Fractal method is a new method to estimate soil structure. It has been shown to be a useful tool in studies related to physical properties of soil as well as erosion and other hydrological processes. Fractal dimension...Fractal method is a new method to estimate soil structure. It has been shown to be a useful tool in studies related to physical properties of soil as well as erosion and other hydrological processes. Fractal dimension was used to study the soil structure in soil at different stages of vegetative succession on the Ziwuling Mountains. The land use and vegetation types included cultivated land, abandoned land, grassland, two types of shrub land, and three types of forests. The grassland, shrub land, and forested areas represented a continuum in vegetative succession that had occurred naturally, as the land was abandoned in 1862. Disturbed and undisturbed soil samples were collected from ten vegetation types from depths of 0-10, 10-20, and 20-30 cm on the Ziwuling Mountains, at a site with an elevation of about 1 500 m. Particle size distribution was determined by the pipette method and aggregate size distribution was determined by wet sieving. The results were used to calculate the particle and aggregate fractal dimension. The results showed that particle and aggregate fractal dimensions varied between vegetation types. There was a positive correlation between the particle fractal dimension and the weight of particles with diameter 〈 0.001 mm, but no relationship between particle fractal dimension and the other particle size classes. Particle fractal dimension was lower in vegetated soils compared to cropland and there was no consistent relationship between fractal dimension and vegetation type. Aggregate fractal dimension was positively correlated with the weight of 〉 0.25 mm aggregates. Aggregate fractal dimension was lower in vegetated soils compared with cropland. In contrast to particle fractal dimension, aggregate fractal dimension described changes in soil structure associated with vegetative succession. The results of this study indicate that aggregate fractal dimension is more effective in describing soil structure and function compared with particle fractal dimension.展开更多
Land cover type is critical for soil organic carbon （SOC） stocks in territorial ecosystems. However, impacts of land cover on SOC stocks in a karst landscape are not fully understood due to discontinuous soil distri...Land cover type is critical for soil organic carbon （SOC） stocks in territorial ecosystems. However, impacts of land cover on SOC stocks in a karst landscape are not fully understood due to discontinuous soil distribution. In this study, considering soil distribution, SOC content and density were investigated along positive successional stages （cropland, plantation, grassland, scrubland, secondary forest, and primary forest） to determine the effects of land cover type on SOC stocks in a subtropical karst area. The proportion of continuous soil on the ground surface under different land cover types ranged between 0.0% and 79.8%. As land cover types changed across the positive successional stages, SOC content in both the 0-20 cm and 20-50 cm soil layers increased significantly. SOC density （SOCD） within O-lOO cm soil depth ranged from 1.45 to 8.72 kg m^-2, and increased from secondary forest to primary forest, plantation, grassland, scrubland, and cropland, due to discontinuous soil distribution. Discontinuous soil distribution had a negative effect on 8OC stocks, highlighting the necessity for accurate determination of soil distribution in karst areas. Generally, ecological restoration had positive impacts on SOC accumulation in karst areas, but this is a slow process. In the short term, the conversion of croplandto grassland was found to be the most efficient way for SOC sequestration.展开更多
The application of straw and biochar is widely practiced for the improvement of soil fertility.However,its impact on microbial functional profiles,particularly with regard to paddy soils,is not well understood.The aim...The application of straw and biochar is widely practiced for the improvement of soil fertility.However,its impact on microbial functional profiles,particularly with regard to paddy soils,is not well understood.The aim of this study was to investigate the diversity of microbial carbon use patterns in paddy soils amended with straw or straw-derived biochar in a 3-year field experiment in fallow soil and at various development stages of a rice crop(i.e.,tillering and blooming).We applied the community level physiological profiling approach,with 15 substrates(sugars,carboxylic and amino acids,and phenolic acid).In general,straw application resulted in the greatest microbial functional diversity owing to the greater number of available C sources than in control or biochar plots.Biochar amendment promoted the use of α-ketoglutaric acid,the mineralization of which was higher than that of any other substrate.Principal component analyses indicated that microbial functional diversity in the biochar-amended soil was separated from those of the straw-amended and control soils.Redundancy analyses revealed that soil organic carbon content was the most important factor regulating the pattern of microbial carbon utilization.Rhizodeposition and nutrient uptake by rice plants modulated microbial functions in paddy soils and stimulated the microbial use of N-rich substances,such as amino acids.Thus,our results demonstrated that the functional diversity of microorganisms in organic amended paddy soils is affected by both physicochemical properties of amendment and plant growth stage.展开更多
