Changes In Soil Organic Carbon Storage Research Articles

Distribution and Storage Characteristics of Soil Organic Carbon in Tidal Wetland of Dandou Sea, Guangxi

In order to study the distribution characteristics of soil organic carbon (SOC) and soil organic carbon storage (SOCS) among different wetland types in Dandou Sea tidal wetland in Guangxi, firstly, based on Sentinel–2 imaging and random forest algorithm, combined with the existing tidal wetland data, a 10 m resolution tidal wetland dataset in Guangxi from 2019 to 2023 was generated, covering mangroves, salt marshes and tidal flats. The results show that the overall accuracy of the recognition results is higher than 96%, and the Kappa coefficient is higher than 0.95, which indicates high accuracy. Subsequently, the distribution characteristics and influencing factors of SOC and SOCS in different habitats were analyzed. The results showed that the SOC content of mangroves and salt marshes was higher than that of tidal flats. The SOC content of mangrove, salt marshes and tidal flats in 0–60 cm soil layer was 5.30–10.42 g/kg, 7.60–9.84 g/kg, and 1.29–2.25 g/kg, respectively. The changes of SOCS were 12.41–26.48 t/ha, 19.58–24.15 t/ha, and 3.61–6.86 t/ha, respectively. With the increase of soil depth, the SOC and SOCS of mangroves decreased gradually, and the SOC and SOCS of salt marshes increased gradually, and SOC and SOCS were mainly affected by soil bulk density (BD), soil moisture content (MC) and pH.

Depth-dependent responses of soil organic carbon under nitrogen deposition.

Emerging evidence points out that the responses of soil organic carbon (SOC) to nitrogen (N) addition differ along the soil profile, highlighting the importance of synthesizing results from different soil layers. Here, using a global meta-analysis, we found that N addition significantly enhanced topsoil (0-30 cm) SOC by 3.7% (±1.4%) in forests and grasslands. In contrast, SOC in the subsoil (30-100 cm) initially increased with N addition but decreased over time. The model selection analysis revealed that experimental duration and vegetation type are among the most important predictors across a wide range of climatic, environmental, and edaphic variables. The contrasting responses of SOC to N addition indicate the importance of considering deep soil layers, particularly for long-term continuous N deposition. Finally, the lack of depth-dependent SOC responses to N addition in experimental and modeling frameworks has likely resulted in the overestimation of changes in SOC storage under enhanced N deposition.

Recovery of soil organic carbon storage driven by microbial communities during long-term natural restoration in wetland ecosystems

Natural restoration offers a positive strategy for maintaining biodiversity and addressing climate change. Wetland is an important “carbon sink”, yet the dynamic of soil organic carbon (SOC) storage and how it is driven by microbial communities and activities remain unclear during natural restoration. In this work, we investigated the variations of soil organic carbon (SOC) storage, bacterial and fungal communities, as well as microbial activities (including microbial biomass carbon, carbon mineralization rate and extracellular enzymes) in naturally restored wetlands with restoration years of 0 (rice field reclaimed from natural wetland), 15, 20 and 40 in the Poyang Lake wetland. Results showed that SOC storage had been restored to its natural level after 20 years of natural rejuvenation, which was driven by microbial communities via impacting oxidase (peroxidase), microbial biomass and microbial quotient. Fungal diversity and community composition had strong positive effects on SOC storage, while the role of bacteria was limited, emphasizing that fungi exerted a more important control over carbon stock during natural restoration. Fungal taxa Sordariomycetes and Eurotiomycetes were the dominant microbial predictors of SOC storage. Besides, natural restoration significantly shifted bacteria and fungi communities, as well as microbial activities toward a pattern similar to that of natural wetlands. To sum up, our results highlight the significance of natural restoration for recovering carbon storage, and the addition of microbial attributes can potentially improve our capacity to predict changes in SOC storage in wetland ecosystems.

Climatic water availability modifies tree functional diversity effects on soil organic carbon storage in European forests.

