土壤碳库构成研究进展

No‐till ( NT ) farming can restore the soil organic carbon ( SOC ) pool of agricultural soils, but the SOC pool size and retention rate can vary with soil type and duration of NT . Therefore, the objectives of this study were to determine the effects of NT and soil drainage characteristics on SOC accumulation across a series of NT fields on Alfisols in Ohio, USA . Sites under NT for 9 ( NT 9), 13 ( NT 13), 36 ( NT 36), 48 ( NT 48) and 49 ( NT 49) years were selected for the study. Soil was somewhat poorly drained at the NT 48 site but moderately well drained at the other sites. The NT 48 and NT 49 on‐station sites were under continuous corn ( Zea mays ), while the other sites were farmers' fields in a corn–soybean ( Glycine max ) rotation. At each location, the SOC pool (0–30 cm) in the NT field was compared to that of an adjacent plough‐till ( PT ) and woodlot ( WL ). At the NT 36, NT 48 and NT 49 sites, the retention rate of corn‐derived C was determined using stable C isotope ( 13 C) techniques. In the 0‐ to 10‐cm soil layer, SOC concentration was significantly larger under NT than PT , but a tillage effect was rarely detected below that depth. Across sites, the SOC pool in that layer averaged 36.4, 20 and 40.8 Mg C/ha at the NT , PT and WL sites, respectively. For the 0‐ to 30‐cm layer, the SOC pool for NT (83.4 Mg C/ha) was still 57% greater than under PT . However, there was no consistent trend in the SOC pool with NT duration probably due to the legacy of past management practices and SOC content differences that may have existed among the study sites prior to their conversion to NT . The retention rate of corn‐derived C was 524, 263 and 203 kg C/ha/yr at the NT 36, NT 48 and NT 49 sites. In contrast, the retention rate of corn‐C under PT averaged 25 and 153 kg C/ha/yr at the NT 49 (moderately well‐drained) and NT 48 (somewhat poorly drained) sites, respectively. The conversion from PT to NT resulted in greater retention of corn‐derived C. Thus, adoption of NT would be beneficial to SOC sequestration in agricultural soils of the region.

The huge background pool of soil organic carbon (SOC) is likely to impede the ready detection of SOC changes. We propose to explore SOC changes by monitoring the dynamics of soil labile organic carbon (LOC); namely if LOC could be largely retained in soils rather than respired rapidly, the SOC would be ready to be sequestered. The effects of the two major functional groups of plants, that is, canopy trees and understory plants, on SOC accumulation were then illustrated with this LOC‐based approach. The characteristics of LOC and SOC of topsoils (0–20 cm) in a field manipulation experiment with 5‐yr treatments of understory removal and tree girdling in both a young and a mature Eucalyptus plantations were examined. The concentration and potential turnover time of soil LOC were used to indicate the state of vegetation‐induced C accumulation in soils, which were estimated by a sequential fumigation‐incubation procedure. Soil natural abundances of 13C and 15N were measured to reflect the proportion of newly retained LOC in soils. We found that, in the young plantation, understory removal did not significantly affect both soil LOC and SOC concentrations, but significantly increased the potential turnover time of soil LOC. In contrast, in the mature plantation, understory removal significantly decreased soil LOC and SOC concentrations, but did not significantly alter the potential turnover time of soil LOC. However, tree girdling did not significantly affect SOC concentration, soil LOC concentration, or potential turnover time in either the young plantation or the mature plantation. These results demonstrated that understory plant‐derived C was one of the major components of LOC pool in topsoils, and it may be readily mineralized in the young plantation but accumulated as an important fraction of SOC in the mature plantation. This study suggests that the LOC‐based approach is potentially useful in monitoring SOC changes and improves our understanding of how plant functional groups and soil fertility status could jointly affect LOC and SOC dynamics. In considering the great contribution of understory plants to SOC processes, we propose that understory plants should be maintained in subtropical plantation ecosystems.

