Phyllosphere algae are common in tropical rainforests,forming visible biofilms or spots on plant leaf surfaces.However,knowledge of phyllosphere algal diversity and the environmental factors that drive that diversity ...Phyllosphere algae are common in tropical rainforests,forming visible biofilms or spots on plant leaf surfaces.However,knowledge of phyllosphere algal diversity and the environmental factors that drive that diversity is limited.The aim of this study is to identify the environmental factors that drive phyllosphere algal community composition and diversity in rainforests.For this purpose,we used single molecule real-time sequencing of full-length 18S rDNA to characterize the composition of phyllosphere microalgal communities growing on four host tree species(Ficus tikoua,Caryota mitis,Arenga pinnata,and Musa acuminata) common to three types of forest over four months at the Xishuangbanna Tropical Botanical Garden,Yunnan Province,China.Environmental 18S rDNA sequences revealed that the green algae orders Watanabeales and Trentepohliales were dominant in almost all algal communities and that phyllosphere algal species richness and biomass were lower in planted forest than in primeval and reserve rainforest.In addition,algal community composition differed significantly between planted forest and primeval rainforest.We also found that algal communities were affected by soluble reactive phosphorous,total nitrogen,and ammonium contents.Our findings indicate that algal community structure is significantly related to forest type and host tree species.Furthermore,this study is the first to identify environmental factors that affect phyllosphere algal communities,significantly contributing to future taxonomic research,especially for the green algae orders Watanabeales and Trentepohliales.This research also serves as an important reference for molecular diversity analysis of algae in other specific habitats,such as epiphytic algae and soil algae.展开更多
To understand the effect of regime shift in Caohai Lake in Yunnan-Guizhou Plateau,SW China from submerged macrophyte dominance to phytoplankton dominance on the specification and distribution of phosphorus and on ecol...To understand the effect of regime shift in Caohai Lake in Yunnan-Guizhou Plateau,SW China from submerged macrophyte dominance to phytoplankton dominance on the specification and distribution of phosphorus and on ecological and environmental states,changes in phosphorus specification in the sediments and water were studied.The form,composition,and distribution of phosphorus in sediment were sampled in July 2020(before regime shift)and July 2021(after regime shift)were analyzed.Results reveal that phosphorus content in sediment was lower than that those of Erhai Lake and Dianchi Lake,Yunnan,SW China,on the same plateau,and was lower than those of Taihu Lake,Chaohu Lake,and Poyang Lake in the middle-lower Changjiang(Yangtze)River Plain.Organic phosphorus(Or-P)was the main form(up to 60%),followed by inactive phosphorus(Ina-P),and the active phosphorus(Act-P),the least,which is opposite to those of Taihu Lake and Poyang Lake in the middle-lower Changjiang River Plain in the eastern China.Or-P content was high,indicating a high potential risk of phosphorous release.After the regime shift,the total phosphorus in sediment decreased from 0.87±0.13 to 0.70±0.13 g/kg.The proportion of Or-P and Act-P decreased from 68.23% to 65.32% and from 5.35% to 4.69%,respectively.In contrast,the proportion of Ina-P increased from 26.42% to 29.99%.The Moran’s I index revealed that the heterogeneity of the spatial distributions of the total phosphorus(S-TP)and Act-P in the sediments before regime shift was significant(P<0.1).However,the heterogeneity of the spatial distributions of S-TP and the various forms of phosphorus after regime shift was not significant(P>0.05).The regime shift aggravated the eutrophication of the lake,the trophic level index(TLI)increased from 48.42 to 54.49(P<0.01),and the previously mesotrophic lake became a mildly eutrophic lake.The results of this study revealed the impact of regime shift in the lake from submerged macrophyte dominance to phytoplankton dominance on the composition and spatial distribution of phosphorus in sediments and provided a basis for the restoration of eutrophicated and aquatic ecosystem degraded lakes.展开更多
