This paper provides a broad review of the existing study on soil aggregate and its responses to land management practices. Soil aggregate is used for structural unit, which is a group of primary soil particles that co...This paper provides a broad review of the existing study on soil aggregate and its responses to land management practices. Soil aggregate is used for structural unit, which is a group of primary soil particles that cohere to each other more strongly than other surrounding particles. The mechanism of soil particle aggregation may be expressed by a hierarchical model, which is based upon the hypothesis that macroaggregates （〉250μm） are collections of smaller microaggregates （〈250μm） held together with organic binding agents. Primary particles form microaggregates and then macroaggregates. Carbon （C）-rich young plant residues form and stabilize macroaggregates, whereas old organic C is occluded in the microaggregates. The interaction of aggregate dynamics with soil organic carbon （SOC） is complex and embraces a range of spatial and temporal processes within macroaggregates and microaggregates. The nature and properties of aggregates are determined by the quantity and quality of coarse residues and humic compounds and by the degree of their interaction with soil particles. The mechanisms resulting in the binding of primary soil particles into stable aggregates vary with soil parent material, climate, vegetation, and land management practices. Land management practices, including tillage methods, residue management, amendments, and soil fertility management, enhance soil aggregation. However, there is still much uncertainty in the dynamics of organic matter in macroaggregation and microaggregation, and research is still needed to understand further the mechanisms of aggregate formation and its responses to human activities.展开更多
Promoting soil carbon sequestration in agricultural land is one of the viable strategies to decelerate the observed climate changes. However, soil physical disturbances have aggravated the soil degradation process by ...Promoting soil carbon sequestration in agricultural land is one of the viable strategies to decelerate the observed climate changes. However, soil physical disturbances have aggravated the soil degradation process by accelerating erosion. Thus, reducing the magnitude and intensity of soil physical disturbance through appropriate farming/agricultural systems is essential to management of soil carbon sink capacity of agricultural lands. Four sites of different land use types/tillage practices, i） no-till （NT） corn （Zea mays L.） （NTC）, ii） conventional till （CT） corn （CTC）, iii） pastureland （PL）, and iv） native forest （NF）, were selected at the North Appalachian Experimental Watershed Station, Ohio, USA to assess the impact of NT farming on soil aggregate indices including water-stable aggregation, mean weight diameter （MWD） and geometric mean diameter （GMD）, and soil organic carbon and total nitrogen contents. The NTC plots received cow manure additions （about 15 t ha-1） every other year. The CTC plots involved disking and chisel ploughing and liquid fertilizer application （110 L ha-l）. The results showed that both water-stable aggregation and MWD were greater in soil for NTC than for CTC. In the 0-10 cm soil layer, the 〉 4.75-mm size fraction dominated NTC and was 46% more than that for CTC, whereas the 〈 0.25-mm size fraction was 380% more for CTC than for NTC. The values of both MWD and GMD in soil for NTC （2.17 mm and 1.19 mm, respectively） were higher than those for CTC （1.47 and 0.72 mm, respectively） in the 0-10 cm soil layer. Macroaggregates contained 6%-42% and 13%-43% higher organic carbon and total nitrogen contents, respectively, than microaggregates in soil for all sites. Macroaggregates in soil for NTC contained 40% more organic carbon and total nitrogen over microaggregates in soil for CTC. Therefore, a higher proportion of microaggregates with lower organic carbon contents created a carbon-depleted environment for CTC. In contrast, soil展开更多
The new results of geologic-structural, petrographic and mineralogic-geochemical researches of Mykert-Sanzheevka ore field—the Uda-Vitim mineragenic zone South-West ending of West Transbaikalia are given. Its main or...The new results of geologic-structural, petrographic and mineralogic-geochemical researches of Mykert-Sanzheevka ore field—the Uda-Vitim mineragenic zone South-West ending of West Transbaikalia are given. Its main ore-controlling structure, represented by losange, consisting of rhombohedral and tetrahedral blocks-duplexes mosaic clusters, which are separated by narrow tectonic sutures, is specified. It is clarified that polycomponent ores clusters are confined with these small-block sutures, made by subvolcanic dykes of shoshonite-latite volcano-plutonic association (233 - 188 million years), apodyke dynamometamorphites (breccias, cataclasite, mylonites) and also mechanometasomatites. Four stages of the dynamometamorphites formation characterized by different species compositions of ore minerals appeared as a result of mechanochemical reactions are determined. A carbonyl model of mineral microaggregates formation with films containing noble metal nanoparticles is proposed. Ore-forming system features of Mykert-Sanzheevka field are considered.展开更多
