This study is the first systematic assessment of the Lower Ordovician microbial carbonates in Songzi,Hubei Province,China.This paper divides the microbial carbonates into two types according to growth patterns,namely ...This study is the first systematic assessment of the Lower Ordovician microbial carbonates in Songzi,Hubei Province,China.This paper divides the microbial carbonates into two types according to growth patterns,namely nongranular and granular.The nongranular types include stromatolites,thrombolites,dendrolites,leiolites and laminites;the granular types are mainly oncolites and may include a small amount of microbiogenic oolite.According to their geometric features,the stromatolites can be divided into four types:stratiform,wavy,columnar and domal.Additionally,dipyramidal columnar stromatolites are identified for the first time and represent a new type of columnar stromatolite.The thrombolites are divided into three types:speckled,reticulated and banded.The grazing gastropod Ecculiomphalus and traces of bioturbation are observed in the speckled and reticulated thrombolites.This paper considers these two kinds of thrombolites to represent bioturbated thrombolites.These findings not only fill gaps in the field of domestic Ordovician bioturbated thrombolites but also provide new information for the study of thrombolites.Based on the analysis of the sedimentary characteristics of microbialites,the depositional environments of the various types of microbialites are described,and the distribution patterns of their depositional environments are summarized.The relationship between the development of microbialites and the evolution and radiation of metazoans during the Early to Middle Ordovician is discussed.Consistent with the correspondence between the stepwise and rapid radiation of metazoans and the abrupt reduction in the number of microbialites between the late Early Ordovician and the early Middle Ordovician,fossils of benthonic grazing gastropods(Ecculiomphalus)were found in the stromatolites and thrombolite of the study area.It is believed that the gradual reduction in microbialites was related to the rapid increase in the abundance of metazoans.Grazers not only grazed on the microorganisms that formed stromatolites,resulting in a continuous reduction in the number of stromatolites,but also disrupted the growth state of the stromatolites,resulting in the formation of unique bioturbated thrombolites in the study area.Hydrocarbon potential analysis shows that the microbialites in the Nanjinguan Formation represent better source rocks than those in the other formations.展开更多
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 bee...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.展开更多
Based on outcrop profiles,drilling cores,cast thin sections etc.,the types,microfacies combinations and distribution pattern of microbial carbonates in the Ordovician middle assemblage of the mid-eastern Ordos Basin h...Based on outcrop profiles,drilling cores,cast thin sections etc.,the types,microfacies combinations and distribution pattern of microbial carbonates in the Ordovician middle assemblage of the mid-eastern Ordos Basin have been systematically analyzed.The middle assemblage of Ordovician in the mid-eastern Ordos Basin has microbial carbonates formed by the calci-fication of cyanobacteria,including microbial biostromes and microbial mounds made of stromatolites,thrombolites,and on-colites.The distribution of the carbonates shows obvious“stratum-control”and“regional”characteristics.The microbial bio-stromes 2–3 m thick each are controlled by sequence cycles and sedimentary facies changes,and were mainly formed in the tidal flat environment during the depositional stages of the Ma56 and Ma55 sub-members.The microbial biostrome in the Ma55 sub-member occurring near the carbonate-evaporite transition interface in the early stage of the transgression is distributed mainly in the Mizhi subsag in the eastern part of the basin;the microbial biostrome in the Ma56 sub-member turns up near the carbonate-evoporite transition zone in ring shape in the east of the central uplift.The ancient landform had noticeable control on the distribution of microbial mounds.The microbial mounds or mound-shoal complexes developing mainly during the de-positional stages of Ma57_Ma510 sub-members are about 15–25 m thick in single layer and distributed largely in the Wushenqi-Jingbian paleouplift.The development model of the microbial carbonate rocks shows that the carbonate-evaporite lithologic transition zone and the Wushenqi-Jingbian paleouplift are favorable exploration zones of microbial carbonates in the Ordovician middle assemblages.展开更多
