A located field experiment was carried out to study the effects of different amount of chemical fertilizer usage on rice yield,economic benefits of rice,soil carbon（C） and total nitrogen（TN） under ploughing back o...A located field experiment was carried out to study the effects of different amount of chemical fertilizer usage on rice yield,economic benefits of rice,soil carbon（C） and total nitrogen（TN） under ploughing back of Chinese milk vetch for 5consecutive years.Six treatments were included in the experiment,they are CK（unfertilized）,CF（100% chemical fertilizer with the amount of N,P2O5,K2 O being150,75,120 kg/hm^2respectively）,A1（22 500 kg/hm^2 Chinese milk vetch and 100%chemical fertilizer）,A2（Chinese milk vetch and 80% nitrogen and potassium fertilizer and 100% phosphate fertilizer）,A3（Chinese milk vetch and 60% nitrogen and potassium fertilizer and 100% phosphate fertilizer）,A4（Chinese milk vetch and 40% nitrogen and potassium fertilizer and 100% phosphate fertilizer）.The results were as follows：application of fertilizer could increase the yield of rice,while Chinese milk vetch combined with fertilizer application had a much more increase effect in rice yield.Under the condition of milk vetch application with 22 500 kg/hm^2,the early rice yield of the treatment A1 was significantly increased by 7.7% compared with that of CF.And the yield of treatment A3 was basically identical to or slight increase in comparison with that of CF.Decreasing amount of fertilizers cloud improve output value of rice in the case of the utilization of Chinese milk vetch.The treatment A1 increased output value of rice by 5.92% in comparison of CF,and treatment A2 was by 4.08% in the next.Treatment A4 showed much better effect in increasing soil organic carbon and total nitrogen in the paddy soil than those of treatments applying mineral fertilizer only.There was a significant reduction on soil organic carbon and TN in treatment A2 in comparison with that of CF.In general,amount of application of milk vetch with 22 500 kg/hm^2 could replace chemical fertilizer partially,it also could improve rice yield,decrease the production cost,and raise the utilization efficiency of nutrients.展开更多
Fungi play a crucial role in the utilization and storage of soil organic carbon(SOC).Biochars can potentially influence soil carbon(C)turnover by mediating extracellular electron transfer,which can be facilitated by f...Fungi play a crucial role in the utilization and storage of soil organic carbon(SOC).Biochars can potentially influence soil carbon(C)turnover by mediating extracellular electron transfer,which can be facilitated by fungi.However,the effects of biochar and soil type on the community,abundance,enzyme secretion,and necromass of fungi mediating SOC storage remain unclear.A mesocosm incubation experiment was conducted using forest and paddy soils from southern China to study the impact of biochars pyrolyzed at low(300℃BL)and high(700℃BH)temperatures on fungal abundance,community composition,necromass abundance,and C-degrading enzyme activities.The SOC retention ratio was higher under BL(84.0%)than under BH(76.3%).Addition of BL increased fungal abundance in the forest soil by 230%.In contrast,addition of BH decreased fungal abundance in the paddy soil by 20.8%.Biochar addition affected fungal necromass accumulation and oxidase activity and regulated SOC turnover.The high available C content and moderate liming effect of BL significantly increased fungal abundance and necromass abundance in the forest soil compared to the paddy soil.Moreover,after 16 weeks of incubation,BL addition decreased peroxidase activity by 32.1%in the forest soil due to the higher C use efficiency of fungi(i.e.,the enrichment of Talaromyces,Umbelopsis,and Trichoderma),decreasing C-degrading enzyme secretion and reducing SOC degradation compared to the paddy soil.However,BH addition increased the Fusarium abundance,which regulated the polyphenol oxidase activity and promoted SOC degradation in the paddy soil.We concluded that biochars could alter the soil environment and extracellular electron transfer to mediate fungal necromass content and C-degrading enzyme activities,thus affecting SOC storage in the forest and paddy soils.展开更多
Dynamics of soil organic matter in a cultivation chronosequence of paddy fields were studied in subtropical China.Mineralization of soil organic matter was determined by measuring CO2 evolution from soil during 20 day...Dynamics of soil organic matter in a cultivation chronosequence of paddy fields were studied in subtropical China.Mineralization of soil organic matter was determined by measuring CO2 evolution from soil during 20 days of laboratoryincubation. In the first 30 years of cultivation, soil organic C and N contents increased rapidly. After 30 years, 0-10 cmsoil contained 19.6 g kg-1 organic C and 1.62 g kg-1 total N, with the corresponding values of 18.1 g kg-1 and 1.50g kg-1 for 10-20 cm, and then remained stable even after 80 years of rice cultivation. During 20 days incubation themineralization rates of organic C and N in surface soil (0-10 cm) ranged from 2.2% to 3.3% and from 2.8% to 6.7%,respectively, of organic C and total N contents. Biologically active C size generally increased with increasing soil organicC and N contents. Soil dissolved organic C decreased after cultivation of wasteland to 10 years paddy field and thenincreased. Soil microbial biomass C increased with number of years under cultivation, while soil microbial biomass Nincreased during the first 30 years of cultivation and then stabilized. After 30 years of cultivation surface soil (0-10 cm)contained 332.8 mg kg-1 of microbial biomass C and 23.85 mg kg-1 of microbial biomass N, which were 111% and 47%higher than those in soil cultivated for 3 years. It was suggested that surface soil with 30 years of rice cultivation insubtropical China would have attained a steady state of organic C content, being about 19 g kg-1.展开更多
Changes in both soil organic C storage and soil respiration in farmland ecosystems may affect atmospheric CO2 concentration and global C cycle. The objective of this field experiment was to study the effects of three ...Changes in both soil organic C storage and soil respiration in farmland ecosystems may affect atmospheric CO2 concentration and global C cycle. The objective of this field experiment was to study the effects of three crop field management practices on soil CO2 emission and C balance in a cotton field in an arid region of Northwest China. The three management practices were irrigation methods（drip and flood）, stubble managements（stubble-incorporated and stubble-removed） and fertilizer amendments（no fertilizer（CK）, chicken manure（OM）, inorganic N, P and K fertilizer（NPK）, and inorganic fertilizer plus chicken manure（NPK＋OM））. The results showed that within the C pool range, soil CO2 emission during the whole growing season was higher in the drip irrigation treatment than in the corresponding flood irrigation treatment, while soil organic C concentration was larger in the flood irrigation treatment than in the corresponding drip irrigation treatment. Furthermore, soil CO2 emission and organic C concentration were all higher in the stubble-incorporated treatment than in the corresponding stubble-removed treatment, and larger in the NPK＋OM treatment than in the other three fertilizer amendments within the C pool range. The combination of flood irrigation, stubble incorporation and application of either NPK＋OM or OM increased soil organic C concentration in the 0-60 cm soil depth. Calculation of net ecosystem productivity（NEP） under different management practices indicated that the combination of drip irrigation, stubble incorporation and NPK＋OM increased the size of the C pool most, followed by the combination of drip irrigation, stubble incorporation and NPK. In conclusion, management practices have significant impacts on soil CO2 emission, organic C concentration and C balance in cotton fields. Consequently, appropriate management practices, such as the combination of drip irrigation, stubble incorporation, and either NPK＋OM or NPK could increase soil C storage in cotton fields of Northwest China.展开更多
Global climate models have indicated high probability of drought occurrences in the coming future decades due to the impacts of climate change caused by a mass release of CO2. Thus, climate change regarding elevated a...Global climate models have indicated high probability of drought occurrences in the coming future decades due to the impacts of climate change caused by a mass release of CO2. Thus, climate change regarding elevated ambient CO2 and drought may consequently affect the growth of crops. In this study, plant physiology, soil carbon, and soil enzyme activities were measured to investigate the impacts of elevated C02 and drought stress on a Stagn[c Anthrosol planted with soybean （Glycine ma,z）. Treatments of two CO2 levels, three soil moisture levels, and two soil cover types were established. The results indicated that elevated CO2 and drought stress significantly affected plant physiology. The inhibition of plant physiology by drought stress was mediated via prompted photosynthesis and water use efficiency under elevated CO2 conditions. Elevated CO2 resulted in a longer retention time of dissolved organic carbon （DOC） in soil, probably by improving the soil water effectiveness for organic decomposition and mineralization. Drought stress significantly decreased C：N ratio and microbial biomass carbon （MBC）, but the interactive effects of drought stress and CO2 on them were not significant. Elevated CO2 induced an increase in invertase and catalase activities through stimulated plant root exudation. These results suggested that drought stress had significant negative impacts on plant physiology, soil carbon, and soil enzyme activities, whereas elevated CO2 and plant physiological feedbacks indirectly ameliorated these impacts.展开更多