Forest stand and environmental factors influence soil organic carbon (SOC) storage, but little is known about their relative impacts in different soil layers. Moreover, how environmental factors modulate the impact of stand factors, particularly species mixing, on SOC storage, is largely unexplored. In this study, conducted in 21 forest triplets (two monocultures of different species and their mixture on the same site) distributed in Europe, we tested the hypothesis that stand factors (functional identity and diversity) have stronger effects on topsoil (FF + 0-10cm) C storage than environmental factors (climatic water availability, clay + silt content, oxalate-extractable Al-Alox) but that the opposite occurs in the subsoil (10-40cm). We also tested the hypothesis that functional diversity improves SOC storage under high climatic water availability, clay + silt contents, and Alox. We characterized functional identity as the basal area proportion of broadleaved species (beech and/or oak), and functional diversity as the product of broadleaved and conifer (pine) proportions. The results show that functional identity was the main driver of topsoil C storage, while climatic water availability had the largest control on subsoil C storage. Functional diversity decreased topsoil C storage under increasing climatic water availability, but the opposite was observed in the subsoil. Functional diversity effects on topsoil C increased with increasing clay + silt content, while its effects on subsoil C were negative at increasing Alox content. This suggests that functional diversity effect on SOC storage changes along gradients in environmental factors and the direction of effects depends on soil depth.

Gypsum, crop rotation, and cover crop impacts on soil organic carbon and biological dynamics in rainfed transitional no-till corn-soybean systems.

Soil organic carbon (SOC), a core soil quality indicator, is influenced by management practices. The objective of our 2012-2016 study was to elucidate the impact of gypsum, crop rotation, and cover crop on SOC and several of its biological indicators under no-till in Alabama (Shorter), Indiana (Farmland), and Ohio (Hoytville and Piketon) in the USA. A randomized complete block design in factorial arrangement with gypsum (at 0, 1.1, and 2.2 Mg/ha annually), rye (Secale cereal L.) vs no cover crop, and rotation (continuous soybean [Glycine max (L) Merr., SS] vs corn [Zea mays, L.]-soybean, both the CS and SC phases) was conducted. Composite soils were collected (0-15 cm and 15-30 cm) in 2016 to analyze microbial biomass C (SMBC), SOC, total N, active C, cold and hot-water extractable C, C and N pool indices (CPI and NPI), and C management index (CMI). Results varied for main effects of gypsum, crop rotation, and cover crop on SOC pools, total N, and SOC lability within and across the sites. Gypsum at 2.2 Mg/ha increased SMBC within sites and by 41% averaged across sites. Likewise, gypsum increased SMBC:SOC, active C, and hot-water C (as indicators of labile SOC) averaged across sites. CS rotation increased SOC, active C, CPI, and CMI compared to SS, but decreased SMBC and SMBC:SOC within and across sites. CPI had a significant relationship with NPI across all sites (R2 = 0.90). Management sensitive SOC pools that responded to the combined gypsum (2.2 Mg/ha), crop rotation (CS), and cover crop (rye) were SMBC, SMBC:SOC, active C, and CMI via SMBC. These variables can provide an early indication of management-induced changes in SOC storage and its lability. Our results show that when SOC accumulates, its lability has decreased, presumably because the SMBC has processed all readily available C into a less labile form.

Differential Responses of Soil Extracellular Enzyme Activities to Salinization: Implications for Soil Carbon Cycling in Tidal Wetlands

AbstractRising sea levels are expected to cause salinization in many historically low‐salinity tidal wetlands. However, the response of soil extracellular enzyme activities to salinization in tidal wetlands and their links to soil organic carbon (SOC) decomposition are largely unknown. Here, we conducted a global meta‐analysis to examine the effect of salinization on hydrolytic and oxidative carbon‐acquiring enzyme activities and their relationships with SOC storage in tidal wetlands. The results showed that salinization reduced hydrolytic carbon‐acquiring enzyme activities by 33% but increased oxidative carbon‐acquiring enzyme activities by 15%. Meanwhile, salinization decreased SOC storage by 14%, and the change in SOC storage was negatively associated with oxidative carbon‐acquiring enzyme activities. These results indicate an important role for oxidative carbon‐acquiring enzymes in SOC loss in tidal wetlands. Moreover, the effect of salinization on oxidative carbon‐acquiring enzyme activities logarithmically declined with increasing salinization, implying that SOC loss was highly sensitive to even minor increases in salinity at the initial stage of salinization. Given increasing salinization over time with rising sea levels in most global tidal wetlands, our results suggest that SOC loss might be greater during early than later stages. Consequently, salinization‐induced SOC loss may be overstated in the long term if extrapolations are merely based on a constant SOC loss rate determined from short‐term studies. Future modeling frameworks should account for this changing sensitivity of microbially mediated SOC loss with increasing salinization over time.

