Organic Matter Carbon Research Articles

Mineral-associated organic matter is heterogeneous and structured by hydrophobic, charged, and polar interactions

The formation of mineral-associated organic matter (MAOM) is a key phenomenon that may explain the slow turnover rates of carbon in soil organic matter (SOM). Despite this, important details pertaining to the structure and dynamics of MAOM remain unknown. In the present study, we use replica-exchange molecular dynamics simulations to gain insight into the structure of MAOM on the surface of prototypical phyllosilicate clay and Fe-oxide minerals, montmorillonite and goethite, fine-grained minerals that strongly impact soil carbon dynamics in temperate and tropical regions, respectively. We examine the impact of aqueous chemistry through the presence of either Na[Formula: see text] or Ca[Formula: see text] charge balancing counterions. Our results are consistent with the hypothesized multilayer sorption ("onion-skin") model of MAOM and help to explain previous observations regarding the patchy distribution of SOM on mineral surfaces. In particular, the SOM coatings are partial and laterally heterogeneous, and water retains extensive access to mineral surfaces even when significant SOM sorption occurs. Low molecular weight neutral SOM molecules ([Formula: see text]200 Da) infrequently interact with the mineral surfaces nor their sorbed organic matter coatings and are increasingly labile with decreasing molecular weight. This observation is inconsistent with a central feature of the predominant soil continuum model of SOM and suggests that further iterations of the conceptual model may be required.

Temperature sensitivity of soil respiration declines with climate warming in subalpine and alpine grassland soils

AbstractWarming as a climate change phenomenon affects soil organic matter dynamics, especially in high elevation ecosystems. However, our understanding of the controls of soil organic matter mineralization and dynamics remains limited, particularly in alpine (above treeline) and subalpine (below treeline) grassland ecosystems. Here, we investigated how downslope (warming) and upslope (cooling) translocations, in a 5-years reciprocal transplanting experiment, affects soil respiration and its temperature sensitivity (Q10), soil aggregation, and soil organic matter carbon (C) and nitrogen (N) composition (C/N ratio). Downslope translocation of the alpine (2440 m a.s.l.) and subalpine (1850 m a.s.l.) to the lowland site (350 m a.s.l.) resulted in a temperature change during the growing seasons of + 4.4K and + 3.3K, respectively. Warming of alpine soils (+ 4.4K) reduced soil organic carbon (SOC) content by 32%, which was accompanied by a significant decrease of soil macroaggregates. Macroaggregate breakdown induced an increased respiration quotient (qCO2) by 27% following warming of alpine soils. The increase in qCO2 respiration was associated with a significant decrease (from 2.84 ± 0.05 to 2.46 ± 0.05) in Q10, and a change in soil organic matter composition (lower C/N ratios). Cooling did not show the opposite patterns to warming, implying that other mechanisms, such as plant and microbial community shifts and adaptation, were involved. This study highlights the important role of SOC degradability in regulating the temperature response of soil organic matter mineralization. To predict the adverse effect of warming on soil CO2 release and, consequently, its negative feedback on climate change, a comprehensive understanding of the mechanisms of C storage and turnover is needed, especially at high elevations in the Alps that are particularly affected by rising temperatures.

Spatiotemporal Evolution and Simulation Prediction of Ecosystem Carbon Storage in the Yellow River Basin Before and After the Grain for Green Project

