Stoichiometry has long been addressed in the studies of ecosystem ecology, but it was almost ignored for a long time. Until recently, ecologists have become aware that stoichiometry could provide a new tool to study e...Stoichiometry has long been addressed in the studies of ecosystem ecology, but it was almost ignored for a long time. Until recently, ecologists have become aware that stoichiometry could provide a new tool to study ecology from genes to the biosphere. Among this trend, N:P stoichiometry is used actively in ecological interactions since nitrogen (N) and phosphorus (P) are the two most important elements in most ecosystems. This article reviews the application of N:P stoichiometry to the studies of ecological problems at different levels, including ecosystem, community and species. Meanwhile, we also provide the cellular basis of N:P stoichiometry, identify the shortages in the use of N:P stoichiometry theory, and put forward some perspectives for future research to be conducted.展开更多
Gap statistic is a well-known index of clustering validity, but its realization is difficult to be comprehended and accurately determined. A direct method is presented to improve the performance of the Gap statistic, ...Gap statistic is a well-known index of clustering validity, but its realization is difficult to be comprehended and accurately determined. A direct method is presented to improve the performance of the Gap statistic, which applies the two-order difference of within-cluster dispersion to replace the constructed null reference distribution in the Gap statistic. Hence, the realization of the Gap statistic becomes easy and is reformulated, and its uncertainty in applications is reduced. Also, the limitation of the Gap statistic is analyzed by two typical examples, that is, the Gap statistic is difficult to be applied to the dataset that contains strong-overlap or uneven-density clusters. Experiments verify the usefulness of the proposed method.展开更多
Aims Leaf nutrient resorption is sensitive to changes in soil nutrients.However,the effects of N deposition on nutrient resorption efficiency(NuRE)in plant macro-nutrients remain unclear.Poplar(Populus deltoids)is one...Aims Leaf nutrient resorption is sensitive to changes in soil nutrients.However,the effects of N deposition on nutrient resorption efficiency(NuRE)in plant macro-nutrients remain unclear.Poplar(Populus deltoids)is one of the most extensively cultivated hardwood species worldwide.We explored general patterns and dominant drivers of NuRE and stoichiometry of poplar plantations in response to N addition.Methods We conducted a 4-year N-addition experiment to explore NuRE and stoichiometric responses to N addition in two poplar(P.deltoids)plantations(8-and 12-year-old stands)in a coastal region of eastern China.We measured soil and foliar(green and senesced leaves)concentrations of nitrogen(N),phosphorus(P),potassium(K),calcium(Ca)and magnesium(Mg)for a series of N addition treatments including N_(0)(0 kg N ha^(−1)yr^(−1)),N_(1)(50 kg N ha^(−1)yr^(−1)),N_(2)(100 kg N ha^(−1)yr^(−1)),N_(3)(150 kg N ha^(−1)yr^(−1))and N_(4)(300 kg N ha^(−1)yr^(−1)).Important Findings Consistent for(both)8-and 12-year-old stands,N addition did not affect the NuRE and stoichiometry(with the exception of CaRE and CaRE:MgRE ratio).N resorption efficiency–P resorption efficiency(NRE–PRE)scaling slopes were consistently less than 1.0 under N addition.These results suggest that NRE generally decouples from PRE within each N treatment.Moreover,these results point to robust control of green leaf nutritional status on nutrient resorption processes as indicated by the positive relationships between NuRE and green leaf nutrient concentrations.Our findings provided a direct evidence that growth in 12-year-old poplar plantations was N-limited in the coastal region of eastern China.展开更多
Among water blooms,cyanobacteria bloom occurs over the widest range and is much more harmful than other blooms.Its occurrence in inland water bodies is affected by many factors,such as meteorology,hydrology,and human ...Among water blooms,cyanobacteria bloom occurs over the widest range and is much more harmful than other blooms.Its occurrence in inland water bodies is affected by many factors,such as meteorology,hydrology,and human activities.Therefore,the study of the causes of cyanobacterial bloom has become a major focus of scholars.The China Knowledge Network Journal Database contains 143 papers from China and abroad from the years 2004 to 2019 that are relevant to the study of cyanobacteria bloom.We begin by analyzing keywords in these studies and creating a keyword distribution map which indicates the factors related to the blooms.Based on parameters such as the frequency of words appearing in the text,the full text of each of the 143 papers is analyzed to form a word cloud created by a program written in Python language.After irrelevant terms are eliminated,the word cloud map can reveal