High Carbon Accumulation Research Articles

Environmental changes and human impacts over the past 1200 years: Evidence from high-resolution pollen records from peat in the Yunnan-Guizhou Plateau, Southwest China

Over the past millennium, the understanding of vegetation and climate changes in mountainous regions, driven by both natural and anthropogenic forces, remains unclear. In this study, we provide a high-resolution vegetation record spanning the past 1200 years from a subalpine peatland in the Niangniang Mountains, southwestern China. By analyzing pollen, charcoal, and loss-on-ignition from the peat sediment, we elucidate the interactions between vegetation, fire, and human impact. Our findings reveal that before 1150 CE, the mountains were covered with dense broadleaf forests and experienced minimal human activity. Natural forcings, primarily climatic conditions, drove vegetation succession and forest fires. After 1150 CE, the Human Influence Index (HII) increased sharply, coinciding with a rise in cereal-type pollen. Significant agricultural activities in the southwestern mountainous regions of China began after 1150 CE, which is later than those in the low-altitude lake basins of southwestern China. During the Medieval Climate Anomaly (MCA, 836–1400 CE), the Niangniang Mountains were characterized by warm and humid climatic conditions, a stable forested landscape, and a high peat carbon accumulation rate. Although human activities increased markedly during this period, the arbors did not undergo notable changes, and climate forcings continued to have a greater impact on vegetation than anthropogenic forcings. During the Little Ice Age (LIA, 1400–1900 CE), the regional vegetation landscape transitioned from dense forests to open grasslands as climate conditions became cold and dry, reducing peat carbon accumulation rate. This period also saw increased forest fires and significant human-driven deforestation, with anthropogenic forcings becoming dominant. After 1900 CE, vegetation changes were increasingly influenced by government policies. Comparison with major climate forcings and spectrum analysis have shown that variations in monsoon intensity, regulated by solar and volcanic activity, have influenced the climate and peat depositional environment in the Niangniang Mountains. Our research offers meaningful insights into forest conservation in the mountainous regions of the Yunnan-Guizhou Plateau.

The Growth and Carbon Sink of Tundra Peat Patches in Arctic Alaska

AbstractRecent amplified climate warming in the Arctic has caused profound changes in terrestrial ecosystems, with the potential for strong feedback on climate change. Arctic tundra landscapes have developed patchy and thin organic soil (peat) layers at the surface that may continue to grow into mature peatlands and become a larger carbon sink under future warming. Here we use paleoecological analyses of multiple soil and peat cores collected from the North Slope of Alaska to document and understand the formation and development histories of tundra peat patches and permafrost peatlands. We find a consistent peat development sequence for peat patches, first from mineral soils to sedge peat during the Little Ice Age, and then to Sphagnum peat during the recent warming with high carbon accumulation rates. These findings suggest that climate cooling is likely critical for the initial peat buildup on tundra soils due to reduced decomposition, whereas climate warming triggers the regime shift into an increased abundance of Sphagnum mosses that are likely central to enhancing their carbon sink capacity. Additionally, peat patches become similar to permafrost peatlands in the vicinity in terms of ecosystem processes and carbon dynamics, and therefore may have developed the same ecohydrological feedback system to maintain their long‐term stability. This study implies that the potential future expansion of peat patches into peatlands may strongly alter the carbon balance of Arctic tundra, supporting the new United Nations Environment Programme's report that calls for incorporating widespread shallow peat into understanding the peatland–carbon–climate nexus.

Water extractable carbon and nitrogen across vegetated and non-vegetated coastal habitats

