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Decomposition of soil organic carbon (SOC) is a critical component of the global carbon cycle, and accurate estimates of SOC decomposition are important for forest carbon modeling and ultimately for decision making relative to car...
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Decomposition of soil organic carbon (SOC) is a critical component of the global carbon cycle, and accurate estimates of SOC decomposition are important for forest carbon modeling and ultimately for decision making relative to carbon sequestration and mitigation of global climate change. We determined the major pools of SOC in four sites representing major forest types in China: temperate forests at Changbai Mountain (CBM) and Qilian Mountain (QLM), and sub-tropical forests at Yujiang (YJ) and Liping (LP) counties. A 90-day laboratory incubation was conducted to measure CO_2 evolution from forest soils from each site, and data from the incubation study were fitted to a three-pool first-order model that separated mineralizable soil organic carbon into active (C_a), slow (C_s) and resistant (C_r) carbon pools. Results indicate that: (1) the rate of SOC decomposition in the sub-tropical zone was faster than that in the temperature zone, (2) The C_a pool comprised ～l-3% of SOC with an average mean residence time (MRT) of 219 days. The C_s pool comprised ～25-65% with an average MRT of 78 yr. The C_r pool accounted for ～35-80% of SOC, (3) The YJ site in the sub-tropical zone had the greatest C_a pool and the lowest MRT, while the QLM in the temperature zone had the greatest MRT for both the C_a and C_s pools. The results suggest a higher capacity for long-term C sequestration as SOC in temperature forests than in subtropical forests.
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A potculture study was conducted in soils collected from long-term fertilizer experiment (LTFE) being kept up as far the past 40 years to determine whether arbuscular mycorrhizal fungus (AMF) Rhizoglomus intraradices colonization ...
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A potculture study was conducted in soils collected from long-term fertilizer experiment (LTFE) being kept up as far the past 40 years to determine whether arbuscular mycorrhizal fungus (AMF) Rhizoglomus intraradices colonization changes the active and passive pools of carbon in a maize (Zea mays) - finger millet (Eleusine crocana)- cowpea (Vigna sinensis) cropping sequence in the Experimental Farm of the Tamil Nadu Agricultural University, Coimbatore, India. Soil samples were processed, sterilized and maize plants were grown in various fertility gradients in the absence (M-) or presence (M+) of AMF (Rhizoglomus intraradices) inoculation. The data have clearly shown that M+ soils had consistently higher active pools such as water soluble carbon, hot water soluble carbon and biomass carbon (M- 189; M + 305 mg kg(-1)), and passive pools such as soil organic carbon (M- 4.17; M + 4.31 mg g(-1)) and total glomalin. Among the fertility gradients, 100% NPK + Farm Yard Manure (FYM) with or without mycorrhizal fungal inoculation registered higher values for both active and passive pools of C but the response was more pronounced in the presence AMF inoculation. Overall, the data suggest that mycorrhizal fungal inoculation assists in effective carbon sequestration in an intensive cereal-legume cropping system.
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Little is known about the labile and recalcitrant sediment organic carbon (SOC) in estuarine ecosystem, and the effects of human activities on SOC sequestration also remain poorly understood. In this study, sediment cores in the P...
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Little is known about the labile and recalcitrant sediment organic carbon (SOC) in estuarine ecosystem, and the effects of human activities on SOC sequestration also remain poorly understood. In this study, sediment cores in the Pearl River Estuary (PRE) and adjacent coastal areas in the South China Sea were collected to analyse variations in the sources of SOC and its labile and recalcitrant pools. Concentrations of SOC, microbial biomass carbon (MBC), and recalcitrant organic carbon (ROC) ranged from 4.37 to 10.4 g/kg, 0.522 to 1.53 g/kg, and 1.59 to 5.42 g/kg, respectively, with their corresponding mean values as 7.20 ± 1.43 g/kg, 0.896 ± 0.228 g/kg, and 3.71 ± 1.01 g/kg, respectively. ROC was the chief fraction of SOC, and SOC, MBC and ROC has a similar source. Higher SOC and MBC were observed in the upper sediments, which might be attributable to the enhancement of seawater nutrient and particulate organic carbon concentrations in recent decades. Higher concentrations of SOC, ROC, and SOC stock were found in the inner estuary relative to the outer estuary due to a higher terrigenous organic carbon contribution, while the ratio of water-soluble organic carbon, salt-extractable carbon, and MBC to SOC exhibited a contrasting trend caused by a higher autochthonous contribution. Sand excavation reduced SOC, ROC, ROC/SOC, and SOC stock. The estimated SOC stock of the top 75 cm of sediment in the PRE was 34.0 Mg C ha−1, and the reduction of SOC stock in the PRE due to sea reclamation from 1973 to 2015 was 1,171,159.6 Mg C. Therefore, measures should be taken to control sea reclamation and sand excavation activities in the PRE to enhance carbon sequestration capacity.
