Spatial Distribution Of Carbon Research Articles

The role of tidal creeks in shaping carbon and nitrogen patterns in a Chinese salt marsh

Tidal creeks play a crucial role in lateral transport of carbon and nutrients from tidal salt marshes. However, the specific impact of tidal creek development on carbon and nutrient distribution within the marsh remains poorly understood. The objective of this study is to assess the influence of lateral tidal flooding through the tidal creeks on the spatial distribution of carbon and nitrogen fractions in the soils of a Chinese temperate salt marsh. We conducted a comprehensive analysis of the relative variations in different carbon and nitrogen fractions, along with soil physicochemical and microbial indicators, between the bank soil of the tidal creek and its lateral inland soils across high, middle, and low flats. Our findings highlight that tidal creek development significantly affects the middle flat, leading to substantial variations in organic carbon and total nitrogen. The low flat mainly experiences changes in dissolved inorganic carbon levels. Furthermore, a lateral increase in microbial biomass is observed in the middle flat, indicating that the significantly lower SOC in the middle flat might be ascribed to enhanced microbial decomposition. The lateral enrichment of dissolved inorganic carbon in the low flat is possibly related to the nearshore location and/or abiotic adsorption in inorganic carbon sequestration. Overall, this study demonstrates the critical role of tidal creek development in shaping the distribution patterns of carbon and nitrogen fractions in tidal salt marshes.

Stochastic 3D Modeling of Nanostructured NVP/C Active Material Particles for Sodium‐Ion Batteries

AbstractA data‐driven modeling approach is presented to quantify the influence of morphology on effective properties in nanostructured sodium vanadium phosphate / carbon composites (NVP/C), which are used as cathode material in sodium‐ion batteries. This approach is based on the combination of advanced imaging techniques, experimental nanostructure characterization and stochastic modeling of the 3D nanostructure consisting of NVP, carbon and pores. By 3D imaging and subsequent post‐processing involving image segmentation, the spatial distribution of NVP is resolved in 3D, and the spatial distribution of carbon and pores is resolved in 2D. Based on this information, a parametric stochastic model, specifically a Pluri‐Gaussian model, is calibrated to the 3D morphology of the nanostructured NVP/C particles. Model validation is performed by comparing the nanostructure of simulated NVP/C composites with image data in terms of morphological descriptors which have not been used for model calibration. Finally, the stochastic model is used for predictive simulation to quantify the effect of varying the amount of carbon while keeping the amount of NVP constant. The presented methodology opens new possibilities for a ressource‐efficient optimization of the morphology of NVP/C particles by modeling and simulation.

The Earth system model CLIMBER-X v1.0 – Part 2: The global carbon cycle

Abstract. The carbon cycle component of the newly developed Earth system model of intermediate complexity CLIMBER-X is presented. The model represents the cycling of carbon through the atmosphere, vegetation, soils, seawater and marine sediments. Exchanges of carbon with geological reservoirs occur through sediment burial, rock weathering and volcanic degassing. The state-of-the-art HAMOCC6 model is employed to simulate ocean biogeochemistry and marine sediment processes. The land model PALADYN simulates the processes related to vegetation and soil carbon dynamics, including permafrost and peatlands. The dust cycle in the model allows for an interactive determination of the input of the micro-nutrient iron into the ocean. A rock weathering scheme is implemented in the model, with the weathering rate depending on lithology, runoff and soil temperature. CLIMBER-X includes a simple representation of the methane cycle, with explicitly modelled natural emissions from land and the assumption of a constant residence time of CH4 in the atmosphere. Carbon isotopes 13C and 14C are tracked through all model compartments and provide a useful diagnostic for model–data comparison. A comprehensive evaluation of the model performance for the present day and the historical period shows that CLIMBER-X is capable of realistically reproducing the historical evolution of atmospheric CO2 and CH4 but also the spatial distribution of carbon on land and the 3D structure of biogeochemical ocean tracers. The analysis of model performance is complemented by an assessment of carbon cycle feedbacks and model sensitivities compared to state-of-the-art Coupled Model Intercomparison Project Phase 6 (CMIP6) models. Enabling an interactive carbon cycle in CLIMBER-X results in a relatively minor slow-down of model computational performance by ∼ 20 % compared to a throughput of ∼ 10 000 simulation years per day on a single node with 16 CPUs on a high-performance computer in a climate-only model set-up. CLIMBER-X is therefore well suited to investigating the feedbacks between climate and the carbon cycle on temporal scales ranging from decades to >100 000 years.