Many coastal ecosystems have a high carbon (C) and nitrogen (N) accumulation capacity. Extractable C and N have been shown to be useful indicators to assess changes in soil C and N in terrestrial systems but have not been widely used in coastal habitats. Here, we quantified cold and hot water extractable organic C (cweC, hweC) and N (cweN, hweN) and determined specific ultraviolet absorbance (SUVA254) to evaluate how water extractable C and N concentration and chemistry change along the transition from mangrove (vegetated) to tidal flat (non-vegetated) and with sediment depth. Sediment cores (20 cm depth) were collected along transects in a muddy (29–46 % clay + silt, Snells Beach) and sandy (8–11% clay + silt, Hobson Bay) estuary in the Auckland region, New Zealand. Cold water exactable C and N concentrations were similar in the muddy and sandy estuary (7–173 μg C g−1 soil; 1–32 μg N g−1 soil). However, cweC and cweN made up a larger proportion of sediment C and N concentration at the sandy estuary. The hweC and hweN concentrations were significantly higher in the muddy (240–2440 μg C g−1 soil; 25–244 μg N g−1 soil) than sandy estuary (50–960 μg C g−1 soil; 6–119 μg N g−1 soil) suggesting a higher release of C and N from the muddy estuary with organic matter rich sediments. Habitat had a strong effect at both sites with extractable C and N concentrations being higher in mangroves compared to tidal flat. The C:N ratios and SUVA254 values of cweC tended to be lower than hweC across all habitats in both estuaries, suggesting a higher proportion of algal-derived organic matter and a lower proportion of aromatic molecules. Our findings demonstrate that water extractable C and N provide valuable insights into the quality and drivers of C and N in coastal habitats.

Cushion Plants from the Andes — an Overview of Current Knowledge and Some Research Needs

Cushion plants are a unique plant life form adapted to the harshest conditions of the alpine and Antarctic environments around the world. Along the rugged topography of the Andes, cushion plants play a key role often serving as keystone species that create milder conditions and microclimates and provide shelter for other organisms. Additionally, some of them have the ability to grow under waterlogged soils in peatlands, where they have deep roots systems and low organic matter decomposition rates, resulting in high carbon accumulation rates. In this article, we will delve into the intriguing world of Andean cushion plants, exploring their adaptations and ecological roles. At the end, we raise and question some issues about cushion plants ecological processes and their implications for future studies.

Biotic response of plankton communities to Middle to Late Miocene monsoon wind and nutrient flux changes in the Oman margin upwelling zone

Abstract. Understanding past dynamics of upwelling cells is an important aspect of assessing potential upwelling changes in future climate change scenarios. Our present understanding of nutrient fluxes throughout the world's oceans emphasizes the importance of intermediate waters transporting nutrients from the Antarctic divergence into the middle and lower latitudes. These nutrient-rich waters fuel productivity within wind-driven upwelling cells in all major oceans. One such upwelling system is located along the Oman margin in the western Arabian Sea (WAS). Driven by cross-hemispheric winds, the WAS upwelling zone's intense productivity led to the formation of one of the most extensive oxygen minimum zones known today. In this study covering the Middle to Late Miocene at Ocean Drilling Program (ODP) Site 722, we investigate the inception of upwelling-derived primary productivity. This study presents new plankton assemblage data in the context of existing model- and data-based evidence constraining the tectonic and atmospheric boundary conditions for upwelling in the WAS. With this research, we build upon the original planktonic foraminifer-based research by Dick Kroon in 1991 as part of his research based on the ODP LEG 117. We show that monsoonal winds likely sustained upwelling since the emergence of the Arabian Peninsula after the Miocene Climatic Optimum (MCO) ∼ 14.7 Ma, with fully monsoonal conditions occurring since the end of the Middle Miocene Climatic Transition (MMCT) at ∼ 13 Ma. However, changing nutrient fluxes through Antarctic Intermediate and sub-Antarctic Mode Waters (AAIW/SAMW) were only established after ∼ 12 Ma. Rare occurrences of diatom frustules correspond to the maximum abundances of Reticulofenestra haqii and Reticulofenestra antarctica, indicating higher upwelling-derived nutrient levels. By 11 Ma, diatom abundance increases significantly, leading to alternating diatom blooms and high-nutrient-adapted nannoplankton taxa. These changes in primary producers are also well reflected in geochemical proxies with increasing δ15Norg. values (> 6 ‰) and high organic carbon accumulation. These proxies provide further independent evidence for high productivity and the onset of denitrification simultaneously. Our multi-proxy-based evaluation of Site 722 primary producers provides evidence for a stepwise evolution of Middle to Late Miocene productivity in the western Arabian Sea for the first time. The absence of a clear correlation with existing deep marine climate records suggests that both local wind patterns and intermediate water nutrient changes likely modulated productivity in the western Arabian Sea during the Middle to Late Miocene. Finally, we show that using a multi-proxy record provides novel insights into how plankton responded to changing nutrient conditions through time in a monsoon-wind-driven upwelling zone.

