Ratio Of Microbial Biomass Carbon Research Articles

Linking microbial carbon‐degrading potential to organic carbon sequestration in fertilized soils: Insights from metagenomics

AbstractThe capacity of soils to store organic carbon (SOC) is vital for agricultural productivity. Soil microorganisms exert a critical role in carbon (C) flow and potentially influence C balance through the decomposition of plant and microbial dead biomass. However, the connection between the microbial degradation potential of plant‐derived and microbial‐derived C and soil organic carbon sequestration (SOCSR) under organic and inorganic nitrogen (N) fertilization treatments remains largely unexplored using metagenomics. In this study, metagenomics was used to investigate the effects of 4 years inorganic (N1: 250 kg N ha−1 yr−1 and N3: 450 kg N ha−1 yr−1) and organic N (O1: N1 + 11,250 kg ha−1 yr−1 sheep manure and O3: N1 + 18,750 kg ha−1 yr−1 sheep manure) fertilizer application on plant biomass decomposition genes, microbial biomass decomposition genes, and microbial properties related to different sources of C decomposition (species composition and diversity). Furthermore, the study explored the relationship between organic matter decomposition genes, microorganisms, and SOCSR. The results revealed that compared with N1 treatment, the increased application of inorganic N fertilizer (N3) significantly enhanced the abundance of genes related to plant and microbial biomass decomposition and microbial diversity involved in SOC decomposition, resulting in reduced SOC content. Conversely, the increased application of organic N fertilizer (O1 and O3) had a minor effect on the abundance of genes related to different sources of C decomposition and C decomposing microbial diversity, but reduced microbial entropy (the ratio of microbial biomass carbon to SOC) and increased SOC content. The random forest model highlighted that plant biomass decomposition genes and bacterial community composition were important factors affecting SOCSR. The Mantel test also indicated that the genes involved in the decomposition of lignin, cellulose, and hemicellulose were closely related to SOCSR. These findings highlighted that increased inorganic N fertilizers greatly enhanced the microbial capacity for SOC decomposition, resulting in reduced SOC accumulation. While the increased application of organic N fertilizer increased SOC stability and reduced the mineralization potential of SOC, contributing to SOCSR. Overall, these findings provide a greater understanding of the relationship between soil C turnover and microbial C‐degrading potential under short‐term fertilization. And in a long time, they may have important implications for global strategies aimed at increasing SOCSR to restore fertility and facilitate sustainable agricultural development.

Microbial fertilizer regulates C:N:P stoichiometry and alleviates phosphorus limitation in flue-cured tobacco planting soil

Fertilization can be optimized and managed during the flue-cured tobacco growing period by studying the response of soil and microbial biomass stoichiometric characteristics to fertilization. In this study, we investigated the effect of compound fertilizers combined with microbial fertilizer treatments on the stoichiometric characteristics of the rhizosphere soil and the limitations of microbial resources during the flue-cured tobacco growing period. The results indicated that soil and microbial C:N:P varied greatly with the growing period. The effect of sampling time was usually greater than that of fertilization treatment, and microbial C:N:P did not vary with the soil resource stoichiometric ratio. The microbial metabolism of the tobacco-growing soil was limited by phosphorus after extending the growing period, and phosphorus limitation gradually increased from the root extension to the maturation periods but decreased at harvest. The rhizosphere soil microbial nitrogen and phosphorus limitations were mainly affected by soil water content, soil pH, microbial biomass carbon, and the ratio of microbial biomass carbon to microbial biomass phosphorus. Applying microbial fertilizer reduced phosphorus limitation. Therefore, applying microbial fertilizer regulated the limitation of microbial resources by affecting the soil and microbial biomass C:N:P in flue-cured tobacco rhizosphere soils.

