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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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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 ca...
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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 degrees 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 degrees 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.
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This study was carried out in agroforestry systems of Eucalyptus tereticornis (clonal) on a sandy loam soil at Salimpur (30° 10'N, 76° 55'E; 268 m msl) in northern India which are characterized by tree density of 567 to 630 tree...
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This study was carried out in agroforestry systems of Eucalyptus tereticornis (clonal) on a sandy loam soil at Salimpur (30° 10'N, 76° 55'E; 268 m msl) in northern India which are characterized by tree density of 567 to 630 trees/ha. The aim of thisstudy was to analyze plant biomass, productivity and the storage of carbon in the plant-soil system. The climate of the study area is tropical monsoonal and semi-arid and characterized by hot summers and cold winters. The basal area of 4 to 6-year old trees under agroforestry was 8.28 to 14.98 m~2/ha. The wheat crop was grown in the interspaces between the rows of planted trees in 4 to 6-year old agroforestry systems during November to April. The soil organic carbon in the agroforestry systems varied from 0.56 to 0.02% (4-year) and 0.63 to 0.03% (6-year) in 0-100 cm soil depths; there were depth dependent variations in soil organic carbon and inorganic carbon. The plant biomass production increased with increase in age of trees in the agroforestry from 4 to 6 years. The biomass accumulation varied from 61.911 to 89.388 Mg dry matter/ha in the tree layer. The total carbon pool in the agroforestry systems was 27.259 to 39.322 Mg C/ha; total flux of carbon in net primary productivity being 8.1 Mg C/ha/year in the tree layer. The soil organic carbon pool was 22.96 to 26.30 Mg C/ha.
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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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Conventional tillage in Northeast China involves complete removal of crop residue and deep plowing, both of which cause significant loss of soil organic carbon (SOC). Our study aimed to evaluate SOC storage and pool sizes in degra...
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Conventional tillage in Northeast China involves complete removal of crop residue and deep plowing, both of which cause significant loss of soil organic carbon (SOC). Our study aimed to evaluate SOC storage and pool sizes in degraded soils when post-harvest residue is returned to degraded soil and different tillage systems are used. We measured SOC under no-tillage (NT), ridge-tillage (RT) and moldboard plow (MP) and compared storage across treatments. We used sulfuric acid hydrolysis to separate and evaluate the size of two labile pools and one recalcitrant pool. There was no difference in crop yields (and hence C inputs) across tillage treatments over 12 years. SOC storage in the plow layer (0-20 cm) increased in all tillage systems compared to soils in the degraded state but the rate of increase was greater under NT and RT than MP. There was increased variability when we assessed deep SOC storage (0-30 cm) and SOC storage at this depth was the same across tillage systems, but still higher than in the initially degraded state. Changes observed in the size of labile and recalcitrant pools indicated these occurred mainly in the surface 0-5 cm and that RT induced slight changes in the chemical composition of SOC. Our results indicate that returning residues to degraded soils: 1) replenished SOC levels but the rate of replenishment was highest under conservation tillage, 2) had no effect on yields (C inputs) and deep SOC storage across tillage treatments, and 3) induced subtle differences in SOC pool size.
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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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Microbial decomposition of soil organic carbon (SOC) is a major determinant of the global climate and terrestrial ecosystem services. Despite the rapid loss of plant species worldwide, it remains unclear how plant species richness...
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Microbial decomposition of soil organic carbon (SOC) is a major determinant of the global climate and terrestrial ecosystem services. Despite the rapid loss of plant species worldwide, it remains unclear how plant species richness impacts SOC decomposition, especially the decomposition of labile vs. recalcitrant SOC. This is partly because of the variable responses of soil C-degrading enzyme activities to plant species richness. Through a global meta-analysis of 490 paired observations of plant mixtures versus monocultures, we show that plant mixtures significantly enhanced soil C-hydrolase (degrades labile C) and C-oxidase (degrades recalcitrant C) activities by 29.4 and 14.9%, respectively. However, in mixtures, C-hydrolase activity marginally (P = 0.051) increased, while C-oxidase activity significantly decreased with plant species richness. In addition, in mixtures, C-hydrolase but not C-oxidase activity significantly increased with plant functional type richness and experimental duration. These plant species richness and functional type effects on C-hydrolase and C-oxidase activities were consistent among diverse terrestrial ecosystems, plant life forms, the presence/absence of legumes, and climate types. Moreover, increases in C-hydrolase but not C-oxidase activity were positively related with increasing microbial biomass C and SOC under plant mixtures, suggesting that faster microbial decomposition and transformation of labile C pools mediate SOC accumulation at higher plant species richness. These results highlight that plant species richness differentially affects labile and recalcitrant C-degrading enzymes, thereby influencing SOC decomposition, dynamics, and accumulation.
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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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Salt-affected soils are widespread, particularly in arid climates, but information on nutrient dynamics and carbon dioxide (CO2) efflux from salt-affected soils is scarce. Four laboratory incubation experiments were conducted with...
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Salt-affected soils are widespread, particularly in arid climates, but information on nutrient dynamics and carbon dioxide (CO2) efflux from salt-affected soils is scarce. Four laboratory incubation experiments were conducted with three soils. To determine the influence of calcium carbonate (CaCO3) on respiration in saline and non-saline soils, a loamy sand (6.3% clay) was left unamended or amended with NaCl to obtain an electrical conductivity (EC) of 1.0 dS m−1 in a 1:5 soil/water extract. Powdered CaCO3 at rates of 0%, 0.5%, 1.0%, 2.5%, 5.0% and 10.0% (w/w) and 0.25-2 mm mature wheat residue at 0% and 2% (w/w) were then added. Cumulative CO2-C emission from the salt amended and unamended soils was not affected by CaCO3 addition. To investigate the effect of EC on microbial activity, soil respiration was measured after amending a sandy loam (18.8% clay) and a silt loam (22.5% clay) with varying amount of NaCl to obtain an EC1:5 of 1.0–8.0 dS m−1 and 2.5 g glucose C kg−1 soil. Soil respiration was reduced by more than 50% at EC1:5 ≥ 5.0 dS m−1. In a further experiment, salinity up to an EC1:5 of 5.0 dS m−1 was developed in the silt loam with NaCl or CaCl2. No differences in respiration at a given EC were obtained between the two salts, indicating that Na and Ca did not differ in toxicity to microbial activity. The effect of different addition rates (0.25–2.0%) of mature wheat residue on the response of respiration to salinity was investigated by adding NaCl to the silt loam to obtain an EC1:5 of 2.0 and 4.0 dS m−1. The clearest difference between salinity levels was with 2% residue rate. At a given salinity level, the modelled decomposition constant ‘k’ increased with increasing residue addition rate up to 1% and then remained constant. Particulate organic carbon left after decomposition from the added wheat residues was negatively correlated with cumulative respiration but positively correlated with EC. Inorganic N (NH4+-N and NO3−-N) and resin P significantly decreased with increasing salinity. Resin P was significantly decreased by addition of CaCl2 and CaCO3.
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