Effects of flue gas desulfurization gypsum and clover planting on qualities of soil and winter jujube in coastal saline-alkali orchard of north China

Flue gas desulfurization gypsum and clover planting alleviated the soil salinization stress.Soil pH and total phosphorus affected the bacterial communi-ties.Total phosphorus affected the fungal communities.Flue gas desulfurization gypsum and clover planting improved jujube quality.The coastal area of Shandong Province,characterized by coastal saline tidal soil,is one of the main production areas of winter jujube in China.However,the low soil fertility and poor soil structure in jujube orchard restricted the development of the jujube industry.The objectives of this study were to 1)evaluate the effect of application of flue gas desulfurization(FGD)gypsum and clover planting on soil quality improvement and soil microbial community structure of jujube orchard;2)investigate the effects of two measures on the nutrition and quality of winter jujube.The results showed that FGD gypsum reduced the soil total salt content by 65.6%,and clover planting increased the soil organic matter content by 30.7%,which effectively alleviated the soil salinization stress and improved the soil structure.Soil pH and total phosphorus(TP)were the main determinants influencing bacterial community composition,and TP was the dominant factor of the fungal community composition in the saline-alkali soils.Meanwhile,FGD gypsum addition and clover planting significantly increased the sugar degree and Vc content of winter jujube,thus improved jujube quality,and further contributed to the ecological sustainable development of winter jujube industry.

Effects of lead pollution on soil microbial community diversity and biomass and on invertase activity

Lead(Pb)pollution is one of the most widespread and harmful environmental problems worldwide.Determination of changes in soil properties and microbial functional diversity due to land use is needed to establish a basis for remediation of soil pollution.This study aimed to investigate soils contaminated by Pb from different sources and to analyze the functional diversity and metabolism of soil microbial communities using Biolog technology.Pb pollution(>300 mg kg-1)significantly influenced the diversity and metabolic functions of soil microbial communities.Specifically,Pb contamination significantly reduced soil microbial biomass carbon(C)and nitrogen(N)levels and catalase activity while increasing invertase activity.Furthermore,Biolog EcoPlate assays revealed that Pb pollution reduced the general activities of soil microorganisms,suppressing their ability to utilize C sources.In Pb-contaminated areas lacking vegetation cover,Shannon,Simpson,and McIntosh diversity indices of soil microorganisms were significantly reduced.The microbial diversity and biomass C and N levels were affected by land use and soil properties,respectively,whereas soil enzyme activity was primarily affected by the interaction between land use and soil properties.Our results provide a reference and a theoretical basis for developing soil quality evaluation and remediation strategies.

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.

CO_(2)emission and source partitioning from carbonate and non-carbonate soils during incubation

The accurate quantification and source partitioning of CO_(2)emitted from carbonate(i.e.,Haplustalf)and non-carbonate(i.e.,Hapludult)soils are critically important for understanding terrestrial carbon(C)cycling.The two main methods to capture CO_(2)released from soils are the alkali trap method and the direct gas sampling method.A 25-d laboratory incubation experiment was conducted to compare the efficacies of these two methods to analyze CO_(2)emissions from the non-carbonate and carbonate-rich soils.An isotopic fraction was introduced into the calculations to determine the impacts on partitioning of the sources of CO_(2)into soil organic carbon(SOC)and soil inorganic carbon(SIC)and into C3 and/or C4 plant-derived SOC.The results indicated that CO_(2)emissions from the non-carbonate soil measured using the alkali trap and gas sampling methods were not significantly different.For the carbonate-rich soil,the CO_(2)emission measured using the alkali trap method was significantly higher than that measured using the gas sampling method from the 14 th day of incubation onwards.Although SOC and SIC each accounted for about 50%of total soil C in the carbonate-rich soil,SOC decomposition contributed 57%–72%of the total CO_(2)emitted.For both non-carbonate and carbonate-rich soils,the SOC derived from C4 plants decomposed faster than that originated from C3 plants.We propose that for carbonate soil,CO_(2)emission may be overestimated using the alkali trap method because of decreasing CO_(2)pressure within the incubation jar,but underestimated using the direct gas sampling method.The gas sampling interval and ambient air may be important sources of error,and steps should be taken to mitigate errors related to these factors in soil incubation and CO_(2)quantification studies.

Microscale heterogeneity of soil bacterial communities under long-term fertilizations in fluvo-aquic soils

Differently sized soil aggregates,with non-uniform distribution of space and nutrients,provide spatially heterogeneous microenvironments for microorganisms and are important for controlling microbial community ecology and biogeochemistry in soils.Here,we investigated the prokaryotic communities within different aggregate-size fractions:macroaggregate(>0.25 mm),microaggre-gate(0.053–0.25 mm)and silt+clay(<0.053 mm).These were isolated from fluvo-aquic soils under 39-year fertilization strategies:no fertilizer(CK),chemical fertilizer(NPK),manure fertilizer(M),and combination of manure and chemical fertilizers(MNPK).The results showed that the proportion of macroaggregate,soil aggregate-associated organic carbon(SOC)content and aggregate stability were all significantly increased by both manure and chemical fertilizations.Organic fertilizations(M and MNPK)more effectively boosted formation and stability of macroaggregates and enhanced SOC concentration than NPK.The distribution patterns of microorganisms in aggregates were primarily shaped by fertilization and aggregate size.They explained 76.9%of the variance in bacterial community compositions.Fertilizations,especially with organic fertilizers primarily transitioned bacterial communities from slow-growing oligotrophic groups(e.g.,Chloroflexi)dominance to fast-growing copiotrophic groups(e.g.,Proteobacteria and Bacteroidetes)dominance across all aggregate sizes.Macroaggregates possessed a more stable bacterial community and efficiency of resource transfer,while smaller aggregates increased antagonism and weakened mutualism among bacterial communities.Overall,combination of manure and chemical fertilizers was crucial for increasing SOC content and aggregation,leading to a clear shift in bacterial community structures at aggregate scale.