The aim of the study was to develop an index to assess the environmental risk of P loss potential in vegetable soils with chronic difference of plantation in the suburbs of Changsha, Hunan Province, China. Chemical me...The aim of the study was to develop an index to assess the environmental risk of P loss potential in vegetable soils with chronic difference of plantation in the suburbs of Changsha, Hunan Province, China. Chemical methodology was used to study soil phosphorus status and the relationships between available P in soil and potential soil leaching P. The results showed that there was a significant linear relationship between Olsen P and CaC12-P or P concentration in soil solution. Olsen P increased sharply when either CaCI2-P or P concentration in soil solution reached a certain level. It was confirmed that 80 mg kg-t of Olsen P was the critical value of soil P leaching in the vegetable soils. P leaching probability over the critical was assessed by GIS and indicator Kriging and four secondary risks of phosphorus leaching loss were defined. In the area with vegetable cropping for over 30 yr （Chenjiadu） and 10-15 planting years （Huangxingzhen）, the indices of phosphorus leaching loss risk were 3 and 2.93, respectively. These two areas belonged to strong secondary of risk of phosphate leaching loss. In the new vegetable planting field less than 2 yr （Ningxiang）, the index was 0.06, which had almost no risk of phosphorus leaching. In vegetable soils in the suburban region of Changsha, the phosphorus leaching peotential is high and the phosphorus leaching loss is related to chronic length of vegetable cropping.展开更多
Continuous application of organic fertilizers can cause accumulation of organic phosphorus(P)in soil,especially in the lowmolecular-weight organic phosphorus(LMWOP)forms.This organic P pool represents a potentially im...Continuous application of organic fertilizers can cause accumulation of organic phosphorus(P)in soil,especially in the lowmolecular-weight organic phosphorus(LMWOP)forms.This organic P pool represents a potentially important source of P for both plants and microorganisms.To understand the effect of long-term fertilization(30 years)(P-rich soil)vs.fallowing(P-poor soil)on the bioavailability and fate of LMWOP in subtropical paddy soils,we determined the sorption and mineralization of 14 C-labeled adenosine,adenosine monophosphate(AMP),adenosine diphosphate(ADP),and adenosine triphosphate(ATP)in each soil.The contents of carbon,nitrogen,and P in the P-rich soil were more than two times greater than those in the P-poor soil.The mineralization rates of the LMWOP compounds were faster in the P-rich soil compared to the P-poor soil,and followed the order AMP>ADP>ATP.Using sterilized soil,all forms of adenosine-P were strongly sorbed to the solid phase and reached saturation in a short time,with the adsorbance increasing with the number of phosphate groups.We concluded that the mineralization of LMWOP compounds was repressed slightly by sorption to the solid phase,but only in the short term.Thus,LMWOP compounds serve as readily available sources of C for microorganisms,making P available for themselves as well as for the plants.However,P accumulation and the progressive saturation of the P sorption sites in highly fertile soils may increase the potential risk of P runoff.展开更多
The forest ecosystem plays a pivotal role in contributing greenhouse gases to the atmosphere.In order to characterize the temporal pattern of nitrous oxide(N_2O) emissions and identify the key factors affecting N_2O e...The forest ecosystem plays a pivotal role in contributing greenhouse gases to the atmosphere.In order to characterize the temporal pattern of nitrous oxide(N_2O) emissions and identify the key factors affecting N_2O emissions from a Masson pine forest in a hilly red-soil region in subtropical central China,we measured the N_2O emissions in Jinjing of Hunan Province using the static chambergas chromatographic method for 3 years(2010-2012) and analyzed the relationships between the N_2O fluxes and the environmental variables.Our results revealed that the N_2O fluxes over the 3 years varied from-36.0 to 296.7 μg N m^(-2) h^(-1),averaging 18.4±5.6 μg N m^(-2) h^(-1)(n=3).The average annual N_2O emissions were estimated to be 1.6±0.3 kg N ha^(-1) year^(-1).The N_2O fluxes exhibited clear intra-annual(seasonal) variations as they were higher in summers and lower in winters.Compared with other forest observations in the subtropics,N_2O emissions at our site were relatively high,possibly due to the high local dry/wet N deposition,and were mostly sensitive to variations in precipitation and soil ammonium N content.In this work,a multiple linear regression model was developed to determine the influence of environmental factors on N_2O emissions,in which a category predictor of "Season" was intentionally used to account for the seasonal variation of the N_2O fluxes.Such a model explained almost 40%of the total variation in daily N_2O emissions from the Masson pine forest soil studied(P<0.001).展开更多
基金funded by the National Natural Science Foundation of China(90302001)CAS Knowledge Innovation(KZCX3-SW-421)the Fund of the State Key Laboratory of Soil Erosion and DrylandFarming on the Loess Plateau(10501-152).