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Vegetation restoration affects the stability of soil organic carbon (SOC) by changing the composition of soil carbon pools, including active carbon (C-a), the labile pool of SOC; slow carbon (C-s), the physically stabilized pool o...
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Vegetation restoration affects the stability of soil organic carbon (SOC) by changing the composition of soil carbon pools, including active carbon (C-a), the labile pool of SOC; slow carbon (C-s), the physically stabilized pool of SOC; and resistant carbon (C-r), the chemically stabilized pool of SOC. The aims of this study were to determine how SOC pools changed during restoration of a subtropical forest and to what extent vegetation characteristics and soil properties affected the changes in SOC pools. Soil samples were collected to 40 cm in four plant communities along a restoration chronosequence: scrub-grassland (4-5 years), shrubs (10-12 years), coniferous and broadleaved mixed forest (45-46 years), and evergreen broadleaved forest (90-91 years). Laboratory incubations were used to measure CO2 production during SOC mineralization, and acid hydrolysis was used to measure C-r. The CO2 production and C-r data were fitted to a three-component first-order kinetic model to determine the C-a and C-s. Pearson's correlations, stepwise multiple line regressions, and variation partitioning analysis were used to determine the key factors that affected SOC pools. The results showed that vegetation restoration increased the contents of SOC from 1.67 to 47.6 g kg(-1), C a from 0.03 to 0.35 g kg(-1), C, from 1.32 to 24.5 g kg(-1), and C-r from 0.33 to 22.8 g kg(-1). During vegetation restoration, the increase in SOC was primarily due to carbon (C) stored in stable pools (i.e., C-s or C-r), and the portion of C-r in total SOC increased markedly from 18.5 to 56.3%. Fine root biomass was the primary driver that controlled SOC pools during vegetation restoration. The C/N ratio of litter had a greater effect on C-a and C-s than that of other factors, whereas the soil clay content contributed secondarily to C-r. The results suggest that vegetation restoration increases not only the amounts of SOC, C-a, C-s, and C-r but also the stability of the SOC pool in subtropical soil. The relatively rapid increases in C-s and C-r following vegetation restoration played a crucial role in C sequestration. Therefore, strong measures to preserve natural forests and facilitate vegetation restoration should be the primary approach to increase long-term soil C sequestration in this region.
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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. ...
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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.
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Land use management exerts a tenacious impact on soil organic carbon (SOC) dynamics; however, the impact varies with climate, soils, and management practices. Therefore, an in-depth understanding of changes in SOC pools and its fr...
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Land use management exerts a tenacious impact on soil organic carbon (SOC) dynamics; however, the impact varies with climate, soils, and management practices. Therefore, an in-depth understanding of changes in SOC pools and its fractions is necessary to reduce carbon (C) emissions and adopt efficient land use planning for sustainable soil management in the North Eastern Himalayan (NEH) region of India. The soils under five prominent land uses [e.g., alder (Alnus nepalensis) + large cardamom (Amomum subulatum), alder + turmeric (Curcuma longa), ginger (Zingiber officinale) + maize (Zea mays), ginger and undisturbed forest] were sampled down to 45 cm depth to assess the impacts of land use systems on SOC content and storage, its fractions, microbial biomass carbon (MBC) and the dehydrogenase (DHA) activities. Results demonstrated that undisturbed forest soil had the highest organic carbon (OC, 145.8 Mg ha(-1)), active C (AC, 73.7 Mg ha(-1)), passive C (PC, 72.1 Mg ha(-1)) pools, MBC and DHA activities followed by alder + large cardamom system (140.7 Mg OC ha(-1), 70.9 Mg AC ha(-1), and 69.8 Mg PC ha(-1), respectively). The soils under undisturbed forest and alder + large cardamom system had a higher share of the very labile C fractions for all depths than other land uses. Conversely, soils under sole ginger and ginger + maize land uses had a greater proportion of non-labile C (NLC) fractions; however, absolute values of the NLC pool were the highest under undisturbed forest soil. Alder + large cardamom land use system had the highest AC: PC pool ratio (1.13) and C stratification (1.02-1.05) compared to the other land uses. Of the various land uses, SOC pools (0-45 cm) in six years were reduced nominally under alder + large cardamom system (4.2%), while the reduction was maximum under the ginger system (11.2%) as compared to the SOC pools of undisturbed forest. The study demonstrated that the cultivation of crops like maize and/or ginger is more degrading and will always have a negative impact on the fertility and overall health of the Himalayan soil. Hence, alder + large cardamom system may be promoted to restore the soil C in the Sikkim Himalayan region of NEH, India, and other similar regions of the world.
