Nutrient acquisition through symbiotic ectomycorrhizal fungi is carbon(C)costly but fundamental for plant growth,community,and ecosystem functioning.Here,we examined the functions of roots and mycorrhiza with respect ...Nutrient acquisition through symbiotic ectomycorrhizal fungi is carbon(C)costly but fundamental for plant growth,community,and ecosystem functioning.Here,we examined the functions of roots and mycorrhiza with respect to nutrient uptake after artificially inducing C limitation-seven months after girdling of an ectomycorrhizal tree,Pinus taeda.Root physiological activity(measured as root nitrogen content and root exudation)declined after girdling and was accompanied with 110%and 340%increases in mycorrhizal colonization and extramatrical hyphal length,respectively.Fungi colonizing roots switched to a community characterized by higher C efficiency(lower C cost)of nutrient acquisition(CENA,the amount of nutrient acquisition per unit C cost)and lower network complexity,indicating a tradeoff between CENA and stability of the fungal community.Root transcriptome analysis suggested a shift in metabolic pathways from a tricarboxylic acid cycle decomposition of carbohydrate to lipid biosynthesis to maintain closer associations with mycorrhiza for nutrient cycling after the girdling.By integrating multi-level evidence,including root transcriptome,fungal composition,and network complexity data,we demonstrate an increased dependence on mycorrhiza for nutrient acquisition under the C limitation condition,which is likely due to a shift to fungal community with higher CENA at the cost of lower stability.展开更多
The relative limitation of microbes by soil organic carbon(SOC),nitrogen(N)and phosphorus(P)is linked with soil microbial activities,so how change of plant species diversity(PSD)affects microbial resource limitation w...The relative limitation of microbes by soil organic carbon(SOC),nitrogen(N)and phosphorus(P)is linked with soil microbial activities,so how change of plant species diversity(PSD)affects microbial resource limitation would partly determine its impacts on SOC dynamics and nutrient cycling.However,the responses of microbial resource limitation to increasing PSD have poorly explored.Here,45 plots covering a natural PSD gradient were used to investigate the effects of PSD on microbial resource limitation in a subtropical forest.Extracellular enzymatic stoichiometry along with a laboratory N and P addition experiment were used to determine microbial resource limitation.Contents of microbial biomass C,N and P significantly increased,but C:P and N:P ratios in microbial biomass were unchanged as PSD increased.Soil microbes were generally co-limited by C and P,but not by N across the 45 plots.Increasing PSD did not alter microbial N limitation,alleviated microbial C limitation and aggravated microbial P limitation.The alleviated microbial C limitation or aggravated microbial P limitation was attributed to increased soil C availability but decreased P availability,which resulted in stimulated soil C:P and N:P ratios and in turn greater C:P and N:P imbalance between soil and microbial biomass under higher PSD.Our results highlight the divergent effects of increasing PSD on microbial resource limitation.Considering that microbial C and P limitations are widespread,the patterns observed in the current study should be applicable broadly.展开更多
Soil erosion accelerates the loss of soil carbon(C)pools and then exacerbates the microbial C limitation.However,the extent to which soil microbial C limitation influences soil C cycling processes in different erosion...Soil erosion accelerates the loss of soil carbon(C)pools and then exacerbates the microbial C limitation.However,the extent to which soil microbial C limitation influences soil C cycling processes in different erosion environments remains unclear.We analyzed the differences in soil organic carbon(SOC)con-tent,extracellular enzyme activities and C limitation between sloping cropland and adjacent forestland in a typical small watershed,and further explored the relationship between soil C limitation and the abundance of C cycling genes in different erosion environments.The results revealed that sloping cropland exhibited a 31.70%higher soil erodibility(K_(erosion))compared to forestland,making it more prone to soil erosion.Moreover,the SOC content in sloping cropland was 61.72%lower than that in forestland.Although there was no significant difference in absolute enzyme activities between sloping cropland and forestland,the specific enzyme activities per unit of SOC(including carbon,nitrogen and phosphorus enzymes)in sloping cropland were significantly higher than those in forestland.The loss of SOC further exacerbated C limitation in sloping cropland and stimulated an increase in the abundance of C cycle genes involved in complex organic C degradation.Additionally,the C cycling genes enriched in sloping cropland demonstrated a significant positive correlation with soil CO_(2) emissions(p<0.01).Therefore,we emphasize that soil erosion stimulates an increase in the abundance of C cycle genes,particularly those involved in complex SOC degradation,as a response to C limitation in erosion-prone sloping cropland.The findings provide scientific support for developing effective soil and water con-servation measures to reduce soil C loss and maintain the ecological balance of sloping cropland.展开更多
