Economics- and policy-driven organic carbon input enhancement dominates soil organic carbon accumulation in Chinese croplands.

Carbon stocks are calculated between from 0 - 100 cm depths of Adana great soil groups (GSG). Total carbon stock is 567.19 Tg in 0 - 100 cm, 168.37 Tg of which is organic carbon (OC) and 398.83 Tg of which is inorganic carbon (IC). While 77.81% of soil organic carbon consists of alluvial, brown and non-calcareous brown forest soils, 59.77% of soil inorganic carbon (SIC) consists of alluvial, colluvial and brown forest soils. Organic carbon stocks are mostly seen in non-calcareous brown forest soils (53.75 Tg or 31.92% of OC stocks, 22.61% of all area). The least stock is determined in alluvial coast soils (0.02 Tg or 0.01% of OC stocks, 0.01% of all area). Inorganic carbon stocks are mostly found in alluvial soils (165.7 Tg or 41.65% of SIC stocks, 19.88% of all area) and it is least seen in alluvial coast soils (0.12 Tg or 0.03% of SIC stocks, 0.01% of all area). While soil organic carbon amount is between 6.01 - 13.78 kg C m-2, soil inorganic carbon amount changes between 26.27-60.01 kg C m-2. Generally, it is seen that soil organic carbon amount is low in the area where intense agriculture techniques are used and it is high in meadow and forest areas which form high areas. Key words: Adana soils, soil organic carbon amounts and stocks, soil inorganic carbon amounts and stocks.

Cropland soils in China have a large potential for carbon sequestration based on literature survey

Effects of contrasting soil management regimes on total and labile soil organic carbon fractions in a loess soil in China

Carbon sequestration significantly aids in mitigating climate change, with its spatial distribution greatly influenced by topographical factors. However, data on organic carbon distribution and its interaction with topographic factors inside the forest of the Far Western Region of Nepal are limited. Therefore, this study aims to analyze forest carbon stock variation under different topographic variables (physiographic region, aspect, and slope) in Far-western Nepal. In this study, stratified systematic cluster sampling was adopted with elevation, aspect, and slope as strata. A total of 181 circular plots were used for dendrometric measurements and soil sample collection. Within each plot, diameter at breast height and height of each tree (diameter at breast height ≥ 5 cm) were measured for biomass carbon assessment. Composite soil samples (0-30 cm) from each soil pit within a plot were collected for determining soil organic carbon stock. Physiographic region-wise, our study reported the highest mean aboveground carbon (174.04 ± 29.75 ton ha-1) and belowground carbon (34.044 ± 5.95 ton ha-1) and soil organic carbon stock (150.62 ± 11.02 ton ha-1) in the Mountain and High Himal region. The East aspect exhibited the highest aboveground carbon (125.9 ± 22.34 ton ha-1) and belowground carbon (27.54 ± 3.44 ton ha-1) stocks, while the North aspect showed the highest soil organic carbon stock (96.85 ± 8.82 ton ha-1). Organic carbon stocks declined with steeper slopes, with the (0-10)° slope category recording the highest aboveground organic carbon (135.17 ± 17.87 ton ha-1), belowground carbon (27.03 ± 3.57 ton ha-1), and soil organic carbon (107.14 ± 12.51 ton ha-1) stocks. Conversely, the (30-40)° slope category exhibited the lowest organic carbon stocks across all pools. This study's findings will support accurate monitoring, reporting, and verification (MRV) processes for initiatives like reducing emissions from deforestation and forest degradation (REDD+) and enhance credibility on United National Framework Convention on Climate Change (UNFCCC) reporting on a national scale. The design and application of site-specific management activities to optimize organic carbon storage are recommended due to the observed variability of organic carbon stock with topographic factors.

Forest mineral soil is one of the terrestrial carbon pools, and changes in forest management practices can affect the carbon stock in forest soil. The purpose of the study is to estimate temporal fertilization impact on mineral soil organic carbon stock, depending on fertilizers applied, forest stand type, different dominant tree species of the stands. Coniferous and birch forest stands with mineral soil in the central and eastern part of Latvia were selected for the experiment. The fertilizers used were wood ash and nitrogen containing mineral fertilizer. No significant differences in organic carbon stock in O horizon were detected 2–5 years after fertilization. A tendency of smaller organic carbon stock in upper mineral soil layers (0–10 cm, 10–20 cm) was found in most part of objects. Significantly smaller organic carbon stock was found in upper mineral soil layers (0–10 cm and 10–20 cm) in birch stands with wet mineral soil treated with ammonium nitrate if compared to the control plots, possibly due to a different soil moisture regime of forest stands. The positive and significant correlations between soil organic carbon and nitrogen stocks were found in most part of the objects.

