The rhizosphere is the most active soil area for material transformation and energy flow of soil,root,and microorganism,which plays an important role in soil biochemical cycling.Although the rhizospheric nitrogen(N)an...The rhizosphere is the most active soil area for material transformation and energy flow of soil,root,and microorganism,which plays an important role in soil biochemical cycling.Although the rhizospheric nitrogen(N)and phosphorous(P)were easily disturbed in the agroecosystem,the effects of rhizosphere on the dynamics of soil N and P cycling have not yet been systematically quantified globally.We summarized the magnitude,direction,and driving forces of rhizosphere effects on agroecosystem's N and P dynamics by 1063 observations and 15 variables from 122 literature.Rhizosphere effects increased available N(AN,9%),available P(AP,11%),and total P(TP,5%),and decreased nitrate N(NO_(3)-N,18%)and ammonia N(NH_(4)-N,16%).The effect of rhizosphere on total N(TN)was not significant.These effects improved AN in tropical(12%)and subtropical(14%)regions.The effect of rhizosphere on TP was greater under subtropical conditions than in other climates.The most substantial effects of the rhizosphere on TP and AP were observed under humid conditions.Rhizosphere effects increased AN and AP in vegetables more than in other crop systems.Application of N>30o kg ha^(-1) had the most significant and positive rhizosphere effects on TN and AN.P application of 100-150 kg ha^(-1) had the greatest rhizosphere effects on TP and AP.These effects also improved the microbial(biomass N and P)and enzymatic aspects(urease,acid phosphatase,and alkaline phosphatase)of soil P and N cycling.Structural equation modeling suggested that aridity indices,fertilizer application rate,soil pH,microbial biomass,and soil enzymes strongly influence the magnitude and direction of the rhizosphere's effect on the P and N cycles.Overall,these findings are critical for improving soil nutrient utilization efficiency and modeling nutrient cycling in the rhizosphereforagricultural systems.展开更多
Complete ammonia oxidizing bacteria,or comammox bacteria(CAOB),can oxidize ammonium to nitrate on its own.Its discovery revolutionized our understanding of biological nitrification,and its distribution in both natural...Complete ammonia oxidizing bacteria,or comammox bacteria(CAOB),can oxidize ammonium to nitrate on its own.Its discovery revolutionized our understanding of biological nitrification,and its distribution in both natural and artificial systems has enabled a reevaluation of the relative contribution of microorganisms to the nitrogen cycle.Its wide distribution,adaptation to oligotrophic medium,and diverse metabolic pathways,means extensive research on CAOB and its application in water treatment can be promoted.Furthermore,the energy-saving characteristics of high oxygen affinity and low sludge production may also become frontier directions for wastewater treatment.This paper provides an overview of the discovery and environmental distribution of CAOB,as well as the physiological characteristics of the microorganisms,such as nutrient medium,environmental factors,enzymes,and metabolism,focusing on future research and the application of CAOB in wastewater treatment.Further research should be carried out on the physiological characteristics of CAOB,to analyze its ecological niche and impact factors,and explore its application potential in wastewater treatment nitrogen cycle improvement.展开更多
River damming is believed to largely intercept nutrients,particularly retain more phosphorus(P)than nitrogen(N),and thus harm primary productivity,fishery catches,and food security downstream,which seriously constrain...River damming is believed to largely intercept nutrients,particularly retain more phosphorus(P)than nitrogen(N),and thus harm primary productivity,fishery catches,and food security downstream,which seriously constrain global hydropower development and poverty relief in undeveloped regions and can drive geo-political disputes between nations along trans-boundary rivers.In this study,we investigated whether reservoirs can instead improve nutrient regimes downstream.We measured different species of N and P as well as microbial functions in water and sediment of cascade reservoirs in the upper Mekong River over 5 years and modelled the influx and outflux of N and P species in each reservoir.Despite partially retaining total N and total P,reservoirs increased the downstream flux of ammonium and soluble reactive phosphorus(SRP).The increase in ammonium and SRP between outflux and influx showed positive linear relationships with the hydraulic residence time of the cascade reservoirs;and the ratio of SRP to dissolved inorganic nitrogen increased along the reservoir cascade.The lentic environment of reservoirs stimulated algae-mediated conversion of nitrate into ammonium in surface water;the hypoxic condition and the priming effect of algae-induced organic matter enhanced release of ammonium from sediment;the synergy of microbial phosphorylation,reductive condition and sediment geochemical properties increased release of SRP.This study is the first to provide solid evidence that hydropower reservoirs improve downstream nutrient bioavailability and N-P balance through a process of retention-transformation-transport,which may benefit primary productivity.These findings could advance our understanding of the eco-environmental impacts of river damming.展开更多