Effect of Biochar on Labile Organic Carbon Fractions and Soil Carbon Pool Management Index

Biochar is useful for soil organic carbon (SOC) sequestration. However, the effects of biochar aging and addition rates on SOC stabilization are unclear. A field experiment with four biochar application rates (0% (control), 1% (LB), 2% (MB), and 4% (HB) of dry fluvo-aquic soil) was conducted. Soil samples were sampled after 8, 12, and 24 months of its application to clarify the question. In general, SOC gradually increased with the biochar application rate. SOC with HB was higher than that in other treatments, while the ratio of microbial biomass carbon (MBC)/SOC and readily oxidizable carbon (ROC)/SOC with HB was lower than that in other treatments (p < 0.05), indicating a positive effect of HB for C stabilization over time. The effects of biochar on the soil carbon pool management index (CPMI) changed from negative to positive after 8 and 24 months of biochar application. The activities of β-D-glucosidase (βG), cellobiohydrolase (CBH), and β-N-acetylglucosaminidase (NAG) under HB were higher than with other treatments after 12 and 24 months of biochar application (p < 0.05) and negatively correlated with the ratio of MBC/SOC and ROC/SOC over time. The CPMI was positively related with βG and CBH activities after 8 and 24 months of biochar application, respectively (p < 0.05). HB increased the relative abundance of oligotrophs, including Acidobacteria, Actinobacteria, and Chloroflexi, but decreased the relative abundance of copiotrophs, including γ-Proteobacteria and Bacteroidetes over time (p < 0.05). The ratio of dissolved organic carbon (DOC)/SOC was positively correlated with the bacterial oligotroph/copiotroph ratio and significantly affected the oligotrophic and copiotrophic bacterial communities, especially after 8 and 12 months of biochar application (p < 0.05). These findings reinforce that increasing the biochar application rate and time enhances SOC stabilization by decreasing the proportions of labile organic carbon and making oligotrophic/copiotrophic communities and enzyme activities more conducive to C sequestration.

Drought is threatening plant growth and soil nutrients of grassland ecosystems: A meta-analysis.

As a widespread direct effect of global warming, drought is currently wreaking havoc on terrestrial ecosystems' structure and function, however, the synthesized analysis is lacked to explore the general rules between drought changes and main functional factors of grassland ecosystems. In this work, meta-analysis was used to examine the impacts of drought on grassland ecosystems in recent decades. According to the results, drought greatly reduced aboveground biomass (AGB), aboveground net primary production (ANPP), height, belowground biomass (BGB), belowground net primary production (BNPP), microbial biomass nitrogen (MBN), microbial biomass carbon (MBC) and soil respiration (SR), and increased dissolved organic carbon (DOC), total nitrogen (TN), total phosphorus (TP), nitrate nitrogen (NO3--N), and the ratio of microbial biomass carbon and nitrogen (MBC/MBN). The drought-related environmental factor mean annual temperature (MAT) was negatively correlated with AGB, height, ANPP, BNPP, MBC, and MBN, however, mean annual precipitation (MAP) had positive effect on these variables. These findings indicate that drought is threatening the biotic environment of grassland ecosystem, and the positive steps should be taken to address the negative effects of drought on grassland ecosystems due to climate change.

Effects of Fertilization on Soil CO<sub>2</sub> Efflux in Chinese Hickory (<i>Carya cathayensis</i>) Stand

Chinese hickory (Carya cathayensis Sarg.) is a popular nut tree in China, but there is little information about the influences of fertilization on soil CO2 efflux and soil microbial biomass. This study evaluated the short-term effects of different fertilizer applications on soil CO2 efflux and soil microbial biomass in Chinese hickory stands. Four fertilizer treatments were established: control (CK, no fertilizer), inorganic fertilizer (IF), organic fertilizer (OF), and equal parts organic and inorganic N fertilizers (OIF). A field experiment was conducted to measure soil CO2 effluxes using closed chamber and gas chromatography techniques. Regardless of the fertilization practices, soil CO2 effluxes of all the treatments showed a similar temporal pattern, with the highest value in summer and the lowest in winter. The mean annual soil CO2 efflux in the IF treatment was significantly higher than that in the CK, OIF, and OF treatments. There was no significant difference in soil CO2 efflux between the OIF, OF, and CK treatments. Soil CO2 effluxes were significantly affected by soil temperature. Soil dissolved organic carbon (DOC) was positively correlated with soil CO2 efflux only in the CK treatment. Regression analysis, including soil temperature, moisture, and DOC, showed that soil temperature was the primary factor influencing soil CO2 effluxes. Both OF and OIF treatments increased concentrations of soil microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN), but decreased the ratio of MBC:MBN. These results reveal that applying organic fertilizer, either alone or combined with inorganic fertilizer, may be the optimal strategy for mitigating soil CO2 emission and improving soil quality in Chinese hickory stands.