Current status, uncertainty and future needs in soil organic carbon monitoring

Thermal analysis techniques have been used to differentiate soil organic carbon (SOC) pools with differing thermal stability. A correlation between thermal and biological stability has been indicated in some studies, while others reported inconsistent relationships. Despite these controversial findings and no standardized method, several recently published studies used thermal analysis techniques to determine the biological stability and quality of SOC in mineral soils. This study examined whether thermal oxidation at temperature levels between 200°C and 400°C, combined with evolving gas analysis and isotope ratio mass spectrometry, is capable of identifying SOC pools with differing biological stability in mineral soils. Soil samples from three sites being under Miscanthus (C4‐plant) cultivation for more than 17 years following former agricultural cropland (only C3‐plant) cultivation were used. Due to natural shifts in 13C content, young and labile Miscanthus‐derived SOC could be distinguished from stable and old C3‐plant‐derived SOC. The proportion of Miscanthus‐derived SOC increased significantly with increasing temperatures up to 350°C in bulk soil samples, indicating increasing oxidation of labile and young SOC with increasing temperatures. Use of density fractions to validate the thermally oxidized SOC from bulk soil samples revealed that the thermal oxidation patterns did not reflect the biological stability of SOC. The suggested biologically labile particulate organic carbon (light fraction from density fractionation) was clearly enriched in Miscanthus‐derived young SOC. The thermal oxidation patterns, however, revealed preferential oxidation of these biologically labile fractions not at low temperatures, but rather at higher temperatures. The reverse was found for the biologically stable mineral‐associated density fraction (heavy fraction). Based on different soil types, it was concluded that the thermal stability of SOC between 200°C and 400°C is not a suitable indicator of the biological stability of SOC and, thus, thermal oxidation is not capable of fractionating SOC pools with differing biological stability.

Conversion of coastal marshes to croplands shifts the pool, composition and functional groups of soil organic carbon.

Soil aggregate-associated carbon and organic carbon pools as affected by conversion of forest lands to agriculture in an acid soil of India

To tackle with the problem of prevailing farmland abandonment in winter, 5 treatments includes Chinese milk vetch-double cropping rice (CRR), rape-double cropping rice (RRR), garlic-double cropping rice (GRR), winter crop multiple cropping rotation (ROT), winter fallow control (WRR) were set up. By measuring soil total organic carbon, active organic carbon and its components and calculating the soil carbon pool management index in 0~15 cm and 15~30 cm soil layers in the early and late rice ripening stage. The effects of different winter planting patterns on the changes of soil organic carbon and carbon pool management index were discussed. In order to provide theoretical basis for the optimization and adjustment of winter planting pattern of double cropping rice field in the middle reaches of Yangtze River. The results showed that soil total organic carbon, active organic carbon and its components in different winter cropping patterns were increased, and ROT and CRR treatments were more beneficial to the accumulation of soil total organic carbon, active organic carbon and its components as well as the improvement of soil carbon pool management index, which should be preferred in the adjustment of cropping patterns.

Tropical forest development after slash‐and‐burn agriculture crucially affects soil carbon accumulation. However, it remains unclear how the dynamics of soil organic carbon (SOC) pools are regulated following tropical forest restoration. Our study aims to quantify the contribution of litter and soil variables to alterations in carbon pools during tropical forest restoration on slash‐and‐burn agricultural land in Xishuangbanna, Yunnan, China. This study observed a significant increase in soil carbon pools along forest restoration. The extent of the increase in labile fractions (1.9–2.5‐times) was higher than that of SOC (1.5‐times) during the restoration from early to later stages. The proportion of microbial carbon to total carbon increased from 3.0 to 7.7% during forest restoration, while those of dissolved (5.3–3.1%) and readily oxidizable (42.9–29.6%) fractions decreased. Clay content determined the accumulation dynamics of SOC (10.5%) and labile fractions (6.0–13.5%) in the later stage, while free Fe oxides (10.4–15.4%) contributed to these pools mainly in the early stage. Microbial carbon explained 22.4–26.7% and 20.6–28.3% of the variation in SOC stocks and labile fractions, respectively, whereas litter carbon accounted for 9.5–15.3% of the change in microbial carbon stock. The contribution (8.2–17.1%) of litter‐soil nutrient interactions to carbon pools increased during forest restoration. Our data suggest that carbon dynamics are mainly determined by variations in the clay content, free Fe oxides, and litter and microbial carbon, possibly through nutrient‐level interactions between the litter and soil during tropical forest restoration.