It is globally accepted that soil carbon （C） dynamics are at the core of interlinked environmental problems, deteriorating soil quality and changing climate. Its management remains a complex enigma for the scientifi...It is globally accepted that soil carbon （C） dynamics are at the core of interlinked environmental problems, deteriorating soil quality and changing climate. Its management remains a complex enigma for the scientific community due to its intricate relationship with soil nitrogen （N） availability and moisture-temperature interactions. This article reviews the management aspects of soil C dynamics in light of recent advances, particularly in relation to the availability of inorganic N pools and associated microbial processes under changing climate. Globally, drastic alterations in soil C dynamics under changing land use and management practices have been primarily attributed to the variation in soil N availability, resulting in a higher decomposition rate and a considerable decline in soil organic C （SOC） levels due to increased soil CO2 emissions, degraded soil quality, and increased atmospheric CO2 concentrations, leading to climate warming. Predicted climate warming is proposed to enhance SOC decomposition, which may further increase soil N availability, leading to higher soil CO2 effiux. However, a literature survey revealed that soil may also act as a potential C sink, if we could manage soil inorganic N pools and link microbial processes properly. Studies also indicated that the relative, rather than the absolute, availability of inorganic N pools might be of key importance under changing climate, as these N pools are variably affected by moisture-temperature interactions, and they have variable impacts on SOC turnover. Therefore, multi-factorial studies are required to understand how the relative availability of inorganic N pools and associated microbial processes may determine SOC dynamics for improved soil C management.展开更多
We report on the effects of forest management practices of understory removal and N-fixing species（Cassia alata） addition on soil CO2 fluxes in an Eucalyptus urophylla plantation（EUp）,Acacia crassicarpa plantation...We report on the effects of forest management practices of understory removal and N-fixing species（Cassia alata） addition on soil CO2 fluxes in an Eucalyptus urophylla plantation（EUp）,Acacia crassicarpa plantation（ACp）,10-species-mixed plantation（Tp）,and 30-species-mixed plantation（THp） using the static chamber method in southern China.Four forest management treatments,including（1） understory removal（UR）;（2） C.alata addition（CA）;（3） understory removal and replacement with C.alata（UR＋CA）;and（4） control without any disturbances（CK）,were applied in the above four forest plantations with three replications for each treatment.The results showed that soil CO2 fluxes rates remained at a high level during the rainy season（from April to September）,followed by a rapid decrease after October reaching a minimum in February.Soil CO2 fluxes were significantly higher（P 〈 0.01） in EUp（132.6 mg/（m2.hr）） and ACp（139.8 mg/（m2.hr）） than in Tp（94.0 mg/（m2.hr）） and THp（102.9 mg/（m2.hr））.Soil CO2 fluxes in UR and CA were significantly higher（P 〈 0.01） among the four treatments,with values of 105.7,120.4,133.6 and 112.2 mg/（m2.hr） for UR＋CA,UR,CA and CK,respectively.Soil CO2 fluxes were positively correlated with soil temperature（P 〈 0.01）,soil moisture（P 〈 0.01）,NO3？-N（P 〈 0.05）,and litterfall（P 〈 0.01）,indicating that all these factors might be important controlling variables for soil CO2 fluxes.This study sheds some light on our understanding of soil CO2 flux dynamics in forest plantations under various management practices.展开更多
Vegetation restoration can alter carbon(C),nitrogen(N),and phosphorus(P)cycles in coastal wetlands affecting C:N:P stoichiometry.However,the effects of restoration age on soil C:N:P stoichiometry are unclear.In this s...Vegetation restoration can alter carbon(C),nitrogen(N),and phosphorus(P)cycles in coastal wetlands affecting C:N:P stoichiometry.However,the effects of restoration age on soil C:N:P stoichiometry are unclear.In this study,we examined the re-sponses of soil C,N,and P contents and their stoichiometric ratios to vegetation restoration age,focusing on below-ground processes and their relationships to aboveground vegetation community characteristics.We conducted an analysis of temporal gradients based on the'space for time'method to synthesize the effects of restoration age on soil C:N:P stoichiometry in the Yellow River Delta wetland of China.The findings suggest that the combined effects of restoration age and soil depth create complex patterns of shifting soil C:N:P stoichiometry.Specifically,restoration age significantly increased all topsoil C:N:P stoichiometries,except for soil total phosphorus(TP)and the C:N ratio,and slightly affected subsoil C:N:P stoichiometry.The effects of restoration age on the soil C:N ratio was well constrained owing to the coupled relationship between soil organic carbon(SOC)and total nitrogen(TN)contents,while soil TP con-tent was closely related to changes in plant species diversity.Importantly,we found that the topsoil C:N:P stoichiometry was signific-antly affected by plant species diversity,whereas the subsoil C:N:P stoichiometry was more easily regulated by pH and electric con-ductivity(EC).Overall,this study shows that vegetation restoration age elevated SOC and N contents and alleviated N limitation,which is useful for further assessing soil C:N:P stoichiometry in coastal restoration wetlands.展开更多
Soil carbon to nitrogen(C/N) ratio is one of the most important variables reflecting soil quality and ecological function,and an indicator for assessing carbon and nitrogen nutrition balance of soils.Its variation ref...Soil carbon to nitrogen(C/N) ratio is one of the most important variables reflecting soil quality and ecological function,and an indicator for assessing carbon and nitrogen nutrition balance of soils.Its variation reflects the carbon and nitrogen cycling of soils.In order to explore the spatial variability of soil C/N ratio and its controlling factors of the Ili River valley in Xinjiang Uygur Autonomous Region,Northwest China,the traditional statistical methods,including correlation analysis,geostatistic alanalys and multiple regression analysis were used.The statistical results showed that the soil C/N ratio varied from 7.00 to 23.11,with a mean value of 10.92,and the coefficient of variation was 31.3%.Correlation analysis showed that longitude,altitude,precipitation,soil water,organic carbon,and total nitrogen were positively correlated with the soil C/N ratio(P < 0.01),whereas negative correlations were found between the soil C/N ratio and latitude,temperature,soil bulk density and soil p H.Ordinary Cokriging interpolation showed that r and ME were 0.73 and 0.57,respectively,indicating that the prediction accuracy was high.The spatial autocorrelation of the soil C/N ratio was 6.4 km,and the nugget effect of the soil C/N ratio was 10% with a patchy distribution,in which the area with high value(12.00–20.41) accounted for 22.6% of the total area.Land uses changed the soil C/N ratio with the order of cultivated land > grass land > forest land > garden.Multiple regression analysis showed that geographical and climatic factors,and soil physical and chemical properties could independently explain 26.8%and 55.4% of the spatial features of soil C/N ratio,while human activities could independently explain 5.4% of the spatial features only.The spatial distribution of soil C/N ratio in the study has important reference value for managing soil carbon and nitrogen,and for improving ecological function to similar regions.展开更多
Biological soil crusts （BSCs） are capable of modifying nutrient availability to favor the establishment of biogeochemical cycles. Microbial activities serve as critical roles for both carbon and nutrient transformat...Biological soil crusts （BSCs） are capable of modifying nutrient availability to favor the establishment of biogeochemical cycles. Microbial activities serve as critical roles for both carbon and nutrient transformation in BSCs. However, little is known about microbial activities and physical-chemical properties of BSCs in the Gurbantunggut Desert, Xinjiang, China. In the present research, a sampling line with 1-m wide and 20-m long was set up in each of five typical interdune areas selected randomly in the Gurbantunggut Desert. Within each sampling line, samples of bare sand sheet, algal crusts, lichen crusts and moss crusts were randomly collected at the depth of 0-2 cm. Varia- tions of microalgal biomass, microbial biomass, enzyme activities and soil physical-chemical properties in different succession of BSCs were analyzed. The relationships between microalgal biomass, microbial biomass, enzymatic activities and soil physical-chemical properties were explored by stepwise regression. Our results indicate that micro- algal biomass, microbial biomass and most of enzyme activities increased as the BSCs developed and their highest values occurred in lichen or moss crusts. Except for total K, the contents of most soil nutrients （organic C, total N, total P, available N, available P and available K） were the lowest in the bare sand sheet and significantly increased with the BSCs development, reaching their highest values in moss crusts. However, pH values significantly decreased as the BSCs developed. Significant and positive correlations were observed between chlorophyll a and microbial biomass C. Total P and N were positively associated with chlorophyll a and microbial biomass C, whereas there was a significant and negative correlation between microbial biomass and available P. The growth of cyanobacteria and microorganism contributed C and N in the soil, which offered substrates for enzyme activities thus increasing enzyme activities. Probably, improvement in enzyme activities increased soil fertility and promoted the growth of cyanobacteria, eukary- otic algae and heterotrophic microorganism, with the accelerating succession of BSCs. The present research found that microalgal-microbial biomass and enzyme activities played important roles on the contents of nutrients in the successional stages of BSCs and helped us to understand developmental mechanism in the succession of BSCs.展开更多
