Influences of sample storage and grinding on the extraction of soil amino sugars

Soil amino sugars have been widely used to evaluate the potential roles of microbes in mediating soil carbon(C)cycling and various pretreatment methods were used for its extraction.However,few studies assessed their potential influences on the soil amino sugar extraction.In this study,we investigated the effects of sample storage method and grinding on amino sugar extraction across different climatic zones and land uses.Results showed that the concentrations of soil amino sugars varied greatly among sample pretreatments and their impacts were highly dependent on climatic condition and land use.Specifically,higher concentrations of amino sugars were extracted from field-moist samples than dried samples in subtropical grassland,temperate forest and arable land with no significant differences among storage methods for the samples from subtropical forest,arable land,and temperate grassland.Moreover,grinding improved the extraction efficiency of amino sugars for the dried soils.Due to the reduced extraction concentration in dried soils,field-moist samples were recommended in priority.For the dried soils used for the long-term storage,grinding can be an option to improve the extraction efficiency.Such information will be valuable for reducing the uncertainty and improving the accuracy during the determination of soil amino sugars.

Afforestation with an age-sequence of Mongolian pine plantation promotes soil microbial residue accumulation in the Horqin Sandy Land, China

Land use change affects the balance of organic carbon(C)reserves and the global C cycle.Microbial residues are essential constituents of stable soil organic C(SOC).However,it remains unclear how microbial residue changes over time following afforestation.In this study,16-,23-,52-,and 62-year-old Mongolian pine stands and 16-year-old cropland were studied in the Horqin Sandy Land,China.We analyzed changes in SOC,amino sugar content,and microbial parameters to assess how microbial communities influence soil C transformation and preservation.The results showed that SOC storage increased with stand age in the early stage of afforestation but remained unchanged at about 1.27-1.29 kg/m2 after 52 a.Moreover,there were consistent increases in amino sugars and microbial residues with increasing stand age.As stand age increased from 16 to 62 a,soil pH decreased from 6.84 to 5.71,and the concentration of total amino sugars increased from 178.53 to 509.99 mg/kg.A significant negative correlation between soil pH and the concentration of specific and total amino sugars was observed,indicating that the effects of soil acidification promote amino sugar stabilization during afforestation.In contrast to the Mongolian pine plantation of the same age,the cropland accumulated more SOC and microbial residues because of fertilizer application.Across Mongolian pine plantation with different ages,there was no significant change in calculated contribution of bacterial or fungal residues to SOC,suggesting that fungi were consistently the dominant contributors to SOC with increasing time.Our results indicate that afforestation in the Horqin Sandy Land promotes efficient microbial growth and residue accumulation in SOC stocks and has a consistent positive impact on SOC persistence.

Synthesis and Crystal Structure of a 3-Arylamino-3-Deoxy Sugar Derivative

3-Deoxy-3-（p-fluorine-phenylamino）-1,2-O-isopropylidene-α-D-ribofuranose 3 was synthesized and characterized by IR, NMR and H R M S, and its crystal structure was detertnined by X-ray diffraction analysis. Crystal data for 3： monoclinic, space group P21, a=7.0403（14）, b = 6.7780（4）, c = 14.932（3） A, β= 94.74（3）°, C14H18FNO4, Mr = 283.29, V= 710.1（2） A^3, Z = 2, Dc = 1.325 g/cm^3, μ = 0.105 mm^-1, F（000） = 300, the final R = 0.0468 and wR = 0.0926 for 1969 observed reflections （I 〉 2σ（I））. Two intermolecular hydrogen bonds are observed. The absolute configuration of this molecule was confirmed by comparison with that of the original material.

Synthesis and Crystal Structure of a New 3-Amino-3-deoxy Derivative from 3-Keto-D-xylose

The title compound 2 was synthesized by the reaction of 3-keto-D-xylose with O-C6H4NH2NH2 and characterized by IR, NMR and HRMS, and its crystal structure was determined by X-ray diffraction analysis. The crystal is of orthorhombic system （C21H22N2O5, Mr = 382.41）, space group P2 1 2 1 2 1 with α = 10.140（2）, b = 10.802（2）, c = 17.840（4） A, β = 90°, V = 1954.1（7）A^3, Z = 4, Dc = 1.300 g/cm^3, F（000） = 808, μ = 0.094 mm^-1, the final R = 0.0354 and wR = 0.0514 for 1924 observed reflections （I 〉 2σ（I））. One intermolecular and one intramolecular hydrogen bonds were found. The absolute configuration of this molecule was confirmed by comparison with that of the original material.

Accumulation of residual soil microbial carbon in Chinese fir plantation soils after nitrogen and phosphorus additions

Nitrogen （N） and phosphorus （P） additions can affect soil microbial carbon （C） accumulation. However, the mechanisms that drive the changes in residual microbial C that occur after N and P additions have not been well-defined for Chinese fir plantations in subtropical China. We set up six different treatments, viz. a control （CK）, two N treatments （NI： 50kgha-1 a-1; N2： 100 kg ha-1 a-1）, one P treatment （P： 50 kg ha-1 a-1）, and two combined N and P treatments （NIP： 50kgha-1a-1 of N ＋50kgha-1a-1 of P; N2P：100 kg ha-1 a-1 of N ＋ 50 kg ha-1 a-1 of P）. We then investigated the influences of N and P additions on residual microbial C. The results showed that soil pH and microbial biomass decreased after N additions, while microbial biomass increased after P additions. Soil organic carbon （SOC） and residual microbial C contents increased in the N and P treatments but not in the control. Residual microbial C accumulation varied according to treatment and declined in the order： N2P 〉 N1P 〉 N2 〉 N1 〉 P 〉 CK. Residual microbial C contents were positively correlated with available N, P, and SOC contents, but were negatively correlated with soil pH. The ratio of residual fungal C to residual bacterial C increased under P additions, but declined under combined N1P additions. The ratio of residual microbial C to SOC increased from 11 to 14% under the N1P and N2P treatments, respectively. Our results suggest that the concentrations of residual microbial C and the stability of SOC would increase under combined applications of N and P fertilizers in subtropical Chinese fir plantation soils.