Can soil nitrate： ammonium ratios influence plant carbon： nitrogen ratios of the early succession plant？ Can plant carbon： nitrogen ratios limit the plant growth in early succession？ To address these two question...Can soil nitrate： ammonium ratios influence plant carbon： nitrogen ratios of the early succession plant？ Can plant carbon： nitrogen ratios limit the plant growth in early succession？ To address these two questions, we performed a two-factor （soil nitrate： ammonium ratio and plant density） randomized block design and a uniform-precision rotatable central composite design pot experiments to examine the relationships between soil nitrate： ammonium ratios, the carbon： nitrogen ratios and growth rate of Artemisia sphaerocephala seedlings. Under adequate nutrient status, both soil nitrate： ammonium ratios and plant density influenced the carbon： nitrogen ratios and growth rate of A. sphaerocephala seedlings. Under the lower soil nitrate： ammonium ratios, with the increase of soil nitrate： ammonium ratios, the growth rates of plant height and shoot biomass of A. sphaerocephala seedlings decreased significantly; with the increase of plant carbon： nitrogen ratios, the growth rates of shoot biomass of A. sphaerocephala seedlings decreased significantly. Soil nitrate： ammonium ratios affected the carbon： nitrogen ratios of A. sphaerocephala seedlings by plant nitrogen but not by plant carbon. Thus, soil nitrate： ammonium ratios influenced the carbon： nitrogen ratios of A. sphaerocephala seedlings, and hence influenced its growth rates. Our results suggest that under adequate nutrient environment, soil nitrate： ammonium ratios can be a limiting factor for the growth of the early succession plant.展开更多
Nonstructural carbohydrates(NSC)are indicators of tree carbon balance and play an important role in regulating plant growth and survival.However,our understanding of the mechanism underlying drought-induced response o...Nonstructural carbohydrates(NSC)are indicators of tree carbon balance and play an important role in regulating plant growth and survival.However,our understanding of the mechanism underlying drought-induced response of NSC reserves remains limited.Here,we conducted a long-term throughfall exclusion(TFE)experiment to investigate the seasonal responses of NSC reserves to manipulative drought in two contrasting tree species(a broadleaved tree Castanopsis hystrix Miq.and a coniferous tree Pinus massoniana Lamb.)of the subtropical China.We found that in the dry season,the two tree species differed in their responses of NSC reserves to TFE at either the whole-tree level or by organs,with significantly depleted total NSC reserves in roots in both species.Under the TFE treatment,there were significant increases in the NSC pools of leaves and branches in C.hystrix,which were accompanied by significant decreases in fine root biomass and radial growth without significant changes in canopy photosynthesis;while P.massoniana exhibited significant increase in fine root biomass without significant changes in radial growth.Our results suggested that under prolonged water limitation,NSC usage for growth in C.hystrix is somewhat impaired,such that the TFE treatment resulted in NSC accumulation in aboveground organs(leaf and branch);whereas P.massoniana is capable of efficiently utilizing NSC reserves to maintain its growth under drought conditions.Our findings revealed divergent NSC allocations under experimental drought between the two contrasting tree species,which are important for better understanding the differential impacts of climate change on varying forest trees and plantation types in subtropical China.展开更多