Under the background of "dual carbon", the impact of the implementation of the Grain for Green project on the carbon storage of the ecosystem in the Yellow River Basin must be explored, which can serve as an important reference for improving the policy implementation of the new round of the Grain for Green project and improving the carbon sink capacity of the ecosystem in the Yellow River Basin. In this study, 1990, before the implementation of the project, was selected as the starting year of the research period, and 2020, after the implementation of the two rounds of the project, was selected as the end year of the research period. Based on the ecosystem type data from 1990 to 2020, the InVEST model was used to calculate the soil carbon pool, underground carbon pool, below carbon pool, dead organic matter carbon pool, and total carbon storage of ecosystems in the Yellow River Basin and the area where the project was implemented from 1990 to 2020. The results showed that： ① From 1990 to 2020, the area of forest ecosystem in the Yellow River Basin expanded by 26 610.06 km2, and the area of farmland decreased by 46 849.06 km2 after the implementation of two rounds of the project. Spatially, the upper reaches of the Yellow River were dominated by grassland and other ecosystems； the middle reaches of the Yellow River were dominated by farmland, forest, and grassland ecosystems； and the lower reaches of the Yellow River were dominated by farmland ecosystems. ② From 1990 to 2020, the carbon storage in the project implementation area showed a fluctuating and increasing trend, and the total carbon storage reached a peak （219.47×108 t） in 2009 and decreased to 218.59×108 t in 2020 due to the decrease of grassland ecosystem from 2010 to 2020. Spatially, the high-value areas of carbon storage were distributed in Aba Tibetan and Qiang Autonomous Prefecture of Sichuan Province and the southern tip of Gansu Province in the upper reaches of the forest and grass accumulation and in the whole of Shanxi Province and the central and southern parts of Shaanxi Province in the middle reaches. Shangluo City in Shaanxi Province and Alxa League in Inner Mongolia Autonomous Region were prefecture-level cities with the highest and lowest average carbon density. ③ In 2035, the carbon storage loss of the natural development scenario was predicted to be 0.83×108 t, and the other three scenarios would increase this loss. Under the moderate farmland return scenario, the Yellow River Basin ecosystem had the strongest carbon sequestration capacity, and the predicted carbon storage would increase by 2.72×108 t compared with that in 2020, and the deep farmland return scenario was the comprehensive optimal scenario. Therefore, in the future, the Yellow River Basin could refer to the deep farmland return scenario to optimize and adjust the implementation plan of the Grain for Green project, and the predicted value of carbon storage can provide some data support for achieving the dual carbon goal.

Hydrodynamics Mediates Biogeochemical Dynamics of Particulate Organic Matter in the Shelf of the Northern South China Sea During Summer

AbstractEnvironmental conditions, physiology and community composition of phytoplankton and the carbon and nitrogen isotope signature (δ13CPOC and δ15NPN) of particulate organic matter (POM) often covary across marine environments. However, little was known on the link of δ13CPOC and δ15NPN and the community and biochemical composition of phytoplankton. In this study, particulate organic carbon (POC) and nitrogen (PN), δ13CPOC, δ15NPN, phytoplankton community composition and biomass were determined during summer, along with environmental variables, in the shelf of the northern South China Sea influenced by the Pearl River plume, upwelling and anticyclonic eddy. Our results show that variability in δ13CPOC and δ15NPN along an environmental gradient is coupled with shifts in phytoplankton community composition and carbon to chlorophyll a (C:Chl a) ratio of phytoplankton. Low δ13CPOC values (−28.4 to −27.0‰) at nearshore stations (salinity <21) were primarily due to terrestrial POM input. High δ13CPOC (>−21.0‰) and δ15NPN (>5.6‰) values are most likely attributed to high abundance of diatoms induced by riverine nutrients in the plume‐impacted waters with intermediate salinity (21< salinity <33). Low δ13CPOC (<−22.0‰) and δ15NPN (−1.1–3.7‰) values are associated with high abundance of slow‐growing cyanobacteria in the oligotrophic area (salinity >33), where the lowest δ15NPN is most likely attributed to high abundance of N2‐fixing Trichodesmium spp., due to the influence of the anticyclonic eddy. Therefore, hydrodynamics modulates the biochemical composition and community composition of phytoplankton, leading to changes in δ13CPOC and δ15NPN. Our findings advance our understanding of the coupling of physical and biogeochemical processes in marginal seas.

Mechanisms of soil organic carbon and nitrogen stabilization in mineral-associated organic matter – insights from modeling in phase space

Abstract. Understanding the mechanisms of plant-derived carbon (C) and nitrogen (N) transformation and stabilization in soil is fundamental for predicting soil capacity to mitigate climate change and support other soil functions. The decomposition of plant residues and particulate organic matter (POM) contributes to the formation of mineral-associated (on average more stable) organic matter (MAOM) in soil. MAOM is formed from the binding of dissolved organic matter (ex vivo pathway) or microbial necromass and bioproducts (in vivo pathway) to minerals and metal colloids. Which of these two soil organic matter (SOM) stabilization pathways is more important and under which conditions remains an open question. To address this question, we propose a novel diagnostic model to describe C and N dynamics in MAOM as a function of the dynamics of residues and POM decomposition. Focusing on relations among soil compartments (i.e., modeling in phase space) rather than time trajectories allows isolating the fundamental processes underlying stabilization. Using this diagnostic model in combination with a database of 36 studies in which residue C and N were tracked into POM and MAOM, we found that MAOM is predominantly fueled by necromass produced by microbes decomposing residues and POM. The relevance of this in vivo pathway is higher in clayey soils but lower in C-rich soils and with N-poor added residues. Overall, our novel modeling in phase space proved to be a sound diagnostic tool for the mechanistic investigation of soil C dynamics and supported the current understanding of the critical role of both microbial transformation and mineral capacity for the stabilization of C in mineral soils.