Transformation of Sucrose to Starch and Protein in Rice Leaves and Grains under Two Establishment Methods

Six rice varieties, PR120, PR116, Feng Ai Zan, PR115, PAU201 and Punjab Mehak 1 were raised under aerobic and transplanting conditions to assess the effects of planting conditions on sucrose metabolising enzymes in relation to the transformation of free sugars to starch and protein in flag leaves and grains. Activities of sucrose synthase, sucrose phosphate synthase and acid invertase increased till flowering stage in leaves and mid-milky stage（14 d after flowering） in grains and thereafter declined in concomitant with the contents of reducing sugar. Under aerobic conditions, the activities of acid invertase and sucrose synthase（cleavage） significantly decreased in conjunction with the decrease in non-reducing sugars and starch content in all the varieties. Disruption of starch biosynthesis under the influence of aerobic conditions in both leaves and grains and the higher build up of sugars possibly resulted in their favoured utilization in nitrogen metabolism. Feng Ai Zan, PR115 and PR120 maintained higher levels of sucrose synthase enzymes in grains and leaves and contents of metabolites（amino acid, protein and non-reducing sugar） under aerobic conditions, while PR116, Punjab Mehak 1 and PAU201 performed better under transplanting conditions, thus showing their adaptation to environmental stress. Yield gap between aerobic and transplanting rice is attributed primarily to the difference in sink activity and strength. Overall, it appear that up-regulation of sucrose synthase（synthesis） and sucrose phosphate synthase under aerobic conditions might be responsible in enhancing growth and productivity of rice varieties.

Hierarchical self-assembly: when sugar meets amino acid

Life is an extremely delicate self-assembly system,where a rich array of small molecules,macromolecules and other entities associate and organize in an intrinsically diverse and precise manner.During the past few decades,scientists

Straw-returning reduces the contribution of microbial anabolism to salt-affected soil organic carbon accumulation over a salinity gradient

●In low-salinity soil,straw-returning did not change necromass contribution to SOC.●In medium-salinity soil,straw-returning reduced necromass contribution to SOC.●Straw-returning reduced POC contribution to SOC in low-salinity soil.●Straw-returning increased POC contribution to SOC in medium-salinity soil.●Salinity affects the contribution of microbial-derived and plant-derived C to SOC.Salinization affects microbial-mediated soil organic carbon(SOC)dynamics.However,the mechanisms of SOC accumulation under agricultural management practices in salt-affected soils remain unclear.We investigated the relative contribution of microbial-derived and plant-derived C to SOC accumulation in coastal salt-affected soils under straw-returning,by determining microbial necromass biomarkers(amino sugars)and particulate organic C(POC).Results showed that,straw-returning increased necromass accumulation in low-salinity soil but did not change its contribution to SOC.In medium-salinity soil,straw-returning did not increase necromass accumulation but decreased its contribution to SOC.In low-and medium-salinity soils,the contribution of POC to SOC showed the opposite direction to that of the necromass.These results suggest that under straw-returning,the relative contribution of microbial-derived C to SOC decreased with increasing salinity,whereas the reverse was true for plant-derived C.Our results highlighted that straw-returning reduces the contribution of microbial anabolism to SOC accumulation in salt-affected soils with increasing salinity.

The soil Microbial Carbon Pump as a new concept for terrestrial carbon sequestration

Soil is a huge terrestrial carbon pool, which has higher carbon storage than the sum of atmospheric and terrestrial vegetation carbon. Small fluctuations in soil carbon pool can affect regional carbon flux and global climate change. As soil organic carbon plays key roles in soil carbon storage and sequestration, studying its composition, sources and stability mechanism is a key to deeply understand the functions of terrestrial ecosystem and how it will respond to climate changes. The recently-proposed concept of soil Microbial Carbon Pump(MCP) emphasizes the importance of soil microbial anabolism and its contributions to soil carbon formation and stabilization, which can be applied for elucidating the source, formation and sequestration of soil organic carbon. This article elaborates MCP-mediated soil carbon sequestration mechanism and its influencing factors, as well as representative scientific questions we may explore with the soil MCP conceptual framework.

Increased microbial sequestration of soil organic carbon under nitrogen deposition over China’s terrestrial ecosystems

Background:China’s terrestrial ecosystems have been receiving increasing amounts of reactive nitrogen(N)over recent decades.External N inputs profoundly change microbially mediated soil carbon(C)dynamics,but how elevated N affects the soil organic C that is derived from microbial residues is not fully understood.Here,we evaluated the changes in soil microbial necromass C under N addition at 11 forest,grassland,and cropland sites over China’s terrestrial ecosystems through a meta-analysis based on available data from published articles.Results:Microbial necromass C accounted for an average of 49.5%of the total soil organic C across the studied sites,with higher values observed in croplands(53.0%)and lower values in forests(38.6%).Microbial necromass C was significantly increased by 9.5%after N addition,regardless of N forms,with greater stimulation observed for fungal(+11.2%)than bacterial(+4.5%)necromass C.This increase in microbial necromass C under elevated N was greater under longer experimental periods but showed little variation among different N application rates.The stimulation of soil microbial necromass C under elevated N was proportional to the change in soil organic C.Conclusions:The stimulation of microbial residues after biomass turnover is an important pathway for the observed increase in soil organic C under N deposition across China’s terrestrial ecosystems.