Leaves are important‘source’organs that synthesize organic matter,providing carbon sources for plant growth.Here,we used Populus talassica×Populus euphratica,the dominant species in ecological and timber forest...Leaves are important‘source’organs that synthesize organic matter,providing carbon sources for plant growth.Here,we used Populus talassica×Populus euphratica,the dominant species in ecological and timber forests,to simulate carbon limitation through artificial 25%,50%,and 75%defoliation treatments and explore the effects on root,stem,and leaf morphology,biomass accumulation,and carbon allocation strategies.At the 60th d after treat-ment,under 25%defoliation treatment,the plant height,specific leaf weight,root surface area and volume,and concentrations of non-structural carbohydrates in stem and root were significantly increased by 9.13%,20.00%,16.60%,31.95%,5.12%,and 9.34%,respectively,relative to the control.There was no significant change in the growth indicators under 50%defoliation treatment,but the concentrations of non-structural carbohydrates in the leaf and stem significantly decreased,showing mostly a negative correlation between them.The opposite was observed in the root.Under 75%defoliation treatment,the plant height,ground diameter,leaf number,single leaf area,root,stem,and total biomass were significantly reduced by 14.15%,10.24%,14.86%,11.31%,11.56%,21.87%,and 16.82%,respectively,relative to the control.The concentrations of non-structural carbohydrates in various organs were significantly reduced,particularly in the consumption of the starch concentrations in the stem and root.These results indicated that carbon allocation strategies can be adjusted to increase the con-centration of non-structural carbohydrates in root and meet plant growth needs under 25%and 50%defoliation.However,75%defoliation significantly limited the distribution of non-structural carbohydrates to roots and stems,reduced carbon storage,and thus inhibited plant growth.Defoliation-induced carbon limitation altered the carbon allocation pattern of P.talassica×P.euphratica,and the relationship between carbon reserves in roots and tree growth recovery after defoliation was greater.This study provides a theoretical basis for the comprehen-sive management of P.talassica×P.euphratica plantations,as well as a reference for the study of plantation car-bon allocation strategies in the desert and semi-desert regions of Xinjiang under carbon-limitation conditions.展开更多
The differences in organic matter abundance and rock composition between shale and mudstone determine the discrepancy of their contributions to the formation of conventional and shale oil/gas reservoirs.The evaluation...The differences in organic matter abundance and rock composition between shale and mudstone determine the discrepancy of their contributions to the formation of conventional and shale oil/gas reservoirs.The evaluation criteria of source rocks are different in the future exploration in self-sourced petroleum systems.Shales are deposited in deep/semi-deep lacustrine,with low sedimentation rate and chemical depositions of various degrees,while mudstones are mostly formed in shallow lacustrine/lakeside,with high deposition rate and density flow characteristics.Three factors contribute to the enrichment of organic matter in shales,including the"fertility effect"caused by volcanic ash deposition and hydrothermal injection,excessive and over-speed growth of organisms promoted by radioactive materials,and deep-water anaerobic environment and low sedimentation rate to protect the accumulation of organic matter from dilution.Lamellations in shales are easy to be stripped into storage space,and acid water produced during hydrocarbon generation can dissolve some particles to generate new pores.The massive mudstones with high clay content are of poor matrix porosity.Shales with high total organic carbon,developed laminations,relatively good reservoir property,and high brittle mineral content,are the most favorable lithofacies for shale oil exploration and development.It is necessary to conduct investigation on the differences between shale and mudstone reservoirs,to identify resources distribution in shale and mudstone formations,determine the type and standard of"sweet-spot"evaluation parameters,optimize"sweet-spot areas/sections",and adopt effective development technologies,which is of great significance to objectively evaluate the total amount and economy of shale oil resources,as well as the scale of effective exploitation.展开更多