Lobelia Lakes' Vegetation and Its Photosynthesis Pathways Concerning Water Parameters and the Stable Carbon Isotopic Composition of Plants' Organic Matter.

Most of the aquatic vegetation produces organic substances via the C3 photosynthetic pathway (mosses, isoetids-Lobelia dortmanna L., Luronium natans (L.) Raf., and vascular plants) or Crassulacean acid metabolism (CAM, e.g., Littorella uniflora (L.) Asch. and Isoëtes lacustris L.) or by their ability to use HCO3- via carbon concentration mechanisms (CCMs-some elodeids and charophytes). Differentiating these predominant photosynthetic pathways in aquatic vegetation based on their organic matter (OM) carbon stable isotopes (δ13CORG) is a complex task, in contrast to terrestrial plants. This study investigates the OM deposition, characterized by δ13CORG values in 10 macrophyte species with different photosynthetic pathways (C3, CAM, and CCM) collected from 14 softwater Lobelia lakes in northern Poland. The higher δ13CORG values distinguish the CCM group, indicating their use of 13C-enriched HCO3¯ in photosynthesis. CAM species show slightly higher δ13CORG values than C3, particularly in lower pH lakes. Principal component analysis of isotopic and environmental data did not yield clear distinctions by the groups, but still, they significantly differ in light of analyzed parameters and isotopic signals (PRMANOVA = 5.08, p < 0.01; K-W H = 27.01, p < 0.001). The first two PCA dimensions showed that the water pH and Ca2+ concentration positively influenced δ13C values. The influence of light conditions on δ13CORG values revealed by third PCA components seems to also be important. In summary, northern Polish Lobelia lakes serve as a key differentiation point between vegetation employing CCMs and those relying on C3/CAM photosynthesis without HCO3- utilization, providing insights into transitions in plant communities within these ecosystems.

Stable isotope spatial patterns for the Southwest Atlantic Ocean towards polar waters

Mapping stable isotope gradients (isoscapes) has become a powerful tool to understand and forecast the status and variability of marine ecosystems at different levels of ecological organization. To differentiate five marine areas from the Southwest Atlantic Ocean towards oceanic and polar waters, a key foraging area for many marine consumers, we built isoscapes at different spatial scales using carbon (δ13C) and nitrogen (δ15N) isotope values of phytoplankton, zooplankton and particulate organic matter in sediment. We analyzed the isotopic variability between marine areas in relation with oceanographic parameters (e.g. temperature, salinity) and geographical sampling site data (e.g. latitude, longitude). We collected samples during 6 oceanographic surveys conducted in spring and autumn between 2014 and 2019 at the Beagle Channel, the Atlantic coast of Tierra del Fuego and Burdwood Bank. We included also published isotopic data of zooplankton from two other oceanic areas (the Polar Frontal Zone and Polar Antarctic Peninsula waters) to construct large-scale isoscapes. We found that the marine areas analyzed have substantially different δ13C and δ15N baselines; some differences exist between spring and autumn but the general pattern of isotopic variability remains similar. Combining different biological components and spatial scale analysis, isotopic variability was found to be related to variables such as seawater temperature, depth, chlorophyll and nutrients. The generated data will enhance the efficacy of isoscapes in long-term monitoring initiatives that documents alterations in attributes and features across marine expanses. This is particularly pertinent to areas under legal protection, such as the oceanic Marine Protected Areas (MPAs) established in Argentine waters.

Links between soil pore structure, water flow and solute transport in the topsoil of an arable field: Does soil organic carbon matter?

