cropland conversion to grassland in Russian temperate zone : measurements versus model simulation

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Coupled effect of temperature and mineral additions facilitates decay of aspen bark

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Dynamics of soil organic carbon in the steppes of Russia and Kazakhstan under past and future climate and land use

Changes in land use and climate are the main drivers of change in soil organic matter contents. We investigated the impact of the largest policy-induced land conversion to arable land, the Virgin Lands Campaign (VLC), from 1954 to 1963, of the massive cropland abandonment after 1990 and of climate change on soil organic carbon (SOC) stocks in steppes of Russia and Kazakhstan. We simulated carbon budgets from the pre-VLC period (1900) until 2100 using a dynamic vegetation model to assess the impacts of observed land-use change as well as future climate and land-use change scenarios. The simulations suggest for the entire VLC region (266 million hectares) that the historic cropland expansion resulted in emissions of 1.6⋅ 1015 g (= 1.6 Pg) carbon between 1950 and 1965 compared to 0.6 Pg in a scenario without the expansion. From 1990 to 2100, climate change alone is projected to cause emissions of about 1.8 (± 1.1) Pg carbon. Hypothetical recultivation of the cropland that has been abandoned after the fall of the Soviet Union until 2050 may cause emissions of 3.5 (± 0.9) Pg carbon until 2100, whereas the abandonment of all cropland until 2050 would lead to sequestration of 1.8 (± 1.2) Pg carbon. For the climate scenarios based on SRES (Special Report on Emission Scenarios) emission pathways, SOC declined only moderately for constant land use but substantially with further cropland expansion. The variation of SOC in response to the climate scenarios was smaller than that in response to the land-use scenarios. This suggests that the effects of land-use change on SOC dynamics may become as relevant as those of future climate change in the Eurasian steppes.BMBFBMBFERA.netdanish ERC programUral Branch, Russian Academy of Sciences https://doi.org/10.13039/501100006422BMBFPotsdam-Institut für Klimafolgenforschung (PIK) e.V. (3500