Content and Spatial Distribution of Carbon in Shuangtaizi Estuary, China

Contents of total organic carbon (TOC), total inorganic carbon (TIC) and total carbon (TC) in water and sediment in Shuangtaizi estuary in China were studied. The results showed that the TIC and TC contents in water were high, and the TOC content was very low. In sediment, the TOC and TC contents were high, while the TIC was very low. TOC, TIC and TC had obvious spatial distribution characteristics in water and sediment in the area. The distribution of TOC and TC in sediment was similar, which was increase along with the distance to the mouth. The distribution of TIC and TC in water was similar. The TIC was mainly distributed at the outer mouth in surface water, while at the inner in deep water was little. The terrigenous input was the main source of carbon in the area. Carbon sequestration in the long range would convert the inorganic carbon to organic carbon.

Carbon, nitrogen, and phosphorus dynamics in China's lakes: climatic and geographic influences.

Given the differences in geomorphology, climate, hydrology, and human activities in various regions, lake chemometrics may also vary. However, the spatial distribution of lake chemistry and the factors affecting such pattern are still unclear. Here, we collected data for carbon, nitrogen, and phosphorus from published literature and databases in 224 lakes and calculated the trophic status index to represent the nutrient classification state of lakes. We found that lakes with high carbon concentrations were located in the Tibet-Qinghai Limnetic Region of western China, whereas lakes with high nitrogen and phosphorus concentrations were located in the Inner Mongolia-Xinjiang Limnetic Region and Northeast Limnetic Region of northern China. Areas with larger cropland and urban residential land (such as the junction of the three lake regions, i.e., the Northeast Limnetic Region, East Limnetic Region, and Inner Mongolia-Xinjiang Limnetic Region) tended to have lakes with high nitrogen and phosphorus concentrations. Our analysis suggested that spatial distribution of carbon, nitrogen, and phosphorus concentrations reflect the effect of climate, geomorphology, and land use in each lake region and nationwide.

Spatial Variability of Soil Organic Carbon and Total Nitrogen in Desert Steppes of China’s Hexi Corridor

Stock estimates are critical to quantifying carbon and nitrogen sequestration, quantifying greenhouse gas emissions, and understanding key biogeochemical processes (i.e., soil carbon and nutrient cycling). Many studies have assessed soil organic matter and nutrients in different ecosystems. However, the spatial distribution of carbon and nitrogen and the key influencing factors in arid desert steppe remain unclear. Here, we investigated the soil organic carbon (SOC) and soil total nitrogen (STN) to a depth of 100 cm at 126 sites in a desert steppe in northwestern China.SOCandSTNcontents decreased with increasing depth; the highest averageSOCandSTNcontents were 12.70 and 0.65 g kg−1in the surface 5 cm, and the lowest were from 80 to 100 cm (4.49 and 0.16 g kg−1, respectively).SOCdensity (SOCD) andSTNdensity (STND) to a depth of 100 cm averaged 8.94 and 0.45 kg m−2, respectively. The top 1 m of the soils stored approximately 1,041 TgSOCand 52 TgSTNin the study area. Geostatistical analysis showed strong and moderate spatial autocorrelation forSOCDin different soil layers, but the autocorrelation forSTNDgradually weakened with increasing depth.SOCDandSTNDdecreased from southwest to northeast in the study area, along an elevation gradient. Both were significantly positively correlated with topographic variables, precipitation, and the normalized-difference vegetation index, but negatively correlated with temperature and aridity. More than 40% of theSOCDandSTNDspatial variation was explained by elevation, which was the dominant factor. The data and high-resolution maps from this study will support future soil carbon and nitrogen analyses.