An improved understanding of preferential solute transport in soil macropores would enable more reliable predictions of the fate of agrochemicals and the protection of water quality in agricultural landscapes. The objective of this study was to investigate how soil organic carbon (SOC) and soil texture shape soil pore structure and thereby determine the susceptibility to preferential transport under steady-state near-saturated flow conditions. To do so, we took intact topsoil samples from an arable field that has large variations in SOC content (1.1–2.7%) and clay content (8–42%). Soil pore structure was quantified by X-ray tomography and soil water retention measurements. Non-reactive solute transport experiments under steady-state near-saturated conditions were carried out at irrigation rates of 2 and 5 mm h−1 to quantify the degree of preferential transport. Near-saturated hydraulic conductivities at pressure heads of −1.3 and −6 cm were also measured using a tension disc infiltrometer. The results showed that larger abundances of small macropores (240–720 µm diameter) and mesopores (5–100 µm diameter) resulted in weaker preferential transport, due to larger hydraulic conductivities in the soil matrix that prevented the activation of water flow and solute transport in large macropores. In particular, the degree of preferential transport was most strongly and negatively correlated with the mesoporosity in the 30–100 µm diameter class. In contrast, the degree of preferential transport was not correlated with connectivity measures (e.g. the percolating fraction and critical pore diameter for the macropore network), probably because i.) the pore space of almost all samples was highly connected, being dominated by one percolating cluster, and ii.) only a part of this percolating macroporosity was active under the near-saturated conditions of the experiment. We also found that the degree of preferential transport was strongly and negatively correlated with clay content, whilst the effects of SOC were not significant. Nevertheless, macroporosity in the 240–720 µm diameter class and mesoporosity were positively correlated with SOC content in our soils and in some previous studies. Therefore, SOC sequestration in arable soils may potentially reduce the risk of preferential transport under near-saturated flow conditions through better developed networks of small macropores and mesopores.

Variations in source-specific soil organic matter components across 32 forest sites in China

Forest soils store substantial amounts of carbon in various soil organic matter (SOM) components due to high plant litter inputs and active microbial turnover. However, the variations in plant- and microbial-derived SOM components in surface and subsurface forest soils across a wide geographic scale remain poorly understood. This study investigated the SOM components from aboveground and belowground plant inputs and fungal and bacterial necromass in surface (soil0–5 cm) and subsurface (soil5–10 cm) soils across 32 forest sites in China and analyzed their relationships with climate and edaphic factors. Compared to soil0–5 cm, soil5–10 cm exhibited lower soil organic carbon content and cutin biomarker concentration but higher concentrations of fungal necromass carbon and lignin phenols. Higher mean annual precipitation led to higher concentrations of cutin and suberin biomarkers in soil0–5 cm and soil5–10 cm, respectively. Higher soil organic carbon content was associated with lower plant-derived lignin biomarkers, higher lignin oxidation degrees, and increased microbial necromass-derived amino sugars across sites, highlighting the pivotal role of microbial necromass in SOM stabilization. Additionally, both fungal and bacterial necromass decreased with increasing mineral weathering across sites. These insights improve the understanding of environmental drivers of source-specific carbon storage in forest soils.Graphical

The Content of Soil Glomalin Concerning Selected Indicators of Soil Fertility

The glomalin content is generally considered an indicator of the soil organic matter (SOM) quality. The content of easily extractable glomalin (EEG) and the total glomalin (TG) content was investigated across 71 different sites in the Czech Republic with arable soil and crop production (12 chernozems, 30 luvisols, 17 cambisols, and 12 fluvisols). The majority of the crops in the crop rotation were cereals (45.5%—mainly winter wheat, winter barley, and spring barley). The proportion of winter canola within the crop rotation was 15.9%. The contribution of other crops was substantially smaller (alfalfa, clover, potatoes, beet, silage maize, grain maize). The representation of crops in the crop rotation is standard for conventional farming in the Czech Republic. Based on the results of long-term field monitoring at 71 sites in different soil–climate conditions, we can state the following. The TG content was significantly correlated with the soil organic matter carbon content (CSOM), as well as another important indicator of SOM quality (humic and fulvic acid carbon content ratio—CHA/CFA). A significant and positive correlation was also determined for the TG and clay content (size &lt; 0.002 mm), as well as particles smaller than 0.01 mm. The easily extractable glomalin content (EEG) did not differ based on the reference soil group (RSG). On the other hand, the total glomalin content (TG) was significantly higher in the chernozem RSG in comparison with other RSGs (luvisols, cambisols, fluvisols). There was no relationship between the pHCaCl2 and glomalin (EEG; TG). The same can be said about the relationship between glomalin (EEG; TG) and the bulk density and porosity. No link was established between the glomalin content (EEG; TG) and phosphorus plant-available content. There was no relationship between the amount of applied organic matter (carbon inputs) and the soil glomalin content (EEG; TG). This relationship was not influenced by the type of applied organic fertilizer. No significant relationship was found for either straw, manure, or compost. The data on the glomalin content are significantly influenced by the site (soil type and soil texture).