Unexpected high alkyl carbon contents in organic matter-rich sandy agricultural soils of Northwest Central Europe

Carbon sequestration in Plaggic Anthrosols is most often investigated by bulk soil carbon inventories, without considering the form in which the carbon is stored (e.g., particulate or mineral-associated organic matter (OM), its capacity, or its chemical composition). Here, we focus on the unusual high organic carbon (OC) accumulation in sandy Plaggic Anthrosols and adjacent reference soils under agricultural use. In these soils, the mineral fraction ≤20 µm which is commonly assumed to be the major factor for OC stabilization, are very low in mass proportion. Soil organic matter (SOM) physical fractionation was done to evaluate the quantity and quality of OC in the topsoil (Ap horizon). For the fraction ≤20 µm (medium and fine silt-, and clay-sized particles), we measured the concentration of OC and calculated its OC storage capacity and contribution. The OC of the fraction ≤20 µm was radiocarbon-dated and analyzed for its chemical composition by solid-state 13C NMR spectroscopy. The highly sandy (∼90 % sand and coarse silt) soils showed an accumulation of OC much higher than the conventionally calculated saturation level controlled by the proportion of the fraction ≤20 µm. Unexpectedly, Plaggic Anthrosols and the respective reference soils showed similar fractional OC concentrations, radiocarbon ages, and OM composition. The isolated fraction ≤20 µm contained, on average, 81 % of the total soil OC in only 9 % of the corresponding soil mass. All soil fractions ≤20 µm are characterized by a high mean OC concentration in the topsoil (reference soils: 226 ± 66.5 mg OC g−1, Plaggic Anthrosols: 202 ± 59.0 mg OC g−1) with a C/N ratio of 15 on average for both soils. The OM composition of the fraction ≤20 µm was specifically rich in alkyl-C, with unusually low proportions of O-alkyl-C and low contents of aryl-C. The radiocarbon concentration (F14C) indicated that topsoil OM of the ≤20 µm fraction is stored for long time periods with high mean conventional radiocarbon ages (14C) not only for Plaggic Anthrosols (F14C: 0.92 ± 0.04; 14C: 639 yBP) but also for the reference soils (F14C: 0.93 ± 0.04; 14C: 575 yBP) and received low inputs of OC derived from recent photosynthesis. Our data indicate the existence of specific SOM accumulation processes in the investigated sandy agricultural soils, resulting particularly large SOM stocks which cannot be explained by mechanistic association of OM with mineral surfaces. It is not clear, if this inherited OM is stable under present-day soil and management conditions.

Effect of temperature on carbon accumulation in northern lake systems over the past 21,000 years

Introduction: Rising industrial emissions of carbon dioxide and methane highlight the important role of carbon sinks and sources in fast-changing northern landscapes. Northern lake systems play a key role in regulating organic carbon input by accumulating carbon in their sediment. Here we look at the lake history of 28 lakes (between 50°N and 80°N) over the past 21,000 years to explore the relationship between carbon accumulation in lakes and temperature changes.Method: For this study, we calculated organic carbon accumulation rates (OCAR) using measured and newly generated organic carbon and dry bulk density data. To estimate new data, we used and evaluated seven different regression techniques in addition to a log-linear model as our base model. We also used combined age-depth modeling to derive sedimentation rates and the TraCE-21ka climate reanalysis dataset to understand temperature development since the Last Glacial Maximum. We determined correlation between temperature and OCAR by using four different correlation coefficients.Results: In our data collection, we found a slightly positive association between OCAR and temperature. OCAR values peaked during warm periods Bølling Allerød (38.07 g·m−2·yr−1) and the Early Holocene (40.68 g·m−2·yr−1), while lowest values occurred during the cold phases of Last Glacial Maximum (9.47 g·m−2·yr−1) and Last Deglaciation (10.53 g·m−2·yr−1). However, high temperatures did not directly lead to high OCAR values.Discussion: We assume that rapid warming events lead to high carbon accumulation in lakes, but as warming progresses, this effect appears to change as increased microbial activity triggers greater outgassing. Despite the complexity of environmental forcing mechanisms affecting individual lake systems, our study showed statistical significance between measured OCAR and modelled paleotemperature for 11 out of 28 lakes. We concluded that air temperature alone appears to drive the carbon accumulation in lakes. We expected that other factors (catchment vegetation, permafrost, and lake characteristics) would influence accumulation rates, but could not discover a conclusive factor that had a statistical significant impact. More data available on long-term records from northern lake systems could lead to more confidence and accuracy on the matter.