Based on comprehensive analysis of seismic,logging,core,thin section data,and stable isotopic compositions of carbon and oxygen,the sedimentary filling characteristics of the Lower Cretaceous Barra Velha Formation seq...Based on comprehensive analysis of seismic,logging,core,thin section data,and stable isotopic compositions of carbon and oxygen,the sedimentary filling characteristics of the Lower Cretaceous Barra Velha Formation sequence in H oil field,Santos Basin,are studied,and the high-frequency sequence stratigraphic framework is established,and the spatial distribution of reef-shoal bodies are predicted and the controlling factors are discussed.During the depositional period of the Barra Velha Formation,the study area is a slope-isolated platform-slope sedimentary pattern from southwest to northeast and the change of climate background from rift to depression periods has resulted in the variation of sedimentary characteristics from the lower third-order sequence SQ1(BVE 300 Member)of low-energy deep water to the upper third-order sequence SQ2(BVE 200 and 100 members)of high-energy shallow water in the Barra Velha Formation.The activities of extensional faults and strike-slip faults in rift period and the sedimentary differentiation from platform margin to intra-platform in depression period made the sedimentary paleogeomorphology in these two periods show features of“three ridges and two depressions”.The reef-shoal bodies mainly developed in the SQ2-LHST period,with vertical development positions restricted by the periodic oscillation of the lake level,and developed on the top of each high-frequency sequence stratigraphic unit in SQ2-LHST in the platform.The strike-slip fault activity controlled the distribution of the reef-shoal bodies on the plane by changing the sedimentary paleogeomorphology.The positive flower-shaped strike-slip faults made the formation of local highlands at the margins of and inside the shallow water platforms and which became high-energy sedimentary zones,creating conditions for the development of reef-shoal bodies.展开更多
Soil microbial biomass is an important indicator to measure the dynamic changes of soil carbon pool.It is of great signifi cance to understand the dynamics of soil microbial biomass in plantation for rational manageme...Soil microbial biomass is an important indicator to measure the dynamic changes of soil carbon pool.It is of great signifi cance to understand the dynamics of soil microbial biomass in plantation for rational management and cultivation of plantation.In order to explore the temporal dynamics and infl uencing factors of soil microbial biomass of Keteleeria fortunei var.cyclolepis at diff erent stand ages,the plantation of diff erent ages(young forest,5 years;middle-aged forest,22 years;mature forest,40 years)at the Guangxi Daguishan forest station of China were studied to examine the seasonal variation of their microbial biomass carbon(MBC)and microbial biomass nitrogen(MBN)by chloroform fumigation extraction method.It was found that among the forests of diff erent age,MBC and MBN diff ered signifi cantly in the 0–10 cm soil layer,and MBN diff ered signifi cantly in the 10–20 cm soil layer,but there was no signifi cant diff erence in MBC for the 10–20 cm soil layer or in either MBC or MBN for the 20–40 cm soil layer.With increasing maturity of the forest,MBC gradually decreased in the 0–10 cm soil layer and increased fi rstly and then decreased in the 10–20 cm and 20–40 cm soil layers,and MBN increased fi rstly and then decreased in all three soil layers.As the soil depth increased,both MBC and MBN gradually decreased for all three forests.The MBC and MBN basically had the same seasonal variation in all three soil layers of all three forests,i.e.,high in the summer and low in the winter.Correlation analysis showed that MBC was signifi cantly positively correlated with soil organic matter,total nitrogen,and soil moisture,whereas MBN was signifi cantly positively correlated with soil total nitrogen.It showed that soil moisture content was the main factor determining the variation of soil microbial biomass by Redundancy analysis.The results showed that the soil properties changed continuously as the young forest grew into the middle-aged forest,which increased soil microbial biomass and enriched the soil nutrients.However,the soil microbial biomass declined as the middle-age forest continued to grow,and the soil nutrients were reduced in the mature forest.展开更多