Soil organic carbon(SOC)can act as a sink or source of atmospheric carbon dioxide;therefore,it is important to understand the amount and composition of SOC in terrestrial ecosystems,the spatial variation in SOC,and th...Soil organic carbon(SOC)can act as a sink or source of atmospheric carbon dioxide;therefore,it is important to understand the amount and composition of SOC in terrestrial ecosystems,the spatial variation in SOC,and the underlying mechanisms that stabilize SOC.In this study,density fractionation and acid hydrolysis were used to assess the spatial variation in SOC,the heavy fraction of organic carbon(HFOC),and the resistant organic carbon(ROC)in soils of the southern Hulun Buir region,northeastern China,and to identify the major factors that contribute to this variation.The results showed that as the contents of clay and silt particles(0–50μm)increased,both methylene blue(MB)adsorption by soil minerals and microaggregate contents increased in the 0–20 and 20–40 cm soil layers(P<0.05).Although varying with vegetation types,SOC,HFOC,and ROC contents increased significantly with the content of clay and silt particles, MB adsorption by soil minerals,and microaggregate content(P<0.05),suggesting that soil texture,the MB adsorption by soil minerals,and microaggregate abundance might be important factors influencing the spatial heterogeneity of carbon contents in soils of the southern Hulun Buir region.展开更多
Soil aggregates are an important controlling factor for the physico-chemical and biological processes such as ammonium(NH;) retention. Straw return to the field is increasingly recommended to promote soil carbon(C) se...Soil aggregates are an important controlling factor for the physico-chemical and biological processes such as ammonium(NH;) retention. Straw return to the field is increasingly recommended to promote soil carbon(C) sequestration and improve crop yields. However, the effects of straw return on NH;retention at soil aggregate level in agricultural soils have seldom been investigated. This study aimed to evaluate the influences of long-term straw return on NH;adsorption and fixation in microaggregates(<0.25 mm) with or without soil organic carbon(SOC) oxidization. Soil samples were collected from plots of three treatments, i.e., no fertilizer(CK), inorganic NPK fertilizers(NPK), and inorganic NPK fertilizers with rice straw return(NPKS), from a 20-year-old field trial with rice-wheat rotations in Taihu Lake Region, China. Soil aggregates were separated using wet-sieving method. The SOC of microaggregates was oxidized by H;O;. The results showed that longterm straw return significantly increased SOC and NH;adsorption, but inhibited NH;fixation in microaggregates. NH;adsorption potential and strength-obtained from adsorption isotherms-increased, but NH;fixation decreased along with increasing SOC in microaggregates, indicating the important role of SOC in NH;adsorption and fixation. This was verified by the SOC oxidization test that showed a relative decrease in NH;adsorption potential for the NPKS treatment and an increase in NH;fixation in all three treatments. Therefore, long-term straw return influences NH;adsorption and fixation by enhancing SOC content and could improve N availability for crop uptake and minimize applied N fertilizer losses in rice-wheat cropping systems.展开更多
Background:Despite the crucial role of nitrogen(N)availability in carbon(C)cycling in terrestrial ecosystems,soil organic C(SOC)mineralization in different sizes of soil aggregates under various land use types and the...Background:Despite the crucial role of nitrogen(N)availability in carbon(C)cycling in terrestrial ecosystems,soil organic C(SOC)mineralization in different sizes of soil aggregates under various land use types and their responses to N addition is not well understood.To investigate the responses of soil C mineralization in different sized aggregates and land use types to N addition,an incubation experiment was conducted with three aggregate-size classes(2000,250,and 53μm)and two land use types(a Chinese fir plantation and a paddy land).Results:Cumulative C mineralization of the<53-μm fractions was the highest and that of microaggregates was the lowest in both forest and paddy soils,indicating that soil aggregates enhanced soil C stability and reduced the loss of soil C.Cumulative C mineralization in all sizes of aggregates treated with N addition decreased in forest soils,but that in microaggregates and the<53-μm fraction increased in paddy soils treated with 100μgNg−1.Moreover,the effect sizes of N addition on C mineralization of forest soils were below zero,but those of paddy soils were above zero.These data indicated that N addition decreased SOC mineralization of forest soils but increased that of paddy soils.Conclusions:Soil aggregates play an important role in soil C sequestration,and decrease soil C loss through the increase of soil C stability,regardless of land use types.N addition has different effects on soil C mineralization in different land use types.These results highlight the importance of soil aggregates and land use types in the effects of N deposition on the global terrestrial ecosystem C cycle.展开更多