Atterberg limits and consistency indices are used for classifications of cohesive(fine-grained) soils in relation with compaction and tillage practices. They also provide information for interpreting several soil mech...Atterberg limits and consistency indices are used for classifications of cohesive(fine-grained) soils in relation with compaction and tillage practices. They also provide information for interpreting several soil mechanical and physical properties such as shear strength, compressibility, shrinkage and swelling potentials. Although, several studies have been conducted regarding the land use effects on various soil mechanical properties, little is known about the effects of land use and slope positions on Atterberg limits and consistency indices. This study was conducted to investigate the effects of land use and slope position on selected soil physical and chemical properties, Atterberg limits and consistency indices in hilly region of western Iran. Three land uses including dryland farming, irrigated farming and pasture and four slope positions(i.e., shoulder, backslope, footslope, and toeslope) were used for soil samplings. One hundred eleven soil samples were collected from the surface soil(0-10 cm). Selected physical and chemical properties, liquid limit(LL), plastic limit(PL) and shrinkage limit(SL) were measured using the standard methods; and consistency indices including plastic index(PI), friability index(FI), shrinkage index(SI) and soil activity(A=PI/clay) were calculated. The results showed that irrigated farming significantly increased organic matter content(OM) and OM/clay ratio, and decreased bulk density(ρb) and relative bulk density(ρb-rel) as a result of higher biomass production and plant residues added to the soil compared to other land uses. Except for sand content, OM, ρb, cation exchange capacity(CEC) and calcium carbonate equivalent(CCE), slope position significantly affected soil physical and chemical properties. The highest values of silt, OM/clay and CEC/clay were found in the toeslope position, predominantly induced by soil redistribution within the landscape. The use of complexed(COC)- noncomplexed organic carbon(NCOC) concept indicated that majority of the studied soils were located below the saturation line and the OM in the soils was mainly in the COC form. The LL, PI, FI and A showed significant differences among the land uses; the highest values belonged to the irrigated farming due to high biomass production and plant residues returned to the soils. Furthermore, slope position significantly affected the Atterberg limits and consistency indices except for SL. The highest values of LL, PI, SI and A were observed in the toeslope position probably because of higher OM and CEC/clay due to greater amount of expandable phyllosilicate clays. Overall, soils on the toeslope under irrigated farming with high LL and SI and low values of FI need careful tillage management to avoid soil compaction.展开更多
Despite a large number of studies examining the effects of abiotic stress factors on plants,the mechanistic explanations of drought-induced tree mortality remain inconclusive and even less is known about how multiple ...Despite a large number of studies examining the effects of abiotic stress factors on plants,the mechanistic explanations of drought-induced tree mortality remain inconclusive and even less is known about how multiple stressors interact.The role of non-structural carbohydrates(NSCs)in preventing or postponing drought mortality is gaining attention.Here,we tested the role of NSCs in mitigating the effects of drought and salinity in New Zealand mangroves,Avicennia marina subsp.australasica.We experimentally manipulated plant NSC levels,prior to subjecting them to combinations of drought and salinity.Plant growth and survival rates were 2-and 3-fold higher in the high-NSC(H-NSC)group than in the low-NSC(L-NSC)group under high salinity and drought conditions,respectively.After 12 weeks under high salinity-high drought conditions,the H-NSC group showed higher stem hydraulic conductivity(281±50 mmol cm^(−1)s^(−1)MPa^(−1))compared with the L-NSC group(134±40 mmol cm^(−1)s^(−1)MPa^(−1)).Although starch levels remained relatively constant,we found a 20%increase in soluble sugars in the stems of H-NSC group under high drought and high salinity in week 8 compared with week 12.Our results suggest(i)an important role of NSCs in mitigating the effects of low soil water potential caused by drought and salinity,and(ii)sink-limited growth under conditions of combined salinity and drought.展开更多
基金funded by the National Natural Science Foundation of China(32471824,32171746,42077450,31870522,31670550,42122054)the leading talents of basic research in Henan Province,the Scientific Research Foundation of Henan Agricultural University(30500854)+4 种基金Excellent Youth Creative Research Group Project in Henan Province(252300421002)Foreign Scientists Studio in Henan province(GZS2025011)the Funding for Characteristic and Backbone Forestry Discipline Group of Henan Province,Guangdong Provincial Key Laboratory of Soil and Groundwater Pollution Control(2023B1212060002)Guangdong Basic and Applied Basic Research Foundation(2021B1515020082)the RUDN University Strategic Academic Leadership Program,Funding for Characteristic and backbone forestry discipline group of Henan Province and Research Funds for overseas returnee in Henan Province,China.We thank Editage Service in improving the English language.