Temperature Sensitivity of Topsoil Organic Matter Decomposition Does Not Depend on Vegetation Types in Mountains.

Rising air temperatures caused by global warming affects microbial decomposition rate of soil organic matter (SOM). The temperature sensitivity of SOM decomposition (Q10) may depend on SOM quality determined by vegetation type. In this study, we selected a long transect (3.6 km) across the five ecosystems and short transects (0.1 km) from grazed and ungrazed meadows to forests in the Northwest Caucasus to consider different patterns in Q10 changes at shift of the vegetation belts. It is hypothesized that Q10 will increase along altitudinal gradient in line with recalcitrance of SOM according to kinetics-based theory. The indicators of SOM quality (BR:C, respiration per unit of soil C; MBC:C, ratio of microbial biomass carbon to soil carbon; soil C:N ratio) were used for checking the hypothesis. It was shown that Q10 did not differ across vegetation types within long and short transects, regardless differences in projective cover (14–99%) and vegetation species richness (6–12 units per plot). However, Q10 value differed between the long and short transects by almost two times (on average 2.4 vs. 1.4). Such a difference was explained by environmental characteristics linked with terrain position (slope steepness, microclimate, and land forms). The Q10 changes across studied slopes were driven by BR:C for meadows (R2 = 0.64; negative relationship) and pH value for forests (R2 = 0.80; positive relationship). Thus, proxy of SOM quality explained Q10 variability only across mountain meadows, whereas for forests, soil acidity was the main driver of microbial activity.

清澜港红树林湿地典型群落类型沉积物活性有机碳组分分布特征

PDF HTML阅读 XML下载 导出引用 引用提醒 清澜港红树林湿地典型群落类型沉积物活性有机碳组分分布特征 DOI: 10.5846/stxb202105081203 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 省属科研院所技术创新专项项目（jscx202023）；海南省科研院所技术创新专项基础性科研工作（jcxk202003） Distribution characteristics of active organic carbon components in sediments of typical community types of mangrove wetland in Qinglan Port Author: Affiliation: 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:滩涂海岸红树林生态系统通常具有较高的土壤养分，尤其是沉积物有机碳含量。海南岛红树林种类丰富且生长较好，通过对红树林沉积物有机碳组分的基础研究有利于提高对红树林湿地固碳能力的评估精度，加深对海洋蓝碳的认识。以清澜港红树林5种典型群落类型为对象，比较分析表层土壤（0-10 cm）总有机碳（TOC）、微生物生物量碳（MBC）、易氧化有机碳（EOC）、可溶性有机碳（DOC）含量差异及其与土壤因子之间的相关性。结果表明：（1）不同群落类型间，土壤TOC、MBC、DOC和EOC含量均值分别为66.76 g/kg、177.08 mg/kg、25.49 mg/kg和2.34 g/kg。对比发现，土壤TOC在角果木群落中含量最高，但各群落间无显著差异；土壤MBC在不同群落间存在显著差异，其中角果木群落和杯萼海桑群落显著高于榄李群落；土壤DOC在不同群落间存在显著差异，其中海莲群落和角果木群落显著高于其余群落；土壤EOC在不同群落间存在显著差异，其中角果木群落显著高于海莲群落和正红树群落。（2）活性有机碳各个组分占总有机碳的比例均值大小依次为EOC>MBC>DOC。土壤EOC、MBC、DOC的分配比例分别介于3.23%-4.02%、0.22%-0.36%、0.02%-0.08%之间。（3）冗余分析表明，土壤TN对土壤有机碳组分含量的单独解释率最高。土壤pH在土壤的单独解释率最低，其对土壤有机碳组分含量影响较小。（4）土壤TOC、MBC、DOC、EOC与土壤TN、含水量（SWC）呈极显著正相关。综上所述，潮位以及不同群系类型引起的土壤理化性质共同影响着土壤活性有机碳组分的浓度。 Abstract:Mangrove ecosystems in tidal flats usually contain a large proportion of soil nutrients, especially organic carbon content in sediments. The basic research on organic carbon components of the sediments in the large variety of luxuriant mangrove forests in Hainan Island can help more accurately evaluate the carbon sequestration capacity of mangrove wetlands and improve the knowledge about marine blue carbon. This paper comparatively analyzes the different contents of total organic carbon (TOC), microbial biomass carbon (MBC), easily oxidized organic carbon (EOC), and dissolved organic carbon (DOC) in the topsoil (0-10 cm) in five typical populations of mangrove in Qinglan Port and their correlation with soil factors. The result shows that (1) the average contents of TOC, MBC, DOC and EOC in the surface soils in different populations of mangrove are 66.76 g/kg, 177.08 mg/kg, 25.49 mg/kg, and 2.34 g/kg, respectively. According to the comparative analysis, the content of TOC is the highest in the soil in the Ceriops tagal community, but it is not significantly different among all the communities;The content of MBC in the soil is significantly different among all flora communities, where the content of MBC in the soil in Ceriops tagal community and Sonneratia alba community is much higher than that in Lumnitzera racemosa community. The content of DOC in the soil in all communities is significantly different, where the content of DOC in the soil in Bruguiera sexangula community and Ceriops tagal community is much higher than that in other communities. The content of EOC in the soil in all communities is significantly different, where the content of EOC in the soil in Ceriops tagal community is much higher than that in Bruguiera sexangula community and Rhizophora Apiculata community. (2) The average ratio of active organic carbon components to total organic carbon in MBC is higher than in DOC, and that in EOC is the highest. The distribution ratios of EOC, MBC and DOC in soil are between 3.23% and 4.02%, 0.22% and 0.36%, and 0.02% and 0.08% respectively. (3) Redundancy analysis shows that total nitrogen (TN) in soil is more justified to exclusively prove organic carbon components in the soil. Soil pH is less justified to exclusively prove the organic carbon component in the soil. (4) TOC, MBC, DOC and EOC in soil are positively correlated with soil TN and soil water content (SWC). In conclusion, tidal level soil physical and chemical properties caused by different biotic communities jointly affect the concentration of soil active organic carbon components. 参考文献 相似文献 引证文献