The high organic carbon accumulation in estuarine wetlands necessarily does not represent a high CO2 sequestration capacity

Estuarine wetlands with high organic carbon (OC) accumulation rates due to their high plant biomass and interception of tide-derived OC are generally considered as large CO2 sinks. However, our previous study found that tidal OC input seems to stimulate soil CO2 emissions, potentially weakening CO2 sequestration in estuarine wetlands. To further verify this phenomenon, we first established a structural equation model, which confirmed a positive correlation between tidal OC input and soil organic carbon (SOC) and soil respiration. We then performed trace analysis to determine the stability of SOC derived from different sources and its effect on soil CO2 emissions by analyzing the input and retention of OC derived from tides and plants in the Yangtze Estuary wetlands. From upstream to downstream, as tidal OC input decreased, the relative retention ratio of the tidal OC in wetland soil increased from 1.259 to 2.148, whereas the relative retention ratio of plant OC in the soil decreased from 61.5% to 14.8%. Our findings indicated that the degradability of tidal OC was higher upstream than that downstream, but both inhibited plant OC degradation, thus providing an important reason for the higher CO2 emissions upstream of wetlands (with higher tidal OC input). In addition, the primarily contributor to CO2 (δ13) emissions’ transforming from plant SOC (81.35%) to tidal SOC (91.18%) was an increase in organic matter input from the tide in a microcosm system. Consequently, a higher CO2 output than CO2 input (plant OC) due to the ready degradation of tidal OC consequently weakens the CO2 sequestration capacity of the estuarine wetlands. This phenomenon is cause for concern regarding the CO2 sink function of estuarine wetlands intercepting large amounts of organic matter.

Organic Carbon Burial in Constructed Ponds in Southern Sweden

Small ponds constructed for nutrient retention, biodiversity conservation or recreation also store large amounts of carbon. The potential role of small ponds for carbon storage and greenhouse gas emissions have been highlighted both in the scientific literature and in management plans. The role of small ponds in the global carbon budget is likely significant, but the potential has not been fully explored. Here we present measurements of yearly sedimentary carbon accumulation and carbon stocks in six small, constructed and restored ponds in southern Sweden. The ponds were constructed or restored during the last 20 years primarily for nutrient retention. The sediment cores span the time from the construction of the ponds until today. The ponds had high carbon accumulation, with mean total carbon stocks in the top 6 cm of sediment of 836 g C m−2 and a yearly mean C accumulation rate of 152 g C m−2 yr−1. The total amount of restored wetlands within the restoration program studied here has a total area of 480 ha, and upscaling the carbon stocks to the whole area of restored ponds and wetlands gave a total carbon stock of 4.013 × 106 kg C in the top 6 cm of the sediments. If considering the potential increase of CO2 and CH4 from the ponds it is likely that the constructed ponds studied here are net carbon sources. We compared our results with published measurements of CO2 and CH4 emissions from small ponds in Sweden. This shows that the CO2 equivalent emissions could be between 1.8 and 37.5 times higher than the sedimentary carbon accumulation. Our data indicate that small constructed ponds are potential net carbon sources. Therefore, we suggest that using small, constructed, or restored ponds as carbon mitigation strategy must be done with caution, and the potential for increased methane emissions must be considered.

Soils, Geoenvironments and Ecosystem Services of a Protected Area in Western Brazilian Amazonia.