文摘Nutrient acquisition through symbiotic ectomycorrhizal fungi is carbon(C)costly but fundamental for plant growth,community,and ecosystem functioning.Here,we examined the functions of roots and mycorrhiza with respect to nutrient uptake after artificially inducing C limitation-seven months after girdling of an ectomycorrhizal tree,Pinus taeda.Root physiological activity(measured as root nitrogen content and root exudation)declined after girdling and was accompanied with 110%and 340%increases in mycorrhizal colonization and extramatrical hyphal length,respectively.Fungi colonizing roots switched to a community characterized by higher C efficiency(lower C cost)of nutrient acquisition(CENA,the amount of nutrient acquisition per unit C cost)and lower network complexity,indicating a tradeoff between CENA and stability of the fungal community.Root transcriptome analysis suggested a shift in metabolic pathways from a tricarboxylic acid cycle decomposition of carbohydrate to lipid biosynthesis to maintain closer associations with mycorrhiza for nutrient cycling after the girdling.By integrating multi-level evidence,including root transcriptome,fungal composition,and network complexity data,we demonstrate an increased dependence on mycorrhiza for nutrient acquisition under the C limitation condition,which is likely due to a shift to fungal community with higher CENA at the cost of lower stability.
基金National Natural Science Foundation of China(U21A2007).
文摘The relative limitation of microbes by soil organic carbon(SOC),nitrogen(N)and phosphorus(P)is linked with soil microbial activities,so how change of plant species diversity(PSD)affects microbial resource limitation would partly determine its impacts on SOC dynamics and nutrient cycling.However,the responses of microbial resource limitation to increasing PSD have poorly explored.Here,45 plots covering a natural PSD gradient were used to investigate the effects of PSD on microbial resource limitation in a subtropical forest.Extracellular enzymatic stoichiometry along with a laboratory N and P addition experiment were used to determine microbial resource limitation.Contents of microbial biomass C,N and P significantly increased,but C:P and N:P ratios in microbial biomass were unchanged as PSD increased.Soil microbes were generally co-limited by C and P,but not by N across the 45 plots.Increasing PSD did not alter microbial N limitation,alleviated microbial C limitation and aggravated microbial P limitation.The alleviated microbial C limitation or aggravated microbial P limitation was attributed to increased soil C availability but decreased P availability,which resulted in stimulated soil C:P and N:P ratios and in turn greater C:P and N:P imbalance between soil and microbial biomass under higher PSD.Our results highlight the divergent effects of increasing PSD on microbial resource limitation.Considering that microbial C and P limitations are widespread,the patterns observed in the current study should be applicable broadly.
基金supported by the China Postdoctoral Science Foundation(2024M763618)China the Agricultural Science and Technology Innovation Program of Chinese Academy of Agricultural Sciences(ASTIP,CAAS-CSAL-202302)+1 种基金China the National Key Research and Development Program of China(2023YFD1900305)China and the National Natural Science Foundation of China(No.41977072),China.
