Ratio Of Dissolved Organic Carbon Research Articles

Effects of carbohydrate supply strategies and biofloc concentrations on the growth performance of African catfish (Clarias gariepinus) cultured in biofloc systems

This study investigated the effect of biofloc concentrations and carbohydrate adding methods on the water quality, bacterial community compositions, and growth performance of African catfish (Clarias gariepinus) cultured in biofloc systems for 140 days. The biofloc systems were run with (PCL) or without (N) polycaprolactone as an external carbohydrate. Within each of these treatments, we included either a low biofloc concentration (LF) or a high biofloc concentration (HF). Because the suspended solid concentrations fluctuated during the experiment, the treatments were designated as N-LF, with an average of 427.84 mg/L total suspended solids (TSS), PCL-LF, with an average of 405.62 mg/L TSS, N-HF, with an average of 608.09 mg/L TSS, and PCL-HF, with an average of 603.83 mg/L TSS. The average concentrations of total ammonia nitrogen (TAN), nitrite nitrogen (NO2−-N), dissolved organic carbon (DOC), and the ratio of DOC to total nitrogen and DOC to dissolved inorganic nitrogen did not differ significantly among the four treatments (p > .05). Nitrate nitrogen (NO3−-N) concentrations accumulated in all four treatments. Higher concentrations of TAN and NO2−-N may be due to the adjustment of biofloc concentrations. The relative abundance of the top five phyla of bacteria did not differ significantly among the treatments (p > .05). The carbohydrate adding strategies and biofloc concentrations significantly affected the bacterial community (p < .05) at the genus level. African catfish survival rates ranged from 89% to 97%, and food conversion rates ranged from 1.17 to 1.43. The growth performance of fish in the LF groups was significantly better than that of fish in the HF groups (p < .05). The systems with PCL as external carbohydrate showed better performance than the systems without additional carbohydrate (p < .05). The system with PCL as an external carbohydrate and with low biofloc concentrations (PCL-LF) showed the best performance among the four treatments.

Effect of annual prescribed burning of wetlands on soil organic carbon fractions: A 5-year study in Poyang, China

Fire is a common disturbance both from natural source and anthropogenic activities and an important factor in driving the variation of soil organic carbons. A 5-year study was conducted to examine the influence of annual prescribed fire on soil organic carbon (SOC) fraction in a fire-prone plant community, Triarrhena lutarioriparia community, in Poyang Lake, China. The results showed that after burning the contents of dissolved organic carbon (DOC), soil microbial biomass carbon (SMBC) and light fraction organic carbon (LFOC) increased significantly from 78.53 mg/kg to 131.72 mg/kg, 365.58 mg/kg to 603.42 mg/kg, and 14.82 g/kg to 20.56 g/kg, respectively, during the 5-year studying period. On the other hand, the contents of total SOC and heavy fraction organic carbon (HFOC) only increased slightly from 53.67 g/kg to 61.39 g/kg and 33.45 g/kg to 37.46 g/kg, respectively. The results strongly suggested that DOC was more sensitive to the prescribed fire than SOC. Moreover, the annual ratios of DOC, SMBC and LFOC to SOC significantly increased after burn treatments. Taken together, prescribed fire could greatly increase the contents of soil active organic carbons, and enhance the carbon cycle in Poyang Lake. Thus, it could be taken as an exercisable measure to improve the carbon capacity and maintain the soil productivity in the lake wetland.

Indirect link between riverine dissolved organic matter and bacterioplankton respiration in a boreal estuary

Increasing loading of terrestrially derived dissolved organic matter tends to enhance bacterioplankton respiration (BR) in boreal estuaries, but knowledge on the mechanisms behind this effect is not complete. We determined the stable isotopic signature of the reactive estuarine dissolved organic carbon (DOC) in the Öre estuary (Baltic Sea) by using the Keeling plot method. The δ13C ratio of the estuarine labile DOC varied from −26.0‰ to −18.7‰ with most values resembling those typical for DOC of coastal phytoplanktonic origin (−18 to −24‰), while being distinctly higher than those of DOC from ter­res­trial sources (−28‰ to −27‰). Furthermore, the δ13C of the respired carbon was positively correlated to DOC concentrations, indicating that carbon of marine origin increasingly dominated the reactive substrates when input of organic matter into the estuary became higher. This suggests that riverine organic matter mainly affects BR indirectly, by providing nutrients that stimulate the production of phytoplankton-derived reactive DOC in the estuary. Thus, riverine derived DOC per se may not be as important for coastal CO2 emissions as previously thought.

Nutrient export and elemental stoichiometry in an urban tropical river.