The Serra do Divisor National Park (SDNP) in the Westernmost Brazilian Amazonia possesses unique Mountain landscapes of sub-andean nature, with high geo-biodiversity and pristine environments, with a potential high contribution in ecosystems services. We studied and mapped the basic geo-environmental units of the main sector of the Park, evaluating soil carbon stocks as a key ecosystem service provided by the Protected Area. For the identification, characterization and mapping of the geoenvironmental units, we integrated pedological, geomorphological and vegetation data obtained by local soil survey and field campaigns, as well as secondary data. Eight geoenvironmental units were identified and mapped, distributed in three main compartments: the Serra do Divisor (SD) the upper Moa River and the medium Moa River. This region presents similar environments to the sub-Andean region, notably the Ceja Forest at the top surface of the SD. Soils at the SD have high organic carbon accumulation, with close association with the nutrient-poor, quartz-rich rocks, and shows organic matter illuviation indicating active podzolization. The SDNP encompasses important ecosystems and services linked with high geo-biodiversity, and high soil carbon stocks, representing a new frontier for scientific research in the only area of transitional sub-andean forested landscape in Brazil.

Carbon Pool in <i>Quercus lanuginose</i> (D. Don) Forest of Askot Wildlife Sanctuary, Western Himalaya in Relation to Stand Attributes

Following the acceptance of the Kyoto Protocol, data on forest biomass must be collected in order to determine the potential ability of forest stands to sequester atmospheric carbon and aid in the reduction of rising carbon dioxide levels in the atmosphere. The aim of this study was to estimate the amount of carbon fixed by one of the overexploited oak species ( Quercus lanuginosa ) in Askot Wildlife Sanctuary Western Himalaya, India. Thirty quadrats of 10x10 m size were placed randomly at three altitudes between 1900 and 2100 m asl and data on biomass and soil characteristics were collected. In three forest sites CBH (circumference at breast height) of 236 individuals with a diameter of ≥31 cm was measured and standing biomass was estimated following growing stock volume equations. Across the sites, the mean aboveground and belowground carbon stock was 475.8±84.9 and 119.8±18.1 Mg C ha -1 , respectively. The total tree carbon stock showed significant (P<0.01) positive correlation with soil carbon (R 2 = 0.71) and nitrogen (R 2 = 0.99). Basal area showed significant positive while diversity showed significant negative correlation with carbon stock. High carbon accumulation potential in old-growth individuals of Rianj oak suggests that they should be maintained in the study area to mitigate the effect of climate change.Â

The influences of volcanic eruptions on the development of peatland: A case study from the Changbai Mountains, Northeast Asia

Peatlands often develop around active volcanoes. However, little research has been conducted on the impacts of volcanic eruptions on peatland development. Here, we investigated the impacts of Holocene volcanic eruptions of the Changbaishan Volcanic field on the development of Dongfanghong peatland by using basal peat ages, geochemical and palaeoecological data. Analytical results suggest that lateral expansion process of the Dongfanghong peatland was due to paludification. This process was mainly controlled by complex volcanic lava terrain rather than climatic changes. Volcanic rocks provided an impervious horizon for the establishment of peat plants. Thick tephra layers resulted in the retrogressive succession of vegetation community that changed from mesomoor community dominated by the mixture of herbs and Sphagnum into the lowmoor community dominated by herbs. The subsequent high carbon accumulation rates were induced through the phosphorus release from tephra layers and formation of a impervious horizon. These results suggest that volcanic eruptions can significantly influence peatland development.

The High Organic Carbon Accumulation in Estuarine Wetlands Necessarily Does Not Represent a High Co2 Sequestration Capacity

The High Organic Carbon Accumulation in Estuarine Wetlands Necessarily Does Not Represent a High Co2 Sequestration Capacity

Mineral–organic associations are enriched in both microbial metabolites and plant residues in a subtropical soil profile under no-tillage and legume cover cropping