River ecosystems are one of the dynamic components of the terrestrial carbon cycle that provide a crucial function in ecosystem processes and high value to ecosystem services. A large amount of carbon is transported from terrestrial to the ocean through river flows. In order to evaluate the contribution of Sile River ecosystem to the global carbon stock, the river ecosystem Organic Carbon (OC) stock was quantified for sediments and dominant submerged aquatic macrophytes (SAMs) during the two sampling periods at three different stations along the Sile River (North Eastern Italy). The total mean ecosystem OC stock was 95.2 ± 13.8 Mg C ha−1 while those of SAMs ranged from 7.0 to 10.9 Mg C ha−1 which accounted for approx. 10% of the total OC stock. The total aboveground biomass retains approx. 90% of the SAM carbon stock, with a mean of 8.9 ± 1.6 Mg C ha−1. The mean sediment OC stock was 86.6 ± 14.5 Mg C ha−1 with low seasonal variations among the sites. Indeed, various environmental parameters and hydrodynamics appear to affect the accumulation of OC within the river ecosystem. The results highlight the role that freshwater river ecosystems play in the global carbon cycle, which consequently provide a baseline for future river ecosystem monitoring programs. Furthermore, future studies with additional sites and seasonal surveys of the river will enhance our understanding of the effects of global climate change on the river ecosystem and improve the ecosystem services.

Recent studies have highlighted the valuable role played by mangrove forests in carbon sequestration and storage. Although Indonesia accounts for a large proportion of global mangrove area, knowledge on the carbon stock and sources in the Indonesian mangrove is still limited. In this study, we quantified the ecosystem organic carbon (OC) stock and its spatial variation at an oceanic mangrove in Wori, North Sulawesi, Indonesia. The sources of soil OC were also investigated. The results showed that the mangrove soil had a substantial OC stock containing 15.4 kg/m2 (calculated by carbon) in the top 50 cm soil, and represented the majority of the ecosystem OC stock at the Wori mangrove. The mangrove biomass and ecosystem OC stock were 8.3 kg/m2 and 23.7 kg/m2, respectively. There was no significantly difference in the soil OC stock among the stations with difference distances offshore, while the highest mangrove biomass OC stock was found at the seaward station. Isotope mixing calculations showed that the rich OC in mangrove soils was attributed to the accumulated autochthonous mangrove source while the suspended organic matter in tidal water and the mangrove-adjacent seagrass contributed less than 20% to the soil OC. The results further demonstrated the importances of the oceanic mangrove in carbon storage and the mangrove plants in contributing OC to their soils.

Regional organic carbon stock variability: A comparison between depth increments and soil horizons

No-tillage with straw mulch is an effective way to achieve soil sustainability. However, the specific redistributions of soil organic carbon composition, stocks, and crop yield remain unclear. The hypothesis that no-tillage had a minor effect on soil organic carbon stocks in 0–50 cm but decreased crop yield compared to plow-tillage under straw return was tested in this study. Soils properties from two decades of rice-wheat rotation field experiment were related to the yield of rice and wheat depending on tillage: 1) plow-tillage without straw return, 2) no-tillage with straw mulch, and 3) plow-tillage with straw return. No-tillage with straw mulch had the highest mean weight diameter of soil aggregates, the contents of macro-aggregates (>0.25 mm) organic carbon, particulate organic carbon (>53 µm), and soil organic carbon across tillage practices in 0–5 cm. However, it decreased the contents of macro-aggregates (>0.25 mm) organic carbon in 5–15 cm, the particulate organic carbon in 5–50 cm, and soil organic carbon in 5–30 cm compared to plow tillage with straw return due to less carbon input from roots and straw. Organic carbon stocks in micro-aggregates (<0.25 mm) and mineral-associated organic matter (<53 µm) did not vary between tillage practices. Hence the soil organic carbon stocks of plow tillage without straw return (48 Mg ha−1) were similar to that of no-tillage with straw mulch (51 Mg ha−1) but lower than that of plow tillage with straw return (57 Mg ha−1) in 0–50 cm. The mean annual yields of wheat and rice under no-tillage with straw mulch (14 t ha−1) were lower than that of plow tillage without straw return (15 t ha−1) and plow tillage with straw return (16 t ha−1). No-tillage-induced high soil bulk densities limited the rice yields. The yield losses of no-tillage with straw mulch were higher in rice than in wheat. The rice yield losses of no-tillage with straw mulch compared to plow tillage with straw return increased with experiment duration due to decreased available nitrogen in 7–14 cm and phosphorus contents in 0–14 cm over time. Conclusively, plow-tillage is more efficient for carbon sequestration and yield increase than no-tillage under straw return in rice-wheat farming by increasing carbon input in deep soils, soil available nutrients, and decreasing soil compactness.