Prescribed fire is a common economical and effective forestry practice, and therefore it is important to understand the effects of fire on soil properties for better soil management. We investigated the impacts of low...Prescribed fire is a common economical and effective forestry practice, and therefore it is important to understand the effects of fire on soil properties for better soil management. We investigated the impacts of low-intensity prescribed fire on the microbial and chemical properties of the top soil in a Hungarian oak(Quercus frainetto Ten.) forest. The research focused on microbial soil parameters(microbial soil respiration(RSM), soil microbial biomass carbon(Cmic) and metabolic quotient(qCO2) and chemical topsoil properties(soil acidity(pH),electrical conductivity(EC), carbon(C), nitrogen(N), C/N ratio and exchangeable cations). Mean annual comparisons show significant differences in four parameters(C/N ratio,soil pH, Cmic and qCO2) while monthly comparisons do not reveal any significant differences. Soil pH increased slightly in the burned plots and had a significantly positive correlation with exchangeable cations Mg, Ca, Mn and K.The mean annual C/N ratio was significantly higher in the burned plots(28.5:1) than in the control plots(27.0:1). The mean annual Cmic(0.6 mg g-1) was significantly lower although qCO2(2.5 lg CO2–C mg Cmic h-1) was significantly higher, likely resulting from the microbial response to fire-induced environmental stress. Low-intensity prescribed fire caused very short-lived changes. The annual mean values of C/N ratio, pH, Cmic and qCO2showed significant differences.展开更多
Backfill mining technology is the practice of returning waste materials underground for both disposal and geotechnical stability,however,a challenge with current technologies is that they commonly require cement-based...Backfill mining technology is the practice of returning waste materials underground for both disposal and geotechnical stability,however,a challenge with current technologies is that they commonly require cement-based binders which have a relatively high environmental impact.Finding alternatives to cement-based binders can improve environmental performance and this paper proposes microbial grouted backfill(MGB)as a potential solution.In this paper,the effects of the cementation solution concentration(CSC),volume ratio of bacterial solution to cementation solution(VRBC),particle sizes of the aggregates,and the number of grouting batches on the mechanical properties of MGB are studied.The experimental results show that MGB strength increased,up to a peak value,as CSC was increased,before decreasing as CSC was increased further.The results also show that MGB strength increased,up to a peak value,as VRBC decreased,before decreasing as the VRBC was decreased further.The peak strength was achieved at a CSC of 2 mol/L and a VRBC of 1:9.The strength of the MGB also increased as the number of grouting batches increased.Graded MGB samples showed the highest UCS,25.12 MPa,at particle sizes of 0.2 to 0.8 mm,while full(non-graded)MGB samples displayed mean UCS values ranging from1.56 MPa when the maximum particle size was 0.2 mm,up to 13 MPa when the maximum particle size was 1.2 mm.MGB samples are consolidated by the calcium carbonate that is precipitated during microbial metabolism,and the strength of MGB increases linearly as calcium carbonate content increases.The calcium carbonate minerals produced in MGB materials are primarily calcite,with secondary amounts of vaterite.展开更多
Background: The loss of soil organic carbon(SOC) following conversion of natural forests to managed plantations has been widely reported. However, how different SOC fractions and microbial necromass C(MNC) respond to ...Background: The loss of soil organic carbon(SOC) following conversion of natural forests to managed plantations has been widely reported. However, how different SOC fractions and microbial necromass C(MNC) respond to forest management practices remains unclear.Methods: We sampled 0–10 cm mineral soil from three different management plantations and one protected forest in Guangxi, Southern China, to explore how forest management practices affect SOC through changing mineralassociated C(MAOC) and particulate organic C(POC), as well as fungal and bacterial necromass C.Results: Compared with the protected forest, SOC and POC in the abandoned, mixed and Eucalyptus plantations significantly decreased, but MAOC showed no significant change, indicating that the loss of SOC was mainly from decreased POC under forest management. Forest management also significantly reduced root biomass, soil extractable organic C, MNC, and total microbial biomass(measured by phospholipid fatty acid), but increased fungi-to-bacteria ratio(F:B) and soil peroxidase activity. Moreover, POC was positively correlated with root biomass, total microbial biomass and MNC, and negatively with F:B and peroxidase activity. These results suggested that root input and microbial properties together regulated soil POC dynamics during forest management.Conclusion: Overall, this study indicates that forest management intervention significantly decreases SOC by reducing POC in Guangxi, Southern China, and suggests that forest protection can help to sequester more soil C in forest ecosystems.展开更多