Impacts of mulching measures on crop production and soil organic carbon storage in a rainfed farmland area under future climate

Mulch planting techniques are used widely to increase the crop yield in the Loess Plateau region of China. However, the impacts of long-term mulching measures on crop productivity and soil organic carbon (SOC) storage under climate change are still unclear. In this study, the denitrification-decomposition (DNDC) biogeochemistry model was calibrated based on field test data from 2013 to 2018, and the downscaling predicted climate data from 33 Global Climate Models (GCMs) were used to assess the future trends in spring maize yield and soil organic carbon storage changes under different mulching tillage measures (i: conventional tillage without mulching as the control (CK); ii ridge–furrow planting with half plastic film mulching (R); iii: straw mulching (S); iv: dual mulching of the ridge (film) and furrow (straw) (RS)) in the Loess Plateau region. The results showed that the precipitation and temperature will increase in the future (2021–2100), especially under RCP8.5. Similarly, crop productivity has been more substantial increase under RCP8.5. Under both scenarios, the predicted yield increase under each treatment was greater in the early period than the later period, and the RS treatment obtained the largest increase. However, when the annual precipitation exceeded 600 mm, the yield increase was not significant under R. Sensitivity analysis showed that ridge and furrow mulching measures reduced the sensitivity of the yield to precipitation changes. In the future, SOC storage increased slightly with both CK and R under RCP4.5, but both showed a downward trend under RCP8.5, respectively. R treatment showed a lower temperature threshold, and when the temperature was increased above 9.60 °C, the carbon loss rate accelerated. Under S and RS, the SOC storage tended to increase due to straw mulching. All these results indicated that in the future period, when the annual precipitation exceeded 600 mm and the annual average temperature exceeded 9.60 °C, ridge-furrow plastic film mulching was not suitable in this area, dual mulching of the ridge with film and furrow with straw may help to achieve sustainable high maize yields in the Loess Plateau region.

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.

Simulated soil organic carbon stocks in northern China’s cropland under different climate change scenarios

The accumulation and dynamic stock of soil organic carbon (SOC) in agricultural land are highly sensitive to changes in climate. However, there is uncertainty about how the global SOC cycle will respond to future climate change. In order to assess changes in SOC storage, basing on the historical weather data and field observations (1951–2018), the study used the DeNitrification-DeComposition (DNDC) model to simulate future SOC storage in an arid oasis under three representational concentration paths (RCPs): RCP2.6, low-end path; RCP4.5, middle stable path; and RCP8.5, high-end path) for the period from 2018 to 2086. Farmland soil in the Yanqi Basin in northern China was divided into grid units using ArcGIS, and then kriging interpolation was used to extract the mean value of the 200 grid units to calculate regional changes in SOC storage. The model indicated that more than 92.75 % of the measured results accurately simulated the SOC storage in Yanqi Basin cropland. The measured SOC storage in the Yanqi Basin was 1.32 Tg C in 2018. The range of SOC density was 653.27–5527.04 kg C/hm2 under the historical climate scenario, and 1863.99–4581.16 kg C/hm2, 2372.74–6910.15 kg C/hm2, and 623.656–5431.95 kg C/hm2 under the RCP 2.6, RCP 4.5, and RCP 8.5 scenarios, respectively. The simulation results show that, compared with the SOC stock in 2018, the SOC stocks in the oasis area in the future will show a rapid decline under the historical climate scenario (7.6 % decrease) as well as in the RCP 2.6 (3% decrease), RCP 4.5 (9.17 % decrease), and RCP 8.5 (16 % decrease) scenarios. These results indicate that organic carbon outputs and density will decrease faster under high emissions and more slowly under low emissions. This study provides supporting data and a scientific basis for increasing soil organic carbon in cropland and for the management of oasis soil to mitigate the effects of future climate change.