基金supported by National Natural Science Foundation of China(42007073)。
文摘The rhizosphere is the most active soil area for material transformation and energy flow of soil,root,and microorganism,which plays an important role in soil biochemical cycling.Although the rhizospheric nitrogen(N)and phosphorous(P)were easily disturbed in the agroecosystem,the effects of rhizosphere on the dynamics of soil N and P cycling have not yet been systematically quantified globally.We summarized the magnitude,direction,and driving forces of rhizosphere effects on agroecosystem's N and P dynamics by 1063 observations and 15 variables from 122 literature.Rhizosphere effects increased available N(AN,9%),available P(AP,11%),and total P(TP,5%),and decreased nitrate N(NO_(3)-N,18%)and ammonia N(NH_(4)-N,16%).The effect of rhizosphere on total N(TN)was not significant.These effects improved AN in tropical(12%)and subtropical(14%)regions.The effect of rhizosphere on TP was greater under subtropical conditions than in other climates.The most substantial effects of the rhizosphere on TP and AP were observed under humid conditions.Rhizosphere effects increased AN and AP in vegetables more than in other crop systems.Application of N>30o kg ha^(-1) had the most significant and positive rhizosphere effects on TN and AN.P application of 100-150 kg ha^(-1) had the greatest rhizosphere effects on TP and AP.These effects also improved the microbial(biomass N and P)and enzymatic aspects(urease,acid phosphatase,and alkaline phosphatase)of soil P and N cycling.Structural equation modeling suggested that aridity indices,fertilizer application rate,soil pH,microbial biomass,and soil enzymes strongly influence the magnitude and direction of the rhizosphere's effect on the P and N cycles.Overall,these findings are critical for improving soil nutrient utilization efficiency and modeling nutrient cycling in the rhizosphereforagricultural systems.
基金supported by the Foundation for Innovation Research Groups of the National Natural Science Foundation of China(No.62021003)Biological Wastewater Treatment and Process Control Technology,Beijing International Science and technology Cooperation Baseand the Founding projects of Beijing Municipal Commission of Education.
文摘Complete ammonia oxidizing bacteria,or comammox bacteria(CAOB),can oxidize ammonium to nitrate on its own.Its discovery revolutionized our understanding of biological nitrification,and its distribution in both natural and artificial systems has enabled a reevaluation of the relative contribution of microorganisms to the nitrogen cycle.Its wide distribution,adaptation to oligotrophic medium,and diverse metabolic pathways,means extensive research on CAOB and its application in water treatment can be promoted.Furthermore,the energy-saving characteristics of high oxygen affinity and low sludge production may also become frontier directions for wastewater treatment.This paper provides an overview of the discovery and environmental distribution of CAOB,as well as the physiological characteristics of the microorganisms,such as nutrient medium,environmental factors,enzymes,and metabolism,focusing on future research and the application of CAOB in wastewater treatment.Further research should be carried out on the physiological characteristics of CAOB,to analyze its ecological niche and impact factors,and explore its application potential in wastewater treatment nitrogen cycle improvement.
基金supported by the National Key Program of Science and Technology(2022YFC3203900)the National Natural Science Foundation of China(52121006 and 92047303)supported by the Xplorer prize。
文摘River damming is believed to largely intercept nutrients,particularly retain more phosphorus(P)than nitrogen(N),and thus harm primary productivity,fishery catches,and food security downstream,which seriously constrain global hydropower development and poverty relief in undeveloped regions and can drive geo-political disputes between nations along trans-boundary rivers.In this study,we investigated whether reservoirs can instead improve nutrient regimes downstream.We measured different species of N and P as well as microbial functions in water and sediment of cascade reservoirs in the upper Mekong River over 5 years and modelled the influx and outflux of N and P species in each reservoir.Despite partially retaining total N and total P,reservoirs increased the downstream flux of ammonium and soluble reactive phosphorus(SRP).The increase in ammonium and SRP between outflux and influx showed positive linear relationships with the hydraulic residence time of the cascade reservoirs;and the ratio of SRP to dissolved inorganic nitrogen increased along the reservoir cascade.The lentic environment of reservoirs stimulated algae-mediated conversion of nitrate into ammonium in surface water;the hypoxic condition and the priming effect of algae-induced organic matter enhanced release of ammonium from sediment;the synergy of microbial phosphorylation,reductive condition and sediment geochemical properties increased release of SRP.This study is the first to provide solid evidence that hydropower reservoirs improve downstream nutrient bioavailability and N-P balance through a process of retention-transformation-transport,which may benefit primary productivity.These findings could advance our understanding of the eco-environmental impacts of river damming.