Patterns and drivers of the degradability of dissolved organic matter in dryland soils on the Tibetan Plateau

Abstract Dryland soils consistently exhibit a low capacity for the long‐term accumulation and storage of organic matter, which has been primarily attributed to low plant biomass inputs under drought suppression. Whether, and how, soil organic matter (SOM) compositions contribute to the consistently low SOM storage have been puzzling. A fundamental understanding of this mechanism is particularly essential to achieve the aspiration of ‘4 per mille Soils for Food Security and Climate’. By screening the molecular composition of dissolved organic matter (DOM), the gatekeeper of SOM decomposition, we explored the transformation processes among the pools of SOM, DOM and microbial biomass carbon (MBC) in soils along a precipitation gradient on dryland grasslands of the Tibetan Plateau. The results revealed that the number and mean weight of DOM molecules significantly decreased, and the soil DOM composition gradually shifted to be more labile along the transition from meadow, steppe, to desert with decreasing precipitation, coinciding with the substantial reduction in SOM. Compared with meadow soils, DOM degradability increased by 8.7% in steppe soils and by 23.4% in desert soils. The ratio of soil MBC to total organic carbon was threefold higher in desert than in meadow, and positively correlated with DOM degradability, indicating that labile DOM accelerated microbial growth and SOM decomposition in desert soils. Structural equation model and correlation analyses demonstrated that the DOM degradability was primarily controlled by soil dissolved nitrogen and soil organic C and soil DOC/DN ratio. Synthesis and application. This study at a molecular level provides a novel insight into the important role of the degradability of dissolved organic matter in carbon accumulation in dryland soils with consistently low organic matter storage. The findings will inform better global managements of soil organic matter under consideration of both food security and climate change.

Straw incorporation plus biochar addition improved the soil quality index focused on enhancing crop yield and alleviating global warming potential