potential factors that were not identified by keywords alone.After completing this macro analysis,we examined approximately 100 related papers from the China Knowledge Network Journal Database and Web of Science Database published from 2014 to 2019.Finally,we summarize the main reasons for the outbreak of water blooms.The factors causing blooms can be divided into natural factors and human factors.Among the natural factors are illumination,water temperature and nutrient salt conditions.The human factors are generally related to large-scale water conservancy projects.This paper analyzes and summarizes these factors,and provides a reference to aid in the prevention and treatment of algal blooms.The information in the paper has a certain practical significance for the protection of water environments.展开更多
Tropical mountain ecosystems are usually colonized by numerous invasive plant species and represent an ideal‘natural laboratory’to study the effects of altitude on plant invasion.The aim of this study was to investi...Tropical mountain ecosystems are usually colonized by numerous invasive plant species and represent an ideal‘natural laboratory’to study the effects of altitude on plant invasion.The aim of this study was to investigate the soil chemical and microbiological properties along an altitudinal gradient on a mountain colonized by the invader Ageratina adenophora.Rhizosphere soil of A.adenophora was collected over an altitudinal gradient(1400–2400 m)in Ailao Shan,China.We determined soil organic carbon(C),nutrient contents,enzyme activities,bacterial community composition as well as C and nitrogen(N)contents of the plant roots.Ecoenzymatic stoichiometric indices were calculated to estimate the relative C,N or P limitations of the microbial community.There was a significant effect of altitude on soil organic C in the rhizosphere,and a turning point in these measured variables was detected at an altitude of 2000 m.At low elevations,the rapid growth of invasive plants depleted the deficient phosphorus(P)in tropical soils,leading to microbial P limitation;at high elevations,microbes invested more energy to obtain C from resistant litter,leading to microbial C limitation.Bacterial beta diversity and soil pH contributed most to the altitudinal differences in ecoenzymatic stoichiometry,and Proteobacteria and Acidobacteria were the dominant bacterial phyla that determined the nutrient uptake status of microorganisms.These results demonstrate how microbial nutrient acquisition belowground of A.adenophora along an altitudinal gradient,which could contribute to further knowledge about the effects of altitude on biological invasion.展开更多
Aims Global change may cause unparalleled supplies of soil nutrients and further lead to stoichiometric imbalance of nitrogen(N)and phosphorus(P)in terrestrial plants.While previous studies had reported the effects of...Aims Global change may cause unparalleled supplies of soil nutrients and further lead to stoichiometric imbalance of nitrogen(N)and phosphorus(P)in terrestrial plants.While previous studies had reported the effects of global change factors on plant N,P contents and their ratios,few had examined whether or how these factors may influence the scaling of these two elements.Methods Taking advantage of a manipulative experiment with altered precipitation,warming and N addition,and using the general scaling function N=βPα,we examined how the scaling of plant N to P may respond to global change factors in a Loess grassland in northwestern China.Important Findings We found that precipitation reduction(PR)and warming decreased plant P concentrations,while N addition increased plant N concentrations,resulting in increased N:P ratios.The slopes of the linear regressions between plant N and P(i.e.log-transformed N versus P)did not change significantly,whereas the intercepts increased significantly under PR,warming and N addition.These results indicate that global change factors may not affect the synergistic variation of plant N and P,showing a closely coupled relationship between them.Our findings may help to better understand plant nutrient dynamics and element balance in a changing world.展开更多
文摘Stoichiometry has long been addressed in the studies of ecosystem ecology, but it was almost ignored for a long time. Until recently, ecologists have become aware that stoichiometry could provide a new tool to study ecology from genes to the biosphere. Among this trend, N:P stoichiometry is used actively in ecological interactions since nitrogen (N) and phosphorus (P) are the two most important elements in most ecosystems. This article reviews the application of N:P stoichiometry to the studies of ecological problems at different levels, including ecosystem, community and species. Meanwhile, we also provide the cellular basis of N:P stoichiometry, identify the shortages in the use of N:P stoichiometry theory, and put forward some perspectives for future research to be conducted.