Nutrient inputs to surface waters are particularly varied in urban areas, due to multiple nutrient sources and complex hydrologic pathways. Because of their close proximity to coastal waters, nutrient delivery from many urban areas can have profound impacts on coastal ecology. Relatively little is known about the temporal and spatial variability in stoichiometry of inorganic nutrients such as dissolved silica, nitrogen, and phosphorus (Si, N, and P) and dissolved organic matter in tropical urban environments. We examined nutrient stoichiometry of both inorganic nutrients and organic matter in an urban watershed in Puerto Rico served by municipal sanitary sewers and compared it to two nearby forested catchments using samples collected weekly from each river for 6yr. Urbanization caused large increases in the concentration and flux of nitrogen and phosphorus (2- to 50-fold), but surprisingly little change in N:P ratio. Concentrations of almost all major ions and dissolved silica were also significantly higher in the urban river than the wildland rivers. Yield of dissolved organic carbon (DOC) was not increased dramatically by urbanization, but the composition of dissolved organic matter shifted toward N-rich material, with a larger increase in dissolved organic nitrogen (DON) than DOC. The molar ratio of DOC:DON was about 40 in rivers draining forested catchments but was only 10 in the urban river. Inclusion of Si in the assessment of urbanization's impacts reveals a large shift in the stoichiometry (Si:N and Si:P) of nutrient inputs. Because both Si concentrations and watershed exports are high in streams and rivers from many humid tropical catchments with siliceous bedrock, even the large increases in N and P exported from urban catchments result in delivery of Si, N, and P to coastal waters in stoichiometric ratios that are well in excess of the Si requirements of marine diatoms. Our data suggest that dissolved Si, often neglected in watershed biogeochemistry, should be included in studies of urban as well as less developed watersheds due to its potential significance for marine and lacustrine productivity.

Application of a microbial fuel cell-based biosensor for the energy-saving operation of macrophyte residues bioreactor with low concentration of dissolved organic carbon in effluents

The increasing application of plant residues bioreactor for aquatic environment remediation may release numerous dissolved organic carbon (DOC) into aquatic ecosystems. In this study, a microbial fuel cell (MFC) sensor was integrated with a macrophyte residues bioreactor (MRBR) to provide an energy-saving way for reduction of DOC concentrations in the effluent. Through re-utilization of macrophyte residues as solid carbon source, DOC concentrations in the effluent of MRBR increased to the maximum on day 5 and then dropped down rapidly to a low value, while the ratio of bioavailable DOC decreased gradually. Interestingly, it was found that there existed a linear relationship between DOC concentrations in initial residue leachate and the voltage from MFC biosensor (R2 = 0.9852). Accordingly, aerobic biofilm through aeration were applied in the upper part of MRBR to enhance the degradation of DOC prior to discharge to aquatic systems, and aeration rate was adjusted based on MFC sensor signal. Further experiments demonstrated that when voltage decreased from 0.18 V to 0.09 V, a half of aeration rate (7.5 L min−1) could still lead to a high DOC degradation efficiency (above 50%) and a low DOC concentration (∼10 mg L−1) in the reactor effluent. Thus, the integrated MFC signal could be used to regulate the aeration rate in order to obtain a low DOC concentration in effluents under an energy-saving way.

Isotope composition of dissolved organic carbon in runoff and peat leachates from a Central European wetland: Temporal and spatial variability in DOC sources

In the near future, climate change will increasingly affect export of carbon (C) from peatlands. Terminal mineralization of dissolved organic carbon (DOC) is a source of greenhouse gases (carbon dioxide, CO2, and methane, CH4) for the atmosphere, and may contribute to climatic warming. Quantitative understanding of sources, dispersion pathways, and degradation of DOC produced in peat bogs is important for predictions of global change dynamics. Here we explore the potential of combining C isotope ratios of isotopically stratified, 210Pb-dated peat deposits and C isotope ratios of DOC exported via runoff to determine the depth and age of the predominant DOC source. In a poorly drained, Sphagnum-derived peat bog in the Czech Republic, δ13C values of bulk peat increased downcore to a depth of 10 cm. The C isotope signatures of fresh DOC and bulk peat differ only insignificantly, because C isotope changes in maturating peat require multiple microbial modifications of the organic matter taking place over relatively long time periods. Based on 41 samplings of runoff, 70% of exported DOC originated from peat substrate 1 to 10 years old, 2–10 cm deep. Recently photosynthesized DOC (<1 year old) contributed about 5% to runoff DOC, whereas approximately 25% of exported DOC was derived from peat layers older than 10 years. Because biogenic methane at the study site contained isotopically extremely light C (δ13C values of −64.2 to −53.2‰), it would seem reasonable to expect residual DOC following partial decomposition to become isotopically heavier. A short-term laboratory incubation of wet peat samples from four depths at mid-summer temperatures indicated more complicated δ13C systematics. The initial limited amount of DOC in the leachate was isotopically heavy, compared to bulk peat, but after 18 days δ13CDOC became lower, converging to the C isotope signature of bulk peat. Such δ13C systematics can be explained by multi-step isotope effects associated with different reaction rates during substrate decomposition. Limitations of using the combination of within-bog δ13C systematics and 210Pb dating of recent peat accretion are discussed. Horizontal heterogeneity in substrate C isotope signatures is one of the main sources of uncertainty of this approach to DOC source apportionment in peaty soils.