Soil organic carbon(SOC)and total nitrogen(TN)stocks are usually calculated with samples collected using core samplers.Although the calculation considers the effects of gravel in soil samples,other coarse fragments su...Soil organic carbon(SOC)and total nitrogen(TN)stocks are usually calculated with samples collected using core samplers.Although the calculation considers the effects of gravel in soil samples,other coarse fragments such as stones or boulders in soil may not be collected due to the restricted diameter of core samplers.This would cause an incorrect estimation of soil bulk density and ultimately SOC and TN stocks.In this study,we compared the relative volume of coarse fragment and bulk density of fine earth determined by large size soil sampler with three core samplers.We also investigated the uncertainties in estimation of SOC and TN stocks caused by this soil sampler procedure in three typical alpine grasslands on the northeast edge of the Qinghai-Tibetan Plateau(QTP),China.Results show that(1)the relative volume and size of coarse fragment collected by large size sampler were significantly(p<0.05)higher and larger than those of core samplers,while bulk density of fine earth,SOC and TN stocks show opposite patterns in all grassland types;(2)SOC and TN stocks determined by core samplers were 17%-45%and 18%-46%higher than larger size sampler for three typical alpine grasslands;and(3)bulk density of fine earth,SOC and TN stocks exponentially decreased with the increasing of coarse fragment content.We concluded that core sampler methods significantly underestimated the volume occupied by coarse fragment but overestimated SOC and TN stocks.Thus,corrections should be made to the results from core samplers using large size samplers on regions with gravel and stone-rich soils in future studies.展开更多
Land-use conversion and unsustainable farming practices are degrading native forest ecosystems of Ghana’s humid savannah agro-ecological zone. This study assessed the impact of land-use change on soil C and N stocks ...Land-use conversion and unsustainable farming practices are degrading native forest ecosystems of Ghana’s humid savannah agro-ecological zone. This study assessed the impact of land-use change on soil C and N stocks in different land-use systems and soil types. A total of eighty (80) composite soil samples at two depths (0 - 20 cm and 20 - 50 cm) were sampled from five land use types (Forest, Woodland savannah, Grassland, Fallow and Cropland) for laboratory analyses. Particle size distribution, bulk density, pH, SOC and TN were determined using standard procedures. Results of the study indicated that C and N stocks were significantly lower in croplands (p < 0.05) compared to other land-use systems. There were significant interactions (p < 0.05) within land-use systems, soil types, and soil depth for soil C and N stocks. Acrisol and associated soils had the highest C and N stocks. A strong positive significant correlation (p < 0.05) was observed between C and N stocks with an R<sup>2</sup> value of 0.85 and 0.93 for the 0 - 20 and 20 - 50 cm depth, respectively. Soil C and N stocks in the study area were estimated to be 34.56 kg/m<sup>2</sup> and 4.63 kg/m<sup>2</sup> for soil types and 26.89 kg/m<sup>2</sup> and 3.39 kg/m2 for land use types, respectively for the 0 to 50 cm soil depth. Our findings indicated that the conversion of native forest to arable land has significantly reduced soil C and N stocks in the top 50 cm (0.50 m) soil layer by 50.77% and 47.77%, respectively. Therefore, we conclude that land-use change, soil type, and soil depth influenced soil C and N stocks of land-use systems in the humid savannah agro-ecological zone of Ghana.展开更多
Advanced field methods of carbon (C) analysis should now be capable of providing repetitive, sequential measurements for the evaluation of spatial and temporal variation at a scale that was previously unfeasible. Some...Advanced field methods of carbon (C) analysis should now be capable of providing repetitive, sequential measurements for the evaluation of spatial and temporal variation at a scale that was previously unfeasible. Some spectroscopy techniques, such as laser-induced breakdown spectroscopy (LIBS), have portable features that may potentially lead to clean and rapid alternative approaches for this purpose. The goal of this study was to quantify the C content of soils with different textures and with high iron and aluminum concentrations using LIBS. LIBS emission spectra from soil pellets were captured, and the C content was estimated (emission line of C (I) at 193.03 nm) after spectral offset and aluminum spectral interference correction. This technique is highly portable and could be ideal for providing the soil C content in a heterogeneous experiment. Dry combustion was used as a reference method, and for calibration a conventional linear model was evaluated based on soil textural classes. The correlation between reference and LIBS values showed r = 0.86 for medium-textured soils and r = 0.93 for fine-textured soils. The data showed that better correlation and lower error (14%) values were found for the fine-textured LIBS model. The limit of detection (LOD) was found to be 0.32% for medium-textured soils and 0.13% for fine-textured soils. The results indicated that LIBS quantification can be affected by the texture and chemical composition of soil. Signal treatment was shown to be very important for mitigation of these interferences and to improve quantification.展开更多
Elevated atmospheric CO2 can influence soil C dynamics in agroecosystems. The effects of free-air CO2 enrichment （FACE） and N fertilization on soil organic C （Corg）, dissolved organic C （DOC）, microbial biomass...Elevated atmospheric CO2 can influence soil C dynamics in agroecosystems. The effects of free-air CO2 enrichment （FACE） and N fertilization on soil organic C （Corg）, dissolved organic C （DOC）, microbial biomass C （Cmic） and soil basal respiration （SBR） were investigated in a Chinese wheat field after expose to elevated CO2 for four full years. The results indicated that elevated CO2 has stimulative effects on soil C concentrations regardless of N fertilization. Following the elevated CO2, the concentrations of Corg and SBR were increased at wheat jointing stage, and those of DOC and Cmic were enhanced obviously across the wheat jointing stage and the fallow period after wheat harvest. On the other hand, N fertilization did not significantly affect the content of soil C. Significant correlations were found among DOC, Cmic, and SBR in this study.展开更多
Due to the Tibetan Plateau’s unique high altitude and low temperature climate conditions,the region’s alpine steppe ecosystem is highly fragile and is suffering from severe degradation under the stress of increasing...Due to the Tibetan Plateau’s unique high altitude and low temperature climate conditions,the region’s alpine steppe ecosystem is highly fragile and is suffering from severe degradation under the stress of increasing population,overgrazing,and climate change.The soil stoichiometry,a crucial part of ecological stoichiometry,provides a fundamental approach for understanding ecosystem processes by examining the relative proportions and balance of the three elements.Understanding the impact of degradation on the soil stoichiometry is vital for conservation and management in the alpine steppe on the Tibetan Plateau.This study aims to examine the response of soil stoichiometry to degradation and explore the underlying biotic and abiotic mechanisms in the alpine steppe.We conducted a field survey in a sequent degraded alpine steppe with seven levels inNorthern Tibet.The plant species,aboveground biomass,and physical and chemical soil properties such as the moisture content,temperature,pH,compactness,total carbon(C),total nitrogen(N),and total phosphorus(P)were measured and recorded.The results showed that the contents of soil C/N,C/P,and N/P consistently decreased along intensifying degradation gradients.Using regression analysis and a structural equation model(SEM),we found that the C/N,C/P,and N/P ratios were positively affected by the soil compactness,soil moisture content and species richness of graminoids but negatively affected by soil pH and the proportion of aboveground biomass of forbs.The soil temperature had a negative effect on the C/N ratio but showed positive effect on the C/P and N/P ratios.The current study shows that degradation-induced changes in abiotic and biotic conditions such as soil warming and drying,which accelerated the soil organic carbon mineralization,as well as the increase in the proportion of forbs,whichwere difficult to decompose and input less organic carbon into soil,resulted in the decreases in soil C/N,C/P,and N/P contents to a great extent.Our results provide a sound basis for sustainable conservation and management of the alpine steppe.展开更多
Bioavailability is a key parameter in assessing contaminant transfer to biota. However, the input patterns and soil use types may impact the metal bioavailability. Several soil parameters were measured including chemi...Bioavailability is a key parameter in assessing contaminant transfer to biota. However, the input patterns and soil use types may impact the metal bioavailability. Several soil parameters were measured including chemical properties, such as pH, organic C, and Cu solution/solid speciation, and biological properties, such as soil microbial biomass C （SMBC）, seed germination, and root elongation, to evaluate the bioavailability of Cu contaminated soils from three different sources, i.e., non-ferrous metal mining, Cu-based fungicides, and Cu-smelting. The results revealed that free Cu2＋ ion in soil solution and the ratios of Cu fractions to total Cu content in the solid phase could not be used to predict total Cu content in soils. The indexes of seed germination and root elongation appeared not to be good biomonitors of Cu contamination in soils, which were more sensitive to soil pH and soil organic carbon （SOC）. Relationships between SMBC and soil Cu forms or the ratio of SMBC/SOC and soil Cu forms showed that free Cu2＋ ion and humie acid-complexed Cu could significantly inhibit soil microbial activities. Our findings suggested that both metal chemical forms and biological bioassays should be considered as a complementary technique rather than an alternative to evaluate the metal bioavailability from different pollution sources.展开更多