Spartina alterniflora invasion controls organic carbon stocks in coastal marsh and mangrove soils across tropics and subtropics

Coastal wetlands are among the most productive ecosystems and store large amounts of organic carbon (C)-the so termed "blue carbon." However, wetlands in the tropics and subtropics have been invaded by smooth cordgrass (Spartina alterniflora) affecting storage of blue C. To understand how S. alterniflora affects soil organic carbon (SOC) stocks, sources, stability, and their spatial distribution, we sampled soils along a 2500km coastal transect encompassing tropical to subtropical climate zones. This included 216 samplings within three coastal wetland types: a marsh (Phragmites australis) and two mangroves (Kandelia candel and Avicennia marina). Using δ13 C, C:nitrogen (N) ratios, and lignin biomarker composition, we traced changes in the sources, stability, and storage of SOC in response to S. alterniflora invasion. The contribution of S. alterniflora-derived C up to 40cm accounts for 5.6%, 23%, and 12% in the P. australis, K. candel, and A. marina communities, respectively, with a corresponding change in SOC storage of +3.5, -14, and -3.9tCha-1 . SOC storage did not follow the trend in aboveground biomass from the native to invasive species, or with vegetation types and invasion duration (7-15years). SOC storage decreased with increasing mean annual precipitation (1000-1900mm) and temperature (15.3-23.4℃). Edaphic variables in P. australis marshes remained stable after S. alterniflora invasion, and hence, their effects on SOC content were absent. In mangrove wetlands, however, electrical conductivity, total N and phosphorus, pH, and active silicon were the main factors controlling SOC stocks. Mangrove wetlands were most strongly impacted by S. alterniflora invasion and efforts are needed to focus on restoring native vegetation. By understanding the mechanisms and consequences of invasion by S. alterniflora, changes in blue C sequestration can be predicted to optimize storage can be developed.

Monitoring Grassland Management Effects on Soil Organic Carbon—A Matter of Scale

Introduction of temporary grasslands into cropping cycles could be a sustainable management practice leading to increased soil organic carbon (SOC) to contribute to climate change adaption and mitigation. To investigate the impact of temporary grassland management practices on SOC storage of croplands, we used a spatially resolved sampling approach combined with geostatistical analyses across an agricultural experiment. The experiment included blocks (0.4- to 3-ha blocks) of continuous grassland, continuous cropping and temporary grasslands with different durations and N-fertilizations on a 23-ha site in western France. We measured changes in SOC storage over this 9-year experiment on loamy soil and investigated physicochemical soil parameters. In the soil profiles (0–90 cm), SOC stocks ranged from 82.7 to 98.5 t ha−1 in 2005 and from 81.3 to 103.9 t ha−1 in 2014. On 0.4-ha blocks, the continuous grassland increased SOC in the soil profile with highest gains in the first 30 cm, while losses were recorded under continuous cropping. Where temporary grasslands were introduced into cropping cycles, SOC stocks were maintained. These observations were only partly confirmed when changing the scale of observation to 3-ha blocks. At the 3-ha scale, most grassland treatments exhibited both gains and losses of SOC, which could be partly related to soil physicochemical properties. Overall, our data suggest that both management practices and soil characteristics determine if carbon will accumulate in SOC pools. For detailed understanding of SOC changes, a combination of measurements at different scales is necessary.

Soil organic carbon and total nitrogen stocks as affected by vegetation types and altitude across the mountainous regions in the Yunnan Province, south-western China

The soil organic carbon (SOC) and nitrogen (N) in the Yunnan Province, southwestern China, is related to the complex topography and multiple vegetation zones. However, the variation in SOC and total nitrogen (TN) stocks under different vegetation types and altitudes in the mountainous regions in Yunnan is still unknown. This study aimed to investigate the spatial distribution of SOC and TN stocks affected by different vegetation types and altitudes within three soil depths (0–20 cm, 20–40 cm, and 40–60 cm) and to determine the factors controlling the SOC and TN stocks across the mountainous regions in western Yunnan. Nine vegetation types, including tropical rainforest (TR), tropical monsoon forest (TM), broad-leaved evergreen forest (BLE), evergreen coniferous and broad-leaved mixed forest (ECB), broadleaved deciduous forest (BLD), coniferous forest (CF), alpine shrub meadow (ASM), dark coniferous forest (DC) and alpine meadow (AM), along with an altitude gradient (600–4500 m), were selected. The results showed that the SOC and TN contents decreased with increasing soil depth in most vegetation types, except DC. Soils under different vegetation types with pH ranging from 3.25 to 3.74 and 5.10 to 6.68 had significantly higher SOC stocks than soils with pH ranging from 3.99 to 5.09 (P < 0.05). The SOC and TN stocks were positively correlated with the mean annual temperature and mean annual precipitation. Higher SOC stocks (64.01–139.88 Mg ha−1) and TN stocks (23.42–49.36 Mg ha−1) were observed in CF, ASM, DC and AM with higher altitudes (3600–4500 m) than other vegetation types with lower altitudes (600–3600 m). The significant linear relationship between SOC and TN stocks (P < 0.01) demonstrated that most of the variations in TN are related to the changes in SOC storage, and the accumulation of SOC could influence TN stocks. Our results also suggest that vegetation type, altitude and pH could be the major factors controlling the spatial distribution of SOC and TN in mountainous regions.