Behind the Scenes: Mechanisms Regulating Climatic Patterns of Dissolved Organic Carbon Uptake in Headwater Streams

AbstractLarge variability in dissolved organic carbon (DOC) uptake rates has been reported for headwater streams, but the causes of this variability are still not well understood. Here we assessed acetate uptake rates across 11 European streams comprising different ecoregions by using whole‐reach pulse acetate additions. We evaluated the main climatic and biogeochemical drivers of acetate uptake during two seasonal periods. Our results show a minor influence of sampling periods but a strong effect of climate and dissolved organic matter (DOM) composition on acetate uptake. In particular, mean annual precipitation explained half of the variability of the acetate uptake velocities (VfAcetate) across streams. Temperate streams presented the lowest VfAcetate, together with humic‐like DOM and the highest stream respiration rates. In contrast, higher VfAcetate were found in semiarid streams, with protein‐like DOM, indicating a dominance of reactive, labile compounds. This, together with lower stream respiration rates and molar ratios of DOC to nitrate, suggests a strong C limitation in semiarid streams, likely due to reduced inputs from the catchment. Overall, this study highlights the interplay of climate and DOM composition and its relevance to understand the biogeochemical mechanisms controlling DOC uptake in streams.

Soil Organic Carbon of Purple Soil as Affected by Different Application of Biochar

Soil organic carbon (SOC) is the most important part of the soil carbon pool and soil labile organic carbon is a key indicator of changes in the soil carbon pool. In order to study changes in SOC and its labile components with different biochar additions to soil, a field experiment was conducted at Chongqing National Purple Soil Fertility and Fertilizer Efficiency of Long-Term Monitoring Station. Different amounts of biochar (0 kg·hm-2, CK; 4000 kg·hm-2, 0.5 BC; 8000 kg·hm-2, BC; 16000 kg·hm-2, 2BC) combined with fertilizer were applied to purple soil in this hilly area. SOC and soil labile carbon content were determined for purple soil rape-maize rotation systems. Results showed that:① Application of biochar can significantly improve SOC content; within a certain range, the amount of added biochar is correlated with SOC content. The content of soil microbial biomass carbon (SMBC) increased with application of 8000 kg·hm-2 biochar, but decreased with application of 4000 and 16000 kg·hm-2. The content of dissolved organic carbon (DOC) and readily oxidized carbon (ROC) in soil increased with different amounts of biochar; the highest DOC (198.83 g·kg-1) and ROC (4.86 g·kg-1) were obtained under low biochar addition treatments. ② The application of biochar significantly decreases the ratio of soil ROC to SOC and microbial entropy. The ratio of soil ROC to SOC and microbial entropy of 0.5 BC treatment are 20.45% and 4.11%, respectively, lower than for CK. Moreover, 0.5 BC and BC treatments can significantly improve the ratio of soil DOC to SOC. In summary, biochar addition in soil leads to low soil microbial activity but higher soil stability. An appropriate biochar treatment can stimulate accumulation of SOC, and 0.5BC treatment can improve soil DOC and ROC.

菌渣化肥配施对稻田土壤微生物量碳氮和可溶性碳氮的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 菌渣化肥配施对稻田土壤微生物量碳氮和可溶性碳氮的影响 DOI: 10.5846/stxb201711272117 作者: 作者单位: 浙江农林大学环境与资源学院,浙江农林大学环境与资源学院,浙江农林大学环境与资源学院,浙江农林大学环境与资源学院,浙江农林大学环境与资源学院,浙江农林大学环境与资源学院,浙江农林大学环境与资源学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金（31601271）；浙江省自然科学基金（LY16D010010） Effects of the combination of fungal residue and chemical fertilizer on soil microbial biomass carbon and nitrogen and dissolved organic carbon and nitrogen in paddy soil Author: Affiliation: School of Environmental and Resource Science，Zhejiang A＆F University,School of Environmental and Resource Science，Zhejiang A＆F 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:菌渣作为一种养分丰富的有机物料还田，可减少化肥施用，同时保持土壤肥力；而土壤微生物量碳、氮和可溶性碳、氮是土壤活性碳氮库的重要组成部分，其含量和比例变化对土壤肥力均具有重要作用。因此，探讨不同比例菌渣化肥配施对土壤微生物量碳、氮及可溶性碳、氮的影响，评价菌渣在优化土壤肥力方面的生态作用具有重要意义。在水稻田间定位试验条件下，设置3个化肥水平（C）0、50%、100%，菌渣相对用量（F）0、50%、100%，共9个处理，分析了各处理土壤微生物量碳（MBC）、氮（MBN）和可溶性碳（DOC）、氮（DON）的变化特征，及其占土壤有机碳（SOC）和全氮（TN）的比例与相关关系。结果表明：菌渣化肥配施后，微生物量碳和可溶性碳、氮均在C100F50最高，微生物量氮在C50F100最高，与不施肥处理相比，分别显著增加了49.40%、43.65%、83.52%、207.19%；MBC/SOC和DOC/SOC均随着菌渣化肥配施量的增加而减少，MBN/TN和DON/TN均在C100F50最高。相关分析表明，MBC、DOC与SOC，MBN与TN均呈极显著正相关，DON和TN呈显著正相关。总体来讲，菌渣化肥配施能够显著提高土壤微生物量碳、氮和可溶性碳、氮含量，但不是随着用量的增加一直呈增加趋势，高量菌渣或者化肥下会有降低趋势；菌渣化肥配施降低了土壤微生物量和可溶性碳氮比，因此适宜的菌渣化肥配施是提高土壤有机碳周转速度、微生物活性及其氮素供应能力和有效性的最佳选择。 Abstract:As an excellent organic material additive to soil, fungal residue can reduce the application of chemical fertilizer and also plays an important role in maintaining soil fertility. As the most active organic components, soil microbial biomass carbon (MBC) and nitrogen (MBN) and dissolved organic carbon (DOC) and nitrogen (DON) are usually regarded as important and sensitive indices for soil fertility change. Therefore, it is vital to evaluate the ecological and soil fertility significance of fungal residue application under different rates return to the paddy soil. In our study, a randomized complete block field experiment with nine treatments(0,50%, and 100% levels of chemical fertilizers (C) and edible fungal residue (F) were considered, C100F50 stands for 100% of chemical fertilizer and 50% of fungal residue application, etc.) was set up. The changes of MBC, MBN, DOC, and DON, and ratios of these parameters to soil organic carbon (SOC) and total nitrogen (TN) were analyzed. Results showed that the highest contents of MBC, DOC and DON were observed under treatment of C100F50, which were 49.40%, 43.65% and 83.52% higher than that under the treatment of control. Meanwhile highest MBN content was found under treatment of C50F100 which was 207.19% higher than that under the treatment of control. Both ratios of MBC and DOC to SOC were decreased with increased application rate of fungal residue and chemical fertilizer; the highest ratios of MBN and DON to TN were observed in C100F50. There were highly significant positive correlations between MBC, DOC and SOC, respectively, and between MBN and TN as well. The correlation between DON and TN was significantly positive too. In conclusion, application of fungal residue with chemical fertilizer in paddy soil could increase the contents of MBC, MBN, DOC, and DON, but over dosage of fungal residue or chemical fertilizer application could lead to a negative effect. Consequently, the appropriate application rate of chemical fertilizer combined with fungal residue was the optimum choice to improve the SOC turnover rate, microbial activity, and nitrogen supply capacity and efficiency in paddy soil. 参考文献 相似文献 引证文献