Increased food demand from the rapidly growing human population has caused intensive land transition from desert to farmland in arid regions of northwest China. In this developing ecosystem, the optimized fertilizatio...Increased food demand from the rapidly growing human population has caused intensive land transition from desert to farmland in arid regions of northwest China. In this developing ecosystem, the optimized fertilization strategies are becoming an urgent need for sustainable crop productivity, efficient resources use, together with the delivery of ecosystems services including soil carbon（C） and nitrogen（N） accumulation. Through a 7-year field experiment with 9 fertilization treatments in a newly cultivated farmland, we tested whether different fertilizations had significant influences on soil C and N accumulation in this developing ecosystem, and also investigated possible mechanisms for this influence. The results showed that applying organic manure in cultivated farmland significantly increased the soil C and N accumulation rates; this influence was greater when it was combined with chemical fertilizer, accumulating 2.01 t C and 0.11 t N ha^（–1） yr^（–1） in the most successful fertilization treatment. These high rates of C and N accumulation were found associated with increased input of C and N, although the relationship between the N accumulation rate and N input was not significant. The improved soil physical properties was observed under only organic manure and integrated fertilization treatments, and the significant relationship between soil C or N and soil physical properties were also found in this study. The results suggest that in newly cultivated farmland, long term organic manure and integrated fertilization can yield significant benefits for soil C and N accumulation, and deliver additional influence on physical properties.展开更多
Soil C /N ratio is an important influencing factor in soil nitrogen cycling. Two-year old apple trees( Borkh. cv. ‘Fuji'/Malus hupehensis) were used to understand the effect of soil C/N ratio [6. 52( CK),10,15,20...Soil C /N ratio is an important influencing factor in soil nitrogen cycling. Two-year old apple trees( Borkh. cv. ‘Fuji'/Malus hupehensis) were used to understand the effect of soil C/N ratio [6. 52( CK),10,15,20,25,30,35 and 40]on apple growth and nitrogen utilization and loss by using15N trace technique. The results showed that,with the increasing of soil C/N ratio,apple shoot length and fresh weight increased at first,and then decreased; the higher apple shoot length and fresh weight appeared in C/N = 15,20 and 25 treatments,and there were no significant differences among these three treatments,but significantly higher than the other treatments. Statistical analysis revealed that there was significant difference in nitrogen utilization rate between the different treatments,the highest N utilization rate was occurred in soil C/N = 25 treatment which value was 22. 87%,and there was no significant difference between soil C/N = 25 and C/N = 20 treatments,but both the two treatments were significantly higher than the other treatments; Soil C/N = 40 had the lowest N utilization rate which value was 15. 43%,and this value was less than CK( 16. 65%). The proportion of plant absorption nitrogen from fertilizer was much higher when the value of soil C/N ratio in the range of 15- 25,but the percentage of plant absorption nitrogen from soil was much higher when the soil C/N ratio was too low( < 15) or high( < 25). Amount of residual nitrogen in soil increased gradually with the soil C/N ratio increasing,the amount of residual nitrogen in C/N = 40 treatment was 1. 32 times than that in CK. With the increasing of soil C/N ratio,fertilizer nitrogen loss decreased at first,and then increased,fertilizer nitrogen loss was the minimum in C/N = 25 treatments( 49. 87%) and the maximum were occurred in CK( 61. 54%). Therefore,regarding the apple growth and nitrogen balance situation,the value of soil C/N ratio in the range of 15- 25 would be favorable for apple growth and could increase effectively nitrogen fixed by soil,reduce nitrogen loss,and improve the nitrogen utilization ratio.展开更多
Cropland expansion has caused the loss of soil organic carbon(SOC)and the degradation of microbial communities.Fallowing is an important strategy for soil restoration,and fungi are critical in soil fertilization.This ...Cropland expansion has caused the loss of soil organic carbon(SOC)and the degradation of microbial communities.Fallowing is an important strategy for soil restoration,and fungi are critical in soil fertilization.This study compared the soil properties and fungal assemblage in two adjacent environments(farmland vs.fallowing)using a 30-year field experiment composed of five treatments:fallowing and agricultural management under no fertilization,chemical fertilization,and chemical fertilization plus cow manure or crop straw.The fallowed soil had more diverse fungi and maintained higher SOC than the artificially managed treatments.Importantly,the relative abundance of Chaetomiaceae was positively correlated with all the carbon components(SOC,dissolved organic carbon,and microbial biomass carbon)simultaneously.An RNA-Seq of Trichocladium uniseriatum,the key fungus affiliated with Chaetomiaceae,showed that straw addition significantly upregulated the genes for T.uniseriatum melanogenesis,resulting in recalcitrant necromass formation.A remarkable carbon dioxide(CO_(2))assimilation capacity of T.uniseriatum was revealed using^(13)C-labelling assay.Therefore,T.uniseriatum improved SOC storage directly by CO_(2)fixation and indirectly by melanogenesis.Fertilization of agricultural systems can stimulate the growth of T.uniseriatum.Inoculation of T.uniseriatum promoted crop growth,facilitating carbon absorption from the roots.This study highlights that the valuable microbial species resources preserved in fallowed soils can improve farmland ecosystems.展开更多
Biological soil crusts(BSCs) play important roles in the carbon(C) balance in arid regions. Net C balance of BSCs is strongly dependent on rainfall and consequent activation of microbes in the BSCs. The compensation-r...Biological soil crusts(BSCs) play important roles in the carbon(C) balance in arid regions. Net C balance of BSCs is strongly dependent on rainfall and consequent activation of microbes in the BSCs. The compensation-rainfall size for BSCs(the minimum rainfall amount for a positive net C balance) is assumed to be different with BSCs of different developmental stages. A field experiment with simulated rainfall amount(SRA) of 0, 1, 5, 10, 20, and 40 mm was conducted to examine the C fluxes and compensation-rainfall size of BSCs in different parts of fixed dunes in the ecotone between the Badain Jaran Desert and the Minqin Oasis. We found algae-lichen crust on the interdunes and crest, algae crust on the leeward side, and lichen-moss crust on the windward. Even a small rainfall(1 mm) can activate both photosynthesis and respiration of all types of BSCs. The gross ecosystem production, ecosystem respiration, and net ecosystem exchange were significantly affected by SRA, hours after the simulated rainfall, position on a dune, and their interactions. The rapid activation of photosynthesis provides a C source and therefore could be responsible for the increase of C efflux after each rewetting. C-uptake and-emission capacity of all the BSCs positively correlated with rainfall size, with the lowest C fluxes on the leeward side. The compensation rainfall for a net C uptake was 3.80, 15.54, 8.62, and 1.88 mm for BSCs on the interdunes, the leeward side, the crest, and the windward side, respectively. The whole dune started to show a net C uptake with an SRA of 5 mm and maximized with an SRA of about 30 mm. The compensation-rainfall size is negatively correlated with chlorophyll content. Our results suggest that BSCs will be favored in terms of C balance, and sand dune stabilization could be sustained with an increasing frequency of 5-10 mm rainfall events in the desert-oasis transitional zone.-展开更多
基金Supported by Special Fund for Agro-scientific Research in the Public Interest(201103005-08)National Science and Technology Support Program during the 12thFive-year Plan(2012BAD05B05-3)International Plant Nutrition Institute S&T Program(Hunan-16)~~
文摘A located field experiment was carried out to study the effects of different amount of chemical fertilizer usage on rice yield,economic benefits of rice,soil carbon（C） and total nitrogen（TN） under ploughing back of Chinese milk vetch for 5consecutive years.Six treatments were included in the experiment,they are CK（unfertilized）,CF（100% chemical fertilizer with the amount of N,P2O5,K2 O being150,75,120 kg/hm^2respectively）,A1（22 500 kg/hm^2 Chinese milk vetch and 100%chemical fertilizer）,A2（Chinese milk vetch and 80% nitrogen and potassium fertilizer and 100% phosphate fertilizer）,A3（Chinese milk vetch and 60% nitrogen and potassium fertilizer and 100% phosphate fertilizer）,A4（Chinese milk vetch and 40% nitrogen and potassium fertilizer and 100% phosphate fertilizer）.The results were as follows：application of fertilizer could increase the yield of rice,while Chinese milk vetch combined with fertilizer application had a much more increase effect in rice yield.Under the condition of milk vetch application with 22 500 kg/hm^2,the early rice yield of the treatment A1 was significantly increased by 7.7% compared with that of CF.And the yield of treatment A3 was basically identical to or slight increase in comparison with that of CF.Decreasing amount of fertilizers cloud improve output value of rice in the case of the utilization of Chinese milk vetch.The treatment A1 increased output value of rice by 5.92% in comparison of CF,and treatment A2 was by 4.08% in the next.Treatment A4 showed much better effect in increasing soil organic carbon and total nitrogen in the paddy soil than those of treatments applying mineral fertilizer only.There was a significant reduction on soil organic carbon and TN in treatment A2 in comparison with that of CF.In general,amount of application of milk vetch with 22 500 kg/hm^2 could replace chemical fertilizer partially,it also could improve rice yield,decrease the production cost,and raise the utilization efficiency of nutrients.