文摘Soil erosion accelerates the loss of soil carbon(C)pools and then exacerbates the microbial C limitation.However,the extent to which soil microbial C limitation influences soil C cycling processes in different erosion environments remains unclear.We analyzed the differences in soil organic carbon(SOC)con-tent,extracellular enzyme activities and C limitation between sloping cropland and adjacent forestland in a typical small watershed,and further explored the relationship between soil C limitation and the abundance of C cycling genes in different erosion environments.The results revealed that sloping cropland exhibited a 31.70%higher soil erodibility(K_(erosion))compared to forestland,making it more prone to soil erosion.Moreover,the SOC content in sloping cropland was 61.72%lower than that in forestland.Although there was no significant difference in absolute enzyme activities between sloping cropland and forestland,the specific enzyme activities per unit of SOC(including carbon,nitrogen and phosphorus enzymes)in sloping cropland were significantly higher than those in forestland.The loss of SOC further exacerbated C limitation in sloping cropland and stimulated an increase in the abundance of C cycle genes involved in complex organic C degradation.Additionally,the C cycling genes enriched in sloping cropland demonstrated a significant positive correlation with soil CO_(2) emissions(p<0.01).Therefore,we emphasize that soil erosion stimulates an increase in the abundance of C cycle genes,particularly those involved in complex SOC degradation,as a response to C limitation in erosion-prone sloping cropland.The findings provide scientific support for developing effective soil and water con-servation measures to reduce soil C loss and maintain the ecological balance of sloping cropland.
基金supported in part by the National Basic Research Program of China (2009CB421303)supported by National Natural Science Foundation of China (30970546)
文摘Can soil nitrate： ammonium ratios influence plant carbon： nitrogen ratios of the early succession plant？ Can plant carbon： nitrogen ratios limit the plant growth in early succession？ To address these two questions, we performed a two-factor （soil nitrate： ammonium ratio and plant density） randomized block design and a uniform-precision rotatable central composite design pot experiments to examine the relationships between soil nitrate： ammonium ratios, the carbon： nitrogen ratios and growth rate of Artemisia sphaerocephala seedlings. Under adequate nutrient status, both soil nitrate： ammonium ratios and plant density influenced the carbon： nitrogen ratios and growth rate of A. sphaerocephala seedlings. Under the lower soil nitrate： ammonium ratios, with the increase of soil nitrate： ammonium ratios, the growth rates of plant height and shoot biomass of A. sphaerocephala seedlings decreased significantly; with the increase of plant carbon： nitrogen ratios, the growth rates of shoot biomass of A. sphaerocephala seedlings decreased significantly. Soil nitrate： ammonium ratios affected the carbon： nitrogen ratios of A. sphaerocephala seedlings by plant nitrogen but not by plant carbon. Thus, soil nitrate： ammonium ratios influenced the carbon： nitrogen ratios of A. sphaerocephala seedlings, and hence influenced its growth rates. Our results suggest that under adequate nutrient environment, soil nitrate： ammonium ratios can be a limiting factor for the growth of the early succession plant.
基金This study was jointly supported by the National Natural Science Foundation of China(Grant No.31930078)the Ministry of Science and Technology of China for Key R&D Program(Grant No.2021YFD2200405).
文摘Nonstructural carbohydrates(NSC)are indicators of tree carbon balance and play an important role in regulating plant growth and survival.However,our understanding of the mechanism underlying drought-induced response of NSC reserves remains limited.Here,we conducted a long-term throughfall exclusion(TFE)experiment to investigate the seasonal responses of NSC reserves to manipulative drought in two contrasting tree species(a broadleaved tree Castanopsis hystrix Miq.and a coniferous tree Pinus massoniana Lamb.)of the subtropical China.We found that in the dry season,the two tree species differed in their responses of NSC reserves to TFE at either the whole-tree level or by organs,with significantly depleted total NSC reserves in roots in both species.Under the TFE treatment,there were significant increases in the NSC pools of leaves and branches in C.hystrix,which were accompanied by significant decreases in fine root biomass and radial growth without significant changes in canopy photosynthesis;while P.massoniana exhibited significant increase in fine root biomass without significant changes in radial growth.Our results suggested that under prolonged water limitation,NSC usage for growth in C.hystrix is somewhat impaired,such that the TFE treatment resulted in NSC accumulation in aboveground organs(leaf and branch);whereas P.massoniana is capable of efficiently utilizing NSC reserves to maintain its growth under drought conditions.Our findings revealed divergent NSC allocations under experimental drought between the two contrasting tree species,which are important for better understanding the differential impacts of climate change on varying forest trees and plantation types in subtropical China.