Effects of long-term straw return on soil organic carbon storage and sequestration rate in North China upland crops: A meta-analysis.

Soil organic carbon (SOC) is essential for soil fertility and climate change mitigation, and carbon can be sequestered in soil through proper soil management, including straw return. However, results of studies of long-term straw return on SOC are contradictory and increasing SOC stocks in upland soils is challenging. This study of North China upland agricultural fields quantified the effects of several fertilizer and straw return treatments on SOC storage changes and crop yields, considering different cropping duration periods, soil types, and cropping systems to establish the relationships of SOC sequestration rates with initial SOC stocks and annual straw C inputs. Our meta-analysis using long-term field experiments showed that SOC stock responses to straw return were greater than that of mineral fertilizers alone. Black soils with higher initial SOC stocks also had lower SOC stock increases than did soils with lower initial SOC stocks (fluvo-aquic and loessial soils) following applications of nitrogen-phosphorous-potassium (NPK) fertilizer and NPK+S (straw). Soil C stocks under the NPK and NPK+S treatments increased in the more-than-20-year duration period, while significant SOC stock increases in the NP and NP+S treatment groups were limited to the 11- to 20-year period. Annual crop productivity was higher in double-cropped wheat and maize under all fertilization treatments, including control (no fertilization), than in the single-crop systems (wheat or maize). Also, the annual soil sequestration rates and annual straw C inputs of the treatments with straw return (NP+S and NPK+S) were significantly positively related. Moreover, initial SOC stocks and SOC sequestration rates of those treatments were highly negatively correlated. Thus, long-term straw return integrated with mineral fertilization in upland wheat and maize croplands leads to increased crop yields and SOC stocks. However, those effects of straw return are highly dependent on fertilizer management, cropping system, soil type, duration period, and the initial SOC content.

Balancing nutrient stoichiometry facilitates the fate of wheat residue‑carbon in physically defined soil organic matter fractions

Preserving and enhancing soil organic carbon (SOC) stocks is one of the major objectives for sustainable agriculture. The exogenous nutrient supply along with returning crop residues, i.e., integrated residue-nutrient management, may increase carbon (C) cycling and residue-derived microbial biomass, and therefore to affect SOC stocks. However, there is a lack of knowledge about how the integrated residue-nutrient management, that balances the resource nutrient stoichiometry, facilitates the fate (or partitioning) of residue-C in physically defined SOC fractions. Hence, through a laboratory study, we quantified the fate of wheat residue (δ13C-enriched, 494‰) into sequentially separated physical SOC fractions, under the interaction of different residue rates (6.7 and 20.0 g kg−1 soil) and nutrient inputs (nil, low and high supplies of nitrogen, phosphorus, and sulfur) in two contrasting soils (Luvisol and Vertisol). The results showed that after 245 days, 42.7–54.2% of the newly-added residue-13C remained in organic matter (OM) fractions in the soils, with 22.1–40.8% in the light fraction [LF; defined as free particulate organic matter (f-POM)] and 13.9–19.5% in the heavy fraction [HF; defined as aggregate- & mineral-protected OM, which included silt-clay OM and occluded POM (o-POM)]. Following the sequential separation of HF, 8.3–15.3% of residue-13C was distributed to silt-clay OM and 4.2–6.1% to o-POM after 245 days. The high-residue rate (cf. low-residue) increased the amount of residue-C in SOC fractions. Narrowing the C-nutrient stoichiometric ratio in the residue treated soils via the exogenous nutrient input affected the proportional distribution of residue-C in SOC fractions at the high-residue rate only. With the high-residue rate in both soils, nutrient input (cf. no-nutrient) at both rates increased “new” residue-derived stable C formation in the HF by 17% or silt-clay associated OM by 27%, while decreased the distribution of residue-13C in the f-POM (LF) by 26% or o-POM by 18%. In the current study, soil type also affected the incorporation of residue-C in the organo-mineral fractions, i.e., 20% higher residue-C was incorporated in the silt-clay OM in the Vertisol than Luvisol. This study improved our knowledge on the distribution of residue-C in SOC fractions in response to integrated residue-nutrient management, which could be used to refine conceptual and mechanistic models for predicting changes in SOC storage.