Long-term phosphorus addition enhances the biodegradability of dissolved organic carbon in a nitrogen-limited temperate freshwater wetland

Phosphorus (P) enrichment is expected to strongly influence dissolved organic carbon (DOC) biodegradation. However, the relationship between P availability and DOC biodegradation is largely unknown in nitrogen (N)-limited ecosystems. Here, we investigated the changes in the ratio of DOC to dissolved total nitrogen (DTN), specific UV absorbance at 254nm (SUVA254), and DOC biodegradation in surface water and soil pore water (0–15cm depth) following eight years of multi-level P addition (0, 1.2, 4.8, and 9.6gPm−2year−1) in an N-limited freshwater marsh in Northeast China. We found that P addition caused an increase in DOC biodegradation in surface water and soil pore water, irrespective of the P addition levels. Compared with the control treatment, the P addition rates of 1.2, 4.8, and 9.6gPm−2year−1 increased DOC biodegradation by 20.7%, 15.2%, and 14.5% in surface waters, and 11.3%, 9.4%, and 12.0% in soil pore waters, respectively. The DOC biodegradation was separately negatively correlated with the DOC:DTN ratio and SUVA254, indicating that the positive effect of P addition on DOC biodegradation was caused by the elevated N concentration and the reduced DOC aromaticity. Our findings suggest that P enrichment enhances the biodegradability of DOC through increased N availability and altered DOC chemical composition, which would accelerate DOC loss from the waters and alter ecosystem C balance in N-limited temperate wetlands.

Dissolved organic matter in soils varies across a chronosequence of Pinus massoniana plantations

AbstractStand age plays a significant role in forest ecosystems nutrient cycling. Unfortunately, less attention was accorded to the changes in dissolved organic matter (DOM) in soil layers of mono‐stand plantations. A field soil sampling experiment was conducted to examine the effects of forest age and soil depth on concentrations and distribution patterns of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) in a chronosequence of 11 stands of Masson pine (Pinus massoniana) plantations. The soil total organic carbon (TOC) and soil total nitrogen (TN) were also investigated. Concentrations of DOC and DON varied with stand age and decreased significantly (P &lt; 0.05) with depth from 503.9 to 337.1 mg/kg and from 67.9 to 45.0 mg/kg, respectively, between the 0‐ to 30‐ and 30‐ to 60‐cm soil layers. Dissolved organic carbon and DON were significantly correlated, the ratios of DOC to TOC and DON to TN increased significantly from 0.11 to 0.20 and 0.16 to 0.39 in the upper to the lower soil layer, whereas the TOC/TN ratio decreased significantly with stand age. Our results suggest that (1) soil C/N ratios decrease with stand age, (2) DOM concentration decreases with depth, (3) soil pH and moisture content affect DOM concentrations, and (4) DOM concentrations are influenced by export of organic matter from litter and the forest floor surface.

Nitrogen addition alters elemental stoichiometry within soil aggregates in a temperate steppe

Abstract. Ongoing increases in anthropogenic nitrogen (N) inputs have largely affected soil carbon (C) and nutrient cycling in most terrestrial ecosystems. Numerous studies have concerned the effects of elevated N inputs on soil dissolved organic carbon (DOC), dissolved inorganic N (DIN), available phosphorus (AP), exchangeable calcium (Ca) and magnesium (Mg), and available iron (Fe) and manganese (Mn). However, few have emphasized the stoichiometric traits of these soil parameters, especially within different soil aggregate fractions. In a semiarid grassland of Inner Mongolia, we studied the effect of N addition on the ratios of DOC : DIN, DOC : AP, DIN : AP, exchangeable Ca : Mg, available Fe : Mn within three soil aggregate classes of large macroaggregates (&gt; 2000 µm), small macroaggregates (250–2000 µm), and microaggregates (&lt; 250 µm). Elevated N inputs significantly decreased the DOC : DIN ratio within three soil aggregates. The soil DOC : AP ratio significantly decreased along with increasing N gradients within large macroaggregates and microaggregates. Nitrogen significantly decreased the ratio of exchangeable Ca : Mg within soil macroaggregates. The ratio of available Fe : Mn decreased with N addition within three soil aggregate classes. Alteration of elemental stoichiometry within soil fractions that are characterized by different nutrient retention capacity will influence the chemical composition of soil microorganisms and plant quality.