基金supported by the National Natural Science Foundation of China(Nos.32101397,42177195,42307527,and 42307567)the Guangdong Basic and Applied Basic Research Foundation,China(Nos.2021A1515011559,2024A1515012566,and 2023A1515012248)+1 种基金the Guangdong Foundation for Program of Science and Technology Research,China(No.2023B1212060044)GDAS'Project of Science and Technology Development,China(Nos.2023 GDASZH-2023010103 and 2020GDASYL-20200103074).
文摘Fungi play a crucial role in the utilization and storage of soil organic carbon(SOC).Biochars can potentially influence soil carbon(C)turnover by mediating extracellular electron transfer,which can be facilitated by fungi.However,the effects of biochar and soil type on the community,abundance,enzyme secretion,and necromass of fungi mediating SOC storage remain unclear.A mesocosm incubation experiment was conducted using forest and paddy soils from southern China to study the impact of biochars pyrolyzed at low(300℃BL)and high(700℃BH)temperatures on fungal abundance,community composition,necromass abundance,and C-degrading enzyme activities.The SOC retention ratio was higher under BL(84.0%)than under BH(76.3%).Addition of BL increased fungal abundance in the forest soil by 230%.In contrast,addition of BH decreased fungal abundance in the paddy soil by 20.8%.Biochar addition affected fungal necromass accumulation and oxidase activity and regulated SOC turnover.The high available C content and moderate liming effect of BL significantly increased fungal abundance and necromass abundance in the forest soil compared to the paddy soil.Moreover,after 16 weeks of incubation,BL addition decreased peroxidase activity by 32.1%in the forest soil due to the higher C use efficiency of fungi(i.e.,the enrichment of Talaromyces,Umbelopsis,and Trichoderma),decreasing C-degrading enzyme secretion and reducing SOC degradation compared to the paddy soil.However,BH addition increased the Fusarium abundance,which regulated the polyphenol oxidase activity and promoted SOC degradation in the paddy soil.We concluded that biochars could alter the soil environment and extracellular electron transfer to mediate fungal necromass content and C-degrading enzyme activities,thus affecting SOC storage in the forest and paddy soils.
基金the National Natural Science Foundation of China (No. 40471066) and the Knowledge InnovationProgram of the Chinese Academy of Sciences (No. KZCX1-SW-01-05).
文摘Dynamics of soil organic matter in a cultivation chronosequence of paddy fields were studied in subtropical China.Mineralization of soil organic matter was determined by measuring CO2 evolution from soil during 20 days of laboratoryincubation. In the first 30 years of cultivation, soil organic C and N contents increased rapidly. After 30 years, 0-10 cmsoil contained 19.6 g kg-1 organic C and 1.62 g kg-1 total N, with the corresponding values of 18.1 g kg-1 and 1.50g kg-1 for 10-20 cm, and then remained stable even after 80 years of rice cultivation. During 20 days incubation themineralization rates of organic C and N in surface soil (0-10 cm) ranged from 2.2% to 3.3% and from 2.8% to 6.7%,respectively, of organic C and total N contents. Biologically active C size generally increased with increasing soil organicC and N contents. Soil dissolved organic C decreased after cultivation of wasteland to 10 years paddy field and thenincreased. Soil microbial biomass C increased with number of years under cultivation, while soil microbial biomass Nincreased during the first 30 years of cultivation and then stabilized. After 30 years of cultivation surface soil (0-10 cm)contained 332.8 mg kg-1 of microbial biomass C and 23.85 mg kg-1 of microbial biomass N, which were 111% and 47%higher than those in soil cultivated for 3 years. It was suggested that surface soil with 30 years of rice cultivation insubtropical China would have attained a steady state of organic C content, being about 19 g kg-1.
基金jointly funded by the National Basic Research Program of China (2006CB708401)the Doctor Subject Foundation of the Ministry of Education of China (20116518110002)
文摘Changes in both soil organic C storage and soil respiration in farmland ecosystems may affect atmospheric CO2 concentration and global C cycle. The objective of this field experiment was to study the effects of three crop field management practices on soil CO2 emission and C balance in a cotton field in an arid region of Northwest China. The three management practices were irrigation methods（drip and flood）, stubble managements（stubble-incorporated and stubble-removed） and fertilizer amendments（no fertilizer（CK）, chicken manure（OM）, inorganic N, P and K fertilizer（NPK）, and inorganic fertilizer plus chicken manure（NPK＋OM））. The results showed that within the C pool range, soil CO2 emission during the whole growing season was higher in the drip irrigation treatment than in the corresponding flood irrigation treatment, while soil organic C concentration was larger in the flood irrigation treatment than in the corresponding drip irrigation treatment. Furthermore, soil CO2 emission and organic C concentration were all higher in the stubble-incorporated treatment than in the corresponding stubble-removed treatment, and larger in the NPK＋OM treatment than in the other three fertilizer amendments within the C pool range. The combination of flood irrigation, stubble incorporation and application of either NPK＋OM or OM increased soil organic C concentration in the 0-60 cm soil depth. Calculation of net ecosystem productivity（NEP） under different management practices indicated that the combination of drip irrigation, stubble incorporation and NPK＋OM increased the size of the C pool most, followed by the combination of drip irrigation, stubble incorporation and NPK. In conclusion, management practices have significant impacts on soil CO2 emission, organic C concentration and C balance in cotton fields. Consequently, appropriate management practices, such as the combination of drip irrigation, stubble incorporation, and either NPK＋OM or NPK could increase soil C storage in cotton fields of Northwest China.