The stimulated N2O emission by straw incorporation (S1) is adverse to mitigating global warming potential (GWP). Thus, this study advocated an optimal straw-based system, i.e. S1 plus biochar (SB), to mitigate the straw-induced N2O emission and further promote soil organic carbon (SOC) sequestration. Moreover, this study addressed research gap on quantification of soil quality focused on enhancing yield and alleviating GWP. Greenhouse gas emission intensity (GHGI) was used to relate yield with GWP. A field experiment was conducted to investigate the response of overall soil quality to S1, SB and no straw inputs (S0) under two nitrogen rates (routine rate [N1] and 70% of routine rate [N0.7]). To comprehensively evaluate soil quality, a wide range of soil physical, chemical, biological and ecological properties closely related to yield and GHGI were measured and integrated into a soil quality index (SQI). Although both S1 and SB enhanced the SQI, the SB achieved the highest SQI under N1 rate. Firstly, this is because N1-SB significantly mitigated the straw-induced N2O emission, associated with the declined soil inorganic nitrogen (SIN) and dissolved organic carbon (DOC) contents. Secondly, N1-SB greatly enhanced SOC sequestration, mainly attributed to the increased ratio of microbial biomass carbon to microbial biomass nitrogen (MBC/MBN) and decreased microbial quotient (MBC/soil organic carbon and MBN/total nitrogen), implying the lower efficiency of soil microorganisms to utilize soil organic matter. Lastly, N1-SB markedly increased maize yield in 2019 compared to S0. Overall, the highest SQI for N1-SB was ascribed to the higher soil quality scores in labile nitrogen/total nitrogen (LN/TN) and MBC/MBN, and lower soil quality scores in SIN and DOC.

Soil amendment in plastic greenhouse using modified biochar: soil bacterial diversity responses and microbial biomass carbon and nitrogen.

The experiment was set up to explore the effect of modified biochar on soil bacterial community structure, and the correlation between soil environmental factors and bacterial community structure changes. Based on the plot experiment in the field, the effect of modified biochar was studied via high-throughput MiSeq sequencing. Compared with the control (CK), the modified biochar (T) significantly increased soil water content, microbial biomass carbon (MBC), microbial biomass nitrogen (MBN) content and the ratio of MBC and MBN by 7.92%, 24.58%, 2.07% and 18.95%. Diversity index analysis showed that the application of modified biochar significantly increased the Shannon index, ACE index and Chao1 index of the bacterial community by 3.05%, 5.07% and 5.24%. Compared with the control, the modified biochar decreased the relative abundance of Actinobacteriota and Chloroflex by 6.81% and 2.19%, and increased the relative abundance of Proteobacteria and Acidobacteriota by 7.34% and 12.52%. Correlation analysis shows that soil bulk density and water content may be important related factors that affect bacterial community structure. This study provides a theoretical basis for the directional control of modified biochar in the soil microecological environment in plastic greenhouse, which is conducive to healthy and sustainable farming.

Root cellulose drives soil fulvic acid carbon sequestration in the grassland restoration process

Revegetation is an effective means to increase the soil organic carbon (SOC) stock and reverse SOC loss worldwide. Restoration through grasslands has great potential primarily due to the contribution of the root system. However, the impacts of grassland restoration remain uncertain, as current understandings of the direction and magnitude of changes in different SOC fractions and the influence of root properties on SOC are still unclear. To address this problem, we conducted a field study to investigate variations in SOC fractions and root properties under different grassland restoration times (1, 5, 10, 15, 25 and 30 years following restoration) in the Loess Plateau, China. Specifically, we measured fractions of soil labile organic carbon including microbial biomass carbon (MBC) and dissolved organic carbon (DOC) and fractions of soil stable organic C including humus carbon (HS), fulvic acid carbon (FA) and humic acid carbon (HA) in the 1 m soil profile. Furthermore, we evaluated root biomass, root C, root lignin and cellulose as potential drivers of SOC patterns. We found that SOC, soil labile organic C and soil stable organic C fractions generally increased with the revegetation time, except for brief decreases at the 5- and 15-year marks. Across the entire period (year 1 to 30), the proportions of HS and FA to SOC increased by 10.64% and 14.72% at 30 years, respectively, while the ratios of MBC and DOC to SOC were relatively stable. The average SOC accumulation rate was 0.72 Mg ha−1 yr−1 in the 1 m soil profile over the 30-year grassland revegetation period. The average rate of change of FA (0.67 Mg ha−1 yr−1) was higher than that of the HA, HS and soil labile organic C fractions, which indicated that SOC stability increased and SOC accumulation was mainly derived from the enhancement of FA. Decreases in root biomass and cellulose storage drove reductions in SOC fraction stores with soil depth. The root cellulose exerted significant influences on the SOC and SOC fractions, especially on FA (R2 = 0.82, p < 0.01). These findings show that grassland restoration plays an important role in improving and increasing SOC; in particular, the increase of FA results from the augmentations of root cellulose.