The function of phytogenic mounds in the accumulation and conservation of soil seed banks in semiarid areas with water erosion

BackgroundPhytogenic mounds are a type of microtopography formed under perennial plants canopies in water erosion areas. However, the function of phytogenic mounds in seed assemblages and their ecological consequences remain poorly understood in semiarid areas with water erosion. Thus, understanding the characteristics of seed banks on mounds is crucial for ecosystem conservation and management in water-eroded areas.MethodsWe compared the quantity and composition of soil seed banks on the upslope and downslope parts of mounds and intercanopy surfaces along four slope gradients. We also explored the relationships among the soil seed bank, aboveground vegetation, and environmental factors. Furthermore, the species similarity between the soil seed bank and aboveground vegetation was analyzed to clarify the important ecological consequences of phytogenic mounds for plant community construction in serious soil erosion area.ResultsFor slopes with α ≤ 46.6%, the intercanopy surfaces had greater soil seed bank species composition, density, and diversity than did the phytogenic mounds, and these characteristics showed no significant differences between the upslope and downslope parts of the mounds. As the slope increased, the soil seed bank density and species composition increased on the upslope part of the mound, and reached a maximum for slopes with α &amp;gt; 70%, while the downslope part of the mound negatively effected on seed aggregation. The sediment accumulation rate, soil moisture, particle size distribution, pH, organic matter carbon, and hardness were significantly correlated with the soil seed bank density and diversity in the study area. For slopes with 0 &amp;lt; α ≤ 26.8%, the species similarity coefficient between the soil seed bank and aboveground vegetation was the highest for the intercanopy surface. This species similarity on the upslope part of the mound showed an increasing trend with increasing slope gradient, while the downslope part of the mound had the opposite trend. For slopes with α &amp;gt; 70%, the upslope part of the mound did not only have more species in the soil seed bank but also had more species in aboveground vegetation than did the downslope part of the mound and intercanopy surface.ConclusionFor slopes with α ≤ 46.6%, phytogenic mounds had barely impact soil seed bank accumulation and conservation in semiarid and eroded areas. For slopes with α &amp;gt; 46.6%, the mounds (particularly on the upslope part of the mound) showed seed assemblage functions, which are coupled with improving edaphic conditions and decreasing microhabitat stress; thus, phytogenic mounds, or areas of microtopography, can be used to promote restoration success in semiarid eroded areas.

Enhanced silicate weathering accelerates forest carbon sequestration by stimulating the soil mineral carbon pump.

Enhanced silicate rock weathering (ERW) is an emerging strategy for carbon dioxide removal (CDR) from the atmosphere to mitigate anthropogenic climate change. ERW aims at promoting soil inorganic carbon sequestration by accelerating geochemical weathering processes. Theoretically, ERW may also impact soil organic carbon (SOC), the largest carbon pool in terrestrial ecosystems, but experimental evidence for this is largely lacking. Here, we conducted a 2-year field experiment in tropical rubber plantations in the southeast of China to evaluate the effects of wollastonite powder additions (0, 0.25, and 0.5 kg m-2) on both soil organic and inorganic carbon at 0-10 cm depth. We found that ERW significantly increased the concentration of SOC and HCO3 -, but the increases in SOC were four and eight times higher than that of HCO3 - with low- and high-level wollastonite applications. ERW had positive effects on the accrual of organic carbon in mineral-associated organic matter (MAOM) and macroaggregate fractions, but not on particulate organic matter. Path analysis suggested that ERW increased MAOM mainly by increasing the release of Ca, Si, and Fe, and to a lesser extent by stimulating root growth and microbial-derived carbon inputs. Our study indicates that ERW with wollastonite can promote SOC sequestration in stable MOAM in surface soils through both the soil mineral carbon pump and microbial carbon pump. These effects may have been larger than the inorganic CDR during our experiment. We argue it is essential to account for the responses of SOC in the assessments of CDR by ERW.

A comparative analysis of soil organic carbon stock and soil aggregation in two crop sequences in the Rolling Pampa (Argentina)

Understanding how farming practices affect soil organic carbon (SOC) accumulation is essential for sustainable agriculture. Agronomic decisions, such as crop sequence, significantly influence various soil properties. However, the overall benefits of crop rotation on soil structure and SOC storage remain uncertain. We compared the effects of soybean (Glycine max L.) monocropping with a three-year crop rotation comprising wheat (Triticum aestivum L.)/soybean double crop, maize (Zea mays L.), and soybean on the vertical distribution of SOC up to one metre depth. Additionally, we examined carbon accumulation as particulate organic matter-carbon (POM-C), soil aggregation, and structural stability in the topsoil. Compared to monocropping, crop rotation increased SOC concentrations (19 vs. 16 gC kg soil⁻¹), stock (12 vs. 10.7 MgC ha⁻¹), and POM-C content (6 vs. 3.2 gC kg soil⁻¹) in the first 5 cm of soil. At 20–65 cm depth, rotation showed a marginal increment of SOC stock with respect to soybean monocropping. The increased surface SOC content in the rotation positively affected the POM-C content and macro-aggregation. However, soil structural stability showed a tendency to be higher in the monocropping, especially at a depth of 5–20 cm. Overall, crop rotation demonstrated potential for enhanced carbon sequestration in temperate agroecosystems within three years, despite not significantly improving soil structural stability.