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Samples of soddy-podzolic soil (long-term overgrown fallow and continuous bare fallow), gray forest soil (forest, farming agrocenosis), and a typical chernozem (virgin steppe, forest area, farming agrocenosis, continuous bare fall...
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Samples of soddy-podzolic soil (long-term overgrown fallow and continuous bare fallow), gray forest soil (forest, farming agrocenosis), and a typical chernozem (virgin steppe, forest area, farming agrocenosis, continuous bare fallow) have been incubated under stable conditions; other samples of these soils have been subjected to six drying-wetting-incubation-freezing-thawing-incubation cycles during 136 days. The wetting of dried soils and the thawing of frozen soils result in an abrupt but short increase in the emission rate of C-CO2 by 2.7-12.4 and 1.6-2.7 times, respectively, compared to the stable incubation conditions. As the soil is depleted in potentially mineralizable organic matter, the rate of the C-CO2 emission pulses initiated by disturbing impacts decreases. The cumulative extra production of C-CO2 by soils of natural lands for six cycles makes up 21-40% of that in the treatments with stable incubation conditions; the corresponding value for cultivated soils, including continuous clean fallow, is in the range of 45-82%. The content of potentially mineralizable organic matter in the soils subjected to recurrent drying-wetting-freezing-thawing cycles decreased compared to the soils without disturbing impacts by 1.6-4.4 times, and the mineralization constants decreased by 1.9-3.6 times. It has been emphasized that the cumulative effect of drying-wetting-freezing-thawing cycles is manifested not only in the decrease in the total Corg from the soil but also in the reduction of the mineralization potential of the soil organic matter.Notes Translated from Pochvovedenie (2014) 4, 443-454 (Ru).
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Abstract Purpose Deforestation is one of the ecosystem disservices associated with accelerated loss of soil organic carbon (SOC) and nitrogen (TN). The objective of our study was to evaluate the impact of deforestation on the part...
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Abstract Purpose Deforestation is one of the ecosystem disservices associated with accelerated loss of soil organic carbon (SOC) and nitrogen (TN). The objective of our study was to evaluate the impact of deforestation on the partition of SOC pools, TN content, and the SOC lability when compared with the well-stocked Red Pine (Pinus brutia Ten.) and Oak (Quercus coccifera) forests.Methods Geo-referenced replicated soils under Red Pine and Oak and their adjacent deforested shrubby sites (control) were sampled at 0 to15 am and 15 to 30 cm depths from the Göksu catchment in Mediterranean region of Turkey. Soils were analyzed for SOC, active C (AC), passive C (PC), and TN contents.Results SOC content under both forests was higher compared to deforested shrubby sites; however, SOC under Red Pine was 22% higher than under Oak. A similar pattern in AC, PC, and TN pools was observed with a higher partition of PC:AC under both forests than under shrubby sites. The equivalent mass SOC, AC, PC, and TN stocks linearly and positively accounted for > 95% of the variability (R2) in their stocks based on equivalent depth. However, the equivalent depth overestimated 5.6 ± 0.71 Mg/ha to predict SOC storage based on equivalent mass. While the C and N pool indices (CPI and NPI) were higher under both forests compared to shrubby sites, SOC lability did not vary consistently among themselves. The CPI non-linearly and inversely accounted for 57% of the variability (R2) in SOC lability, suggesting increasing SOC accumulation significantly decreased its lability. In contrast, the CPI accounted for 42% of the variability (R2) in the NPI with a slope of only 0.57; suggesting both SOC and TN are disproportionately coupled in soil organic matter (SOM) under existing forest ecosystems.Conclusion Deforestation affected both SOC and TN stocks. However, increasing SOC sequestration under well-stocked forests is responsible for decreasing SOC lability (higher PC:AC) and partially decoupled C:N stoichiometry in SOM. Future research is needed to evaluate the impact of forest management practices on SOC and TN stocks and their lability across geographic landscape-scale under Mediterranean climates.