基金supported by the National Natural Science Fund of China(Grant No.41572322)Hubei Innovation Group Fund(Grant No.2015CFA024)
文摘This study is the first systematic assessment of the Lower Ordovician microbial carbonates in Songzi,Hubei Province,China.This paper divides the microbial carbonates into two types according to growth patterns,namely nongranular and granular.The nongranular types include stromatolites,thrombolites,dendrolites,leiolites and laminites;the granular types are mainly oncolites and may include a small amount of microbiogenic oolite.According to their geometric features,the stromatolites can be divided into four types:stratiform,wavy,columnar and domal.Additionally,dipyramidal columnar stromatolites are identified for the first time and represent a new type of columnar stromatolite.The thrombolites are divided into three types:speckled,reticulated and banded.The grazing gastropod Ecculiomphalus and traces of bioturbation are observed in the speckled and reticulated thrombolites.This paper considers these two kinds of thrombolites to represent bioturbated thrombolites.These findings not only fill gaps in the field of domestic Ordovician bioturbated thrombolites but also provide new information for the study of thrombolites.Based on the analysis of the sedimentary characteristics of microbialites,the depositional environments of the various types of microbialites are described,and the distribution patterns of their depositional environments are summarized.The relationship between the development of microbialites and the evolution and radiation of metazoans during the Early to Middle Ordovician is discussed.Consistent with the correspondence between the stepwise and rapid radiation of metazoans and the abrupt reduction in the number of microbialites between the late Early Ordovician and the early Middle Ordovician,fossils of benthonic grazing gastropods(Ecculiomphalus)were found in the stromatolites and thrombolite of the study area.It is believed that the gradual reduction in microbialites was related to the rapid increase in the abundance of metazoans.Grazers not only grazed on the microorganisms that formed stromatolites,resulting in a continuous reduction in the number of stromatolites,but also disrupted the growth state of the stromatolites,resulting in the formation of unique bioturbated thrombolites in the study area.Hydrocarbon potential analysis shows that the microbialites in the Nanjinguan Formation represent better source rocks than those in the other formations.
基金jointly financed by the Programs of the National Natural Science Foundation of China(Nos.41571251,41571130043)the Major State Basic Research Development Program of China(No.2012CB416903)
文摘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.
基金Supported by the China National Science and Technology Major Project(2016ZX05004-006)the CNPC Science and Technology Major Project(2016E-0514).
文摘Based on outcrop profiles,drilling cores,cast thin sections etc.,the types,microfacies combinations and distribution pattern of microbial carbonates in the Ordovician middle assemblage of the mid-eastern Ordos Basin have been systematically analyzed.The middle assemblage of Ordovician in the mid-eastern Ordos Basin has microbial carbonates formed by the calci-fication of cyanobacteria,including microbial biostromes and microbial mounds made of stromatolites,thrombolites,and on-colites.The distribution of the carbonates shows obvious“stratum-control”and“regional”characteristics.The microbial bio-stromes 2–3 m thick each are controlled by sequence cycles and sedimentary facies changes,and were mainly formed in the tidal flat environment during the depositional stages of the Ma56 and Ma55 sub-members.The microbial biostrome in the Ma55 sub-member occurring near the carbonate-evaporite transition interface in the early stage of the transgression is distributed mainly in the Mizhi subsag in the eastern part of the basin;the microbial biostrome in the Ma56 sub-member turns up near the carbonate-evoporite transition zone in ring shape in the east of the central uplift.The ancient landform had noticeable control on the distribution of microbial mounds.The microbial mounds or mound-shoal complexes developing mainly during the de-positional stages of Ma57_Ma510 sub-members are about 15–25 m thick in single layer and distributed largely in the Wushenqi-Jingbian paleouplift.The development model of the microbial carbonate rocks shows that the carbonate-evaporite lithologic transition zone and the Wushenqi-Jingbian paleouplift are favorable exploration zones of microbial carbonates in the Ordovician middle assemblages.
基金Supported by the National Science and Technology Major Project of China(2016ZX05033-002-008).