Aquifer connectivity could greatly affect groundwater flow and further control the contaminant transport in fractured medium.However,assessing connectivity of fractured aquifer at regional scales is still a challenge ...Aquifer connectivity could greatly affect groundwater flow and further control the contaminant transport in fractured medium.However,assessing connectivity of fractured aquifer at regional scales is still a challenge because such connectivity is difficult to be measured directly.This study proposes a framework for assessing connectivity of a fractured aquifer,with Qitaihe area,Heilongjiang Province,northeastern China as an illustrating study area.The 3-D finite difference numerical models were established to interpret the results of three multi-well pumping tests and inversely estimate the distribution of hydraulic conductivity(K)in the fractured aquifer.A static connectivity metric of the minimum hydraulic resistance(MHR)was calculated,based on the optimized K-field,to evaluate the hydraulic connectivity in the aquifer,and the corresponding least resistance paths(LRPs)were identified.The results indicate a better horizontal connectivity in the fractured aquifer in the northeastern and middle parts than in the southwestern part of the study area.The identified LRP indicated that the preferential flow channels at regional scales were controlled mainly by aquifer connectivity instead of local high-K zones.The results of this study can provide a method for aquifer connectivity estimation at regional scales.展开更多
Na Cl O has been widely used to restore membrane flux in practical membrane cleaning processes,which would induce the formation of toxic halogenated byproducts.In this study,we proposed a novel heatactivated peroxydis...Na Cl O has been widely used to restore membrane flux in practical membrane cleaning processes,which would induce the formation of toxic halogenated byproducts.In this study,we proposed a novel heatactivated peroxydisulfate(heat/PDS)process to clean the membrane fouling derived from humic acid(HA).The results show that the combination of heat and PDS can achieve almost 100%recovery of permeate flux after soaking the HA-fouled membrane in 1 mmol/L PDS solution at 50℃ for 2 h,which is attributed to the changes of HA structure and enhanced detachment of foulants from membranes.The properties of different treated membranes are characterized by scanning electron microscopy(SEM),atomic force microscope(AFM),attenuated total reflection Fourier transform infrared spectroscopy(ATRFTIR),and X-ray photoelectron spectroscopy(XPS),demonstrating that the reversible and irreversible foulants could be effectively removed by heat/PDS cleaning.The filtration process and fouling mechanism of the cleaned membrane were close to that of the virgin membrane,illustrating the good reusability of the cleaned membrane.Additionally,heat/PDS which can avoid the generation of halogenated byproducts shows comparable performance to Na Cl O on membrane cleaning and high performance for the removal of fouling caused by sodium alginate(SA),HA-bovine serum albumin(BSA)-SA mixture and algae,further suggesting that heat/PDS would be a potential alternative for membrane cleaning in practical application.展开更多
The normalized difference vegetation index(NDVI)is the most widely used vegetation index for monitoring vegetation vigor and cover.As NDVI time series are usually derived at coarse or medium spatial resolutions,pixel ...The normalized difference vegetation index(NDVI)is the most widely used vegetation index for monitoring vegetation vigor and cover.As NDVI time series are usually derived at coarse or medium spatial resolutions,pixel size often represents a mixture of vegetated and non-vegetated surfaces.In heterogeneous urban areas,mixed pixels impede the accurate estimation of gross primary productivity(GPP).To address the mixed pixel effect on'NDVI time series and GPP estimation,we proposed a framework to extract subpixel vegetation NDVI(NDVI_(vege))from Landsat OLI images in urban areas,using endmember fractions,mixed NDVI(NDVI_(mix)),and NDVI.of non-vegetation,endmembers.Results demonstrated that the NDVI_(vege) extracted by this framework agreed well with the true NDVI_(vege) cross seasons and vegetation fractions,with R^(2) ranging from 0.74 to 0.82 and RMSE ranging from 0.03 to 0.04.The NDVI_(vege) time series was applied to evaluate vegetation GP in Wuhan,China.The total annual GPp estimated with NDVI_(vege) was 28-35%higher than the total annual GPP estimated with NDVI_(mix) implying uncertainty in the GPP estimations caused by mixed pixels.This study showed the potential of the proposed framework to resolve NDVI_(vege) for characterizing vegetation dynamics in heterogeneous areas.展开更多