Analyzing how forest-based amenity values and carbon storage benefits affect spatial targeting for conservation investment

We analyze how two different ecosystem services: forest-based amenity values and carbon storage benefits, affect spatial targeting for conservation investment for protected area acquisition using selected forest clusters in Knox County, Tennessee in the United States. We determine return-on-investment (ROI) for these two different forest-based ecosystem services by estimating amenity values and carbon storage amounts using hedonic price model and dynamic Terrestrial Ecosystem Model (TEM), respectively, and corresponding acquisition costs at the forest cluster level. Our findings of the optimal protected area acquisition in the form of forest clusters serve as an empirically informed knowledge base to help both the conservation and planning agencies in prioritizing acquisition of potential protected areas depending on their preferences. By using carbon and amenity ROIs in spatial targeting of forest clusters within the multi-objective optimization set up, we not only addressed the spatial heterogeneity in the carbon storage benefits and amenity values but also the spatial heterogeneity in cluster acquisition costs. We also found that selection decisions were dictated by the weakly negative correlation (−0.16) between the carbon and amenity ROIs instead of weakly positive correlation (0.14) between carbon storage benefits and amenity values. Since the spatial distribution of carbon and amenity ROIs were weakly negatively correlated, there were apparent conflicts between the objectives of maximizing forest carbon storage and amenity value. This resulted in concave frontiers with tradeoffs between the objectives implying variation in spatial distribution of the selected forest clusters letting the conservation and planning agencies decide combination of strategies which best fit their preferences.

Spatial distribution of carbon, nitrogen and sulfur in surface soil across the Pearl River Delta area, South China

In the present study, 885 surface soil samples were collected to study the spatial variations and correlations between total contents of organic carbon (C), nitrogen (N) and sulfur (S) in surface soil across the Pearl River Delta (PRD) area. The results showed that soil C and N had similar spatial patterns, and the soil C:N ratio had a relative stable value of 9.63, suggesting that soil biological processes were the primary factor determining the soil C:N ratio. The spatial distribution of soil S was different from that of soil C and N, and there was no correlation between soil S and C. Soil samples with relatively high S content were mainly distributed along the regional rivers. The mean of soil C:S ratios was 42.6, and a constant C:S ratio did not exist. This finding revealed that the geochemical processes of soil S cycling and exogenous S inputs had more important effects on the spatial distribution of soil S, and soil C:S ratio than plant/microbe-related nutrient cycling. The present results revealed that soils with higher C and N content were more likely to accumulate C and N, while soils with lower C and N content could lose these nutrients more easily. Furthermore, the fertile farmland with high C and N content had excessive N input, while the poor farmland with low C content had an obvious N loss. The results demonstrated that the soil C:N ratio remained constant across the study area that is attributed to soil biological processes, whereas higher fluctuations were detected for the soil C:S ratio, which was primarily driven by geochemical processes and exogenous S inputs.

Longitudinal variation characteristics of stable isotope ratios of suspended particulate organic matter in the headwaters of the Qingjiang River, China

To determine the sources and characteristics of suspended particulate organic matter (SPOM), the spatial distribution of carbon and nitrogen and their isotopic values (δ13C and δ15N) were measured from upstreamto downstream (i.e. site 1 to site 4) in the head waters of the Qingjiang River in central China. The mean annual SPOM δ15N and δ13C values varied between sites but exhibited a unimodal pattern. The mean annual δ15N increased from site 1 (2.5‰) to 3 (5.3‰), followed by a major decrease to 2.2‰ at site 4. Furthermore, the mean annual δ13C varied unimodally, being the most positiveat sites 1 (−21.6‰) and 4 (−22.8‰) followed by sites 2 (−24.5‰) and 3 (−26.4‰). In particular, the mean SPOM δ15N and δ13C in the tailwaters from a domestic wastewater treatment plant, which was located approximately 0.3 km upstream of site 4, were 2.2‰ and −25.6‰, respectively. The SPOM C/N values from stream water at site 4 (8.5 ± 1.5) and tailwater (6.2 ± 0.9) were similar. Collectively, the results suggested that wastewater treatment plant tailwater influenced the stable isotope values of SPOM in the stream and affected the variation trendfrom upstream to downstream.

