In karst regions,the spatial heterogeneity of soil mineral oxides and environmental variables is still not clear.We investigated the spatial heterogeneity of SiO2,Al2O3,Fe2O3,CaO,MgO,P2O5,K2O,and MnO contents in the s...In karst regions,the spatial heterogeneity of soil mineral oxides and environmental variables is still not clear.We investigated the spatial heterogeneity of SiO2,Al2O3,Fe2O3,CaO,MgO,P2O5,K2O,and MnO contents in the soils of slope land,plantation forest,secondary forest,and primary forest,as well as their relationships with environmental variables in a karst region of Southwest China.Geostatistics,principal component analysis(PCA),and canonical correlation analysis(CCA)were applied to analyze the field data.The results show that SiO2was the predominant mineral in the soils(45.02%–67.33%),followed by Al2O3and Fe2O3.Most soil mineral oxide components had a strong spatial dependence,except for CaO,MgO,and P2O5in the plantation forest,MgO and P2O5in the secondary forest,and CaO in the slope land.Dimensionality reduction in PCA was not appropriate due to the strong spatial heterogeneity in the ecosystems.Soil mineral oxide components,the main factors in all ecosystems,had greater influences on vegetation than those of conventional soil properties.There were close relationships between soil mineral oxide components and vegetation,topography,and conventional soil properties.Mineral oxide components affected species diversity,organic matter and nitrogen levels.展开更多
Understanding the factors that drive variation in species distribution is a central theme of ecological research. Although several studies focused on alpine vegetation, few efforts have been made to identify the envir...Understanding the factors that drive variation in species distribution is a central theme of ecological research. Although several studies focused on alpine vegetation, few efforts have been made to identify the environmental factors that are responsible for the variations in species composition and richness of alpine shrublands using numerical methods. In the present study, we investigated vegetation and associated environmental variables from 45 sample plots in the middle Qilian Mountains of the northwestern China to classify different community types and to elucidate the species- environment relationships. We also estimated the relative contributions of topography and site conditions to spatial distribution patterns of the shrub communities using the variation partitioning. The results showed that four shrub community types were identified and striking differences in fioristic composition were found among them. Species composition greatly depended on elevation, slope, shrub cover, soil pH and organic carbon. The important determinants of species richness were soil bulk density and slope. No significant differences in species richness were detected among the community types. Topography and site conditions had almost equal effects on compositional variation. Nonetheless,a large amount of the variation in species composition remained unexplained.展开更多
Underwater direction of arrival(DOA)estimation has always been a very challenging theoretical and practical problem.Due to the serious non-stationary,non-linear,and non-Gaussian characteristics,machine learning based ...Underwater direction of arrival(DOA)estimation has always been a very challenging theoretical and practical problem.Due to the serious non-stationary,non-linear,and non-Gaussian characteristics,machine learning based DOA estimation methods trained on simulated Gaussian noised array data cannot be directly applied to actual underwater DOA estimation tasks.In order to deal with this problem,environmental data with no target echoes can be employed to analyze the non-Gaussian components.Then,the obtained information about non-Gaussian components can be used to whiten the array data.Based on these considerations,a novel practical sonar array whitening method was proposed.Specifically,based on a weak assumption that the non-Gaussian components in adjacent patches with and without target echoes are almost the same,canonical cor-relation analysis(CCA)and non-negative matrix factorization(NMF)techniques are employed for whitening the array data.With the whitened array data,machine learning based DOA estimation models trained on simulated Gaussian noised datasets can be used to perform underwater DOA estimation tasks.Experimental results illustrated that,using actual underwater datasets for testing with known machine learning based DOA estimation models,accurate and robust DOA estimation performance can be achieved by using the proposed whitening method in different underwater con-ditions.展开更多