Analysis of organic and mineral nitrogen, total organic carbon and humic fractions in Ferralsols: an approach using Vis-NIR-SWIR, MIR and X-ray fluorescence spectroscopy

This work aimed to develop suitable predictive models for ammonium, nitrate, total nitrogen, total organic carbon and soil humic fractions, for Ferralsols, using Vis-NIR-SWIR, MIR and X-ray fluorescence spectroscopic techniques in conjunction with machine learning algorithms, Cubist, PLSR, Random Forest and Support Vector Machine. Chemical analyzes were carried out to determine nitrate, total nitrogen, total organic carbon and chemical fractionation of soil organic matter, as well as spectral analyzes using Vis-NIR-SWIR spectroscopy, MIR and X-ray fluorescence. The spectroscopy results were processed using RStudio v. 4.1.3, applying Cusbist, PLSR, Random Forest and Support Vector Machine machine learning algorithms to create predictive models and describe spectral curves and Pearson correlation. Of the prediction models developed for nitrogen, total organic carbon and humic fractions, the PLSR and Support Vector Machine algorithms presented the best predictive performances. The descriptive analysis of the spectra identified the main absorption bands and the location of the bands sensitive to the attributes of interest. The correlation analysis proposed that the use of Vis-NIR-SWIR, MIR and XRF spectroscopic techniques were effective in predicting the contents of nitrogen, total organic carbon and humic fractions in soil with a medium sandy texture. However, it is important to highlight that each technique has its characteristic mechanism of action, Vis-NIR-SWIR and MIR detect the element based on overtones and fundamental tones, while XRF is based on the atomic number of the elements or elemental association.

Responses of Soil Carbon and Nitrogen Dynamics and GHG Fluxes in Forest Ecosystems to Climate Change and Human Activity

Forest soils are considered the largest carbon and nitrogen pools in soil organic matter among terrestrial ecosystems, and soil carbon and nitrogen dynamics and greenhouse gas (GHG) emissions are normally affected by climate change and human activity. The collection of recent research on this scientific theme would provide a basis for understanding the responses of soil carbon and nitrogen dynamics and GHG fluxes in forest ecosystems to climate change and human activity. A Special Issue was, thus, organized to discuss recent research achievements, including a total of nine research articles and one review. This Special Issue includes the effects of climate changes such as changes in throughfall, snow cover, and permafrost degradation; human activities such as nitrogen and/or phosphorus addition and the use of biochar; and soil–plant interactions on soil carbon and nitrogen dynamics and GHG fluxes in forest ecosystems. Although this collection of papers reflects only a small part of this scientific theme, it can, to some extent, provide a basis for understanding some important research aspects related to the future of forest soil carbon and nitrogen dynamics and GHG fluxes in a changing world, thereby enabling sustainable development and the mitigation of climate change.

Landscape and paleoenvironmental change in stream valleys of the Central Great Plains, North America, during Marine Isotope Stage 3 (ca. 59–27 ka)

Recent studies of late Quaternary landscape evolution in stream valleys throughout the central Great Plains of North America have identified thick packages of MIS 3-age alluvium and colluvium beneath terraces, alluvial fans, and footslopes. Here, we review and build on these studies to highlight the geomorphic history of river systems in the Central Plains during MIS 3 and reconstruct the paleoclimatic conditions and vegetation communities that existed in the region at that time.A suite of 50 radiocarbon and optically stimulated luminescence ages indicate that late MIS 3 was a period of widespread landscape stability and soil development in the Central Plains. In general, river systems were actively aggrading during early MIS 3, but aggradation slowed after ca. 40 ka, allowing soils to develop until ca. 30–27 ka. In some river valleys, a second pulse of aggradation occurred shortly after that time followed by a period of landscape stability and pedogenesis during early MIS 2 (ca. 24–19 ka). Evidence for widespread landscape stability in stream valleys implies that high magnitude flooding was minimal. Atmospheric circulation patterns that favor these conditions include zonal airflow that inhibits incursions of moist, maritime air from the Gulf of Mexico.Paleoenvironmental conditions during late MIS 3 were reconstructed using the stable carbon, oxygen, and hydrogen isotopic composition of pedogenic phyllosilicates, carbonates, and organic matter. Estimated paleotemperatures ranged from 6 to 9 °C ± 3 °C and are approximately 4–7 °C lower than modern mean annual temperature. The estimated δ18O values of soil water from phyllosilicates range from −10.6‰ to −9.6‰. These estimates are lower (18O-depleted) by about 1.5–3‰ relative to modern meteoric δ18O values and we estimate that the δ18O of paleoprecipitation was likely 18O-depleted by up to 8.5‰ relative to modern values. Our estimated δ18O values for soil waters in the Central Plains during late MIS 3 can be explained by climatic conditions characterized by 1) cooler temperatures, 2) precipitation being sourced primarily from Pacific/Arctic air masses, 3) seasonal changes in precipitation patterns (i.e., predominantly winter precipitation), or 4) a combination of the above. δ13C values indicate the presence of a notable proportion of C4 vegetation in the Central Plains during late MIS 3. We suggest that C4 productivity was likely favored at that time by a low atmospheric CO2 environment that had sufficiently warm temperatures and effective precipitation during the growing season.