Spatial variability of carbon and nitrogen stocks in integrated management systems and pasture in a cerrado region

The conversion of the native Cerrado into agricultural systems promotes a reduction in the input of organic residues on the soil, which can compromise the contents of soil organic carbon. The spatial distribution of carbon and nitrogen stocks in the soil is normally influenced by environmental and anthropogenic factors. This research aimed to map and evaluate the spatial variability of carbon and nitrogen stocks in the soil, in different integrated systems and pasture areas in the edaphoclimatic conditions of the Cerrado biome, in the state of Maranhão. The work was set up in a Red-Yellow Latosol with different management methods: crop-livestock integration with no-till farming, crop-livestock integration with patch scarification and harrowing, crop-livestock-forest integration, and pasture. The samples were removed at a depth of 0.0-0.20 m, in a grid with a regular interval of 50 m, totaling 193 points. The data were subjected to descriptive statistics, geostatistics, and kriging interpolation. The mean and median values are similar for the carbon and nitrogen stocks, in their respective management systems, indicating symmetric data distribution, confirmed by the asymmetry and kurtosis values close to zero. The spatial distribution of the carbon stocks is more homogeneous in the crop-livestock integration with no-till farming, whereas the crop-livestock integration with patch scarification and harrowing presents greater homogeneity in nitrogen distribution.

Predicting soil organic carbon stocks under commercial forest plantations in KwaZulu-Natal province, South Africa using remotely sensed data

ABSTRACT Commercial forest plantations are increasing globally, absorbing a large amount of carbon valuable for climate change mitigation. Whereas most carbon assimilation studies have mainly focused on natural forests, understanding the spatial distribution of carbon in commercial forests is central to determining their role in the global carbon cycle. Forest soils are the largest carbon reservoir; hence soils under commercial forests could store a significant amount of carbon. However, the variability of soil organic carbon (SOC) within forest landscapes is still poorly understood. Due to limitations encountered in traditional systems of SOC determination, especially at large spatial extents, remote sensing approaches have recently emerged as a suitable option in mapping soil characteristics. Therefore, this study aimed at predicting soil organic carbon (SOC) stocks in commercial forests using Landsat 8 data. Eighty-one soil samples were processed for SOC concentration and fifteen Landsat 8 derived variables, including vegetation indices and bands were used as predictors to SOC variability. The random forest (RF) was adopted for variable selection and regression method for SOC prediction. Variable selection was done using RF backward elimination to derive three best subset predictors and improve prediction accuracy. These variables were then used to build the RF final model for SOC prediction. The RF model yielded good accuracies with root mean square error of prediction (RMSE) of 0.704 t/ha (16.50% of measured mean SOC) and 10-fold cross-validation of 0.729 t/ha (17.09% of measured mean SOC). The results demonstrate the effectiveness of Landsat 8 bands and derived vegetation indices and RF algorithm in predicting SOC stocks in commercial forests. This study provides an effective framework for local, national or global carbon accounting as well as helps forest managers constantly evaluate the status of SOC in commercial forest compartments.

Effects of multi-cropping system on temporal and spatial distribution of carbon and nitrogen footprint of major crops in China

Life cycle assessments (LCA) of staple food (rice, wheat and corn) production and assessments of the associated greenhouse gas (GHG) and reactive nitrogen (Nr) releases from environmental and ecological perspectives help to develop effective mitigation options. Therefore, carbon (C) and nitrogen (N) footprint reductions in agroecosystems have become an increasingly popular topic related to global climate change and agricultural adaptation. The LCA method was used to calculate the product and farm C footprint (CF) and N footprint (NF) of double rice, rice-wheat and wheat-maize production based on governmental statistical datasets and published results. The spatial and temporal patterns of CF and NF were analyzed in China during 2004–2017, and their driving factors were analyzed to identify potential mitigation strategies. The results showed that of the various inputs, fertilizer application and diesel oil consumption contributed the most to both GHG and Nr emissions from farm inputs in the grain crop production process. The CFs for double rice, rice-wheat and wheat-maize were 0.83, 0.74, and 0.37 kg CO2-eq kg−1 year−1 at the yield scale, respectively. In addition, the NFs were 11.6, 13.4, and 15.4 gN-eq kg−1 year−1 at the yield scale for double rice, rice-wheat and wheat-maize, respectively. The largest fraction of CF and NF was the share of CH4 emissions and NH3 volatilization from the field soil, respectively. The annual CFs and NFs of the multiple crop in the southwestern provinces were higher than those in the central and northern provinces. The annual GHG and Nr emissions from the multiple crop maintained a relatively stable state from 2004 to 2017. The proportion of CO2/Nr production was partly reflected a soil C/N ratio, suggesting a higher C abundance for the double rice production, which could be used as a reference parameter for crop structure adjustment in the future. Based on our results and other studies, some effective solutions, especially optimized fertilization, farm machinery operation efficiencies and changes in regional allocation of grain cropping areas, are needed to mitigate the impacts of climate change and eutrophication on the main grain crop production in China.