An approach to assess the soil organic carbon (SOC) pools in megapolises and in small settlements with due account for the natural, economic, and historical heterogeneity of urban territories; the degree of the soil sealing; and the specific features of their functional use is discussed. Cartographic information, satellite imagery, geoinformation systems, and field and literature data have been applied to adapt this approach for Moscow and for the town of Serebryanye Prudy in Moscow oblast. The pool of SOC has been calculated for the topsoil horizons (0–10 cm) and for the total thickness of the cultural layer (habitation deposits) in these urban areas. The total SOC pool comprises 13 833.0 × 103 t (with an error of 30–40%) for Moscow and 2 996.6 × 103 t (with an error of 50–70%) for Serebryanye Prudy. The specific carbon pools for these territories reach 128 and 810 t/ha, respectively. The cultural layer of Moscow concentrates about 75% of the total SOC pool; in Serebryanye Prudy, it contains about 95% of the total SOC pool. The SOC pools in the urban soils are comparable with or exceed the SOC pools in the corresponding natural zonal soils.

PDF HTML阅读 XML下载 导出引用 引用提醒 黄土丘陵区三种典型退耕还林地土壤固碳效应差异 DOI: 10.5846/stxb201201020003 作者: 作者单位: 西北农林科技大学资源与环境学院,西北农林科技大学农学院,西北农林科技大学资源与环境学院,西北农林科技大学资源与环境学院,西北农林科技大学资源与环境学院,西北农林科技大学资源与环境学院 作者简介: 通讯作者: 中图分类号: 基金项目: 陕西省自然科学基础研究计划资助项目(2010JQ5001); 教育部高等学校博士点基金(20090204120038); 国家自然基金(30971695); 西北农林科技大学基本科研业务费专项(QN2011153); 西北农林科技大学博士启动金(2010BSJJ032) Variance analysis of soil carbon sequestration under three typical forest lands converted from farmland in a Loess Hilly Area Author: Affiliation: Northwest Agricultural & Forestry University,Northwest Agricultural & Forestry University,,,, 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:探讨了黄土丘陵区退耕种植10-40a的柠条、沙棘及刺槐林地土壤总有机碳库及其活性组分密度随退耕时间、土层分布及相对比例的变化差异。结果表明:100 cm深土壤碳库在退耕10a时仅柠条林地碳库未比坡耕地显著增加,但退耕20-40a 3种林地比退耕10a时都已有显著增加,且增幅均为刺槐＞沙棘＞柠条,其中总有机碳的最大增幅分别达到90.92、27.87、14.89 Mg/hm2,活性有机碳的分别达到30.28、10.51、9.67 Mg/hm2。各还林地碳库增加在退耕10a时主要来自0-40 cm浅层土,而40-100 cm深层土碳库到退耕20a起才开始显著增加。对比退耕10a时,到退耕40a时柠条、沙棘及刺槐林地0-20 cm表层土分别平均累积了35.4%、27.9%、27.1%的总有机碳,20.2%、45.1%、23.1%的活性有机碳,而20-100 cm各土层间对碳库累积比例大小变化无一致规律,平均每20 cm厚土层累积了17.4%的总有机碳和17.6%活性有机碳。并且相比坡耕地,各林地均使100 cm深土壤活性有机碳占总有机碳的比例提高,改良了碳库质量。综上分析,长期退耕下3种林地固碳效应有明显差异,以刺槐林地碳累积效应较强。 Abstract:Quantifying soil carbon sequestration may be an important consideration under large scale afforestation because it has been counted in global carbon budgets according to the Kyoto Protocol. The conversion of cropland to forest as part of a huge ecological afforestation engineering scheme has played a very important role in reversing ecological destruction in the Loess Plateau and strongly affects the carbon cycle. This research was conducted to determine the changes in total soil organic carbon and its labile fraction in soil to 100 cm under three typical forested lands. These typical forest lands are Caragana, Buckthorn, and Robinia, which have been converted from farmland between 10 and 40 years ago in a Loess Hilly Area. The results showed that, compared with sloped farmland, the concentration of total organic carbon and labile organic carbon in soil at 100 cm was not higher in Caragana forest land 10 years after conversion from farmland. The carbon pool was significantly increased in Buckthorn and Robinia after the same period. Compared with 10 years since farmland conversion, the total organic carbon and labile carbon was further increased in all forest lands after 20 to 40 years of conversion from farmland. This increase followed the order Robinia > Buckthorn > Caragana, and the highest increase in total organic carbon reached 90.92, 27.87, and 14.89 Mg/hm2, and for labile organic carbon was 30.28, 10.51, and 9.67 Mg/hm2 respectively. The changes in soil organic carbon in different soil layers were also significantly different with time since farmland conversion. The soil organic carbon and its labile fraction was increased mainly in the 0-40 cm soil layer 10 years after farmland conversion in all forest lands. The soil organic carbon pools in the 40-100 cm layer were increased significantly 20 years after farmland conversion. As a result, all soil layers showed a contribution to soil organic carbon increase with long term conversion of cropland to forest. Forty years after farmland conversion 35.4%, 27.9%, and 27.1% of the increased total organic carbon and 20.2%, 45.1%, and 23.1% of the increased labile organic carbon in the soil to 100 cm was sequestrated in the 0-20 cm layer under Caragana, Buckthorn, Robinia forest land respectively. By contrast, the proportion of soil organic carbon sequestration showed inconsistent changes among the forest lands in the 20-100 cm soil layer, with an average of 17.4% of the increased total organic carbon and 17.6% of the increased labile organic carbon sequestrated in each 20 cm layer. Additionally, in comparison with sloped farmland, the ratio of labile organic carbon to total organic carbon was significantly different in each soil layer of all forest lands 40 years after farmland conversion. This was especially so in the 60-100 cm soil layer where the ratio was increased by 146.7%, 76.9%, and 126.1% in Caragana, Buckthorn, and Robinia forest lands, respectively. The ratio in the 100 cm soil layer also increased by 63.7%, 34.0%, and 47.0% in Caragana, Buckthorn, and Robinia, respectively, which indicated the activation of soil carbon pools had been enhanced, and the quality of soil was improved indirectly. Consequently, conversion of cropland to forest could sequestrate carbon in soil and Robinia is the better forest land to improve the soil organic carbon pool. Soil carbon sequestration following the afforestation of former arable land would be a powerful carbon sink for anthropogenic CO2 production in the Loess Plateau in the future. 参考文献 相似文献 引证文献