基金supported by the National Natural Science Foundation of China (Grant no.31870189 and 32000168)。
文摘Phyllosphere algae are common in tropical rainforests,forming visible biofilms or spots on plant leaf surfaces.However,knowledge of phyllosphere algal diversity and the environmental factors that drive that diversity is limited.The aim of this study is to identify the environmental factors that drive phyllosphere algal community composition and diversity in rainforests.For this purpose,we used single molecule real-time sequencing of full-length 18S rDNA to characterize the composition of phyllosphere microalgal communities growing on four host tree species(Ficus tikoua,Caryota mitis,Arenga pinnata,and Musa acuminata) common to three types of forest over four months at the Xishuangbanna Tropical Botanical Garden,Yunnan Province,China.Environmental 18S rDNA sequences revealed that the green algae orders Watanabeales and Trentepohliales were dominant in almost all algal communities and that phyllosphere algal species richness and biomass were lower in planted forest than in primeval and reserve rainforest.In addition,algal community composition differed significantly between planted forest and primeval rainforest.We also found that algal communities were affected by soluble reactive phosphorous,total nitrogen,and ammonium contents.Our findings indicate that algal community structure is significantly related to forest type and host tree species.Furthermore,this study is the first to identify environmental factors that affect phyllosphere algal communities,significantly contributing to future taxonomic research,especially for the green algae orders Watanabeales and Trentepohliales.This research also serves as an important reference for molecular diversity analysis of algae in other specific habitats,such as epiphytic algae and soil algae.
基金Supported by the Guizhou Province Science and Technology Plan Project(No.2021470)。
文摘To understand the effect of regime shift in Caohai Lake in Yunnan-Guizhou Plateau,SW China from submerged macrophyte dominance to phytoplankton dominance on the specification and distribution of phosphorus and on ecological and environmental states,changes in phosphorus specification in the sediments and water were studied.The form,composition,and distribution of phosphorus in sediment were sampled in July 2020(before regime shift)and July 2021(after regime shift)were analyzed.Results reveal that phosphorus content in sediment was lower than that those of Erhai Lake and Dianchi Lake,Yunnan,SW China,on the same plateau,and was lower than those of Taihu Lake,Chaohu Lake,and Poyang Lake in the middle-lower Changjiang(Yangtze)River Plain.Organic phosphorus(Or-P)was the main form(up to 60%),followed by inactive phosphorus(Ina-P),and the active phosphorus(Act-P),the least,which is opposite to those of Taihu Lake and Poyang Lake in the middle-lower Changjiang River Plain in the eastern China.Or-P content was high,indicating a high potential risk of phosphorous release.After the regime shift,the total phosphorus in sediment decreased from 0.87±0.13 to 0.70±0.13 g/kg.The proportion of Or-P and Act-P decreased from 68.23% to 65.32% and from 5.35% to 4.69%,respectively.In contrast,the proportion of Ina-P increased from 26.42% to 29.99%.The Moran’s I index revealed that the heterogeneity of the spatial distributions of the total phosphorus(S-TP)and Act-P in the sediments before regime shift was significant(P<0.1).However,the heterogeneity of the spatial distributions of S-TP and the various forms of phosphorus after regime shift was not significant(P>0.05).The regime shift aggravated the eutrophication of the lake,the trophic level index(TLI)increased from 48.42 to 54.49(P<0.01),and the previously mesotrophic lake became a mildly eutrophic lake.The results of this study revealed the impact of regime shift in the lake from submerged macrophyte dominance to phytoplankton dominance on the composition and spatial distribution of phosphorus in sediments and provided a basis for the restoration of eutrophicated and aquatic ecosystem degraded lakes.
基金financially funded by the National Natural Science Foundation of China(Nos.41722208 and 41521001)the Natural Sciences Foundation of Hubei Province of China(No.2019CFA013)the State Administration of Foreign Experts Affairs&the Ministry of Education of China(No.B18049).
