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The soil organic carbon is critical in determining the sustainability, ecosystem services and atmospheric stability of any land use system. In this study, SOC and nitrogen pools across ten types of land use systems (LUSs) in the mid-hills of the northwestern Himalayas were estimated, namely sole cropping (SC), natural forest (NF), agri-silvi-horticulture (ASH), agri-silviculture (AS), fruit-based agroforestry system (FB), fodder-based agroforestry system (FTB), bamboo-based agroforestry system (BB), melia-based agroforestry system (MB), poplar-based agroforestry system (PB), and silvi-pasture (SP) at three different soil depths i.e., 0–20 cm (D 1 ), 20–40 cm (D 2 ) and 40–60 cm (D 3 ). Based on the labile and non-labile C fractions, various indices like lability index, carbon pool index and carbon management index were worked out. It was found that the active carbon pool was greater in NF (4.30 mg g −1 ), followed by the FB (4.17 mg g −1 ). The maximum passive carbon pool was found in NF (13.01 mg g −1 ), followed by the SP system (11.41 mg g −1 ). The SP system had the lowest value of lability index (LI:0.24), and the highest (LI:1.35) was reported from the FB. The maximum carbon management index (CMI) was also reported in NF (184.08), followed by the BB (161.35). Ammonical and nitrate nitrogen were reported maximum in NF, i.e., 6.93 mg kg −1 and 4.34 mg kg −1 , respectively. On average, the carbon and nitrogen pool declined at deeper soil depth, irrespective of the land use. Findings of this study demonstrated that agroforestry LUSs in the north-western Himalayas have a remarkable ability to sequester significant amounts of carbon and nitrogen in the soil thus provide a solid basis for adopting agroforestry practices to promote eco-friendly agriculture in a sensitive Himalayan region.

The objective of this study was to investigate the temperature sensitivity of labile and relatively recalcitrant forest soil carbon (C) pools amended with biochar during short-term incubation. Biochars were prepared using sugar cane residue under pyrolysis temperatures of 300 and 700 °C (i.e., BC300 and BC700), respectively. Coarse particulate organic matter and acid hydrolysis residue were separated from a forest soil and treated as the labile and recalcitrant C pools of the soil, respectively. Temperature sensitivity of the soil C pools was characterized using the Q 10 values (i.e., the proportional increase in respiration per 10 °C rise). The increased Q 10 values of treatments in the earlier stage were attributable to instantaneously increased aromatic C content. The following decreased Q 10 values were related to the consumption of labile C. However, the two types of biochars led to similar Q 10 values in the same C pools at the later stage of incubation, which was closely related to the nearly humic-like component content in the dissolved organic matter. The different temporal distributions of Q 10 values were attributable to changes of aromatic C content and continuous consumption of labile components.

Terrestrial carbon storage is split predominantly between vegetation and soils. However, the spatial distribution of terrestrial carbon and its presence in each carbon pool remains unclear. This study explored the spatial distribution of terrestrial carbon in these two carbon pools across Chinese ecosystems, which differ in vegetation types. Carbon storage was estimated using the carbon transfer rate method, which uses net primary productivity (NPP) and the turnover rate to estimate vegetation and soil carbon pools under the assumption of steady state. The distribution of carbon storage per unit area (carbon density) was shown based on the latest vegetation map (2008). Compared with recent estimates of 89.27 Pg C, our results showed that a total of only 55.46 Pg C have been stored over recent decades. Of this total, 18.19 and 37.27 Pg C were stored, respectively, in vegetation and in soil carbon pools. Among the eleven vegetation types in this study, needleleaf forest had the largest carbon storage (13.57 Pg C). The eleven vegetation types were classified into four major vegetation classes (forest, scrub, grass, and cultivated), of which forests had the higher carbon storage (21.7 Pg C) and the highest carbon density. Our estimates of the spatial distribution of carbon were consistent with previous studies. Both terrestrial and soil carbon pools exhibited higher carbon density in northeast China and the southeastern part of the Tibetan Plateau. Vegetation exhibited a high carbon density in eastern China but low carbon density in western China. Furthermore, our results had a higher spatial resolution of carbon distribution (75,000 polygon patches of the latest vegetation map) than previous studies. These results contribute to understanding carbon accumulation in different ecosystems.