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摘要 :Measuring soil organic carbon (SOC) mineralization in macro-aggregates (250-2000 micro m), micro-aggregates (250-53 micro m) and the <53 micro m fraction helps to understand how spatial separation of SOC inside soil aggregates regulates its dynamics. We hypothesized that (i) compared with macro-aggregates SOC mineralization rate of micro-aggregates would be slower, (ii) adsorption of SOC on <53 micro m fraction decreases the SOC mineralization rate, and (iii) land use has a significant influence on SOC decomposition rate. To test these hypotheses we collected topsoil from Dermosol (Acrisols in FAO Soil Classification) sites under three contrasting land uses namely native pasture (NP), crop-pasture rotation (CP) and woodland (WL). Macro-aggregates, micro-aggregates and the <53 micro m fraction were separated from bulk soil by wet sieving. The three aggregate size ranges were then incubated for six months and CO2 evolution was measured at different time intervals. The chemically stable SOC of <53 micro m fraction of macro-aggregates, micro-aggregates and the <53 micro m fraction (separated by wet sieving) was measured by oxidation of SOC with 10% H2O2. On averag...
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Measuring soil organic carbon (SOC) mineralization in macro-aggregates (250-2000 micro m), micro-aggregates (250-53 micro m) and the <53 micro m fraction helps to understand how spatial separation of SOC inside soil aggregates regulates its dynamics. We hypothesized that (i) compared with macro-aggregates SOC mineralization rate of micro-aggregates would be slower, (ii) adsorption of SOC on <53 micro m fraction decreases the SOC mineralization rate, and (iii) land use has a significant influence on SOC decomposition rate. To test these hypotheses we collected topsoil from Dermosol (Acrisols in FAO Soil Classification) sites under three contrasting land uses namely native pasture (NP), crop-pasture rotation (CP) and woodland (WL). Macro-aggregates, micro-aggregates and the <53 micro m fraction were separated from bulk soil by wet sieving. The three aggregate size ranges were then incubated for six months and CO2 evolution was measured at different time intervals. The chemically stable SOC of <53 micro m fraction of macro-aggregates, micro-aggregates and the <53 micro m fraction (separated by wet sieving) was measured by oxidation of SOC with 10% H2O2. On average, cumulative mineralization, Cmin (g CO2-C kg-1 aggregate) of the <53 micro m fraction, was 28% lower than that of macro-aggregates and micro-aggregates. However, SOC mineralized (SOCmin) was similar in all size fractions. The size of slow SOC pool (percent of SOC concentration in aggregates) was also significantly higher in the <53 micro m fraction and ranged from 58 to 96%, across aggregate sizes. However, the chemically stable SOC (percent of SOC concentration in aggregates) was significantly higher in macro-aggregates and micro-aggregates than that of the <53 micro m fraction. Mean residence time (MRT) of slow SOC pool (MRTs) was higher in the <53 micro m fraction than for either macro-aggregates or micro-aggregates. Among the land uses NP had higher SOCmin compared with CP and WL. In conclusion, the insignificant difference in SOCmin, slow SOC pool sizes and MRTs between macro-aggregates and micro-aggregates indicated that SOC mineralization rate and thus the protection of SOC was similar in both macro-aggregates and micro-aggregates.
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Using active (C-a) and slow (C-s) soil organic carbon (SOC) pools to simulate changes in SOC stocks has been determined to be a major improvement over treating SOC as a single, homogeneous pool. However, regional patterns and prim...
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Using active (C-a) and slow (C-s) soil organic carbon (SOC) pools to simulate changes in SOC stocks has been determined to be a major improvement over treating SOC as a single, homogeneous pool. However, regional patterns and primary controls of the mean residence times of the C-a (MRTa) and C-s (MRTs) pools in China's croplands are largely unknown. In this study, a total of 373 samples from six regions were analysed based on a 100-d incubation experiment. The data from acid hydrolysis-incubation experiments were fitted to a three-pool first-order kinetics model that estimated MRTa = 1/K-a and MRTs = 1/K-s (K-a and K-s represent the decomposition rate constants of the C-a and C-s pools, respectively). The results showed that significant regional differences were found in the MRTa and MRTs in the surface upland soils (0-20 cm) across China, in which the longest MRTa and MRTs values were 72 d in the north China and 24.0 yr in the northeast China, the shortest MRTa and MRTs values were 12 d and 4.7 yr, respectively, both in the south-central China, while relatively small regional differences were observed in the values of the surface paddy soils (0-20 cm). Both the MRTa and the MRTs in upland soils (average: 30 d and 13.5 yr) were longer than the corresponding values in the paddy soils (average: 11 d and 5.4 yr), especially in the southwest China. Thus, the carbon sequestration potential of paddy soils needs to be revalued. The climate could partly explain the regional distribution of the MRTa and MRTs in the surface upland and paddy soils in China; however, as Chinese agricuture intensified from 1980 to 2010, the regional variabilities of MRTa and MRTs in the surface upland and paddy soils were primarily dominated by the soil texture. Therefore, more attention should be paid to the destruction of mechanical composition caused by land-use change or conventional tillage methods when faced with future carbon sequestration in croplands.
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