This study examines the responses of soil organic carbon (SOC) pools and their components to agricultural water drainage in paddy fields, with a focus on the wetland–paddy field ecotone of Xingkai Lake, a transboundary lake shared by China and Russia. Field investigations targeted three representative wetland vegetation types: Glyceria spiculosa (G), Phragmites australis (P), and Typha orientalis (T), across drainage durations ranging from 0 to over 50 years. SOC fractions, including light fraction organic carbon (LFOC), heavy fraction organic carbon (HFOC), dissolved organic carbon (DOC), and microbial biomass carbon (MBC), were systematically analyzed. The results revealed that SOC components in T and P wetlands steadily increased with drainage duration, whereas those in G wetlands exhibited a fluctuating pattern. SOC dynamics were primarily driven by LFOC, while MBC displayed species-specific variations. Correlation analyses and structural equation modeling (SEM) demonstrated that soil physicochemical properties, such as total nitrogen and moisture content, exerted a stronger influence on SOC fractions than microbial biomass. Overall, water drawdown significantly altered SOC dynamics, with distinct responses observed across vegetation types and wetland ages. This study provides critical data and theoretical insights for optimizing carbon sequestration and hydrological management in wetland–paddy field systems.

Can a ramped high-temperature carbon analyser with thermal oxidation be used to quantify soil organic carbon pools?

Nitrogen (N) deposition rates of terrestrial ecosystems have gradually declined but are still high in some areas. Previous studies have reported that N addition elicits diverse impacts on soil organic carbon (SOC) pools. SOC can be divided into different functional fractions, namely, particulate organic carbon (POC) and mineral-associated organic carbon (MAOC). The responses of these fractions to N addition should be elucidated to better understand the changes in SOC pools. Here, we conducted a N addition experiment (0, 40, and 80 kg N ha−1 yr−1) in a subtropical Castanopsis fabri forest to simulate N deposition. The surface (0−10 cm) SOC fractions, aboveground litter product, fine root (diameter < 2 mm) biomass, soil exchangeable cation content, and soil enzyme activity under different N addition treatments were measured. The results showed the following: (1) N addition showed a positive effect on POC and SOC contents but did not significantly affect MAOC content; (2) POC content was negatively correlated with pH and soil enzyme activity and positively correlated with aboveground litter product, suggesting that POC accumulation was influenced by aboveground litter input and microbial decomposition; (3) a close negative relationship was observed between exchangeable Al3+ and Ca2+ or K+ contents, indicating that there is likely to be a trade-off between the mineral sorption and desorption, thus resulting in an insignificant reaction of MAOC to N addition. Overall, the accumulation of SOC under short-term N addition was found to be primarily driven by POC, and the response of different SOC functional fractions to N addition was inconsistent. By incorporating these nuances into ecosystem models, it is possible to predict SOC dynamics more accurately in response to global change.