基金funded by the Talents ans its Youth Project of Xinjiang Production and Construction Corps(38000020924,380000358).
文摘Leaves are important‘source’organs that synthesize organic matter,providing carbon sources for plant growth.Here,we used Populus talassica×Populus euphratica,the dominant species in ecological and timber forests,to simulate carbon limitation through artificial 25%,50%,and 75%defoliation treatments and explore the effects on root,stem,and leaf morphology,biomass accumulation,and carbon allocation strategies.At the 60th d after treat-ment,under 25%defoliation treatment,the plant height,specific leaf weight,root surface area and volume,and concentrations of non-structural carbohydrates in stem and root were significantly increased by 9.13%,20.00%,16.60%,31.95%,5.12%,and 9.34%,respectively,relative to the control.There was no significant change in the growth indicators under 50%defoliation treatment,but the concentrations of non-structural carbohydrates in the leaf and stem significantly decreased,showing mostly a negative correlation between them.The opposite was observed in the root.Under 75%defoliation treatment,the plant height,ground diameter,leaf number,single leaf area,root,stem,and total biomass were significantly reduced by 14.15%,10.24%,14.86%,11.31%,11.56%,21.87%,and 16.82%,respectively,relative to the control.The concentrations of non-structural carbohydrates in various organs were significantly reduced,particularly in the consumption of the starch concentrations in the stem and root.These results indicated that carbon allocation strategies can be adjusted to increase the con-centration of non-structural carbohydrates in root and meet plant growth needs under 25%and 50%defoliation.However,75%defoliation significantly limited the distribution of non-structural carbohydrates to roots and stems,reduced carbon storage,and thus inhibited plant growth.Defoliation-induced carbon limitation altered the carbon allocation pattern of P.talassica×P.euphratica,and the relationship between carbon reserves in roots and tree growth recovery after defoliation was greater.This study provides a theoretical basis for the comprehen-sive management of P.talassica×P.euphratica plantations,as well as a reference for the study of plantation car-bon allocation strategies in the desert and semi-desert regions of Xinjiang under carbon-limitation conditions.
基金Supported by the China National Science and Technology Major Project(2016ZX05046,2017ZX05001)
文摘The differences in organic matter abundance and rock composition between shale and mudstone determine the discrepancy of their contributions to the formation of conventional and shale oil/gas reservoirs.The evaluation criteria of source rocks are different in the future exploration in self-sourced petroleum systems.Shales are deposited in deep/semi-deep lacustrine,with low sedimentation rate and chemical depositions of various degrees,while mudstones are mostly formed in shallow lacustrine/lakeside,with high deposition rate and density flow characteristics.Three factors contribute to the enrichment of organic matter in shales,including the"fertility effect"caused by volcanic ash deposition and hydrothermal injection,excessive and over-speed growth of organisms promoted by radioactive materials,and deep-water anaerobic environment and low sedimentation rate to protect the accumulation of organic matter from dilution.Lamellations in shales are easy to be stripped into storage space,and acid water produced during hydrocarbon generation can dissolve some particles to generate new pores.The massive mudstones with high clay content are of poor matrix porosity.Shales with high total organic carbon,developed laminations,relatively good reservoir property,and high brittle mineral content,are the most favorable lithofacies for shale oil exploration and development.It is necessary to conduct investigation on the differences between shale and mudstone reservoirs,to identify resources distribution in shale and mudstone formations,determine the type and standard of"sweet-spot"evaluation parameters,optimize"sweet-spot areas/sections",and adopt effective development technologies,which is of great significance to objectively evaluate the total amount and economy of shale oil resources,as well as the scale of effective exploitation.