Soil is one of the largest carbon reservoirs sequestering more carbon than vegetation and atmosphere. Due to the enormous potential of soil to sequester atmospheric CO2, it becomes a feasible option to alleviate the current and impending effects of changing climate. Soil is a vulnerable resource globally because it is highly susceptible to global environmental problems such as land degradation, biodiversity loss, and climate change. Therefore, protecting and monitoring worldwide soil carbon pools is a complicated challenge. Soil organic carbon (SOC) is a vital factor affecting soil health since it is a major component of SOM and contributes to food production. This review attempts to summarize the information on carbon sequestration, storage, and carbon pools in the major terrestrial ecosystems and underpin soil carbon responses under climate change and mitigation strategies. Topography, pedogenic, and climatic factors mainly affect carbon input and stabilization. Humid conditions and low temperature favor high soil organic carbon content. Whereas warmer and drier regions have low SOC stocks. Tropical peatlands and mangrove ecosystems have the highest SOC stock. The soil of drylands stores 95% of the global Soil Inorganic Carbon (SIC) stock. Grasslands include rangelands, shrublands, pasturelands, and croplands. They hold about 1/5th of the world’s total soil carbon stocks.

The soil carbon pool holds an enormous amount of carbon, making it the largest reservoir in the terrestrial ecosystem. However, there is growing concern that unsustainable logging methods damage the soil ecosystem, thus triggering the release of soil carbon into the atmosphere hence contributing to ongoing climate change. This study uses a replicated (n = 4) logging experiment to examine the impact of supervised logging with climber cutting (SLCC) and conventional logging (CL) on basic soil characteristics, litter input to soils, soil carbon pools, and soil respiration in a mixed dipterocarp forest 26 years after logging. This study found that there was no significant difference observed in the soil physicochemical properties and total carbon pools between the logging treatments and the virgin forest. Soil carbon pools dominated the total carbon pools, and the highest mean value was recorded in SLCC (87.95 ± 13.67 Mg C ha−1). Conventional logging had a lower mean value (71.17 ± 12.09 Mg C ha−1) than virgin forest (83.20 ± 11.97 Mg C ha−1). SLCC also shows a higher value of soil respiration rate (161.75 ± 21.67 mg C m−2 h−1) than CL (140.54 ± 12.54 mg C m−2 h−1). These findings highlight the importance of accurate quantification of the effect of different logging methods on the forest’s carbon pools.

Soil carbon and its fractions are important in understanding the mechanism of soil carbon sequestration. The present study evaluated the impact of seven commercial bamboo species, viz., Bambusa balcooa , B. bambos , B. vulgaris , B. nutans , Dendrocalamus hamiltonii , D. stocksii , and D. strictus , on labile and non-labile carbon fractions. In the 0–15-cm layer, B. nutans had the highest very labile C (7.65 g kg −1 ) followed by B. vulgaris  >  B. balcooa  >  D. stocksii  >  D. hamiltonii  >  B. bambos  >  D. strictus  > open. The active carbon pool was significantly low under the control plot (i.e. the open) indicating the positive influence of bamboo in soil C build-up in the top 0–15 cm soil layer. Amongst the different species of bamboo evaluated in this study, D. strictus accumulated the highest active C pool in 0–30-cm soil layer followed by B. vulgaris. Of the total organic C in the 0–30 cm soil depth, majority (55–60%) was contributed by the passive C pool comprising the less labile and the non-labile fraction of SOC. A high value of carbon stratification ratio (> 2) was observed for D. strictus , B. bambos , and D. hamiltonii which proves their potential for restoration of the degraded lands . The majority of bamboo species except for B. balcooa and D. stocksii showed a higher carbon management index than open systems, thereby indicating higher rates of soil C rehabilitation. Of the seven bamboo species, B. vulgaris , D. strictus , and B. nutans can be adopted for cultivation in the northwest Himalayas given their ability to positively impact the SOC and its fractions in both surface and sub-surface soil.

This experiment takes typical chernozem soil as the research object to investigate the effects of adding various livestock and poultry manures during in situ strip composting of corn straw on the decomposition characteristics of the straw and the soil organic carbon content. This study set up a total of four treatments under the condition of following the equal carbon principle: (1) corn straw (T1); (2) corn straw + chicken manure (T2); (3) corn straw + cow dung (T3); (4) corn straw + decomposition agent (T4). The cumulative mass loss rate of straw in the treatment of adding livestock and poultry manure ranged from 51.60% to 54.33%, with a carbon release rate of 75.34% to 76.64%. Correlation analysis revealed a significant positive relationship between SOC, straw mass loss rate, and straw carbon release rate. Furthermore, there was a significant positive correlation between organic carbon components such as DOC, EOC, POC, and MBC with CPMI, while showing a significant negative correlation with the oxidation stability coefficient (KOS). Incorporating corn straw into livestock and poultry manure and returning it to the field in in situ strips effectively enhances the decomposition process of straw, leading to an increase in the organic carbon content of chernozem soil.