Carbonaceous matter deposition in the high glacial regions of the Tibetan Plateau

Carbonaceous matter at glacial region plays important role in river ecosystems fed by glacier and albedo reduction of glacier surface. However, currently, limited knowledge are available on the carbonaceous matter within the glacial region of the Tibetan Plateau (TP). In this study, the data from six snowpits in the glacial region across the TP were reported. The results showed that dissolved organic carbon (DOC) concentrations of snowpit samples of the TP were comparable to those of European Alps and the Arctic. The ratio of DOC to carbonaceous matter (40.25 ± 8.98%) was lower than that of Alpine glaciers, thus indicating greater particulate carbon content in the TP glacial region. In addition, the DOC was significantly correlated with insoluble particulate carbon (IPC), indicating that IPC and DOC likely came from the same sources. Spatially, the DOC concentration decreased from the north (0.42 ± 0.29 mg-C L−1) to the south TP (0.15 ± 0.06 mg-C L−1), which was consistent with variations in the distribution of dust storm on the TP. Principal component analysis of major ions and DOC showed that mineral dust contributed the major part of DOC, followed by biogenic sources such as agriculture and livestock. Finally, based on DOC concentrations and precipitation amounts at different periods, the mean annul flux of DOC in the glacial region of the TP was calculated to be 0.11 ± 0.05 g-C m−2 yr−1.

New strategies for submicron characterization the carbon binding of reactive minerals in long-term contrasting fertilized soils: implications for soil carbon storage

Abstract. Mineral binding is a major mechanism for soil carbon (C) stabilization. However, the submicron information about the in situ mechanisms of different fertilization practices affecting organo-mineral complexes and associated C preservation remains unclear. Here, we applied nano-scale secondary ion mass spectrometry (NanoSIMS), X-ray photoelectron spectroscopy (XPS), and X-ray absorption fine structure spectroscopy (XAFS) to examine differentiating effects of inorganic versus organic fertilization on interactions between highly reactive minerals and soil C preservation. To examine such interactions, soils and their extracted colloids were collected during a 24-year long-term fertilization period (1990–2014) (no fertilization, control; chemical nitrogen (N), phosphorus (P), and potassium (K) fertilization, NPK; and NPK plus swine manure fertilization, NPKM). The results for different fertilization conditions showed a ranked soil organic matter concentration with NPKM &gt; NPK &gt; control. Meanwhile, oxalate-extracted Al (Alo), Fe (Feo), short-range ordered Al (Alxps), Fe (Fexps), and dissolved organic carbon (DOC) ranked with NPKM &gt; control &gt; NPK, but the ratios of DOC ∕ Alxps and DOC ∕ Fexps ranked with NPKM &gt; NPK &gt; control. Compared with the NPK treatment, the NPKM treatment enhanced the C-binding loadings of Al and Fe minerals in soil colloids at the submicron scale. Furthermore, a greater concentration of highly reactive Al and Fe minerals was presented under NPKM than under NPK. Together, these submicron-scale findings suggest that both the reactive mineral species and their associations with C are differentially affected by 24-year long-term inorganic and organic fertilization.

Effects of simulated warming on soil DOC and DON concentrations in the alpine forest of western Sichuan based on altitudinal gradient experiment.

In order to understand the effects of climate warming on the process of soil carbon and nitrogen in the alpine forest, intact soil columns were collected in the alpine fir forest, and dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) concentrations in both soil organic layer (OL) and mineral soil layer (ML) placed at different altitudes were measured from May 2010 to April 2011 (the first incubation period) and from May 2011 to April 2012 (the second incubation period). The results indicated that both DOC and DON concentrations in OL and ML va-ried greatly during the sampling period. The DOC concentration in soil columns at the altitudes of 3300 and 3000 m increased 6.8 and 26.6 mg·kg-1 compared with that at 3600 m, respectively. The highest DOC concentrations in soil columns at the altitudes of 3600, 3300 and 3000 m were 408.0, 317.9 and 448.2 mg·kg-1, respectively, which were all detected in LG (late growth pe-riod) during the first incubation period, while the lowest concentrations were 33.1, 32.4 and 36.5 mg·kg-1, respectively, which were all detected in MG (mid growth period) during the second incubation period. Moreover, the DON concentration in soil columns at the altitudes of 3300 and 3000 m increased 2.3 and 30.4 mg·kg-1 respectively compared with that at 3600 m. The highest DON concentrations at the altitudes of 3600 and 3300 m were 65.9 and 64.6 mg·kg-1, which were both detected in MG in the first incubation period, while the lowest concentrations were 31.9 and 37.1 mg·kg-1, both detected in ET (early thawing period) in the second incubation period. Simulated warming increased the concentrations of DOC and DON in the OL, but decreased the concentration of DOC in ML and the ratio of DOC to DON in OL and ML. The ratio of DOC to DON was significantly positively related with DOC concentration and negatively related with DON concentration in OL, whereas the ratio of DOC to DON was significantly negatively related with DOC concentration and positively with DON concentration in ML. The results indicated that climate warming would increase the concentrations of DOC and DON in soils of the high-frigid forest by changing soil tempe-rature and freeze-thaw pattern, and in turn alter the process of soil carbon and nitrogen.