Diagenetic history and porosity evolution of the Middle Permian clastic-carbonate mixed system, Indus Basin, Pakistan: Implications for reservoir development

This study deals with unraveling the diagenesis-induced porosity evolution in a mixed clastic-carbonate sequence of the Middle Permian Indus Basin, Pakistan. Multiple data sets including outcrop, petrography, cathodoluminescence, scanning electron microscopy (SEM), mineralogy, and geochemical isotopic compositions were integrated to establish a link between porosity evolution and diagenesis. The spatial thickness and facies variations of the strata at outcrop scale are inherently controlled by the underlying bathymetry of the basin with deepening westward trend. The low values of δ18O of the target strata, relative to average values of the Permian carbonate, hints to diagenetic alteration in the strata. The data sets used in this study reveal modification of the strata in four environments, that is, i) early marine diagenesis indicated by micritization, pervasive dolomitization and isopachous fibrous cements, followed by ii) meteoric dissolution, and iii) shallow burial diagenetic processes including the precipitation of blocky cement, compaction of skeletal and non-skeletal allochems, and stylolites, and iv) a deep burial environment, characterized by pressure solution, and micro-fractures. The clastic intervals host subangular to subrounded quartz grains, floating textures, and almost complete absence of deleterious clay minerals, consequently resulting in the preservation of primary porosity. The primary porosity of carbonate intervals is preserved in the form of intercrystalline and intracrystalline porosity. The secondary porosity evolved through various diagenetic phases in the form of fractures and dissolution. The diagenetic solution mediated by organic matter in carbonates may have experienced both bacterial decomposition and thermochemical sulfate reduction, precipitating sulfides within the pores. The plug porosity/permeability analyses generally suggest high porosity in the siliciclastic unit, and carbonates with wackestone fabric while lower values were observed for the inner shelf pure carbonate facies. However, both intervals show very low permeability values probably due to isolated moldic pores and intense micritization. Therefore, clastic intervals may provide an opportunity to serve as a moderate reservoir; however, the carbonate intervals possess very low permeability values and could generally be considered as low-moderate reservoir potential.

Quantitative evaluation of soil health based on a minimum dataset under various short-term crop rotations on the Canadian prairies

Maintaining and improving soil health (SH) is essential for the long-term sustainability and productivity of agriculture, notably in the face of climate change. This study addressed the challenge of selecting appropriate soil indicators, scoring methods, and indexing approaches for SH evaluation under no-till crop rotations. This study aimed to develop minimum datasets (MDS) and assess SH in six crop rotations (denoted as conventional, diversified, high-risk and high-reward, market-driven, pulse-oilseed intensified, and soil health-enhanced rotations) at three sites on the Canadian prairies. Fourteen soil indicators in the total dataset (TDS) were examined, encompassing both chemical (0–7.5 cm depth) and physical (5–10 cm depth) properties. Principal component analysis (PCA) identified MDSs from the TDS. Two scoring [linear (L) and non-linear (NL)] and two SH indexing approaches [additive (A) and weighted additive (WA)] were used to calculate the SH index (SHI). One-way ANOVA evaluated the SHI among crop rotations. The PCA revealed variations in the number of indicators in the MDS across sites, with soil organic carbon, bulk density, macroporosity, and plant-available water capacity as the common indicators for MDS across sites. Other indicators such as particulate organic matter carbon, aggregate stability, field capacity, and microporosity were found to be important, depending on the site. The non-linear weighted additive SH indexing (SHI.NLWA) proved to be the most sensitive and effective for differentiating among crop rotations in the short-term across study sites (R2 = 0.89–0.94, P < 0.05). Crop rotations significantly influenced SHI, with the diversified and high-risk and high-reward rotations having the highest SHI at Lethbridge and Scott, respectively. Overall, the diversified rotation at Lethbridge and Swift Current, along with the high-risk and high-reward rotation at Scott, exhibited better soil function than other rotations. Monitoring SHI over time and selecting crop rotations that improve SH can collectively enhance soil functions and agroecosystem productivity.