Effects of management measures on organic carbon, nitrogen and chemical structure of different soil fractions in Phyllostachys edulis plantations.

To examine the effects of management measures on carbon and nitrogen contents, as well as their distribution and structural characteristics of different soil fractions in Moso bamboo plantations, we compared three types of the bamboo forests (undisturbed, extensively managed, and intensively managed) and the control secondary broadleaved evergreen forest using the methods of physical fractionation, chemical and biological analysis and Fourier-transform infrared spectroscopy (FTIR). The results showed that soil total organic carbon (TOC) and total nitrogen (TN) content, as well as free particulate organic carbon and nitrogen, soluble organic carbon and nitrogen (DOC, DON), and mineral-associated organic carbon and nitrogen in the undisturbed and extensively managed Moso bamboo plantations were significantly increased compared with that in the control. The distribution ratio of free particulate organic carbon and nitrogen in the undisturbed Moso bamboo plantation significantly increased, with mineral-associated organic carbon being the largest reservoir of soil organic carbon (67.6%). Intensive management resulted in the decrease of soil organic carbon, total nitrogen storage, and the contents of each component, but significantly increased DOC/TOC, the ratio of microbial biomass nitrogen to TN as well as the ratio of microbial biomass carbon to TOC (microbial quotient). Management measures significantly affected the chemical structure of SOC. Compared with the control, the relative intensities of phenolic and alcoholic-OH, aliphatic methyl and methylene, aromatic C=C, and carbonyl C=O absorption were higher in the SOC of undisturbed and extensively managed Moso bamboo plantations, and soil hydrophobicity was significantly increased. Results from correlation analysis showed that soil hydrophobicity and the content of aliphatic and aromatic groups were negatively correlated with microbial quotient and positively correlated with TOC and TN content. In conclusion, the increased inputs of organic matter residues (such as litter and roots) could contribute to the relative accumulation of chemical resistance compounds with reduced human disturbance, which significantly enhanced chemical stability of soil organic carbon. Soil clay minerals played a key role in protecting soil organic carbon through the formation of mineral-organic compounds, which facilitate the stability of soil carbon storage and the long-term preservation of soil carbon.

Aridity thresholds of soil microbial metabolic indices along a 3,200 km transect across arid and semi-arid regions in Northern China.

Soil microbial processes are crucial for understanding the ecological functions of arid and semi-arid lands which occupy approximately 40% of the global terrestrial ecosystems. However, how soil microbial metabolic activities may change across a wide aridity gradient in drylands remains unclear. Here, we investigated three soil microbial metabolic indices (soil organic carbon (SOC)-based microbial respiration, metabolic quotient, and microbial biomass as a proportion of total SOC) and the degree of carbon limitation for microbial respiration along a 3,200 km transect with a wide aridity gradient. The aridity gradient was customarily expressed using the aridity index (AI) which was calculated as the ratio of mean annual precipitation to mean annual evaporation, therefore, a lower AI value indicated a higher degree of aridity. Our results showed non-linear relationships between AI values and the metabolic indices with a clear aridity threshold for each of the three metabolic indices along the aridity gradient, respectively (AI = 0.13 for basal respiration, AI = 0.17 for metabolic quotient, and AI = 0.17 for MBC:SOC ratio). These metabolic indices linearly declined when AI was above the thresholds, but did not show any clear patterns when AI was below the thresholds. We also found that soil microbial respiration was highly limited by available carbon substrates at locations with higher primary production and relatively lower level of water limitation when AI was above the threshold, a counter-intuitive pattern that microbes were more starved in ecosystems with more substrate input. However, the increasing level of carbon limitation did correspond to the declining trend of the three metabolic indices along the AI gradient, which indicates that the carbon limitation influences microbial metabolism. We also found that the ratio of microbial biomass carbon to SOC in arid regions (AI < 0.2) with extremely low precipitation and primary production were not quantitatively related to SOC content. Overall, our results imply that microbial metabolism is distinctively different in arid lands than in non-arid lands.

The interactions between tree-herb layer diversity and soil properties in the oriental beech (Fagus orientalis Lipsky) stands in Hyrcanian forest.

