Biodegradation of polycyclic aromatic hydrocarbons （PAHs） is very difficult in saline-alkaline soil due to the inhibition of microbial growth under saline-alkaline stress. The microorganisms that can most effectivel...Biodegradation of polycyclic aromatic hydrocarbons （PAHs） is very difficult in saline-alkaline soil due to the inhibition of microbial growth under saline-alkaline stress. The microorganisms that can most effectively degrade PAHs were screened by introducing microorganisms immobilized on farm byproducts and assessing the validity of the immobilizing technique for PAHs degradation in pyrene-contaminated saline-alkaline soil. Among the microorganisms examined, it was found that Mycobacterium sp. B2 is the best, and can degrade 82.2% and 83.2% of pyrene for free and immobilized cells after 30 days of incubation. The immobilization technique could increase the degradation of pyrene significantly, especially for fungi. The degradation of pyrene by the immobilized microorganisms Mucor sp. F2, fungal consortium MF and co-cultures of MB＋MF was increased by 161.7% （P 〈 0.05）, 60.1% （P 〈 0.05） and 59.6% （P 〈 0.05） after 30 days, respectively, when compared with free F2, MF and MB＋ME Scanning electron micrographs of the immobilized microstructure proved the positive effects of the immobilized microbial technique on pyrene remediation in saline- alkaline soil, as the interspace of the carder material structure was relatively large, providing enough space for cell growth. Co-cultures of different bacterial and fungal species showed different abilities to degrade PAHs. The present study suggests that Mycobacterium sp. B2 can be employed for in situ bioremediation of PAHs in saline-alkaline soil, and immobilization of fungi on farm byproducts and nutrients as carriers will enhance fungus PAil-degradation ability in saline-alkaline soil.展开更多
Background:Forest succession is an important ecological process and has been studied for more than a century.However,changes in nitrogen(N)availability during succession remain unclear as they may lead to either N sat...Background:Forest succession is an important ecological process and has been studied for more than a century.However,changes in nitrogen(N)availability during succession remain unclear as they may lead to either N satura-tion or N limitation.Here,we propose a conceptual model to illustrate changes in N availability during four stages of secondary succession using the natural abundance of ^(15) N in plant leaves(foliarδ^(15)N).We predicted that N availability would decline in the early stages of succession and then increase in late stages,coinciding with the changes in foliarδ^(15)N,with the inflection point varying in different climate zones.Data on foliarδ^(15)N from 16 succession sequences were synthesized to explore changes in N availability during forest succession.Results:The compiled data were consistent with the proposed conceptual model.Foliarδ^(15)N in boreal and temperate forests decreased significantly in the first two stages of succession(estimated to last at least 66 years in temperate forests),at a rate of 0.18‰and 0.38‰per decade,respectively,and decreased slightly in tropical forests in the first 23 years.Foliarδ^(15)N is projected to increase in later stages in all forests,which is supported by observations in both temperate and tropical forests.The inflection points of N availability when N limitation peaked during succession were different in different climate zones,implying different ecosystem N turnovers.Conclusions:Our study reconciles the controversies regarding changes in N availability during forest secondary succession.Our findings are also useful for predicting the recovery of N and carbon accumulation during succession.Nonetheless,studies on forest secondary succession using foliarδ^(15)N have thus far been limited,and more research should be conducted to further verify the conceptual model proposed here.展开更多
基金supported by the National Science Foundation of China(No.41101295)the Natural Science Fund Project of Liaoning Province(No.201102226)+1 种基金the Open Foundation of Key Laboratory of Industrial Ecology and Environmental Engineering(MOE)(No.KLIEEE-09-04)the Key Program of National Science Foundation of China(No.40930739)
文摘Biodegradation of polycyclic aromatic hydrocarbons （PAHs） is very difficult in saline-alkaline soil due to the inhibition of microbial growth under saline-alkaline stress. The microorganisms that can most effectively degrade PAHs were screened by introducing microorganisms immobilized on farm byproducts and assessing the validity of the immobilizing technique for PAHs degradation in pyrene-contaminated saline-alkaline soil. Among the microorganisms examined, it was found that Mycobacterium sp. B2 is the best, and can degrade 82.2% and 83.2% of pyrene for free and immobilized cells after 30 days of incubation. The immobilization technique could increase the degradation of pyrene significantly, especially for fungi. The degradation of pyrene by the immobilized microorganisms Mucor sp. F2, fungal consortium MF and co-cultures of MB＋MF was increased by 161.7% （P 〈 0.05）, 60.1% （P 〈 0.05） and 59.6% （P 〈 0.05） after 30 days, respectively, when compared with free F2, MF and MB＋ME Scanning electron micrographs of the immobilized microstructure proved the positive effects of the immobilized microbial technique on pyrene remediation in saline- alkaline soil, as the interspace of the carder material structure was relatively large, providing enough space for cell growth. Co-cultures of different bacterial and fungal species showed different abilities to degrade PAHs. The present study suggests that Mycobacterium sp. B2 can be employed for in situ bioremediation of PAHs in saline-alkaline soil, and immobilization of fungi on farm byproducts and nutrients as carriers will enhance fungus PAil-degradation ability in saline-alkaline soil.
基金partially supported by the National Key Research and Development Program of China(2016YFA0600104)supported by donations made by Delos Living LLC,and the Cyrus Tang Foundation+2 种基金supported by the National Natural Science Foundation of China(41471419)Beijing Institute of Urban Planningsupported by the Fundamental Research Funds for the Central Universities(CCNU19TD002).
基金supported by National Key Research and Development Program of China(No.2016YFA0600802)K.C.Wong Education Foundation(GJTD-2018–07)+1 种基金Liaoning Vitalization Talents Program(XLYC1902016)the National Natural Science Foundation of China(41773094,31901134)。
文摘Background:Forest succession is an important ecological process and has been studied for more than a century.However,changes in nitrogen(N)availability during succession remain unclear as they may lead to either N satura-tion or N limitation.Here,we propose a conceptual model to illustrate changes in N availability during four stages of secondary succession using the natural abundance of ^(15) N in plant leaves(foliarδ^(15)N).We predicted that N availability would decline in the early stages of succession and then increase in late stages,coinciding with the changes in foliarδ^(15)N,with the inflection point varying in different climate zones.Data on foliarδ^(15)N from 16 succession sequences were synthesized to explore changes in N availability during forest succession.Results:The compiled data were consistent with the proposed conceptual model.Foliarδ^(15)N in boreal and temperate forests decreased significantly in the first two stages of succession(estimated to last at least 66 years in temperate forests),at a rate of 0.18‰and 0.38‰per decade,respectively,and decreased slightly in tropical forests in the first 23 years.Foliarδ^(15)N is projected to increase in later stages in all forests,which is supported by observations in both temperate and tropical forests.The inflection points of N availability when N limitation peaked during succession were different in different climate zones,implying different ecosystem N turnovers.Conclusions:Our study reconciles the controversies regarding changes in N availability during forest secondary succession.Our findings are also useful for predicting the recovery of N and carbon accumulation during succession.Nonetheless,studies on forest secondary succession using foliarδ^(15)N have thus far been limited,and more research should be conducted to further verify the conceptual model proposed here.
基金This work was supported by National Natural Science Foundation of China （No.81560502）, Newcomer Award for Doctoral Student in Yunnan Province （No.601152706） and PhD Innovation Fund of Kunming Medical University （No.2017D004）.