文摘Aquifer connectivity could greatly affect groundwater flow and further control the contaminant transport in fractured medium.However,assessing connectivity of fractured aquifer at regional scales is still a challenge because such connectivity is difficult to be measured directly.This study proposes a framework for assessing connectivity of a fractured aquifer,with Qitaihe area,Heilongjiang Province,northeastern China as an illustrating study area.The 3-D finite difference numerical models were established to interpret the results of three multi-well pumping tests and inversely estimate the distribution of hydraulic conductivity(K)in the fractured aquifer.A static connectivity metric of the minimum hydraulic resistance(MHR)was calculated,based on the optimized K-field,to evaluate the hydraulic connectivity in the aquifer,and the corresponding least resistance paths(LRPs)were identified.The results indicate a better horizontal connectivity in the fractured aquifer in the northeastern and middle parts than in the southwestern part of the study area.The identified LRP indicated that the preferential flow channels at regional scales were controlled mainly by aquifer connectivity instead of local high-K zones.The results of this study can provide a method for aquifer connectivity estimation at regional scales.
基金supported by the Natural Science Foundation of China(Nos.52070081,51578258 and 51878308)the National Key Research and Development Program of China(No.2022YFC3203500)。
文摘Na Cl O has been widely used to restore membrane flux in practical membrane cleaning processes,which would induce the formation of toxic halogenated byproducts.In this study,we proposed a novel heatactivated peroxydisulfate(heat/PDS)process to clean the membrane fouling derived from humic acid(HA).The results show that the combination of heat and PDS can achieve almost 100%recovery of permeate flux after soaking the HA-fouled membrane in 1 mmol/L PDS solution at 50℃ for 2 h,which is attributed to the changes of HA structure and enhanced detachment of foulants from membranes.The properties of different treated membranes are characterized by scanning electron microscopy(SEM),atomic force microscope(AFM),attenuated total reflection Fourier transform infrared spectroscopy(ATRFTIR),and X-ray photoelectron spectroscopy(XPS),demonstrating that the reversible and irreversible foulants could be effectively removed by heat/PDS cleaning.The filtration process and fouling mechanism of the cleaned membrane were close to that of the virgin membrane,illustrating the good reusability of the cleaned membrane.Additionally,heat/PDS which can avoid the generation of halogenated byproducts shows comparable performance to Na Cl O on membrane cleaning and high performance for the removal of fouling caused by sodium alginate(SA),HA-bovine serum albumin(BSA)-SA mixture and algae,further suggesting that heat/PDS would be a potential alternative for membrane cleaning in practical application.
基金supported by the National Key Research and Development Program of China(No..2022YFB3903405)National Natural Science Foundation of China(General Program:42171466 and 42171350)the Fundamental Research Funds for the Central Universities(2662021JC002).
文摘The normalized difference vegetation index(NDVI)is the most widely used vegetation index for monitoring vegetation vigor and cover.As NDVI time series are usually derived at coarse or medium spatial resolutions,pixel size often represents a mixture of vegetated and non-vegetated surfaces.In heterogeneous urban areas,mixed pixels impede the accurate estimation of gross primary productivity(GPP).To address the mixed pixel effect on'NDVI time series and GPP estimation,we proposed a framework to extract subpixel vegetation NDVI(NDVI_(vege))from Landsat OLI images in urban areas,using endmember fractions,mixed NDVI(NDVI_(mix)),and NDVI.of non-vegetation,endmembers.Results demonstrated that the NDVI_(vege) extracted by this framework agreed well with the true NDVI_(vege) cross seasons and vegetation fractions,with R^(2) ranging from 0.74 to 0.82 and RMSE ranging from 0.03 to 0.04.The NDVI_(vege) time series was applied to evaluate vegetation GP in Wuhan,China.The total annual GPp estimated with NDVI_(vege) was 28-35%higher than the total annual GPP estimated with NDVI_(mix) implying uncertainty in the GPP estimations caused by mixed pixels.This study showed the potential of the proposed framework to resolve NDVI_(vege) for characterizing vegetation dynamics in heterogeneous areas.