Context Knowledge of the impacts of no-tillage and cover cropping on carbon accumulation and stabilisation in highly weathered agricultural soils of subtropical regions is scant. We hypothesised that implementation of no-tillage coupled with high-quality legume residues in highly weathered agricultural soils would result in high carbon accumulation rates, mainly as microbe- and plant-derived materials in fine mineral–organic complexes. Aims and methods We sampled soil profiles down to 100 cm in a long-term field experiment and used density and particle size fractionation in combination with carbohydrate analyses to compare the effect of conventional tillage vs no-tillage, combined or not with legume cover cropping, and combined or not with mineral nitrogen fertilisation. Key results Both no-tillage and legume cover crops favoured the accumulation and enrichment in plant-derived carbohydrates in the surface soil layer, due to the accumulation of plant residues. The ratio of microbe- to plant-derived carbohydrates increased with soil depth indicating that the soil carbon (C) was more microbially processed than at the surface. Conservation management systems also increased soil C at depth and this was most visible in the clay fraction. The additional clay-size C accumulating at depth under conservation treatments was of both microbial and plant origin. Conclusions Our results support the hypothesis that mineral-associated C is composed of both plant and microbial residues and is positively influenced by conservation management practices. Implications Our results demonstrate that no-till and legume cover cropping are efficient practises to foster C accumulation and stabilisation in heavily weathered agricultural soil profiles in a subtropical climate.

Forest Structure, Diversity and Dynamics in Terra Firme and Igapó Gallery Forests in the Colombian Orinoco Basin

Studies of dynamics and biomass accumulation are essential for understanding forest functioning and productivity. They are also valuable when planning strategies for the conservation and sustainable use of natural resources. This study was conducted in five one-hectare plots of gallery forest in the Orinoco basin (three in terra firme and two in igapó floodplains), located in the Tomogrande Reserve, Santa Rosalía municipality, Vichada, Colombia. The differences between these forest types were determined and quantified considering diversity, floristic composition, aboveground biomass, forest dynamics and the influence of soils’ physicochemical composition. Terra firme forests were more diverse (Fisher’s α = 30.4) and had higher mortality and recruitment rates than igapó forests but there were no significant differences in stem turnover rates between forest types. Relative tree growth rate was also higher in terra firme than in igapó, but the opposite was found for biomass change (1.47 t/ha/year in igapó), resulting in an average carbon accumulation rate of 0.33 t/ha/year in terra firme and 0.66 t/ha/year in igapó. Igapó forest has high carbon accumulation potential given the high wood density of certain dominant species. Igapó soils contained a higher concentration of sand, silt, phosphorus and potassium ions, while terra firme soils had a higher clay content with lower pH. In general, the demographic and growth rates were consistent with those described for Amazonian forests. This study highlights the potential of igapó forest in the Orinoco basin as important carbon sinks, which should be included in the management and conservation strategies for this region.

Integrated Bioplant and Groundnut Husk Biochar Compost Application on Yield of Lettuce in a Rhodic Kandiustalf

Bioplant is a liquid soil conditioner that contains a consortium of beneficial fungi and bacteria manufactured by Artemis and Angel Company Limited in Bangkok. Bioplant is purported to stimulate beneficial microbial activity in soil and hence increase crop yield. However, the efficacy of Bioplant has not been evaluated on Ghanaian soils. A screen house trial was consequently conducted to evaluate the efficacy or otherwise of Bioplant on the yield of lettuce in a Rhodic Kandiustalf amended with or without compost. The soil was mixed with compost at 20 parts soil to 80 parts compost and 60 parts soil to 40 parts compost (v/v) and potted in 1.7-L pots. There was another potted soil with no compost amendment. To each of these potted soils, Bioplant was applied at four rates, viz., zero, half the manufacturer's recommended rate, the manufacturer's recommended rate, and twice the manufacturer's recommended rate, and allowed to equilibrate for 2 weeks. Seedlings of lettuce of the variety Eden were transplanted into the pots, and the treatments kept at 80% field capacity. The treatments were replicated four times in a completely randomized design. At physiological maturity, the lettuce was harvested, and fresh and dry matter yields were taken. The C and N contents and N uptake in the harvested plants were also determined. Results indicate that conditioning the soil with Bioplant at half and the manufacturer's recommended rates increased N uptake, resulting in higher carbon accumulation with concomitant increases in both fresh and dry matter yields. The results also show that amending the Rhodic Kandiustalf with Bioplant at twice the manufacturer's rate suppressed yield. Application of Bioplant at the manufacturer's recommended rate in combination with compost amended at 40 parts to 60 parts soil (v/v) saw a 47 and 90% respective significant yield increases in fresh weight and dry matter when only Bioplant was applied at the manufacturer's recommended rate. It is therefore recommended for Bioplant to be applied at the manufacturer's recommended rate of 825 mL/ha in combination with 40 parts of compost to 60 parts of soil (v/v).