Microscale hydrogen, carbon, and nitrogen isotopic diversity of organic matter in asteroid Ryugu

We report the H, C, and N isotopic compositions of microscale (0.2 to 2 µm) organic matter in samples of asteroid Ryugu and the Orgueil CI carbonaceous chondrite. Three regolith particles of asteroid Ryugu, returned by the Hayabusa2 spacecraft, and several fragments of Orgueil were analyzed by NanoSIMS isotopic imaging. The isotopic distributions of the Ryugu samples from two different collection spots are closely similar to each other and to the Orgueil samples, strengthening the proposed Ryugu-CI chondrite connection. Most individual sub-μm organic grains have isotopic compositions within error of bulk values, but 2–10 % of them are outliers exhibiting large isotopic enrichments or depletions in D, 15N, and/or 13C. The H, C and N isotopic compositions of the outliers are not correlated with each other: while some organic grains are both D- and 15N-enriched, many are enriched or depleted in one or the other system. This most likely points to a diversity in isotopic fractionation pathways and thus diversity in the local formation environments for the individual outlier grains. The observation of a relatively small population of isotopic outlier grains can be explained either by escape from nebular and/or parent body homogenization of carbonaceous precursor material or addition of later isotopic outlier grains. The strong chemical similarity of isotopically typical and isotopically outlying grains, as reflected by synchrotron x-ray absorption spectra, suggests a genetic connection and thus favors the former, homogenization scenario. However, the fact that even the least altered meteorites show the same pattern of a small population of outliers on top of a larger population of homogenized grains indicates that some or most of the homogenization occurred prior to accretion of the macromolecular organic grains into asteroidal parent bodies.

Terrestrial carbon dynamics and economic valuation of ecosystem service for land use management in the Mediterranean region

Land use change is a significant cause of land degradation, resulting in the removal of carbon and its transfer to the hydrosphere or atmosphere, which can have a detrimental impact on essential ecosystem functions and services. In contrast, rural landscapes offer both ecological and economic benefits to people due to their carbon storage properties. This benefit is often evaluated within the framework of Ecosystem Services (ES). The rural landscapes offer unique structures and ecosystem services. The aim of this study is to provide an economic quantification of carbon storage and sequestration in rural landscapes as an ecosystem service and to introduce carbon-based rural landscape management. The study enables the integration of carbon-based strategies and policies by generating quantitative outputs for landscape plans that have not yet been included in the spatial planning hierarchy. The Upper Seyhan Basin (USB), located on the Eastern Mediterranean coast of Turkiye, was modelled using spatiotemporal and economic valuation approaches to assess terrestrial carbon storage and sequestration in this context. The study modelled and mapped the four main terrestrial carbon storage components in the rural landscape: (i) above-ground biomass, (ii) below-ground biomass, (iii) Soil Organic Carbon (SOC), and (iv) dead organic matter carbon. The future land cover of 2055 was modelled using the Multilayer Perceptron (MLP)-Markov Chain (MC) algorithm based on the “Business-As-Usual” (BAU) scenario to determine future carbon sequestration. The Social Cost of Carbon (SCC) was estimated for Turkiye using the Regional Integrated Model of Climate and Economy (RICE) to economically model carbon services. In the final stage of the study, modelling outputs, including carbon storage pools/sinks, projected land cover dynamics, and SCC components, were used within the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model to map the carbon dynamics of the rural landscape at the regional level. This paper demonstrates the role of geospatial modelling and proposes a new planning and design logic that considers carbon-based inputs and global climate change in an appropriate format for land management by bridging the interface between earth sciences and spatial planning. The study results indicate that, the rural landscape in the study area provided an ecosystem service of 70,266 TgC carbon in 2014 with a storage value of USD 222,853,170. For the 2014–2025 projection, an estimated 1.042 TgC of carbon sequestration was valued at USD 6,234,137. The 2014–2055 projection estimated 3.185 TgC of carbon sequestration valued at USD 58,745,265.