基金National Natural Science Foundation of China(No.60572065, 60772080, 60532020)
文摘Gap statistic is a well-known index of clustering validity, but its realization is difficult to be comprehended and accurately determined. A direct method is presented to improve the performance of the Gap statistic, which applies the two-order difference of within-cluster dispersion to replace the constructed null reference distribution in the Gap statistic. Hence, the realization of the Gap statistic becomes easy and is reformulated, and its uncertainty in applications is reduced. Also, the limitation of the Gap statistic is analyzed by two typical examples, that is, the Gap statistic is difficult to be applied to the dataset that contains strong-overlap or uneven-density clusters. Experiments verify the usefulness of the proposed method.
基金This study is financially supported by the Natural Science Key Fund for Colleges and Universities of Jiangsu Province of China(17KJA180006)the Six Talent Peaks Program of Jiangsu Province(JY-041 and TD-XYDXX-006)+1 种基金the'5151'Talent Program of Nanjing Forestry University,the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD),the Doctorate Fellowship Foundation of Nanjing Forestry University,the Research Innovation Program for College Graduates of Jiangsu Province(KYLX16_0833)the Scientific and Technological Innovation Program for College Students of Nanjing Forestry University(DXSKC-201617).
文摘Aims Leaf nutrient resorption is sensitive to changes in soil nutrients.However,the effects of N deposition on nutrient resorption efficiency(NuRE)in plant macro-nutrients remain unclear.Poplar(Populus deltoids)is one of the most extensively cultivated hardwood species worldwide.We explored general patterns and dominant drivers of NuRE and stoichiometry of poplar plantations in response to N addition.Methods We conducted a 4-year N-addition experiment to explore NuRE and stoichiometric responses to N addition in two poplar(P.deltoids)plantations(8-and 12-year-old stands)in a coastal region of eastern China.We measured soil and foliar(green and senesced leaves)concentrations of nitrogen(N),phosphorus(P),potassium(K),calcium(Ca)and magnesium(Mg)for a series of N addition treatments including N_(0)(0 kg N ha^(−1)yr^(−1)),N_(1)(50 kg N ha^(−1)yr^(−1)),N_(2)(100 kg N ha^(−1)yr^(−1)),N_(3)(150 kg N ha^(−1)yr^(−1))and N_(4)(300 kg N ha^(−1)yr^(−1)).Important Findings Consistent for(both)8-and 12-year-old stands,N addition did not affect the NuRE and stoichiometry(with the exception of CaRE and CaRE:MgRE ratio).N resorption efficiency–P resorption efficiency(NRE–PRE)scaling slopes were consistently less than 1.0 under N addition.These results suggest that NRE generally decouples from PRE within each N treatment.Moreover,these results point to robust control of green leaf nutritional status on nutrient resorption processes as indicated by the positive relationships between NuRE and green leaf nutrient concentrations.Our findings provided a direct evidence that growth in 12-year-old poplar plantations was N-limited in the coastal region of eastern China.