文摘Fractal method is a new method to estimate soil structure. It has been shown to be a useful tool in studies related to physical properties of soil as well as erosion and other hydrological processes. Fractal dimension was used to study the soil structure in soil at different stages of vegetative succession on the Ziwuling Mountains. The land use and vegetation types included cultivated land, abandoned land, grassland, two types of shrub land, and three types of forests. The grassland, shrub land, and forested areas represented a continuum in vegetative succession that had occurred naturally, as the land was abandoned in 1862. Disturbed and undisturbed soil samples were collected from ten vegetation types from depths of 0-10, 10-20, and 20-30 cm on the Ziwuling Mountains, at a site with an elevation of about 1 500 m. Particle size distribution was determined by the pipette method and aggregate size distribution was determined by wet sieving. The results were used to calculate the particle and aggregate fractal dimension. The results showed that particle and aggregate fractal dimensions varied between vegetation types. There was a positive correlation between the particle fractal dimension and the weight of particles with diameter 〈 0.001 mm, but no relationship between particle fractal dimension and the other particle size classes. Particle fractal dimension was lower in vegetated soils compared to cropland and there was no consistent relationship between fractal dimension and vegetation type. Aggregate fractal dimension was positively correlated with the weight of 〉 0.25 mm aggregates. Aggregate fractal dimension was lower in vegetated soils compared with cropland. In contrast to particle fractal dimension, aggregate fractal dimension described changes in soil structure associated with vegetative succession. The results of this study indicate that aggregate fractal dimension is more effective in describing soil structure and function compared with particle fractal dimension.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDA05070403)the National Natural Science Foundation of China (Grant Nos. 41171246, 41301273)the National Science-technology Support Plan Projects (Grant No. 2012BAD05B03-6)
文摘Land cover type is critical for soil organic carbon （SOC） stocks in territorial ecosystems. However, impacts of land cover on SOC stocks in a karst landscape are not fully understood due to discontinuous soil distribution. In this study, considering soil distribution, SOC content and density were investigated along positive successional stages （cropland, plantation, grassland, scrubland, secondary forest, and primary forest） to determine the effects of land cover type on SOC stocks in a subtropical karst area. The proportion of continuous soil on the ground surface under different land cover types ranged between 0.0% and 79.8%. As land cover types changed across the positive successional stages, SOC content in both the 0-20 cm and 20-50 cm soil layers increased significantly. SOC density （SOCD） within O-lOO cm soil depth ranged from 1.45 to 8.72 kg m^-2, and increased from secondary forest to primary forest, plantation, grassland, scrubland, and cropland, due to discontinuous soil distribution. Discontinuous soil distribution had a negative effect on 8OC stocks, highlighting the necessity for accurate determination of soil distribution in karst areas. Generally, ecological restoration had positive impacts on SOC accumulation in karst areas, but this is a slow process. In the short term, the conversion of croplandto grassland was found to be the most efficient way for SOC sequestration.
基金financially supported by the National Key Research and Development Program of China(2016YFE0101100)the National Natural Science Foundation of China(41771334,41771337 and 31470629)+2 种基金the Youth Innovation Team Project of the Institute of Subtropical Agriculture,Chinese Academy of Sciences(2017QNCXTD_GTD)the Chinese Academy of Sciences Instrument Function Development Project,the Government Program of Competitive Growth of Kazan Federal University and by the “RUDN University program5–100”
文摘The application of straw and biochar is widely practiced for the improvement of soil fertility.However,its impact on microbial functional profiles,particularly with regard to paddy soils,is not well understood.The aim of this study was to investigate the diversity of microbial carbon use patterns in paddy soils amended with straw or straw-derived biochar in a 3-year field experiment in fallow soil and at various development stages of a rice crop(i.e.,tillering and blooming).We applied the community level physiological profiling approach,with 15 substrates(sugars,carboxylic and amino acids,and phenolic acid).In general,straw application resulted in the greatest microbial functional diversity owing to the greater number of available C sources than in control or biochar plots.Biochar amendment promoted the use of α-ketoglutaric acid,the mineralization of which was higher than that of any other substrate.Principal component analyses indicated that microbial functional diversity in the biochar-amended soil was separated from those of the straw-amended and control soils.Redundancy analyses revealed that soil organic carbon content was the most important factor regulating the pattern of microbial carbon utilization.Rhizodeposition and nutrient uptake by rice plants modulated microbial functions in paddy soils and stimulated the microbial use of N-rich substances,such as amino acids.Thus,our results demonstrated that the functional diversity of microorganisms in organic amended paddy soils is affected by both physicochemical properties of amendment and plant growth stage.
