Tall clonal grasses commonly display competitive advantages with nitrogen(N)enrichment.However,it is currently unknown whether the height is derived from the vegetative or reproductive module.Moreover,it is unclear wh...Tall clonal grasses commonly display competitive advantages with nitrogen(N)enrichment.However,it is currently unknown whether the height is derived from the vegetative or reproductive module.Moreover,it is unclear whether the height of the vegetative or reproductive system regulates the probability of extinction and colonization,and determines species diversity.In this study,the impacts on clonal grasses were studied in a field experiment employing two frequencies(twice a year vs.monthly)crossing with nine N addition rates in a temperate grassland,China.We found that the N addition decreased species frequency and increased extinction probability,but did not change the species colonization probability.A low frequency of N addition decreased species frequency and colonization probability,but increased extinction probability.Moreover,we found that species reproductive height was the best index to predict the extinction probability of clonal grasses in N-enriched conditions.The low frequency of N addition may overestimate the negative effect from N deposition on clonal grass diversity,suggesting that a higher frequency of N addition is more suitable in assessing the ecological effects of N deposition.Overall,this study illustrates that reproductive height was associated with the clonal species extinction probability under N-enriched environment.展开更多
The research of seafloor massive sulfide cutting characteristics is in the initial stage,and experimental methods are rarely used to conduct research.In addition,the mechanism of cutting parameters influencing cutting...The research of seafloor massive sulfide cutting characteristics is in the initial stage,and experimental methods are rarely used to conduct research.In addition,the mechanism of cutting parameters influencing cutting characteristics is not clear.In order to clarify the influence mechanism,the influences of cutting depth and cutting velocity on cutting characteristics are studied experimentally.It is found that with the increase of cutting depth,the load fluctuation is more severe,the breaking yield is increased,the size of the chip is increased,the powdered percentage is decreased,and the externally expanded breaking zone of rock is wider.However,the cutting depth has little effect on the cutting angle,and the breaking angle is between 48°and 61°With the increase in cutting velocity,the number of load fluctuations per unit of time increases significantly,and the size of the chip decreases.However,the breaking yield,powdered percentage,breaking angle and external expansion area remain basically unchanged.The research is of guiding significance to the optimization of the mining head structure and the selection of cutting parameters.展开更多
Nitrogen(N)deposition decreases the temporal stability of ecosystem aboveground biomass production(ecosystem stability).However,little is known about how the responses of ecosystem stability differ based on seasonal N...Nitrogen(N)deposition decreases the temporal stability of ecosystem aboveground biomass production(ecosystem stability).However,little is known about how the responses of ecosystem stability differ based on seasonal N enrichment.By adding N in autumn,winter,or growing season,from October 2014 to May 2020,in a temperate grassland in northern China,we found that only N addition in autumn resulted in a significantly positive correlation between ecosystem mean aboveground net primary productivity(ANPP)and its standard deviation and significantly reduced ecosystem stability.Autumn N-induced reduction in ecosystem stability was associated with the vanished negative effect of community-wide species asynchrony(asynchronous dynamics among populations to environmental perturbations)on the standard deviation of ecosystem ANPP in combination with the emerged positive effect of dominance(Simpson's dominance index that indicates the relative weight of dominant species in a community).Our findings indicate that autumn N addition might overestimate the negative effect of annual atmospheric N deposition on ecosystem stability,suggesting that to better evaluate the influence of N deposition in temperate grasslands,both field experiments and global modeling should consider not only the annual N load but also its seasonal dynamics.Moreover,further studies should pay more attention to the alteration in the ecosystem temporal deviations,which might be more sensitive to human-induced environmental changes.展开更多
基金supported by a grant from the National Natural Science Foundation of China(grant no.32071603 and 32122055)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA26020101)。
文摘Tall clonal grasses commonly display competitive advantages with nitrogen(N)enrichment.However,it is currently unknown whether the height is derived from the vegetative or reproductive module.Moreover,it is unclear whether the height of the vegetative or reproductive system regulates the probability of extinction and colonization,and determines species diversity.In this study,the impacts on clonal grasses were studied in a field experiment employing two frequencies(twice a year vs.monthly)crossing with nine N addition rates in a temperate grassland,China.We found that the N addition decreased species frequency and increased extinction probability,but did not change the species colonization probability.A low frequency of N addition decreased species frequency and colonization probability,but increased extinction probability.Moreover,we found that species reproductive height was the best index to predict the extinction probability of clonal grasses in N-enriched conditions.The low frequency of N addition may overestimate the negative effect from N deposition on clonal grass diversity,suggesting that a higher frequency of N addition is more suitable in assessing the ecological effects of N deposition.Overall,this study illustrates that reproductive height was associated with the clonal species extinction probability under N-enriched environment.
基金supported by the State Key Laboratory of Ocean Engineeringsupported by the Project of Sanya Yazhou Bay Science and Technology City(SCKJ-JYRC-2022-39)+1 种基金Major Projects of Strategic Emerging Industries in Shanghai(BH3230001,19DZ1207300)the Fundamental Research Funds for the Central Universities.
文摘The research of seafloor massive sulfide cutting characteristics is in the initial stage,and experimental methods are rarely used to conduct research.In addition,the mechanism of cutting parameters influencing cutting characteristics is not clear.In order to clarify the influence mechanism,the influences of cutting depth and cutting velocity on cutting characteristics are studied experimentally.It is found that with the increase of cutting depth,the load fluctuation is more severe,the breaking yield is increased,the size of the chip is increased,the powdered percentage is decreased,and the externally expanded breaking zone of rock is wider.However,the cutting depth has little effect on the cutting angle,and the breaking angle is between 48°and 61°With the increase in cutting velocity,the number of load fluctuations per unit of time increases significantly,and the size of the chip decreases.However,the breaking yield,powdered percentage,breaking angle and external expansion area remain basically unchanged.The research is of guiding significance to the optimization of the mining head structure and the selection of cutting parameters.
基金This work was supported by the National Natural Science Foundation of China(32122055 and 32071603)the Key Research Program of Frontier Sciences,Chinese Academy of Sciences(ZDBS-LY-DQC034).
基金funded by the National Natural Science Foundation of China (32122055 and 32071603)the Strategic Priority Research Program of the Chinese Academy of Sciences (XDA26020101).
文摘Nitrogen(N)deposition decreases the temporal stability of ecosystem aboveground biomass production(ecosystem stability).However,little is known about how the responses of ecosystem stability differ based on seasonal N enrichment.By adding N in autumn,winter,or growing season,from October 2014 to May 2020,in a temperate grassland in northern China,we found that only N addition in autumn resulted in a significantly positive correlation between ecosystem mean aboveground net primary productivity(ANPP)and its standard deviation and significantly reduced ecosystem stability.Autumn N-induced reduction in ecosystem stability was associated with the vanished negative effect of community-wide species asynchrony(asynchronous dynamics among populations to environmental perturbations)on the standard deviation of ecosystem ANPP in combination with the emerged positive effect of dominance(Simpson's dominance index that indicates the relative weight of dominant species in a community).Our findings indicate that autumn N addition might overestimate the negative effect of annual atmospheric N deposition on ecosystem stability,suggesting that to better evaluate the influence of N deposition in temperate grasslands,both field experiments and global modeling should consider not only the annual N load but also its seasonal dynamics.Moreover,further studies should pay more attention to the alteration in the ecosystem temporal deviations,which might be more sensitive to human-induced environmental changes.