From savanna to suburb: Effects of 160 years of landscape change on carbon storage in Silicon Valley, California

Landscape changes such as urbanization can dramatically affect the provision of ecosystem services such as carbon storage. However, while cities have been shown to store substantial amounts of carbon in soils and vegetation, we have little information from long-term studies about how contemporary carbon storage in urban areas compares to carbon storage in the natural ecosystems that characterized these landscapes prior to urbanization. We used historical archival sources and land-cover data to quantify and map historical tree carbon storage in the now-urban Santa Clara Valley, California, USA prior to substantial Euro-American modification (ca. 1850) and to analyze change in the amount and distribution of carbon storage over the past ca. 160 years. We estimate that total tree carbon storage in the study area was ~784,000 to 2.2 million Mg (13.6–38.1 Mg C/ha) when the region was characterized by oak savanna and woodland habitats, compared to ~895,000 Mg C (15.5 Mg C/ha) today. This represents a non-significant gain of 14% to a significant loss of 60% depending on scenario. We also demonstrate changes in the spatial distribution of carbon on the landscape, as losses in carbon storage in areas of former oak woodland were partially offset by gains in carbon storage in historical habitat types that historically had few or no trees. This challenges the hypothesis that aboveground carbon storage increases with urbanization in Mediterranean-climate ecosystems due to irrigation and tree planting. Our study demonstrates the utility of using pre-1900s historical sources to reconstruct changes in ecosystem services such as carbon storage over century time scales.

The relevance of using in situ carbon and nitrogen data and satellite images to assess aboveground carbon and nitrogen stocks for supporting national REDD\u2009+\u2009programmes in Africa

BackgroundTo reduce the uncertainty in estimates of carbon emissions resulting from deforestation and forest degradation, better information on the carbon density per land use/land cover (LULC) class and in situ carbon and nitrogen data is needed. This allows a better representation of the spatial distribution of carbon and nitrogen stocks across LULC. The aim of this study was to emphasize the relevance of using in situ carbon and nitrogen content of the main tree species of the site when quantifying the aboveground carbon and nitrogen stocks in the context of carbon accounting. This paper contributes to that, by combining satellite images with in situ carbon and nitrogen content in dry matter of stem woods together with locally derived and published allometric models to estimate aboveground carbon and nitrogen stocks at the Dassari Basin in the Sudan Savannah zone in the Republic of Benin.ResultsThe estimated mean carbon content per tree species varied from 44.28 ± 0.21% to 49.43 ± 0.27%. The overall mean carbon content in dry matter for the 277 wood samples of the 18 main tree species of the region was 47.01 ± 0.28%—which is close to the Tier 1 coefficient of 47% default value suggested by the Intergovernmental Panel on Climate Change (IPCC). The overall mean fraction of nitrogen in dry matter was estimated as 0.229 ± 0.016%. The estimated mean carbon density varied from 1.52 ± 0.14 Mg C ha−1 (for Cropland and Fallow) to 97.83 ± 27.55 Mg C ha−1 (for Eucalyptus grandis Plantation). In the same order the estimated mean nitrogen density varied from 0.008 ± 0.007 Mg ha−1 of N (for Cropland and Fallow) to 0.321 ± 0.088 Mg ha−1 of N (for Eucalyptus grandis Plantation).ConclusionThe results show the relevance of using the in situ carbon and nitrogen content of the main tree species for estimating aboveground carbon and nitrogen stocks in the Sudan Savannah environment. The results provide crucial information for carbon accounting programmes related to the implementation of the REDD + initiatives in developing countries.