文摘This paper provides a broad review of the existing study on soil aggregate and its responses to land management practices. Soil aggregate is used for structural unit, which is a group of primary soil particles that cohere to each other more strongly than other surrounding particles. The mechanism of soil particle aggregation may be expressed by a hierarchical model, which is based upon the hypothesis that macroaggregates （〉250μm） are collections of smaller microaggregates （〈250μm） held together with organic binding agents. Primary particles form microaggregates and then macroaggregates. Carbon （C）-rich young plant residues form and stabilize macroaggregates, whereas old organic C is occluded in the microaggregates. The interaction of aggregate dynamics with soil organic carbon （SOC） is complex and embraces a range of spatial and temporal processes within macroaggregates and microaggregates. The nature and properties of aggregates are determined by the quantity and quality of coarse residues and humic compounds and by the degree of their interaction with soil particles. The mechanisms resulting in the binding of primary soil particles into stable aggregates vary with soil parent material, climate, vegetation, and land management practices. Land management practices, including tillage methods, residue management, amendments, and soil fertility management, enhance soil aggregation. However, there is still much uncertainty in the dynamics of organic matter in macroaggregation and microaggregation, and research is still needed to understand further the mechanisms of aggregate formation and its responses to human activities.
基金the research fellowship granted by the Department of Biotechnology,Government of India,in the form of Overseas Associateship(No. BT/20/NE/2011/2014)
文摘Promoting soil carbon sequestration in agricultural land is one of the viable strategies to decelerate the observed climate changes. However, soil physical disturbances have aggravated the soil degradation process by accelerating erosion. Thus, reducing the magnitude and intensity of soil physical disturbance through appropriate farming/agricultural systems is essential to management of soil carbon sink capacity of agricultural lands. Four sites of different land use types/tillage practices, i） no-till （NT） corn （Zea mays L.） （NTC）, ii） conventional till （CT） corn （CTC）, iii） pastureland （PL）, and iv） native forest （NF）, were selected at the North Appalachian Experimental Watershed Station, Ohio, USA to assess the impact of NT farming on soil aggregate indices including water-stable aggregation, mean weight diameter （MWD） and geometric mean diameter （GMD）, and soil organic carbon and total nitrogen contents. The NTC plots received cow manure additions （about 15 t ha-1） every other year. The CTC plots involved disking and chisel ploughing and liquid fertilizer application （110 L ha-l）. The results showed that both water-stable aggregation and MWD were greater in soil for NTC than for CTC. In the 0-10 cm soil layer, the 〉 4.75-mm size fraction dominated NTC and was 46% more than that for CTC, whereas the 〈 0.25-mm size fraction was 380% more for CTC than for NTC. The values of both MWD and GMD in soil for NTC （2.17 mm and 1.19 mm, respectively） were higher than those for CTC （1.47 and 0.72 mm, respectively） in the 0-10 cm soil layer. Macroaggregates contained 6%-42% and 13%-43% higher organic carbon and total nitrogen contents, respectively, than microaggregates in soil for all sites. Macroaggregates in soil for NTC contained 40% more organic carbon and total nitrogen over microaggregates in soil for CTC. Therefore, a higher proportion of microaggregates with lower organic carbon contents created a carbon-depleted environment for CTC. In contrast, soil
文摘The new results of geologic-structural, petrographic and mineralogic-geochemical researches of Mykert-Sanzheevka ore field—the Uda-Vitim mineragenic zone South-West ending of West Transbaikalia are given. Its main ore-controlling structure, represented by losange, consisting of rhombohedral and tetrahedral blocks-duplexes mosaic clusters, which are separated by narrow tectonic sutures, is specified. It is clarified that polycomponent ores clusters are confined with these small-block sutures, made by subvolcanic dykes of shoshonite-latite volcano-plutonic association (233 - 188 million years), apodyke dynamometamorphites (breccias, cataclasite, mylonites) and also mechanometasomatites. Four stages of the dynamometamorphites formation characterized by different species compositions of ore minerals appeared as a result of mechanochemical reactions are determined. A carbonyl model of mineral microaggregates formation with films containing noble metal nanoparticles is proposed. Ore-forming system features of Mykert-Sanzheevka field are considered.