Evolvement rules of basin flood risk under low-carbon mode. Part I: response of soil organic carbon to land use change and its influence on land use planning in the Haihe basin

Soil organic carbon (SOC) plays an important role in the global carbon cycle. The aim of this study was to evaluate the response of SOC to land use change and its influence on land use planning in the Haihe basin, and provide planning land use pattern for basin flood risk assessment. Firstly, the areas of different land use types in 1980, 2008, and the planning year (2020) were counted by area statistics function of ArcGIS. Then, the transfer matrixes of land use were produced by spatial overlay analysis function. Lastly, based on the land use maps, soil type map and soil profile database, SOC storage of different land use types in three different periods were calculated. The results showed the patterns of land use have changed a lot from 1980 to 2008, among the 19,835km2 of grassland was transformed into forestland, which was the largest conversion landscape. And land use conversion brought the SOC storage changes. Total carbon source was 88.83Tg, and total carbon sink was 85.49Tg. So, the Haihe basin presented as a carbon source from 1980 to 2008. From 2008 to 2020, the changes of forestland and grassland are the biggest in Haihe basin, which cause the SOC pool change from a carbon source to a carbon sink. SOC storage will increase from 2420.5Tg in 2008 to 2495.5Tg in 2020. The changing trend is conducive to reducing atmospheric concentrations. Therefore, land use planning in Haihe basin is reasonable and can provide the underlying surface condition for flood risk assessment.

Spatial Expansion and Soil Organic Carbon Storage Changes of Croplands in the Sanjiang Plain, China

Soil is the largest pool of terrestrial organic carbon in the biosphere and interacts strongly with the atmosphere, climate and land cover. Remote sensing (RS) and geographic information systems (GIS) were used to study the spatio-temporal dynamics of croplands and soil organic carbon density (SOCD) in the Sanjiang Plain, to estimate soil organic carbon (SOC) storage. Results show that croplands increased with 10,600.68 km2 from 1992 to 2012 in the Sanjiang Plain. Area of 13,959.43 km2 of dry farmlands were converted into paddy fields. Cropland SOC storage is estimated to be 1.29 ± 0.27 Pg C (1 Pg = 103 Tg = 1015 g) in 2012. Although the mean value of SOCD for croplands decreased from 1992 to 2012, the SOC storage of croplands in the top 1 m in the Sanjiang Plain increased by 70 Tg C (1220 to 1290). This is attributed to the area increases of cropland. The SOCD of paddy fields was higher and decreased more slowly than that of dry farmlands from 1992 to 2012. Conversion between dry farmlands and paddy fields and the agricultural reclamation from natural land-use types significantly affect the spatio-temporal patterns of cropland SOCD in the Sanjiang Plain. Regions with higher and lower SOCD values move northeast and westward, respectively, which is almost consistent with the movement direction of centroids for paddy fields and dry farmlands in the study area. Therefore, these results were verified. SOC storages in dry farmlands decreased by 17.5 Tg·year−1 from 1992 to 2012, whilst paddy fields increased by 21.0 Tg·C·year−1.

Soil Organic Carbon Storage Changes in Coastal Wetlands of the Liaohe Delta, China, Based on Landscape Patterns

Growing wetland loss along a coastal area in China was examined through shoreline recession and land use changes. Carbon storage or sequestration in coastal wetland soils was based on vertical marsh accretion and aerial change data. Marshes sequester significant amounts of carbon through vertical accretion; however, large amounts of carbon previously sequestered in the soil profile are lost through rapid land use changes and shoreline recessions. The Liaohe Delta (LHD) was divided into nine landscape types based on Landsat TM digital images from 1991 to 2011. The distributed areas and transfer matrices of each landscape type were calculated. Combined with the organic carbon content and bulk density of 202 soil surface samples from field investigations in 2012, the soil organic carbon pools and stocks were estimated. Results showed that the soil organic carbon pools varied from 0.58 to 9.75 kg m−2, and organic carbon storage in the upper 20 cm of soil was 1935.92 × 104 and 1863.87 × 104 t in 1991 and 2011, respectively. We attributed these large losses of carbon to rapid land use changes. The construction of levees along the shoreline has triggered large instantaneous losses of previously sequestered carbon through the destruction of 278.06 km2 of tidal flats. Our results reveal that the LHD wetlands might not serve as a desired sink of carbon if maladministration practices are applied. These results can provide scientific guidance for decision makers in determining an effective way to maintain the soil carbon pool in the wetlands of the LHD.