Assessing edge effect on the spatial distribution of selected forest biochemical properties derived using the Worldview data in Dukuduku forests, South Africa

AbstractThis work explores the potential of the high‐resolution WorldView‐2 sensor in quantifying edge effects on the spatial distribution of selected forest biochemical properties in fragmented Dukuduku forest in KwaZulu‐Natal, South Africa. Specifically, we sought to map fragmented patches within forested areas in Dukuduku area, using very high spatial resolution WorldView‐2 remotely sensed data and to statistically determine the effect of these fragmented patches on the spatial distribution of selected forest biochemical properties. Edge effects on carbon, LAI and foliar nitrogen were quantified based on the models derived by Omer et al. (IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 2015, 8, 4825). Edge effect statistical results on the spatial distribution of carbon, LAI and nitrogen showed significant (α = 0.05) variations with change in distance from fragmented patches (>150 m2). Forest foliar carbon concentrations significantly (p‐value = 0.016) increased from 44.8% to 45.3% with increasing distance (25–375 m) from fragmented patches. A similar trend was observed for LAI. Nevertheless, for nitrogen the results show that its concentration significantly (p = 0.016) decreased with increase in distance from the fragmented patches. Overall, the findings of this work underscore the invaluable potential and strength of WorldView‐2 data set in assessing edge effect on the spatial distribution of selected forest biochemical properties.

The importance of ecosystem services to smallholder farmers in climate change adaptation: learning from an ecosystem-based adaptation pilot in Vietnam

Smallholder farmers strongly connect to their surrounding environment and depend on ecosystems for their daily subsistence and welfare. Different climate change phenomena in recent years have affected resilience of smallholder farmers in Vietnam and ecosystems where they live. The importance of ecosystem services in climate change adaptation was investigated in surveys, focus group discussions, meetings and interviews with key district and commune staff, male and female farmers of Son Tho commune in rural North Central Region of Vietnam. In conjunction with surveys an Ecosystem-based Adaptation (EbA) pilot was conducted in 2016 and 2017 with a group of 26 smallholder households. All survey respondents acknowledged that they depend on ecosystems and services for their livelihoods. Extreme weather events are predicted to increase with climate change. Smallholder farmers and ecosystems were most vulnerable to the effects of droughts and heat waves that limited supplies of clean water and impacted crop harvests, and by storms, whirlwinds and cold spells. The EbA pilot identified that all ecological patches provided direct and indirect benefits through multiple goods and services generated for provision, regulation, supporting and cultural services. The pilot demonstrated that ecosystem services supported smallholder farmers to adapt to extreme events and climate change, in particular, by mitigating the effects of droughts. Management of ecosystem services can provide joint benefits for both climate change mitigation and adaptation, particularly where the spatial distributions of carbon, hydrological services or biodiversity are positively correlated.

Spatial Distribution of Carbon, Nitrogen and Phosphorus within Surface Sediments in the Lower Lancang River: Pollution Assessment Related to Dams

Surface sediment is one of the main sources of nutrients in overlying water environments, and these can also indirectly reflect the degree of eutrophication. In this paper, the spatial distribution characteristics of total organic carbon (TOC), total nitrogen (TN) and total phosphorus (TP) in the surface sediments of 11 sections in the lower Lancang River during flood season are analyzed, as well as the distribution of phosphorus in different forms. The main sources of TOC and its correlation with TN and TP are discussed and, finally, the pollution levels of the surface sediments are evaluated. The results show that the average content of TOC in the surface sediments of the lower Lancang River is 9003.75 mg/kg. The average TN content is 893.79 mg/kg, while the average TP content is 521.35 mg/kg. The TOC in the surface sediments of the lower Lancang River is derived mainly from algae and plankton in the river, and the TN and TP have similar sources. The total phosphorus in the surface sediments of the lower Lancang River is composed mainly of calcium-bound phosphorus (Ca-P). The evaluations of the organic pollution index and comprehensive pollution index show that the surface sediment pollution degree at the upper sections of the Nuozhadu and Jinghong Dams are more serious than those below the dams. Furthermore, the tributary sections are all slightly polluted, with the exception of the Mengyang River, which is considered moderately polluted.