Dissimilatory nitrate reduction to ammonium in a soil under greenhouse vegetable cultivation as affected by organic amendments

Excessive nitrate (NO3 −) accumulation in greenhouse vegetable soils often results in nitrogen (N) loss through leaching or gaseous emission as a result of denitrification. Dissimilatory NO3 − reduction to ammonium (NH4 +) (DNRA) as affected by organic amendments in a greenhouse vegetable soil was studied. Soil incubations were carried out following the amendment of rice straw (RS), Chinese milk vetch (CMV), and a control (CK) without organic amendment using two 15 N isotope methods in the laboratory. Gross DNRA rates were 15.2–26.2 and 0.21–1.06 mg N kg−1 day−1 when estimated by the recovery of 15NO3 − in NH4 + and organic N (ON) pools (M1) and by mean residence time (MRT) of NH4 + (M2), respectively. Microbial NO3 − assimilation might occur due to high NO3 − content in the tested soil (1.27 g N kg−1), and thus, M1 probably overestimated gross DNRA rates. Gross DNRA rates estimated by M2 were higher in RS and CMV treatments than those in CK and were significantly (p < 0.05) correlated with soil dissolved organic carbon (DOC) content and the ratio of DOC to NO3 −–N. Therefore, the DNRA rate was promoted by organic amendments attributed to the enhancement of soil DOC to NO3 −–N ratio. Further studies on DNRA in more soil types under different conditions are required in order to better understand the potential contribution of DNRA to N transformation and conservation in vegetable soils.

三江平原不同湿地类型土壤活性有机碳组分及含量差异

PDF HTML阅读 XML下载 导出引用 引用提醒 三江平原不同湿地类型土壤活性有机碳组分及含量差异 DOI: 10.5846/stxb201405060894 作者: 作者单位: 中国科学院东北地理与农业生态研究所,河南南阳师范学院生命科学与技术学院,中国科学院东北地理与农业生态研究所,中国科学院东北地理与农业生态研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 中国科学院战略性先导科技专项课题(XDA05050508);国家自然科学基金项目(31100320,41171047)联合资助 Compositions and contents of active organic carbon in different wetland soils in Sanjiang Plain, Northeast China Author: Affiliation: Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences,Department of Life Science and Technology, Nanyang Normal University, Henan province,Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences,Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences 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:土壤活性有机碳对土壤干扰的反应较快,是土壤有机碳早期变化的敏感性指标。近50年来,三江平原湿地土壤有机碳库受农事活动影响较大。为了探讨不同湿地类型土壤活性有机碳主要组分土壤可溶性有机碳(Dissolved organic carbon, DOC)、微生物量碳(Microbial biomass carbon, MBC)和易氧化有机碳(Easily oxidized organic carbon, EOC)的分布差异及主要影响因子,选择了三江平原洪河自然保护区4种典型的湿地类型(小叶章+沼柳湿地、小叶章湿地、毛苔草湿地和芦苇湿地)为研究对象。分析了不同湿地类型土壤可溶性有机碳,微生物量碳和易氧化有机碳在0-30 cm土层内的分布特征和分配比例及其与有机碳、土壤养分和酶活性指标(蔗糖酶、纤维素酶和过氧化氢酶)之间的相关关系。结果表明:(1) 4种湿地类型土壤DOC、MBC和EOC含量均随土层深度的增加而减少。不同湿地类型之间土壤活性有机碳含量在0-30 cm土层内存在显著性差异(P < 0.05),相对于长期淹水的毛苔草湿地和芦苇湿地而言,未淹水的小叶章+沼柳湿地和小叶章湿地具有较高的DOC,MBC和EOC含量。(2) 土壤DOC、MBC和EOC占有机碳比例分别为0.27%-0.63%,1.27%-5.94%和19.63%-41.25%。土壤DOC所占比例呈先增后减的变化趋势,最大的比例均出现在10-20 cm。MBC所占比例在土壤剖面上则未表现出一致的变化规律,而EOC所占比例则随土层深度的增加而逐渐减少。(3) 土壤DOC占SOC比例以小叶章湿地最高,MBC和EOC占SOC的比例则以小叶章+沼柳湿地最高。而长期淹水的毛苔草湿地和芦苇湿地则具有更低的DOC,MBC和EOC比例。(4) 综合分析表明,4种湿地类型土壤DOC, MBC 和EOC两两之间存在极显著相关性关系,它们除了与碳氮比相关性不显著外,与土壤有机碳,全氮,全磷养分和酶活性指标间相关性均达到极显著水平,尤其是与有机碳和全氮的相关性系数更高,此外DOC与纤维素酶,MBC与过氧化氢酶相关性更大。由此可见,土壤碳氮磷养分和酶活性是影响土壤活性有机碳组分分布的重要因素。 Abstract:Soil active organic carbon (AOC) fractions are good indicators of soil carbon stock change because of their rapid response to soil disturbances in natural ecosystems. Agricultural activities in the last 50 years have greatly influenced the soil organic carbon (SOC) of natural wetlands on Sanjiang Plain, China. The main objective of this study was to assess differences in the distribution of soil AOC fractions, including dissolved organic carbon (DOC), microbial biomass carbon (MBC), and easily oxidized organic carbon (EOC), and the main influencing factors in four different types of wetlands in the Honghe National Natural Reserve of Sanjiang Plain. The contents and allocation ratios of soil DOC, MBC, and EOC were investigated at three soil depths (0-10, 10-20, and 20-30 cm) in four types of wetlands: (1) a mixed Calamagrostis angustifolia and Salix brachypoda wetland (CSW), (2) a C. angustifolia wetland (CAW), (3) a Carex lasiocarpa wetland (CLW), and (4) a Phragmites australis wetland (PAW). The relationships among the three soil AOC fractions and soil nutrient contents (SOC, total nitrogen [TN], total phosphorus [TP]) and enzyme activity (sucrase, cellulase, and catalase) were also analyzed. The results showed that DOC, MBC, and EOC content gradually decreased with increasing soil depth in the 0-30 cm soil layer of all four wetlands. However, significant differences (P < 0.05) were noted for the soil AOC fractions among the four wetlands. The DOC, MBC, and EOC content was significantly higher in non-flooding CSW and CAW compared to long-term flooding CLW and PAW. In the four wetlands, the ratios of soil DOC, MBC, and EOC to SOC content at the three soil depths ranged from 0.27% to 0.63%, 1.27% to 5.94%, and 19.63% to 41.25%, respectively. In addition, the trend in the changes of soil DOC to SOC ratios initially increased, followed by a decrease along the soil profiles, with peak values being documented for the 10-20 cm soil layer. No specific trend was noted for MBC to SOC ratios, but EOC to SOC ratios decreased with soil depth. The highest DOC to SOC ratio was obtained for CAW, whereas the highest MBC and EOC to SOC ratios were obtained for CSW. In contrast, lower DOC, MBC, and EOC to SOC ratios were observed in the long-term flooding CLW and PAW. Furthermore, positive correlations were observed among DOC, MBC, and EOC in all four wetlands. Our results showed that DOC, MBC, and EOC content was strongly correlated with SOC, TN, and TP content as well as with the enzyme activity indicators in the four wetland soils, but no significant correlation was noted for the C/N ratio. A higher correlation coefficient was observed between these three AOC fractions with SOC and TN content. Furthermore, highly significant relationships were observed between DOC content and cellulase activity, as well as between MBC content and catalase activity. In conclusion, the soil AOC fractions were mainly influenced by soil nutrient content (SOC, TN, and TP) and enzyme activity, which are associated with the C cycle. 参考文献 相似文献 引证文献