文摘Based on comprehensive analysis of seismic,logging,core,thin section data,and stable isotopic compositions of carbon and oxygen,the sedimentary filling characteristics of the Lower Cretaceous Barra Velha Formation sequence in H oil field,Santos Basin,are studied,and the high-frequency sequence stratigraphic framework is established,and the spatial distribution of reef-shoal bodies are predicted and the controlling factors are discussed.During the depositional period of the Barra Velha Formation,the study area is a slope-isolated platform-slope sedimentary pattern from southwest to northeast and the change of climate background from rift to depression periods has resulted in the variation of sedimentary characteristics from the lower third-order sequence SQ1(BVE 300 Member)of low-energy deep water to the upper third-order sequence SQ2(BVE 200 and 100 members)of high-energy shallow water in the Barra Velha Formation.The activities of extensional faults and strike-slip faults in rift period and the sedimentary differentiation from platform margin to intra-platform in depression period made the sedimentary paleogeomorphology in these two periods show features of“three ridges and two depressions”.The reef-shoal bodies mainly developed in the SQ2-LHST period,with vertical development positions restricted by the periodic oscillation of the lake level,and developed on the top of each high-frequency sequence stratigraphic unit in SQ2-LHST in the platform.The strike-slip fault activity controlled the distribution of the reef-shoal bodies on the plane by changing the sedimentary paleogeomorphology.The positive flower-shaped strike-slip faults made the formation of local highlands at the margins of and inside the shallow water platforms and which became high-energy sedimentary zones,creating conditions for the development of reef-shoal bodies.
文摘Soil microbial biomass is an important indicator to measure the dynamic changes of soil carbon pool.It is of great signifi cance to understand the dynamics of soil microbial biomass in plantation for rational management and cultivation of plantation.In order to explore the temporal dynamics and infl uencing factors of soil microbial biomass of Keteleeria fortunei var.cyclolepis at diff erent stand ages,the plantation of diff erent ages(young forest,5 years;middle-aged forest,22 years;mature forest,40 years)at the Guangxi Daguishan forest station of China were studied to examine the seasonal variation of their microbial biomass carbon(MBC)and microbial biomass nitrogen(MBN)by chloroform fumigation extraction method.It was found that among the forests of diff erent age,MBC and MBN diff ered signifi cantly in the 0–10 cm soil layer,and MBN diff ered signifi cantly in the 10–20 cm soil layer,but there was no signifi cant diff erence in MBC for the 10–20 cm soil layer or in either MBC or MBN for the 20–40 cm soil layer.With increasing maturity of the forest,MBC gradually decreased in the 0–10 cm soil layer and increased fi rstly and then decreased in the 10–20 cm and 20–40 cm soil layers,and MBN increased fi rstly and then decreased in all three soil layers.As the soil depth increased,both MBC and MBN gradually decreased for all three forests.The MBC and MBN basically had the same seasonal variation in all three soil layers of all three forests,i.e.,high in the summer and low in the winter.Correlation analysis showed that MBC was signifi cantly positively correlated with soil organic matter,total nitrogen,and soil moisture,whereas MBN was signifi cantly positively correlated with soil total nitrogen.It showed that soil moisture content was the main factor determining the variation of soil microbial biomass by Redundancy analysis.The results showed that the soil properties changed continuously as the young forest grew into the middle-aged forest,which increased soil microbial biomass and enriched the soil nutrients.However,the soil microbial biomass declined as the middle-age forest continued to grow,and the soil nutrients were reduced in the mature forest.