基金supported by the National Natural Science Foundation of China (No.51309053)the Fundamental Research Funds for the Central Universities-Donghua University (DHU) Distinguished Young Professor Program, China (No.B201310)
文摘Global climate models have indicated high probability of drought occurrences in the coming future decades due to the impacts of climate change caused by a mass release of CO2. Thus, climate change regarding elevated ambient CO2 and drought may consequently affect the growth of crops. In this study, plant physiology, soil carbon, and soil enzyme activities were measured to investigate the impacts of elevated C02 and drought stress on a Stagn[c Anthrosol planted with soybean （Glycine ma,z）. Treatments of two CO2 levels, three soil moisture levels, and two soil cover types were established. The results indicated that elevated CO2 and drought stress significantly affected plant physiology. The inhibition of plant physiology by drought stress was mediated via prompted photosynthesis and water use efficiency under elevated CO2 conditions. Elevated CO2 resulted in a longer retention time of dissolved organic carbon （DOC） in soil, probably by improving the soil water effectiveness for organic decomposition and mineralization. Drought stress significantly decreased C：N ratio and microbial biomass carbon （MBC）, but the interactive effects of drought stress and CO2 on them were not significant. Elevated CO2 induced an increase in invertase and catalase activities through stimulated plant root exudation. These results suggested that drought stress had significant negative impacts on plant physiology, soil carbon, and soil enzyme activities, whereas elevated CO2 and plant physiological feedbacks indirectly ameliorated these impacts.
文摘It is globally accepted that soil carbon （C） dynamics are at the core of interlinked environmental problems, deteriorating soil quality and changing climate. Its management remains a complex enigma for the scientific community due to its intricate relationship with soil nitrogen （N） availability and moisture-temperature interactions. This article reviews the management aspects of soil C dynamics in light of recent advances, particularly in relation to the availability of inorganic N pools and associated microbial processes under changing climate. Globally, drastic alterations in soil C dynamics under changing land use and management practices have been primarily attributed to the variation in soil N availability, resulting in a higher decomposition rate and a considerable decline in soil organic C （SOC） levels due to increased soil CO2 emissions, degraded soil quality, and increased atmospheric CO2 concentrations, leading to climate warming. Predicted climate warming is proposed to enhance SOC decomposition, which may further increase soil N availability, leading to higher soil CO2 effiux. However, a literature survey revealed that soil may also act as a potential C sink, if we could manage soil inorganic N pools and link microbial processes properly. Studies also indicated that the relative, rather than the absolute, availability of inorganic N pools might be of key importance under changing climate, as these N pools are variably affected by moisture-temperature interactions, and they have variable impacts on SOC turnover. Therefore, multi-factorial studies are required to understand how the relative availability of inorganic N pools and associated microbial processes may determine SOC dynamics for improved soil C management.
基金supported by the National Natural Science Foundation of China (No. 30630015,30771704)
文摘We report on the effects of forest management practices of understory removal and N-fixing species（Cassia alata） addition on soil CO2 fluxes in an Eucalyptus urophylla plantation（EUp）,Acacia crassicarpa plantation（ACp）,10-species-mixed plantation（Tp）,and 30-species-mixed plantation（THp） using the static chamber method in southern China.Four forest management treatments,including（1） understory removal（UR）;（2） C.alata addition（CA）;（3） understory removal and replacement with C.alata（UR＋CA）;and（4） control without any disturbances（CK）,were applied in the above four forest plantations with three replications for each treatment.The results showed that soil CO2 fluxes rates remained at a high level during the rainy season（from April to September）,followed by a rapid decrease after October reaching a minimum in February.Soil CO2 fluxes were significantly higher（P 〈 0.01） in EUp（132.6 mg/（m2.hr）） and ACp（139.8 mg/（m2.hr）） than in Tp（94.0 mg/（m2.hr）） and THp（102.9 mg/（m2.hr））.Soil CO2 fluxes in UR and CA were significantly higher（P 〈 0.01） among the four treatments,with values of 105.7,120.4,133.6 and 112.2 mg/（m2.hr） for UR＋CA,UR,CA and CK,respectively.Soil CO2 fluxes were positively correlated with soil temperature（P 〈 0.01）,soil moisture（P 〈 0.01）,NO3？-N（P 〈 0.05）,and litterfall（P 〈 0.01）,indicating that all these factors might be important controlling variables for soil CO2 fluxes.This study sheds some light on our understanding of soil CO2 flux dynamics in forest plantations under various management practices.
基金Under the auspices of Natural Science Foundation of China(No.U2106209,42071126)Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA23050202)International Science Partnership Program of the Chinese Academy of Sciences(No.121311KYSB20190029)。
文摘Vegetation restoration can alter carbon(C),nitrogen(N),and phosphorus(P)cycles in coastal wetlands affecting C:N:P stoichiometry.However,the effects of restoration age on soil C:N:P stoichiometry are unclear.In this study,we examined the re-sponses of soil C,N,and P contents and their stoichiometric ratios to vegetation restoration age,focusing on below-ground processes and their relationships to aboveground vegetation community characteristics.We conducted an analysis of temporal gradients based on the'space for time'method to synthesize the effects of restoration age on soil C:N:P stoichiometry in the Yellow River Delta wetland of China.The findings suggest that the combined effects of restoration age and soil depth create complex patterns of shifting soil C:N:P stoichiometry.Specifically,restoration age significantly increased all topsoil C:N:P stoichiometries,except for soil total phosphorus(TP)and the C:N ratio,and slightly affected subsoil C:N:P stoichiometry.The effects of restoration age on the soil C:N ratio was well constrained owing to the coupled relationship between soil organic carbon(SOC)and total nitrogen(TN)contents,while soil TP con-tent was closely related to changes in plant species diversity.Importantly,we found that the topsoil C:N:P stoichiometry was signific-antly affected by plant species diversity,whereas the subsoil C:N:P stoichiometry was more easily regulated by pH and electric con-ductivity(EC).Overall,this study shows that vegetation restoration age elevated SOC and N contents and alleviated N limitation,which is useful for further assessing soil C:N:P stoichiometry in coastal restoration wetlands.
基金Under the auspices of National Science and Technology Support Program of China(No.2014BAC15B03)the West Light Funds of Chinese Academy of Sciences(No.YB201302)
文摘Soil carbon to nitrogen(C/N) ratio is one of the most important variables reflecting soil quality and ecological function,and an indicator for assessing carbon and nitrogen nutrition balance of soils.Its variation reflects the carbon and nitrogen cycling of soils.In order to explore the spatial variability of soil C/N ratio and its controlling factors of the Ili River valley in Xinjiang Uygur Autonomous Region,Northwest China,the traditional statistical methods,including correlation analysis,geostatistic alanalys and multiple regression analysis were used.The statistical results showed that the soil C/N ratio varied from 7.00 to 23.11,with a mean value of 10.92,and the coefficient of variation was 31.3%.Correlation analysis showed that longitude,altitude,precipitation,soil water,organic carbon,and total nitrogen were positively correlated with the soil C/N ratio(P < 0.01),whereas negative correlations were found between the soil C/N ratio and latitude,temperature,soil bulk density and soil p H.Ordinary Cokriging interpolation showed that r and ME were 0.73 and 0.57,respectively,indicating that the prediction accuracy was high.The spatial autocorrelation of the soil C/N ratio was 6.4 km,and the nugget effect of the soil C/N ratio was 10% with a patchy distribution,in which the area with high value(12.00–20.41) accounted for 22.6% of the total area.Land uses changed the soil C/N ratio with the order of cultivated land > grass land > forest land > garden.Multiple regression analysis showed that geographical and climatic factors,and soil physical and chemical properties could independently explain 26.8%and 55.4% of the spatial features of soil C/N ratio,while human activities could independently explain 5.4% of the spatial features only.The spatial distribution of soil C/N ratio in the study has important reference value for managing soil carbon and nitrogen,and for improving ecological function to similar regions.