基金Project supported by the National Natural Science Foundation of China(Nos.40321101 and 40071036)the Major State Basic Research Development Program of China(973 Program)(No.2002CB412503)
文摘Soil organic carbon(SOC)can act as a sink or source of atmospheric carbon dioxide;therefore,it is important to understand the amount and composition of SOC in terrestrial ecosystems,the spatial variation in SOC,and the underlying mechanisms that stabilize SOC.In this study,density fractionation and acid hydrolysis were used to assess the spatial variation in SOC,the heavy fraction of organic carbon(HFOC),and the resistant organic carbon(ROC)in soils of the southern Hulun Buir region,northeastern China,and to identify the major factors that contribute to this variation.The results showed that as the contents of clay and silt particles(0–50μm)increased,both methylene blue(MB)adsorption by soil minerals and microaggregate contents increased in the 0–20 and 20–40 cm soil layers(P<0.05).Although varying with vegetation types,SOC,HFOC,and ROC contents increased significantly with the content of clay and silt particles, MB adsorption by soil minerals,and microaggregate content(P<0.05),suggesting that soil texture,the MB adsorption by soil minerals,and microaggregate abundance might be important factors influencing the spatial heterogeneity of carbon contents in soils of the southern Hulun Buir region.
基金funded by the National Key Research and Development Program of China(2016YFD0200307 and 2016YFD0200108)the National Natural Science Foundation of China(41401295 and 41271309)。
文摘Soil aggregates are an important controlling factor for the physico-chemical and biological processes such as ammonium(NH;) retention. Straw return to the field is increasingly recommended to promote soil carbon(C) sequestration and improve crop yields. However, the effects of straw return on NH;retention at soil aggregate level in agricultural soils have seldom been investigated. This study aimed to evaluate the influences of long-term straw return on NH;adsorption and fixation in microaggregates(<0.25 mm) with or without soil organic carbon(SOC) oxidization. Soil samples were collected from plots of three treatments, i.e., no fertilizer(CK), inorganic NPK fertilizers(NPK), and inorganic NPK fertilizers with rice straw return(NPKS), from a 20-year-old field trial with rice-wheat rotations in Taihu Lake Region, China. Soil aggregates were separated using wet-sieving method. The SOC of microaggregates was oxidized by H;O;. The results showed that longterm straw return significantly increased SOC and NH;adsorption, but inhibited NH;fixation in microaggregates. NH;adsorption potential and strength-obtained from adsorption isotherms-increased, but NH;fixation decreased along with increasing SOC in microaggregates, indicating the important role of SOC in NH;adsorption and fixation. This was verified by the SOC oxidization test that showed a relative decrease in NH;adsorption potential for the NPKS treatment and an increase in NH;fixation in all three treatments. Therefore, long-term straw return influences NH;adsorption and fixation by enhancing SOC content and could improve N availability for crop uptake and minimize applied N fertilizer losses in rice-wheat cropping systems.
基金The National Natural Science Foundation of China(41630755 and 31971718).
文摘Background:Despite the crucial role of nitrogen(N)availability in carbon(C)cycling in terrestrial ecosystems,soil organic C(SOC)mineralization in different sizes of soil aggregates under various land use types and their responses to N addition is not well understood.To investigate the responses of soil C mineralization in different sized aggregates and land use types to N addition,an incubation experiment was conducted with three aggregate-size classes(2000,250,and 53μm)and two land use types(a Chinese fir plantation and a paddy land).Results:Cumulative C mineralization of the<53-μm fractions was the highest and that of microaggregates was the lowest in both forest and paddy soils,indicating that soil aggregates enhanced soil C stability and reduced the loss of soil C.Cumulative C mineralization in all sizes of aggregates treated with N addition decreased in forest soils,but that in microaggregates and the<53-μm fraction increased in paddy soils treated with 100μgNg−1.Moreover,the effect sizes of N addition on C mineralization of forest soils were below zero,but those of paddy soils were above zero.These data indicated that N addition decreased SOC mineralization of forest soils but increased that of paddy soils.Conclusions:Soil aggregates play an important role in soil C sequestration,and decrease soil C loss through the increase of soil C stability,regardless of land use types.N addition has different effects on soil C mineralization in different land use types.These results highlight the importance of soil aggregates and land use types in the effects of N deposition on the global terrestrial ecosystem C cycle.