Evidence for large scale fractionation of carbon isotopes and of nitrogen impurity during crystallization of gem quality cubic diamonds from placers of North Yakutia

The spatial distribution of carbon and nitrogen isotopes and of nitrogen concentrations is studied in detail in three gem quality cubic diamonds of variety II according to Orlov’s classification. Combined with the data on composition of fluid inclusions our results point to the crystallization of the diamonds from a presumably oxidized carbonate fluid. It is shown that in the growth direction δ13C of the diamond becomes systematically lighter by 2–3‰ (from –13.7 to –15.6‰ for one profile and from –11.7 to –14.1‰ for a second profile). Simultaneously, we observe substantial decrease in the nitrogen concentration (from 400–1000 to 10–30 at ppm) and a previously unrecognized enrichment of nitrogen in light isotope, exceeding 30‰. The systematic and substantial changes of the chemical and isotopic composition can be explained using the Burton-Prim-Slichter model, which relates partition coefficients of an impurity with the crystal growth rate. It is shown that changes in effective partition coefficients due to a gradual decrease in crystal growth rate describes fairly well the observed scale of the chemical and isotopic variations if the diamond-fluid partition coefficient for nitrogen is significantly smaller than unity. This model shows that nitrogen isotopic composition in diamond may result from isotopic fractionation during growth and not reflect isotopic composition of the mantle fluid. Furthermore, it is shown that the infra-red absorption at 1332 сm-1 is an integral part of the Y-defect spectrum. In the studied natural diamonds the 1290 сm-1 IR absorption band does not correlate with boron concentration.

Comparing soil carbon estimates in glaciated soils at a farm scale using geospatial analysis of field and SSURGO data

Soil carbon is a key soil property related to ecosystem services and it is often used in soil carbon content estimates at various scales. Uncertainties in soil carbon estimates often arise from variability in field, laboratory, and/or geospatial data at a farm scale. The objectives of this study were to quantify and compare levels of soil organic carbon (SOC), soil inorganic carbon (SIC), and total soil carbon (TC) for a 147-hectare field site in upstate New York based on three alternative analysis procedures: a) using carbon concentrations reported by the Soil Survey Geographic (SSURGO) spatial databases for each soil map unit (SMU) present at the field site and applying that value across each SMU; b) averaging the carbon contents of soil cores collected within a specific SMU boundary and applying the averaged value across each SMU; and c) interpolating carbon contents across the field site based on the individual soil cores. Maps of SOC, SIC, and TC contents based on the interpolated core samples were different from maps created by applying averaged core results or SSURGO values across the SMUs. Differences in the magnitudes and spatial distributions of carbon can be attributed to several factors. For example, SSURGO soil carbon values are frequently measured for a selected pedon(s) from a “type location” and not from the actual study location. These “type locations” can be located far from study sites and even in different states. Also, SSURGO soil carbon values may overestimate the actual contents when compared to systematic field measurements because the SSURGO values at lower depths are often extrapolated from upper soil horizons. Such extrapolations affect inorganic carbon to a much greater extent than organic carbon, therefore better agreement is observed in the present study between SOC estimates from the SSURGO database and field measurements. Because regional and/or global carbon estimates are rarely made with detailed field data due to the high costs of field and laboratory measurements, additional field sampling is needed to constrain and improve these estimates and also to assess the potential variability present.

Effect of variable soil texture, metal saturation of soil organic matter (SOM) and tree species composition on spatial distribution of SOM in forest soils in Poland

In this study we investigated the effect of fine (ϕ<0.05mm) fraction, i.e., silt+clay (FF) content in soils, site moisture, metal (Al and Fe) of soil organic matter (SOM) and forest species composition on the spatial distribution of carbon (C) pools in forest soils at the landscape scale. We established 275 plots in regular 200×200m grid in a forested area of 14.4km2. Fieldwork included soil sampling of the organic horizon, mineral topsoil and subsoil down to 40cm deep. We analysed the vertical and horizontal distribution of soil organic carbon (SOC) stocks, as well as the quantity of physically separated fractions including the free light (fLF), occluded light (oLF) and mineral associated fractions (MAF) in the mineral topsoil (A, AE) horizons. Distribution of C in soils was predominantly affected by the variation in the FF content. In soils richer in the FF more SOC was accumulated in mineral horizons and less in the organic horizons. Accumulation of SOC in mineral soil was also positively affected by the degree of saturation of SOM with Al and Fe. The increasing share of beech influenced the distribution of C stock in soil profiles by reducing the depth of O horizon and increasing C stored in mineral soil. The content of FF was positively correlated with the content of C in MAF and fLF fractions. The content of oLF and MAF fractions was also positively influenced by a higher degree of metal saturation, particularly Al. Our results confirmed that Al plays an important role in the stabilization of SOM inside aggregates (CoLF) and as in CMAF fractions. We also found a significant, positive effect of beech on the CfLF and fir on the CoLF content.