&amp;lt;p&amp;gt;The decline in organic carbon (OC) stocks after conversion from grassland to cropland under conventional soil tillage practices was 24-32% for American prairie soils. The respective decreases in OC stocks ranged from 27% to more than 40% for steppe soils of the European part of Russia and was about 31% in semi-arid steppe soils of South Siberia. Here, we present results on the soil OC stocks in steppe soils of Northern Kazakhstan, which partly were converted to arable land over the last 60 to 90 years. We sampled soils by genetic horizons along a north-south transect, where precipitation increased towards north but negligible variation in temperature. Soil samples were analyzed for organic and inorganic carbon as well as bulk density.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;Surprisingly, we found along the transect on average only 3.5% smaller OC stocks at 0-10 cm depth in arable than in natural soils. Even more astonishing, all arable soils tested had larger OC stocks in the layers beneath 10 cm depth than the natural steppe soils. On average, the OC stocks in 10-100 cm depth were 34% larger in soils under arable management than in natural steppe soils. We credit the enhanced deep soil accumulation of OC in arable soils of Northern Kazakhstan to colloidal translocation of OC-rich particles along vertical pores. The cause of the increased in colloidal transport under arable management is still under evaluation but appears connected to the clayey soil texture and the large abundance of expandable clay minerals. We conclude that despite of the intense land use and severe climatic conditions accumulation of subsoil carbon is possible even after many decades of cultivation history. Our findings stress the importance of considering whole soil profiles for analyzing the consequences of land use change on the net carbon balance of soils.&amp;lt;/p&amp;gt;

Sedimentary organic carbon and nitrogen stocks of intertidal seagrass meadows in a dynamic and impacted wetland: Effects of coastal infrastructure constructions and meadow establishment time

Legacy of plaggen agriculture: High soil organic carbon stocks as result from high carbon input and volume increase

Small scale spatial variability of organic carbon stocks in litter and solum of a forested Luvisol

Organic layer and clay content control soil organic carbon stocks in density fractions of differently managed German beech forests

Soil organic carbon (SOC) in cropland is of great importance to the global carbon (C) balance and to agricultural productivity, but it is highly sensitive to human activities such as irrigation and crop rotation. It has been observed that under certain improved management practices, cropland soils can sequestrate additional C beyond their existing SOC level before reaching the C saturation state. Here we use data from worldwide, long‐term agricultural experiments to develop two statistical models to determine the saturated SOC level (SOCS) in upland and paddy agroecosystems, respectively. We then use the models to estimate SOC sequestration potential (SOCP) in Chinese croplands. SOCP is the difference between SOCS and existing SOC level (SOCE). We find that the models for both the upland and paddy agroecosystems can reproduce the observed SOCS data from long‐term experiments. The SOCE and SOCS stock in Chinese upland and paddy croplands (0–30 cm soil) are estimated to be 5.2 and 7.9 Pg C with national average densities of 37.4 and 56.8 Mg C ha−1, respectively. As a result, the total SOC sequestration potential is estimated to be 2.7 Pg C or 19.4 Mg C ha−1 in Chinese cropland. Paddy has a relatively higher SOCE (45.4 Mg C ha−1) than upland (34.7 Mg C ha−1) and also a greater SOCP at 26.1 Mg C ha−1 compared with 17.2 Mg C ha−1 in the upland. The SOC varies dramatically among different regions. Northeast China has the highest SOCE and SOCS density, while the Loess Plateau has the greatest SOCP density. The time required to reach SOC saturation in Chinese cropland is highly dependent on management practices applied. Chinese cropland has relatively low SOC density in comparison to the global average but could have great potentials for C sequestration under improved agricultural management strategies.