Distributions of dissolved organic carbon and nitrogen in the western Okhotsk Sea and their effluxes to the North Pacific

The Okhotsk Sea is considered the only ventilation source area for North Pacific Intermediate Water (NPIW), which is widely distributed in the low and middle latitudes of the North Pacific. Previous studies have confirmed high levels of dissolved organic carbon (DOC) in NPIW, yet the amounts and the processes driving DOC export from the Okhotsk Sea are poorly understood. In this study, concentrations of DOC and dissolved organic nitrogen (DON) were measured in the western Okhotsk Sea during the summer of 2006, and additional DOC measurements were made during the late spring of 2010. Results indicate that DOC transport to the intermediate waters (26.7–27.0 σθ) occurs through two processes. The first process involves the spread of water discharged from the continental shelf (Dense Shelf Water), which contributes to a DOC and turbidity maxima in the 250–300m layer of Okhotsk Sea Mode Water (OSMW) located off the eastern Sakhalin coast. The second process involves diapycnal mixing in the Kuril Basin and the Bussol’ Strait, where DOC is transported to a depth greater than 800m. The ratio of DOC:DON in OSMW was significantly higher in the Kuril Basin and Bussol’ Strait than off of the Sakhalin coast, which suggests that the transport of terrigenous organic matter from the bottom occurs in the former regions. DOC and DON efflux from the Okhotsk Sea to the intermediate layer in the North Pacific water (26.7–27.0 σθ) were estimated to be 68–72TgCyr−1 and 5.4TgNyr−1, respectively, for which the DOC transported by diapycnal mixing accounts for 37%. We conclude that diapycnal mixing in the Kuril Basin and Bussol’ Strait regions could play a significant role in regulating the quality and quantity of DOC exported to the intermediate water in the North Pacific.

Distribution characteristic of soil organic carbon fraction in different types of wetland in Hongze Lake of China.