This study investigated the interactions between tree-herb layer diversity and some physico-chemical and eco-physiological characteristics of soil in natural oriental beech stand in western Guilan, Iran. The data were collected from nine research sites (50m × 50m) which were described as a gradient from pure oriental beech (Fagus orientalis Lipsky) stands to mixed stands with up to nine deciduous tree species (n= 27) in Hyrcanian forest. Herbaceous plants were sampled within ten 1m × 1m sub-plots in two plots of 400m2 which were installed randomly in each research site. Composite soil samples were taken at five positions in each research site. We found that the increase in tree diversity in mature oriental beech stands brought about an increase in microbial biomass carbon, soil carbon content, and the ratio of microbial biomass carbon to the organic carbon (Cmic/Corg). Increased soil organic carbon raised microbial biomass carbon through creating suitable environment for microorganisms. The findings also indicated that the ratio of microbial biomass carbon to the organic carbon (Cmic/Corg) increased as a quantitative indicator of soil carbon dynamics that finally benefits soil fertility of mixed oriental beech stands compared to pure oriental beech stands. The results showed that humus layer and litter thickness were negatively correlated with tree layer richness. Generally, it can be stated that maintaining a mixture of tree layer species in natural oriental beech stands results in an increase in richness and diversity values of herb plants as well as carbon content and microbial biomass carbon of soil.

Labile and recalcitrant sediment organic carbon pools in the Pearl River Estuary, southern China

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.

Effects of an integrated rice-crayfish farming system on soil organic carbon, enzyme activity, and microbial diversity in waterlogged paddy soil

A 10-year (2005–2015) field experiment was conducted to study the effects of an integrated rice-crayfish (CR) model on soil organic carbon, enzyme activity, and microbial diversity at soil depths of 0–10 cm, 10–20 cm, 20–30 cm, and 30–40 cm. Compared with a mid-season rice monoculture (MR) model, total organic carbon (TOC), particle organic carbon (POC), and water-soluble organic carbon (WSOC) were significantly higher in the 0–40 cm soil layers, and the content of microbial biomass carbon (MBC) was significantly higher in the 30–40 cm soil layer in the CR model. The ratios of WSOC to TOC and POC to TOC in the 0–40 cm soil layers in CR model exhibited an increasing trend, whereas the ratio of MBC to TOC in the 0–30 cm layers exhibited a decreasing trend with respect to that of the MR model, however, these differences were not statistically significant. The activity of soil invertase, acid phosphatase, and urease in the 0–40 cm soil layers in the CR model exhibited a decreasing trend with respect to that of the MR model, and the activity of urease in the 10–20 cm soil layer in the CR model was significantly lower than that in the MR model. Compared with the MR model, the CR model significantly enhanced the carbon utilization capacity of soil microbes, and the richness index, dominance index, and diversity index of the soil microbial community in the 20–30 cm layer, whereas it significantly decreased the number of dominant soil microorganism species and the carbon utilization capacity of soil microbes in the 0–10 cm layer. Soil organic carbon and its active components had a significant direct correlation with the microbial diversity index, and significantly positive correlations with invertase, urease, and acid phosphatase. With respect to the soil microbial diversity index, soil organic carbon and its active components had a closer relationship with soil enzyme activity.

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

The linkage between vegetation and soil nutrients and their variation under different grazing intensities in an alpine meadow on the eastern Qinghai-Tibetan Plateau

The grassland degradation caused by overgrazing is the result of imbalance of energy flow and material cycle under grazing pressure in the ecosystem, and numerous ecological restoration and ecological engineering techniques widely used to restore some ecosystem. However, little research known focused on the relationship (energy flow and material cycle) between plant and soil under different grazing intensity, especially at the rhizosphere which is the most powerful area of plant and soil interaction. In this research we conducted a 5-year grazing experiment including 4 different grazing intensities (no grazing, UG; light grazing, LG; moderate grazing, MG; and heavy grazing, HG) in an alpine meadow on the northeastern margin of Qinghai-Tibetan Plateau (QTP). Plants and soil materials were sampled in July 2015, and to examine the nutrients concentration and ecological stoichiometric of vegetation and soil, the soil microbial biomass and activity, as well as their relationship with vegetation and soil characteristics. We found that grazing increased vegetation and soil nutrient concentrations and increased the ratio of microbial biomass carbon (MBC) to microbial biomass nitrogen (MBC), but the grazing intensity did not significantly influence the nutrients enrichment ratio of rhizosphere soil. There was significant relationship between total carbon (TC) concentration of vegetation and soil, and between vegetation total phosphorus (TP) and soil PO43−-P concentration. These results suggested that vegetation and soil nutrient concentrations respond differently to the grazing intensity. Coupling relationship exists in specific nutrients of vegetation and soil and rhizosphere is a powerful tool to understanding the linkage between plant and soil.