基金Isfahan University of Technology for the financial support of this study
文摘Atterberg limits and consistency indices are used for classifications of cohesive(fine-grained) soils in relation with compaction and tillage practices. They also provide information for interpreting several soil mechanical and physical properties such as shear strength, compressibility, shrinkage and swelling potentials. Although, several studies have been conducted regarding the land use effects on various soil mechanical properties, little is known about the effects of land use and slope positions on Atterberg limits and consistency indices. This study was conducted to investigate the effects of land use and slope position on selected soil physical and chemical properties, Atterberg limits and consistency indices in hilly region of western Iran. Three land uses including dryland farming, irrigated farming and pasture and four slope positions(i.e., shoulder, backslope, footslope, and toeslope) were used for soil samplings. One hundred eleven soil samples were collected from the surface soil(0-10 cm). Selected physical and chemical properties, liquid limit(LL), plastic limit(PL) and shrinkage limit(SL) were measured using the standard methods; and consistency indices including plastic index(PI), friability index(FI), shrinkage index(SI) and soil activity(A=PI/clay) were calculated. The results showed that irrigated farming significantly increased organic matter content(OM) and OM/clay ratio, and decreased bulk density(ρb) and relative bulk density(ρb-rel) as a result of higher biomass production and plant residues added to the soil compared to other land uses. Except for sand content, OM, ρb, cation exchange capacity(CEC) and calcium carbonate equivalent(CCE), slope position significantly affected soil physical and chemical properties. The highest values of silt, OM/clay and CEC/clay were found in the toeslope position, predominantly induced by soil redistribution within the landscape. The use of complexed(COC)- noncomplexed organic carbon(NCOC) concept indicated that majority of the studied soils were located below the saturation line and the OM in the soils was mainly in the COC form. The LL, PI, FI and A showed significant differences among the land uses; the highest values belonged to the irrigated farming due to high biomass production and plant residues returned to the soils. Furthermore, slope position significantly affected the Atterberg limits and consistency indices except for SL. The highest values of LL, PI, SI and A were observed in the toeslope position probably because of higher OM and CEC/clay due to greater amount of expandable phyllosilicate clays. Overall, soils on the toeslope under irrigated farming with high LL and SI and low values of FI need careful tillage management to avoid soil compaction.
文摘Despite a large number of studies examining the effects of abiotic stress factors on plants,the mechanistic explanations of drought-induced tree mortality remain inconclusive and even less is known about how multiple stressors interact.The role of non-structural carbohydrates(NSCs)in preventing or postponing drought mortality is gaining attention.Here,we tested the role of NSCs in mitigating the effects of drought and salinity in New Zealand mangroves,Avicennia marina subsp.australasica.We experimentally manipulated plant NSC levels,prior to subjecting them to combinations of drought and salinity.Plant growth and survival rates were 2-and 3-fold higher in the high-NSC(H-NSC)group than in the low-NSC(L-NSC)group under high salinity and drought conditions,respectively.After 12 weeks under high salinity-high drought conditions,the H-NSC group showed higher stem hydraulic conductivity(281±50 mmol cm^(−1)s^(−1)MPa^(−1))compared with the L-NSC group(134±40 mmol cm^(−1)s^(−1)MPa^(−1)).Although starch levels remained relatively constant,we found a 20%increase in soluble sugars in the stems of H-NSC group under high drought and high salinity in week 8 compared with week 12.Our results suggest(i)an important role of NSCs in mitigating the effects of low soil water potential caused by drought and salinity,and(ii)sink-limited growth under conditions of combined salinity and drought.