The fertility and soil health of organic agroecosystems are determined in part by the size and turnover rate of soil carbon (C) and nitrogen (N) pools. Our research contrasts the effects of best management practices (BMP) (reduction in soil disturbance, addition of organic amendments) on C and N cycling in soils from two field sites representing five organic agroecosystems. Total soil organic C (SOC), a standard measure of soil health, contains equal amounts of biologically and non-biologically active C that is not associated with release of mineral N. A three-pool first-order model can be used to estimate the size and turnover rates of C pools but requires data from a long-term incubation. Our research highlights the use of two rapid C fractions, hydrolysable and permanganate (0.02 M) oxidizable C, to assess shifts in biologically active C. Adoption of BMP in organic management systems reduced the partitioning of C to the active pool while augmenting the slow pool C. These pools are associated with potentially mineralizable N supplied by residues, amendments and soil organic matter affecting the concentration and release of mineral N to crops. Our data show that minimizing disturbance (no tillage, pasture) and mixed compost additions have the potential to reduce carbon dioxide emissions while enhancing slow pool C and or its turnover, a reservoir of nutrients available to the soil biota. Use of these rapid, sensitive indicators of biological C activity will aid growers in determining whether a BMP fosters nutrient loss or retention prior to shifts in total SOC.

Topsoil is very sensitive to human disturbance under the changing climate. Estimates of topsoil soil organic carbon (SOC) pool may be crucial for understanding soil C dynamics under human land uses and soil potential of mitigating the increasing atmospheric CO₂ by soil C sequestration. China is a country with long history of cultivation. In this paper, we present an estimate of topsoil SOC pool and cultivation-induced pool reduction of China soils based upon the data of all the soil types identified in the 2nd national soil survey conducted during 1979-1982. The area of cultivated soils of China amounted to 138 × 10⁶ ha while the uncultivated soils occupied 740 × 10⁶ ha in 1980. Topsoil SOC density ranged from 0.77 to 1489 t$\\text{Cha}^{-1}$in uncultivated soils and 3.52 to 591 t$\\text{Cha}^{-1}$in cultivated soils with the average being 50 ± 47 t$\\text{Cha}^{-1}$and 35 ± 32 t$\\text{Cha}^{-1}$, respectively. Geographically, the maximum mean topsoil SOC density was found in northeastern China, being of 70 ± 104 t$\\text{Cha}^{-1}$for uncultivated soils and of 57 ± 54 t$\\text{Cha}^{-1}$for cultivated soils, respectively. The lowest topsoil SOC density for uncultivated soils was found in East China, being of 38 ± 33 t$\\text{Cha}^{-1}$and that for cultivated soils in North China, being of 30 ± 30 t$\\text{Cha}^{-1}$. There is still uncertainty in estimating the total topsoil SOC of uncultivated soils because a large portion of them was not surveyed during the 2nd Soil Survey. However, an estimate of total SOC for cultivated soils amounted to 5.1 Pg. On average, cultivation of China's soils had induced a decrease of SOC density of 15 t$\\text{Cha}^{-1}$giving rise to an overall pool reduction at 2 Pg. This is significantly smaller than the total SOC pool decline of 7 Pg due to cultivation of natural soils in China reported by Wu et al. (Glob, Change Biol, 2003, 9: 305-315), who made a pool estimation of whole soil profile assuming 1 m depth for all soils. As the mean topsoil SOC density of China was lower than the world average value given by Batjes (J. Soil Sci. 1996, 47: 151-163), China may be considered as a country with low SOC density and may have great potential for C sequestration under well defined management. However, the dynamics of topsoil C storage in China agricultural soils since 1980's and the effects of modern agricultural developments on C dynamics need further study for elucidating the role of China agriculture in global climatic change.

Mineralisable soil organic carbon (SOC) pools vary with ecosystem type in response to changes in climate, vegetation and soil properties. Understanding the effect of climate and soil factors on SOC pools is critical for predicting change over time. Surface soil samples from six ecoregions of the United States were analyzed for permanganate oxidizable C (KMnO 4 -C) and mineralizable C pools. Variations of SOC ranged from 7.9 mg g −1 (Florida site) to 325 mg g −1 (Hawaii site). Mineralisable C pools and KMnO 4 -C were highest in soils from the Hawaii site. Mean annual precipitation explains SOC and resistant C pool variations. Clay content was related to mineralisable active C pools and bacterial abundance. Mean annual precipitation and clay content are potential variables for predicting changes in SOC pools at large spatial scales.