Influences of drip and flood irrigation on soil carbon dioxide emission and soil carbon sequestration of maize cropland in the North China Plain

The need is pressing to investigate soil CO2 (carbon dioxide) emissions and soil organic carbon dynamics under water-saving irrigation practices in agricultural systems for exploring the potentials of soil carbon sequestration. A field experiment was conducted to compare the influences of drip irrigation (DI) and flood irrigation (FI) on soil organic carbon dynamics and the spatial and temporal variations in CO2 emissions during the summer maize growing season in the North China Plain using the static closed chamber method. The mean CO2 efflux over the growing season was larger under DI than that under FI. The cumulative CO2 emissions at the field scale were 1959.10 and 1759.12 g/m2 under DI and FI, respectively. The cumulative CO2 emission on plant rows (OR) was larger than that between plant rows (BR) under FI, and the cumulative CO2 emission on the irrigation pipes (OP) was larger than that between irrigation pipes (BP) under DI. The cumulative CO2 emissions of OP, BP and bare area (BA) under DI were larger than those of OR, BR and BA under FI, respectively. Additionally, DI promoted root respiration more effectively than FI did. The average proportion of root respiration contributing to the soil CO2 emissions of OP under DI was larger than that of OR under FI. A general conclusion drawn from this study is that soil CO2 emission was significantly influenced by the soil water content, soil temperature and air temperature under both DI and FI. Larger concentrations of dissolved organic carbon (DOC), microbial biomass carbon (MBC) and total organic carbon (TOC) were observed under FI than those under DI. The observed high concentrations (DOC, MBC, and TOC) under FI might be resulted from the irrigation-associated soil saturation that in turn inhibited microbial activity and lowered decomposition rate of soil organic matter. However, DI increased the soil organic matter quality (the ratio of MBC to TOC) at the depth of 10–20 cm compared with FI. Our results suggest that the transformation from conventional FI to integrated DI can increase the CO2 emissions and DI needs to be combined with other management practices to reduce the CO2 emissions from summer maize fields in the North China Plain.

Response of Robinia pseudoacacia L. rhizosphere microenvironment to Cd and Pb contamination and elevated temperature

Elevated air temperature and contamination of soil with heavy metals co-occur in natural ecosystems and have important effects on the soil microenvironment by influencing plant physiology. Effects of elevated temperature and cadmium (Cd) pollution on the rhizosphere microenvironment have been examined for wheat seedlings, but rhizosphere responses to elevated temperature might differ among plant species and for other heavy metals. This study examined the response of the black locust rhizosphere microenvironment to slightly elevated temperature in combination with Cd and lead (Pb) contamination. Elevated temperature combined with Cd and Pb exposure corresponded to an increase in soluble sugars, free amino acids, and organic acids and to a decrease in soluble phenolic acids in rhizosphere soils. These combined variables also corresponded to a decrease in microbial abundance, microbial biomass carbon, fluorescein diacetate hydrolysis, and the ratio of microbial biomass carbon (C) to total organic C compared to elevated temperature alone or to individual metals. The combination of elevated temperature plus exposure to heavy metals had varying effects on the different enzymes relative to the individual stress factors. The removal rate of Cd and Pb in rhizosphere soils increased significantly under elevated temperature and was greater for Cd than for Pb. Generally, elevated temperature led to increased microbial activity in rhizosphere soil of black locust seedlings exposed to heavy metals by stimulating microbial abundance, microbial biomass C, and enzyme activity. Variability in plant species and heavy metals might lead to different responses of phenolic acids to elevated temperature+heavy metals. Increased removal of heavy metals indicated that elevated temperature might improve the phytoremediation efficiency of heavy metal-contaminated soils by black locust seedlings. A capsule abstractElevated temperature led to increased microbial activity in rhizosphere soil of black locust seedlings exposed to heavy metals.