Strategic tillage achieves lower carbon footprints with higher carbon accumulation and grain yield in a wheat-maize cropping system

Continuous single tillage has the potential to increase greenhouse gas (GHG) emissions and decrease the accumulation of soil organic carbon (SOC), thus increasing carbon footprints (CFs). However, in a wheat-maize cropping system, limited information was available about the effects of strategic tillage on CFs. Thus, a four-year field experiment was conducted, including continuous rotary tillage (RT), continuous no-till (NT), RT + subsoiling (RS), and NT + subsoiling (NS), to investigate the effects of NS (strategic tillage) on the unit area and unit yield. The results showed that CO2 emission was the highest contributor to CFs (73.92%) in a winter wheat-summer maize cropping system, following the order of NS < NT < RS < RT. The direct N2O emissions from fertilizers and residues were 4.43–4.51 t CO2-eq ha−1 yr−1 during the wheat and maize seasons, and indirect N2O emissions from irrigation and fertilizer inputs had a proportion of >80% from total agricultural inputs. The differences in SOC storage significantly affected the CFs. Although the NS treatment increased the amount of GHG emissions from the residues returned and consumption of diesel, the enhancement of SOC storage by deeper SOC increased. Thus, lower area-scaled CFs were observed in the NS treatment. Furthermore, a higher grain yield and an annual change of SOC storage compared with other treatments were observed under the NS system, which helped to reduce the CFs. The yield-scaled CFs followed the order of RT > RS > NT > NS when considering the changes in SOC storage. Therefore, the NS treatment resulted in a higher grain yield and SOC sequestration with lower CFs, and thus, it could be recommended as the best tillage method to achieve sustainable production and environmental balance in a wheat-maize cropping system.

High carbon accumulation rates in sediment adjacent to constructed oyster reefs, Northeast Florida, USA

High carbon accumulation rates in sediment adjacent to constructed oyster reefs, Northeast Florida, USA

In-Situ Synchrotron X-ray Diffraction Investigation of Microstructural Evolutions During Low-Pressure Carburizing

An experimental heat treatment chamber and control system were developed to perform in-situ X-ray diffraction experiments during low-pressure carburizing (LPC) processes. Results from the experimental chamber and industrial furnace were compared, and it was proven that the built system is reliable for LPC experiments. In-situ X-ray diffraction investigations during LPC treatment were conducted at the German Electron Synchrotron Facility in Hamburg Germany. During the boost steps, carbon accumulation and carbide formation was observed at the surface. These accumulation and carbide formation decelerated the further carbon diffusion from atmosphere to the sample. In the early minutes of the diffusion steps, it is observed that cementite content continue to increase although there is no presence of gas. This effect is attributed to the high carbon accumulation at the surface during boost steps which acts as a carbon supply. During quenching, martensite at higher temperature had a lower c/a ratio than later formed ones. This difference is credited to the early transformation of austenite regions having lower carbon content. Also, it was noticed that the final carbon content dissolved in martensite reduced compared to carbon in austenite before quenching. This reduction was attributed to the auto-tempering effect.

Colonization by native species enhances the carbon storage capacity of exotic mangrove monocultures

BackgroundThe fast-growing introduced mangrove Sonneratia apetala is widely used for mangrove afforestation and reforestation in China. Some studies suggested that this exotic species outperforms native species in terms of carbon sequestration potential. This study tested the hypothesis that multi-species mangrove plantations might have higher carbon sequestration potential than S. apetala monocultures.ResultsOur field measurements at Hanjiang River Estuary (Guangdong province, China) showed that the carbon stock (46.0 ± 3.0 Mg/ha) in S. apetala plantations where the native Kandelia obovata formed an understory shrub layer was slightly higher than that in S. apetala monocultures (36.6 ± 1.3 Mg/ha). Moreover, the carbon stock in monospecific K. obovata stands (106.6 ± 1.4 Mg/ha) was much larger than that of S. apetala monocultures.ConclusionsOur results show that K. obovata monocultures may have a higher carbon accumulation rate than S. apetala monocultures. Planting K. obovata seedlings in existing S. apetala plantations may enhance the carbon sink associated with these plantations.