Soil organic carbon fractions included microbial biomass carbon (MBC), dissolved organic carbon (DOC), and labile organic carbon (LOC), which was investigated over a 0–20 cm depth profile in three types of wetland in Hongze Lake of China. Their ecoenvironmental effect and the relationships with soil organic carbon (SOC) were analyzed in present experiment. The results showed that both active and SOC contents were in order reduced by estuarine wetland, flood plain, and out-of-lake wetland. Pearson correlative analysis indicated that MBC and DOC were positively related to SOC. The lowest ratios of MBC and DOC to SOC in the estuarine wetland suggested that the turnover rate of microbial active carbon pool was fairly low in this kind of wetland. Our results showed that estuarine wetland had a strong carbon sink function, which played important role in reducing greenhouse gas emissions; besides, changes of water condition might affect the accumulation and decomposition of organic carbon in the wetland soils.

富营养化湖泊溶解性有机碳生物可利用性研究进展

PDF HTML阅读 XML下载 导出引用 引用提醒 富营养化湖泊溶解性有机碳生物可利用性研究进展 DOI: 10.5846/stxb201209241349 作者: 作者单位: 南通大学地理科学学院,中国科学院南京地理与湖泊研究所湖泊与环境国家重点实验室,中国科学院南京地理与湖泊研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金资助项目（41201076，31270507，31070420）；湖泊与环境国家重点实验室开放基金资助项目（2012SKL006） The bioavailability of dissolved organic carbon in the eutrophic lakes Author: Affiliation: Geographical Sciences College,Nantong University,State key Laboratory of Lake Environment Science,Nanjing Institute of Geography and Limnology,Chinese Academy of Sciences,State key Laboratory of Lake Environment Science,Nanjing Institute of Geography and Limnology,Chinese Academy of Sciences 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:富营养化湖泊溶解性有机碳（DOC）包括内源和外源性碳源，不同来源碳源在物质化学结构组成和分子量级等方面具有显著差异，进而影响到对细菌的生物可利用性和碳素在食物网中的传递效率。根据国内外文献，综述了内外源DOC在碳稳定同位素值域上的显著差异，建议通过对DOC碳稳定同位素的分析来识别富营养化湖泊中DOC的主要来源；通过对比内外源DOC在碳水化合物、结合态中性糖和腐殖质含量上的差异，并结合细菌生长参数如细菌二级生产力、细菌呼吸作用及细菌生长效率来分析内外源DOC对细菌的生物可利用性。从富营养化湖泊DOC来源的角度探讨其生物可利用性和碳素传递效率，有助于了解富营养化湖泊食物网中碳素循环特征，加强对湖泊生态学的认识，为湖泊环境治理与保护提供科学依据。 Abstract:The dissolved organic carbon (DOC) pool is composed of both autochthonous and allochthonous DOC, and its concentration in lakes generally increases with the trophic status. Accumulation of the autochthonous DOC was observed in the eutrophic lake, and the allochthonous DOC was highest in the dystrophic lake. Carbohydrates constitute a large component of the DOC, the consumption of DOC by heterotrophic bacteria is one of the largest fluxes of carbon in most aquatic ecosystems, but the bioavailability and the efficiency of carbon transfer in lakes food web is affected by the distribution of molecular weight and chemical composition. The DOC can be separated into high and low molecular weight DOC fractions by cross-flow ultrafiltration, but which fraction is more bioreactive is still in dispute.Stable carbon isotope can be used to trace the origins of organic carbon, and the approach depends on the fact that DOC from different origins has different stable isotopic compositions. The riverine DOC has a δ13C value of -27‰, which is different from freshwater phytoplankton, with a range from -35‰ to -25‰. This paper reviewed the researches on the stable carbon isotope ratio of the autochthonous and allochthonous DOC, suggesting that the main sources of DOC in eutrophic lakes can be identified by using natural stable carbon isotope ratio of DOC; the difference on the total dissolved carbohydrates (TCHO) and dissolved combined neutral sugar (DCNS) concentrations, as well as the humic substances (HS) was compared between the autochthonous and allochthonous DOC. Net increases in TCHO and DCNS were observed in the autochthonous DOC during phytoplankton blooms, whereas the HS fraction was quantitatively important in the allochthonous DOC. Many studies have reported the bacterial availability of TCHO and DCNS, and the ratio of TCHO/DOC is used to characterize the bioavailability of DOC, whereas HS can also increase bacterial secondary production and support bacterial growth if labile substrates are abundant.Furthermore, to elucidate the bioavailability of the two sources of DOC, the bacterial secondary production, bacterial respiration and bacteria growth efficiency (BGE) was analyzed together. The DOC can be either transformed to bacterial secondary production or respired to inorganic carbon. BGE is the fraction of assimilated organic carbon that supports growth. The source of DOC and its chemical composition could be a key regulator of BGE. Traditionally, the autochthonous DOC has been considered to be the main source for bacterial as well as other secondary production, the allochthonous DOC was long considered relatively recalcitrant to bacterial degradation. However, in lakes which are both humic-rich and oligotrophic, the ecosystem respiration exceeds gross primary production, suggesting that the allochthonous DOC can be incorporated into the bacteria biomass and makes a significant carbon and energy subsidy for lakes food web, but little of the allochthonous carbon assimilated by bacteria is likely to reach higher consumers. Recent studies suggest that bacterial BGE increases with the concentration of the low molecular weight DOC in allochthonous DOC.Discussing the bioavailability and efficiency of carbon transfer in the food web from the sources of DOC, will be helpful to investigate the characterization of carbon cycling in the eutrophic lakes, enhance our understanding of the lake ecology and to provide scientific references for the lake management and protection. 参考文献 相似文献 引证文献