基金supported by the National Nature Science Foundation of China (NSFC4077111 andKZCX2-YW-437)
文摘The aim of the study was to develop an index to assess the environmental risk of P loss potential in vegetable soils with chronic difference of plantation in the suburbs of Changsha, Hunan Province, China. Chemical methodology was used to study soil phosphorus status and the relationships between available P in soil and potential soil leaching P. The results showed that there was a significant linear relationship between Olsen P and CaC12-P or P concentration in soil solution. Olsen P increased sharply when either CaCI2-P or P concentration in soil solution reached a certain level. It was confirmed that 80 mg kg-t of Olsen P was the critical value of soil P leaching in the vegetable soils. P leaching probability over the critical was assessed by GIS and indicator Kriging and four secondary risks of phosphorus leaching loss were defined. In the area with vegetable cropping for over 30 yr （Chenjiadu） and 10-15 planting years （Huangxingzhen）, the indices of phosphorus leaching loss risk were 3 and 2.93, respectively. These two areas belonged to strong secondary of risk of phosphate leaching loss. In the new vegetable planting field less than 2 yr （Ningxiang）, the index was 0.06, which had almost no risk of phosphorus leaching. In vegetable soils in the suburban region of Changsha, the phosphorus leaching peotential is high and the phosphorus leaching loss is related to chronic length of vegetable cropping.
基金funded by the Natural Science Foundation of Hunan Province,China(2020JJ4563)the National Natural Science Foundation of China(4181101348)+2 种基金the Innovation Groups of Natural Science Foundation of Hunan Province(2019JJ10003)the Chinese Academy of Sciences President’s International Fellowship Initiative to Anna Gunina(2019VCC0003)the Talented Young Scientist Program(TYSP)to Mostafa Zhran supported by the China Science and Technology Exchange Center(Egypt-19-004)。
文摘Continuous application of organic fertilizers can cause accumulation of organic phosphorus(P)in soil,especially in the lowmolecular-weight organic phosphorus(LMWOP)forms.This organic P pool represents a potentially important source of P for both plants and microorganisms.To understand the effect of long-term fertilization(30 years)(P-rich soil)vs.fallowing(P-poor soil)on the bioavailability and fate of LMWOP in subtropical paddy soils,we determined the sorption and mineralization of 14 C-labeled adenosine,adenosine monophosphate(AMP),adenosine diphosphate(ADP),and adenosine triphosphate(ATP)in each soil.The contents of carbon,nitrogen,and P in the P-rich soil were more than two times greater than those in the P-poor soil.The mineralization rates of the LMWOP compounds were faster in the P-rich soil compared to the P-poor soil,and followed the order AMP>ADP>ATP.Using sterilized soil,all forms of adenosine-P were strongly sorbed to the solid phase and reached saturation in a short time,with the adsorbance increasing with the number of phosphate groups.We concluded that the mineralization of LMWOP compounds was repressed slightly by sorption to the solid phase,but only in the short term.Thus,LMWOP compounds serve as readily available sources of C for microorganisms,making P available for themselves as well as for the plants.However,P accumulation and the progressive saturation of the P sorption sites in highly fertile soils may increase the potential risk of P runoff.
基金supported by the National Basic Research Program of China(No.2012CB417105)the International Partnership Program for Creative Research Team of Chinese Academy of Sciences/the State Administration of Foreign Experts Affairs of China(Nos.KZCX2-YW-T07 and 20100491005-8)the 100 Talents Programme of Chinese Academy of Sciences
文摘The forest ecosystem plays a pivotal role in contributing greenhouse gases to the atmosphere.In order to characterize the temporal pattern of nitrous oxide(N_2O) emissions and identify the key factors affecting N_2O emissions from a Masson pine forest in a hilly red-soil region in subtropical central China,we measured the N_2O emissions in Jinjing of Hunan Province using the static chambergas chromatographic method for 3 years(2010-2012) and analyzed the relationships between the N_2O fluxes and the environmental variables.Our results revealed that the N_2O fluxes over the 3 years varied from-36.0 to 296.7 μg N m^(-2) h^(-1),averaging 18.4±5.6 μg N m^(-2) h^(-1)(n=3).The average annual N_2O emissions were estimated to be 1.6±0.3 kg N ha^(-1) year^(-1).The N_2O fluxes exhibited clear intra-annual(seasonal) variations as they were higher in summers and lower in winters.Compared with other forest observations in the subtropics,N_2O emissions at our site were relatively high,possibly due to the high local dry/wet N deposition,and were mostly sensitive to variations in precipitation and soil ammonium N content.In this work,a multiple linear regression model was developed to determine the influence of environmental factors on N_2O emissions,in which a category predictor of "Season" was intentionally used to account for the seasonal variation of the N_2O fluxes.Such a model explained almost 40%of the total variation in daily N_2O emissions from the Masson pine forest soil studied(P<0.001).