基金financially supported by the National Natural Science Foundation of China (41071041, U1203301)the West Light Foundation of Chinese Academy of Sciences (RCPY201101)
文摘Biological soil crusts （BSCs） are capable of modifying nutrient availability to favor the establishment of biogeochemical cycles. Microbial activities serve as critical roles for both carbon and nutrient transformation in BSCs. However, little is known about microbial activities and physical-chemical properties of BSCs in the Gurbantunggut Desert, Xinjiang, China. In the present research, a sampling line with 1-m wide and 20-m long was set up in each of five typical interdune areas selected randomly in the Gurbantunggut Desert. Within each sampling line, samples of bare sand sheet, algal crusts, lichen crusts and moss crusts were randomly collected at the depth of 0-2 cm. Varia- tions of microalgal biomass, microbial biomass, enzyme activities and soil physical-chemical properties in different succession of BSCs were analyzed. The relationships between microalgal biomass, microbial biomass, enzymatic activities and soil physical-chemical properties were explored by stepwise regression. Our results indicate that micro- algal biomass, microbial biomass and most of enzyme activities increased as the BSCs developed and their highest values occurred in lichen or moss crusts. Except for total K, the contents of most soil nutrients （organic C, total N, total P, available N, available P and available K） were the lowest in the bare sand sheet and significantly increased with the BSCs development, reaching their highest values in moss crusts. However, pH values significantly decreased as the BSCs developed. Significant and positive correlations were observed between chlorophyll a and microbial biomass C. Total P and N were positively associated with chlorophyll a and microbial biomass C, whereas there was a significant and negative correlation between microbial biomass and available P. The growth of cyanobacteria and microorganism contributed C and N in the soil, which offered substrates for enzyme activities thus increasing enzyme activities. Probably, improvement in enzyme activities increased soil fertility and promoted the growth of cyanobacteria, eukary- otic algae and heterotrophic microorganism, with the accelerating succession of BSCs. The present research found that microalgal-microbial biomass and enzyme activities played important roles on the contents of nutrients in the successional stages of BSCs and helped us to understand developmental mechanism in the succession of BSCs.
基金jointly supported by grants from the National Natural Science Foundation(42071139)Gansu province Science Fund for Distinguished Young Scholars(21JR7RA066)the independent grants from the State Key Laboratory of Cryosphere Sciences(SKLCS-ZZ-2021)
文摘Soil organic carbon(SOC)and total nitrogen(TN)stocks are usually calculated with samples collected using core samplers.Although the calculation considers the effects of gravel in soil samples,other coarse fragments such as stones or boulders in soil may not be collected due to the restricted diameter of core samplers.This would cause an incorrect estimation of soil bulk density and ultimately SOC and TN stocks.In this study,we compared the relative volume of coarse fragment and bulk density of fine earth determined by large size soil sampler with three core samplers.We also investigated the uncertainties in estimation of SOC and TN stocks caused by this soil sampler procedure in three typical alpine grasslands on the northeast edge of the Qinghai-Tibetan Plateau(QTP),China.Results show that(1)the relative volume and size of coarse fragment collected by large size sampler were significantly(p<0.05)higher and larger than those of core samplers,while bulk density of fine earth,SOC and TN stocks show opposite patterns in all grassland types;(2)SOC and TN stocks determined by core samplers were 17%-45%and 18%-46%higher than larger size sampler for three typical alpine grasslands;and(3)bulk density of fine earth,SOC and TN stocks exponentially decreased with the increasing of coarse fragment content.We concluded that core sampler methods significantly underestimated the volume occupied by coarse fragment but overestimated SOC and TN stocks.Thus,corrections should be made to the results from core samplers using large size samplers on regions with gravel and stone-rich soils in future studies.
文摘Land-use conversion and unsustainable farming practices are degrading native forest ecosystems of Ghana’s humid savannah agro-ecological zone. This study assessed the impact of land-use change on soil C and N stocks in different land-use systems and soil types. A total of eighty (80) composite soil samples at two depths (0 - 20 cm and 20 - 50 cm) were sampled from five land use types (Forest, Woodland savannah, Grassland, Fallow and Cropland) for laboratory analyses. Particle size distribution, bulk density, pH, SOC and TN were determined using standard procedures. Results of the study indicated that C and N stocks were significantly lower in croplands (p < 0.05) compared to other land-use systems. There were significant interactions (p < 0.05) within land-use systems, soil types, and soil depth for soil C and N stocks. Acrisol and associated soils had the highest C and N stocks. A strong positive significant correlation (p < 0.05) was observed between C and N stocks with an R<sup>2</sup> value of 0.85 and 0.93 for the 0 - 20 and 20 - 50 cm depth, respectively. Soil C and N stocks in the study area were estimated to be 34.56 kg/m<sup>2</sup> and 4.63 kg/m<sup>2</sup> for soil types and 26.89 kg/m<sup>2</sup> and 3.39 kg/m2 for land use types, respectively for the 0 to 50 cm soil depth. Our findings indicated that the conversion of native forest to arable land has significantly reduced soil C and N stocks in the top 50 cm (0.50 m) soil layer by 50.77% and 47.77%, respectively. Therefore, we conclude that land-use change, soil type, and soil depth influenced soil C and N stocks of land-use systems in the humid savannah agro-ecological zone of Ghana.
基金The authors express their gratitude for the grant from FAPESP(2010/09211-6),CNPq(560292/2010-4)CAPES,Embrapa and Pecus Research Network.
文摘Advanced field methods of carbon (C) analysis should now be capable of providing repetitive, sequential measurements for the evaluation of spatial and temporal variation at a scale that was previously unfeasible. Some spectroscopy techniques, such as laser-induced breakdown spectroscopy (LIBS), have portable features that may potentially lead to clean and rapid alternative approaches for this purpose. The goal of this study was to quantify the C content of soils with different textures and with high iron and aluminum concentrations using LIBS. LIBS emission spectra from soil pellets were captured, and the C content was estimated (emission line of C (I) at 193.03 nm) after spectral offset and aluminum spectral interference correction. This technique is highly portable and could be ideal for providing the soil C content in a heterogeneous experiment. Dry combustion was used as a reference method, and for calibration a conventional linear model was evaluated based on soil textural classes. The correlation between reference and LIBS values showed r = 0.86 for medium-textured soils and r = 0.93 for fine-textured soils. The data showed that better correlation and lower error (14%) values were found for the fine-textured LIBS model. The limit of detection (LOD) was found to be 0.32% for medium-textured soils and 0.13% for fine-textured soils. The results indicated that LIBS quantification can be affected by the texture and chemical composition of soil. Signal treatment was shown to be very important for mitigation of these interferences and to improve quantification.
基金supported by the National Natural Science Foundation of China(No.30770400,40231003)the Knowledge Innovation Program of Chinese Academy of Sciences(No.KZCX2-408)
文摘Elevated atmospheric CO2 can influence soil C dynamics in agroecosystems. The effects of free-air CO2 enrichment （FACE） and N fertilization on soil organic C （Corg）, dissolved organic C （DOC）, microbial biomass C （Cmic） and soil basal respiration （SBR） were investigated in a Chinese wheat field after expose to elevated CO2 for four full years. The results indicated that elevated CO2 has stimulative effects on soil C concentrations regardless of N fertilization. Following the elevated CO2, the concentrations of Corg and SBR were increased at wheat jointing stage, and those of DOC and Cmic were enhanced obviously across the wheat jointing stage and the fallow period after wheat harvest. On the other hand, N fertilization did not significantly affect the content of soil C. Significant correlations were found among DOC, Cmic, and SBR in this study.
基金supported by the State Key Research Development Program of China (Grant 2016YFC0502002)Youth Innovation Research Team Project (LENOM2016Q0003)
文摘Due to the Tibetan Plateau’s unique high altitude and low temperature climate conditions,the region’s alpine steppe ecosystem is highly fragile and is suffering from severe degradation under the stress of increasing population,overgrazing,and climate change.The soil stoichiometry,a crucial part of ecological stoichiometry,provides a fundamental approach for understanding ecosystem processes by examining the relative proportions and balance of the three elements.Understanding the impact of degradation on the soil stoichiometry is vital for conservation and management in the alpine steppe on the Tibetan Plateau.This study aims to examine the response of soil stoichiometry to degradation and explore the underlying biotic and abiotic mechanisms in the alpine steppe.We conducted a field survey in a sequent degraded alpine steppe with seven levels inNorthern Tibet.The plant species,aboveground biomass,and physical and chemical soil properties such as the moisture content,temperature,pH,compactness,total carbon(C),total nitrogen(N),and total phosphorus(P)were measured and recorded.The results showed that the contents of soil C/N,C/P,and N/P consistently decreased along intensifying degradation gradients.Using regression analysis and a structural equation model(SEM),we found that the C/N,C/P,and N/P ratios were positively affected by the soil compactness,soil moisture content and species richness of graminoids but negatively affected by soil pH and the proportion of aboveground biomass of forbs.The soil temperature had a negative effect on the C/N ratio but showed positive effect on the C/P and N/P ratios.The current study shows that degradation-induced changes in abiotic and biotic conditions such as soil warming and drying,which accelerated the soil organic carbon mineralization,as well as the increase in the proportion of forbs,whichwere difficult to decompose and input less organic carbon into soil,resulted in the decreases in soil C/N,C/P,and N/P contents to a great extent.Our results provide a sound basis for sustainable conservation and management of the alpine steppe.