Three-decade long fertilization-induced soil organic carbon sequestration depends on edaphic characteristics in six typical croplands.

Fertilizations affect soil organic carbon (SOC) content but the relative influences of the edaphic and climate factors on SOC storage are rarely studied across wide spatiotemporal scales. This study synthesized long-term datasets of fertilization experiments in six typical Chinese croplands, and calculated annual C input from crops and manure amendments, changes in SOC storage (ΔSOC) and C sequestration efficiency (i.e. the percentage of soil C change per unit of C input, hereafter referred as CSE) in 0–20 cm soil over three decades. Three fertilization treatments include no fertilization (CK), chemical nitrogen, phosphorus and potassium fertilizers (NPK) and combined chemical fertilizers and manure (NPKM). Results showed significant fertilization effects on C input and ΔSOC (NPKM>NPK>CK), and significantly higher CSE in Qiyang at Hunan than Zhengzhou at Henan and Heihe at Heilongjiang. The variance partitioning analysis (VPA) showed more variance of CSE can be explained by edaphic factors (up to 39.7%) than other factors. Furthermore, soil available N content and pH were identified as the major soil properties explaining CSE variance. This study demonstrated key controls of soil fertility factors on SOC sequestration and informs the need to develop strategic soil management plan to promote soil carbon sequestration under long-term intensive fertilization.

Carbono orgánico del suelo en bosques riparios, arrozales y pasturas en Piedras, Tolima, Colombia.

&lt;p class="p1"&gt;El objetivo del estudio fue estimar el almacenamiento de carbono orgánico del suelo (COS) en la interface entre bosques riparios y una matriz de arrozales y pasturas con manejo orgánico. La investigación se efectuó en el municipio de Piedras, Departamento del Tolima, Colombia. Se seleccionaron dos lotes en producción (arroz y pastura) y se estimó el COS en ellos y en borde e interior de bosques riparios adyacentes a 0-20 cm de profundidad. Se cuantificó la densidad aparente y la concentración de carbono orgánico entre mayo y julio de 2013. Se estimó el potencial cambio en el COS por cambios de uso del suelo entre el arroz, pastura y los bosques riparios. Las interfaces arroz-bosque ripario y pastura-bosque ripario almacenaron en promedio 65,6 y 61,3 t C/ha, respectivamente, sin diferencias significativas (p&amp;gt;0,05). No se detectaron diferencias estadísticas (p&amp;gt;0,05) entre matrices agropecuarias (arroz y pastura) en ninguna de las variables. La posición de muestreo (matriz y borde e interior de los bosques) tuvo impacto significativo (p&amp;gt;0,05) solo en la densidad aparente: 1,7 vs 1,1 vs 1,0 g/cm&lt;span class="s2"&gt;3 &lt;/span&gt;al interior y el borde de los bosques y la matriz, respectivamente. El COS no fue afectado estadísticamente (p&amp;gt;0,05) por la posición en la interface bosque ripario-matriz. La conversión de bosques riparios a arrozales o pasturas con manejo orgánico no está emitiendo gases de efecto invernadero, por el contrario, está incrementando el COS en 3,2 t C/ha.&lt;/p&gt;