基金Development and Testing Project of Algal Bloom Remote Sensing Processing Module(2018-S018)。
文摘Among water blooms,cyanobacteria bloom occurs over the widest range and is much more harmful than other blooms.Its occurrence in inland water bodies is affected by many factors,such as meteorology,hydrology,and human activities.Therefore,the study of the causes of cyanobacterial bloom has become a major focus of scholars.The China Knowledge Network Journal Database contains 143 papers from China and abroad from the years 2004 to 2019 that are relevant to the study of cyanobacteria bloom.We begin by analyzing keywords in these studies and creating a keyword distribution map which indicates the factors related to the blooms.Based on parameters such as the frequency of words appearing in the text,the full text of each of the 143 papers is analyzed to form a word cloud created by a program written in Python language.After irrelevant terms are eliminated,the word cloud map can reveal potential factors that were not identified by keywords alone.After completing this macro analysis,we examined approximately 100 related papers from the China Knowledge Network Journal Database and Web of Science Database published from 2014 to 2019.Finally,we summarize the main reasons for the outbreak of water blooms.The factors causing blooms can be divided into natural factors and human factors.Among the natural factors are illumination,water temperature and nutrient salt conditions.The human factors are generally related to large-scale water conservancy projects.This paper analyzes and summarizes these factors,and provides a reference to aid in the prevention and treatment of algal blooms.The information in the paper has a certain practical significance for the protection of water environments.
基金supported by Yunnan Fundamental Research Projects(202101AU070150)the National Natural Science Foundation of China(31870524,32071663,32071661).
文摘Tropical mountain ecosystems are usually colonized by numerous invasive plant species and represent an ideal‘natural laboratory’to study the effects of altitude on plant invasion.The aim of this study was to investigate the soil chemical and microbiological properties along an altitudinal gradient on a mountain colonized by the invader Ageratina adenophora.Rhizosphere soil of A.adenophora was collected over an altitudinal gradient(1400–2400 m)in Ailao Shan,China.We determined soil organic carbon(C),nutrient contents,enzyme activities,bacterial community composition as well as C and nitrogen(N)contents of the plant roots.Ecoenzymatic stoichiometric indices were calculated to estimate the relative C,N or P limitations of the microbial community.There was a significant effect of altitude on soil organic C in the rhizosphere,and a turning point in these measured variables was detected at an altitude of 2000 m.At low elevations,the rapid growth of invasive plants depleted the deficient phosphorus(P)in tropical soils,leading to microbial P limitation;at high elevations,microbes invested more energy to obtain C from resistant litter,leading to microbial C limitation.Bacterial beta diversity and soil pH contributed most to the altitudinal differences in ecoenzymatic stoichiometry,and Proteobacteria and Acidobacteria were the dominant bacterial phyla that determined the nutrient uptake status of microorganisms.These results demonstrate how microbial nutrient acquisition belowground of A.adenophora along an altitudinal gradient,which could contribute to further knowledge about the effects of altitude on biological invasion.
基金supported by the National Natural Science Foundation of China(31800382 and 31971435)the Fundamental Research Funds for the Central Universities(KJQN201917).
文摘Aims Global change may cause unparalleled supplies of soil nutrients and further lead to stoichiometric imbalance of nitrogen(N)and phosphorus(P)in terrestrial plants.While previous studies had reported the effects of global change factors on plant N,P contents and their ratios,few had examined whether or how these factors may influence the scaling of these two elements.Methods Taking advantage of a manipulative experiment with altered precipitation,warming and N addition,and using the general scaling function N=βPα,we examined how the scaling of plant N to P may respond to global change factors in a Loess grassland in northwestern China.Important Findings We found that precipitation reduction(PR)and warming decreased plant P concentrations,while N addition increased plant N concentrations,resulting in increased N:P ratios.The slopes of the linear regressions between plant N and P(i.e.log-transformed N versus P)did not change significantly,whereas the intercepts increased significantly under PR,warming and N addition.These results indicate that global change factors may not affect the synergistic variation of plant N and P,showing a closely coupled relationship between them.Our findings may help to better understand plant nutrient dynamics and element balance in a changing world.