基金Supported by the National Natural Science Foundation of China(No.41101305)
文摘Bioavailability is a key parameter in assessing contaminant transfer to biota. However, the input patterns and soil use types may impact the metal bioavailability. Several soil parameters were measured including chemical properties, such as pH, organic C, and Cu solution/solid speciation, and biological properties, such as soil microbial biomass C （SMBC）, seed germination, and root elongation, to evaluate the bioavailability of Cu contaminated soils from three different sources, i.e., non-ferrous metal mining, Cu-based fungicides, and Cu-smelting. The results revealed that free Cu2＋ ion in soil solution and the ratios of Cu fractions to total Cu content in the solid phase could not be used to predict total Cu content in soils. The indexes of seed germination and root elongation appeared not to be good biomonitors of Cu contamination in soils, which were more sensitive to soil pH and soil organic carbon （SOC）. Relationships between SMBC and soil Cu forms or the ratio of SMBC/SOC and soil Cu forms showed that free Cu2＋ ion and humie acid-complexed Cu could significantly inhibit soil microbial activities. Our findings suggested that both metal chemical forms and biological bioassays should be considered as a complementary technique rather than an alternative to evaluate the metal bioavailability from different pollution sources.
基金funded by the National Natural Science Foundation of China (41201284, 41401337)the China Postdoctoral Science Foundation (2013M542406)
文摘Increased food demand from the rapidly growing human population has caused intensive land transition from desert to farmland in arid regions of northwest China. In this developing ecosystem, the optimized fertilization strategies are becoming an urgent need for sustainable crop productivity, efficient resources use, together with the delivery of ecosystems services including soil carbon（C） and nitrogen（N） accumulation. Through a 7-year field experiment with 9 fertilization treatments in a newly cultivated farmland, we tested whether different fertilizations had significant influences on soil C and N accumulation in this developing ecosystem, and also investigated possible mechanisms for this influence. The results showed that applying organic manure in cultivated farmland significantly increased the soil C and N accumulation rates; this influence was greater when it was combined with chemical fertilizer, accumulating 2.01 t C and 0.11 t N ha^（–1） yr^（–1） in the most successful fertilization treatment. These high rates of C and N accumulation were found associated with increased input of C and N, although the relationship between the N accumulation rate and N input was not significant. The improved soil physical properties was observed under only organic manure and integrated fertilization treatments, and the significant relationship between soil C or N and soil physical properties were also found in this study. The results suggest that in newly cultivated farmland, long term organic manure and integrated fertilization can yield significant benefits for soil C and N accumulation, and deliver additional influence on physical properties.
基金Special Fund for Agro-scientific Research in the Public Interest(201103003)the Earmarked Fund for China Agriculture ResearchSystem(CARS-28)
文摘Soil C /N ratio is an important influencing factor in soil nitrogen cycling. Two-year old apple trees( Borkh. cv. ‘Fuji'/Malus hupehensis) were used to understand the effect of soil C/N ratio [6. 52( CK),10,15,20,25,30,35 and 40]on apple growth and nitrogen utilization and loss by using15N trace technique. The results showed that,with the increasing of soil C/N ratio,apple shoot length and fresh weight increased at first,and then decreased; the higher apple shoot length and fresh weight appeared in C/N = 15,20 and 25 treatments,and there were no significant differences among these three treatments,but significantly higher than the other treatments. Statistical analysis revealed that there was significant difference in nitrogen utilization rate between the different treatments,the highest N utilization rate was occurred in soil C/N = 25 treatment which value was 22. 87%,and there was no significant difference between soil C/N = 25 and C/N = 20 treatments,but both the two treatments were significantly higher than the other treatments; Soil C/N = 40 had the lowest N utilization rate which value was 15. 43%,and this value was less than CK( 16. 65%). The proportion of plant absorption nitrogen from fertilizer was much higher when the value of soil C/N ratio in the range of 15- 25,but the percentage of plant absorption nitrogen from soil was much higher when the soil C/N ratio was too low( < 15) or high( < 25). Amount of residual nitrogen in soil increased gradually with the soil C/N ratio increasing,the amount of residual nitrogen in C/N = 40 treatment was 1. 32 times than that in CK. With the increasing of soil C/N ratio,fertilizer nitrogen loss decreased at first,and then increased,fertilizer nitrogen loss was the minimum in C/N = 25 treatments( 49. 87%) and the maximum were occurred in CK( 61. 54%). Therefore,regarding the apple growth and nitrogen balance situation,the value of soil C/N ratio in the range of 15- 25 would be favorable for apple growth and could increase effectively nitrogen fixed by soil,reduce nitrogen loss,and improve the nitrogen utilization ratio.
基金supported by the Excellent Youth Science Fund of Henan Province,China(No.242300421147)the National Key Research and Development Program of China(No.2022YFD1500203)+1 种基金the National Natural Science Foundation of China(Nos.42377334 and 42007005)the Joint Fund Project of Henan Province,China(No.232103810009)。
文摘Cropland expansion has caused the loss of soil organic carbon(SOC)and the degradation of microbial communities.Fallowing is an important strategy for soil restoration,and fungi are critical in soil fertilization.This study compared the soil properties and fungal assemblage in two adjacent environments(farmland vs.fallowing)using a 30-year field experiment composed of five treatments:fallowing and agricultural management under no fertilization,chemical fertilization,and chemical fertilization plus cow manure or crop straw.The fallowed soil had more diverse fungi and maintained higher SOC than the artificially managed treatments.Importantly,the relative abundance of Chaetomiaceae was positively correlated with all the carbon components(SOC,dissolved organic carbon,and microbial biomass carbon)simultaneously.An RNA-Seq of Trichocladium uniseriatum,the key fungus affiliated with Chaetomiaceae,showed that straw addition significantly upregulated the genes for T.uniseriatum melanogenesis,resulting in recalcitrant necromass formation.A remarkable carbon dioxide(CO_(2))assimilation capacity of T.uniseriatum was revealed using^(13)C-labelling assay.Therefore,T.uniseriatum improved SOC storage directly by CO_(2)fixation and indirectly by melanogenesis.Fertilization of agricultural systems can stimulate the growth of T.uniseriatum.Inoculation of T.uniseriatum promoted crop growth,facilitating carbon absorption from the roots.This study highlights that the valuable microbial species resources preserved in fallowed soils can improve farmland ecosystems.
基金supported by funds from the National Key R&D Program of China (2016YFC0500909)the TU-ITP and the MRA programs from Tottori UniversitySAKURA Exchange Program in Science from the Japan Science and Technology Agency
文摘Biological soil crusts(BSCs) play important roles in the carbon(C) balance in arid regions. Net C balance of BSCs is strongly dependent on rainfall and consequent activation of microbes in the BSCs. The compensation-rainfall size for BSCs(the minimum rainfall amount for a positive net C balance) is assumed to be different with BSCs of different developmental stages. A field experiment with simulated rainfall amount(SRA) of 0, 1, 5, 10, 20, and 40 mm was conducted to examine the C fluxes and compensation-rainfall size of BSCs in different parts of fixed dunes in the ecotone between the Badain Jaran Desert and the Minqin Oasis. We found algae-lichen crust on the interdunes and crest, algae crust on the leeward side, and lichen-moss crust on the windward. Even a small rainfall(1 mm) can activate both photosynthesis and respiration of all types of BSCs. The gross ecosystem production, ecosystem respiration, and net ecosystem exchange were significantly affected by SRA, hours after the simulated rainfall, position on a dune, and their interactions. The rapid activation of photosynthesis provides a C source and therefore could be responsible for the increase of C efflux after each rewetting. C-uptake and-emission capacity of all the BSCs positively correlated with rainfall size, with the lowest C fluxes on the leeward side. The compensation rainfall for a net C uptake was 3.80, 15.54, 8.62, and 1.88 mm for BSCs on the interdunes, the leeward side, the crest, and the windward side, respectively. The whole dune started to show a net C uptake with an SRA of 5 mm and maximized with an SRA of about 30 mm. The compensation-rainfall size is negatively correlated with chlorophyll content. Our results suggest that BSCs will be favored in terms of C balance, and sand dune stabilization could be sustained with an increasing frequency of 5-10 mm rainfall events in the desert-oasis transitional zone.-