基金supported by Scientific Research Projects Coordination Unit of Istanbul University,Project Number:International Research Projects:IRP-27803,as a part of an international collaboration between Istanbul University,IstanbulTurkey and Korea University,Seoul-Korea
文摘Prescribed fire is a common economical and effective forestry practice, and therefore it is important to understand the effects of fire on soil properties for better soil management. We investigated the impacts of low-intensity prescribed fire on the microbial and chemical properties of the top soil in a Hungarian oak(Quercus frainetto Ten.) forest. The research focused on microbial soil parameters(microbial soil respiration(RSM), soil microbial biomass carbon(Cmic) and metabolic quotient(qCO2) and chemical topsoil properties(soil acidity(pH),electrical conductivity(EC), carbon(C), nitrogen(N), C/N ratio and exchangeable cations). Mean annual comparisons show significant differences in four parameters(C/N ratio,soil pH, Cmic and qCO2) while monthly comparisons do not reveal any significant differences. Soil pH increased slightly in the burned plots and had a significantly positive correlation with exchangeable cations Mg, Ca, Mn and K.The mean annual C/N ratio was significantly higher in the burned plots(28.5:1) than in the control plots(27.0:1). The mean annual Cmic(0.6 mg g-1) was significantly lower although qCO2(2.5 lg CO2–C mg Cmic h-1) was significantly higher, likely resulting from the microbial response to fire-induced environmental stress. Low-intensity prescribed fire caused very short-lived changes. The annual mean values of C/N ratio, pH, Cmic and qCO2showed significant differences.
基金supported by the National Natural Science Foundation of China(Nos.5180430852034009)+3 种基金the China Postdoctoral Science Foundation(Nos.2020T1302692020M670689)the Yue Qi Young Scholar Project(No.2020QN03)the Postdoctoral Research Project of Hebei Province(No.B2020003029)。
文摘Backfill mining technology is the practice of returning waste materials underground for both disposal and geotechnical stability,however,a challenge with current technologies is that they commonly require cement-based binders which have a relatively high environmental impact.Finding alternatives to cement-based binders can improve environmental performance and this paper proposes microbial grouted backfill(MGB)as a potential solution.In this paper,the effects of the cementation solution concentration(CSC),volume ratio of bacterial solution to cementation solution(VRBC),particle sizes of the aggregates,and the number of grouting batches on the mechanical properties of MGB are studied.The experimental results show that MGB strength increased,up to a peak value,as CSC was increased,before decreasing as CSC was increased further.The results also show that MGB strength increased,up to a peak value,as VRBC decreased,before decreasing as the VRBC was decreased further.The peak strength was achieved at a CSC of 2 mol/L and a VRBC of 1:9.The strength of the MGB also increased as the number of grouting batches increased.Graded MGB samples showed the highest UCS,25.12 MPa,at particle sizes of 0.2 to 0.8 mm,while full(non-graded)MGB samples displayed mean UCS values ranging from1.56 MPa when the maximum particle size was 0.2 mm,up to 13 MPa when the maximum particle size was 1.2 mm.MGB samples are consolidated by the calcium carbonate that is precipitated during microbial metabolism,and the strength of MGB increases linearly as calcium carbonate content increases.The calcium carbonate minerals produced in MGB materials are primarily calcite,with secondary amounts of vaterite.
基金supported by the National Natural Science Foundation of China(Grant Nos.31988102 and 42141006)。
文摘Background: The loss of soil organic carbon(SOC) following conversion of natural forests to managed plantations has been widely reported. However, how different SOC fractions and microbial necromass C(MNC) respond to forest management practices remains unclear.Methods: We sampled 0–10 cm mineral soil from three different management plantations and one protected forest in Guangxi, Southern China, to explore how forest management practices affect SOC through changing mineralassociated C(MAOC) and particulate organic C(POC), as well as fungal and bacterial necromass C.Results: Compared with the protected forest, SOC and POC in the abandoned, mixed and Eucalyptus plantations significantly decreased, but MAOC showed no significant change, indicating that the loss of SOC was mainly from decreased POC under forest management. Forest management also significantly reduced root biomass, soil extractable organic C, MNC, and total microbial biomass(measured by phospholipid fatty acid), but increased fungi-to-bacteria ratio(F:B) and soil peroxidase activity. Moreover, POC was positively correlated with root biomass, total microbial biomass and MNC, and negatively with F:B and peroxidase activity. These results suggested that root input and microbial properties together regulated soil POC dynamics during forest management.Conclusion: Overall, this study indicates that forest management intervention significantly decreases SOC by reducing POC in Guangxi, Southern China, and suggests that forest protection can help to sequester more soil C in forest ecosystems.