秦岭南坡红桦林土壤有机碳密度影响因素

PDF HTML阅读 XML下载 导出引用 引用提醒 秦岭南坡红桦林土壤有机碳密度影响因素 DOI: 10.5846/stxb201406271326 作者: 作者单位: 西北农林科技大学林学院,西北农林科技大学林学院,西北农林科技大学林学院,西北农林科技大学林学院 作者简介: 通讯作者: 中图分类号: 基金项目: 林业公益性行业科研专项项目(201204502) Factors affecting soil organic carbon density in Betula albo-sinensis forests on the southern slope of the Qinling Mountains Author: Affiliation: College of Forestry,Northwest A&F University,Yangling,College of Forestry,Northwest A&F University,Yangling,College of Forestry,Northwest A&F University,Yangling,College of Forestry,Northwest A&F University,Yangling Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:以秦岭南坡红桦林为研究对象,利用标准地调查法获得林分、地形、土壤相关数据,分析红桦林土壤有机碳密度(SOCD)分异特征及其与林分因子和地形因子间的关系。结果表明:秦岭南坡红桦林土壤有机碳密度总体均值为(69.02±12.90)t/hm2,原始红桦林土壤有机碳密度均值为(76.21±10.83)t/hm2,次生红桦林为(65.24±12.32)t/hm2,原始红桦林土壤有机碳密度比次生红桦林高16.81%,t-检验结果显示两者存在显著差异;在不同林区间,红桦林土壤有机碳密度亦存在显著差异(P < 0.05)。从地形因子看,红桦林土壤有机碳密度在不同坡位和坡向间未表现出显著差异,而海拔和坡度对红桦林土壤有机碳密度有较为显著的影响。土壤有机碳密度与海拔、林龄、乔木生物量和草本生物量呈显著正相关,与坡度和林分密度呈显著负相关;主成分分析表明:特征值大于1的四个主成分对土壤有机碳密度的方差累积贡献率为85.62%,海拔、坡度、林分密度和郁闭度是影响秦岭南坡红桦林土壤有机碳密度的主要因子;通过逐步回归分析得到利用海拔、坡度、林龄、林分密度、乔木生物量和草本生物量估算红桦林土壤有机碳密度的模型:SOCD=0.015E-0.332G-0.026FD+0.304SA+0.105BA+21.673BH+36.358。 Abstract:Soil organic carbon, the main part of the terrestrial ecosystem carbon pool, is an essential component of the terrestrial carbon cycle, and one of the most important components of research on global change. Accurate estimation of soil organic carbon storage is important for determining the role that soil organic carbon plays in the terrestrial ecosystem carbon cycle, and thus in changes in the global environment. Forest soil organic carbon storage changes according to topography and forest conditions; therefore, research on forest organic carbon in a variety of such conditions is essential to determine the relationship between soil organic carbon storage, and factors related to topography and forest conditions. Betula albo-sinensis forest is one of the principal forest types in the Qinling Mountains. This study aimed to analyze the distribution patterns of soil organic carbon density (SOCD), and to reveal the relationship between soil organic carbon density and factors influencing Betula albo-sinensis forest on the southern slopes of the Qinling Mountains. We investigated topographical, stand, and soil factors of 122 plots, each of which was 20×30 m. Inventory data (i.e., elevation, gradient, slope position, slope aspect, canopy density, plant cover, biomass, mean height, and mean diameter at breast height) of Betula albo-sinensis individuals in each plot were measured and recorded. Soil samples were tested for SOCD, moisture density, and bulk density. Results indicated that the average SOCD was (69.02±12.90) t/hm2. In virgin forest, the average SOCD was (76.21±10.83) t/hm2, in secondary forest, (65.24±12.32) t/hm2. The difference in average SOCD between them was significant. The average SOCD decreased with soil depth increasing, and the average SOCD for soil layers A-C was (31.52±6.57), (27.18±6.49), and (10.32±2.65) t/hm2, respectively. The average SOCD (t/hm2) differed by forest region (Xunyangba=(58.80±10.29), Huoditang=(67.95±10.25), Huangbaiyuan=(69.63±12.78), and Guanyinshan=(75.82±12.30)). One-way ANOVA analysis showed that differences in average SOCD were significant for the four forest regions and soil layers, but not significant for slope positions. Differences in SOCD between shady and sunny slopes were insignificant, based on t-tests. Correlation analysis showed that SOCD was positively correlated with elevation, stand age, arbor biomass, and herb biomass, but negatively correlated with surface gradient and forest density. Principal component analysis showed that elevation and gradient were the first principal components affecting SOCD. Canopy density and forest density were the second principal components, stand age the third, and arbor biomass and herb biomass the fourth. These four principal components accounted for 85.62% of the variance of SOCD. Stepwise regression analysis showed that the effect of different factors on soil organic carbon density was unclear. However, stand age, elevation, gradient, arbor biomass, and herb biomass were the predominant factors affecting SOCD. 参考文献 相似文献 引证文献