Salinity–induced land degradation poses a threat to environment and food production globally. Farmers' participatory research (2014–18) was carried out to assess the potential of gypsum (Gyp) and pressmud (PM) in alleviating the sodicity stress, and improvement in soil organic carbon (SOC) pools and its stability in the Trans Indo–Gangetic Plains of India. Intensive rice–wheat cultivation using alkali water increased soil pH, exchangeable sodium percentage (ESP), and bulk density (BD) causing a net depletion in SOC. Gypsum (supplies soluble Ca2+) and pressmud (mobilizes native CaCO3) mediated amelioration (Gyp + PM) significantly decreased soil sodification and compaction, and improved total organic carbon (TOC; 32%–64%) over the unamended control. Higher left–over C for SOC stabilization, crop biomass, and rhizodeposition returned through Gyp + PM significantly improved SOC pools and C sequestration culminating in ~25% yield superiority over the unamended control. Within SOC pools, highest proportion was equally retained in very labile and non–labile C pools. On average, the passive pool contained ~45% of TOC; albeit to a greater contribution through PM followed by Gyp + PM and Gyp. Rice–wheat system yield (RWSY) was positively correlated with SOC pools and indices while negatively correlated with soil pH, ESP, BD, CaCO3, and recalcitrant index. Multiple regression analysis showed stratification ratio, CaCO3, sensitivity index, and BD as key variables for yield prediction under the existing levels of soil sodicity. The key insights suggest ecosystem‐based approach using Gyp + PM in restoring the degraded lands, enhancing crop resilience and system (SOC enrichment and storage) stability, and achieving UN–Sustainable Development Goals related to food security and land degradation neutrality.

World soils have been a source of atmospheric carbon dioxide since the dawn of settled agriculture, which began about 10 millennia ago. Most agricultural soils have lost 30% to 75% of their antecedent soil organic carbon (SOC) pool or 30 to 40 t C ha−1. The magnitude of loss is often more in soils prone to accelerated erosion and other degradative processes. On a global scale, CO2-C emissions since 1850 are estimated at 270 ± 30 giga ton (billion ton or Gt) from fossil fuel combustion compared with 78 ± 12 Gt from soils. Consequently, the SOC pool in agricultural soils is much lower than their potential capacity. Furthermore, depletion of the SOC pool also leads to degradation in soil quality and declining agronomic/biomass productivity. Therefore, conversion to restorative land uses (e.g., afforestation, improved pastures) and adoption of recommended management practices (RMP) can enhance SOC and improve soil quality. Important RMP for enhancing SOC include conservation tillage, mulch farming, cover crops, integrated nutrient management including use of manure and compost, and agroforestry. Restoration of degraded/desertified soils and ecosystems is an important strategy. The rate of SOC sequestration, ranging from 100 to 1000 kg ha−1 year−1, depends on climate, soil type, and site-specific management. Total potential of SOC sequestration in the United States of 144 to 432 Mt year−1 (288 Mt year−1) comprises 45 to 98 Mt in cropland, 13 to 70 Mt in grazing land, and 25 to 102 Mt in forestland. The global potential of SOC sequestration is estimated at 0.6 to 1.2 Gt C year−1, comprising 0.4 to 0.8 Gt C year−1 through adoption of RMP on cropland (1350 Mha), and 0.01 to 0.03 Gt C year−1 on irrigated soils (275 Mha), and 0.01 to 0.3 Gt C year−1 through improvements of rangelands and grasslands (3700 Mha). In addition, there is a large potential of C sequestration in biomass in forest plantations, short rotation woody perennials, and so on. The attendant improvement in soil quality with increase in SOC pool size has a strong positive impact on agronomic productivity and world food security. An increase in the SOC pool within the root zone by 1 t C ha−1 year−1 can enhance food production in developing countries by 30 to 50 Mt year−1 including 24 to 40 Mt year−1 of cereal and legumes, and 6 to 10 Mt year−1 of roots and tubers. Despite the enormous challenge of SOC sequestration, especially in regions of warm and arid climates and predominantly resource-poor farmers, it is a truly a win-win strategy. While improving ecosystem services and ensuring sustainable use of soil resources, SOC sequestration also mitigates global warming by offsetting fossil fuel emissions and improving water quality by reducing nonpoint source pollution.