To understand the influence patterns and interactions of three important environmental factors,i.e.soil water content,oxygen concentration,and ammonium addition,on methane oxidation,the soils from landfill cover layer...To understand the influence patterns and interactions of three important environmental factors,i.e.soil water content,oxygen concentration,and ammonium addition,on methane oxidation,the soils from landfill cover layers were incubated under full factorial parameter settings.In addition to the methane oxidation rate,the quantities and community structures of methanotrophs were analyzed to determine the methane oxidation capacity of the soils.Canonical correspondence analysis was utilized to distinguish the important impact factors.Water content was found to be the most important factor influencing the methane oxidation rate and Type II methanotrophs,and the optimum value was 15%(w/w),which induced methane oxidation rates 10-and 6-times greater than those observed at 5%(w/w)and 20%(w/w),respectively.Ambient oxygen conditions were more suitable for methane oxidation than 3%oxygen.The addition of 100 mg-N·kg^(-1) drysoil of ammonium induced different effects on methane oxidation capacity when conducted at low or high water content.With regard to the methanotrophs,Type II was sensitive to the changes of water content,while Type I was influenced by oxygen content.Furthermore,the methanotrophic acidophile,Verrucomicrobia,was detected in soils with a pH of 4.9,which extended their known living environments.展开更多
The impacts of rainfall direction on the degree of hydrological response to rainfall properties were investigated using comparative rainfall-runoff experiments on a small-scale slope(4 m×1 m),as well as canonical...The impacts of rainfall direction on the degree of hydrological response to rainfall properties were investigated using comparative rainfall-runoff experiments on a small-scale slope(4 m×1 m),as well as canonical correlation analysis(CCA).The results of the CCA,based on the observed data showed that,under conditions of both upstream and downstream rainfall movements,the hydrological process can be divided into instantaneous and cumulative responses,for which the driving forces are rainfall intensity and total rainfall,and coupling with splash erosion and wash erosion,respectively.The response of peak runoff(Pr)to intensity-dominated rainfall action appeared to be the most significant,and also runoff(R)to rainfall-dominated action,both for upstream-and downstream-moving conditions.Furthermore,the responses of sediment erosion in downstream-moving condition were more significant than those in upstream-moving condition.This study indicated that a CCA between rainfall and hydrological characteristics is effective for further exploring the rainfall-runoff-erosion mechanism under conditions of moving rainfall,especially for the downstream movement condition.展开更多
Kalam Kohistan is a dry,temperate hilly region in the Hindu Raj Series of the Greater Hindu Kush Mountains with diverse forests.As plant distribution and composition is expression of a range of various environmental v...Kalam Kohistan is a dry,temperate hilly region in the Hindu Raj Series of the Greater Hindu Kush Mountains with diverse forests.As plant distribution and composition is expression of a range of various environmental variables,ecological and floristic attributes of vegetation in the Laikot Forests were therefore evaluated via consecutive explorative trips.These forests have not been evaluated ecologically before due to harsh climatic conditions and issues of accessibility and the study in hand is one of the first in its nature.Quantitative ecological techniques were used to sample forest vegetation and identify species in quadrats of 2 m×2 m for herbs,5 m×5 m for shrubs and 10 m×10 m for trees.All the data of 195 plant species and environmental factors were analyzed via Two-way Cluster Analysis and Canonical Correspondence Analysis using PCORD and CANOCO software.Among 195 plant species from 63 families were 27 species of Asteraceae,the most-speciose family,followed by Poaceae(20 spp.).The dominant life form was therophyte(86 spp.;44%share),followed by phanerophyte(41 spp.;21%share).For the leaf size spectrum,most prevalent was nanophyll(73 spp.;44%)followed by microphyll(66 spp.,34%)and mesophyll(44 spp.;23%).Calcium carbonate,pH,potassium,sand,silt,organic matter,slope aspect and grazing significantly influenced species composition,distribution and habitat.The floristic variation in the region was diverse due to elevational and aspect gradients and thus devided into three zones.This vegetation zonation can be utilized for forest management,species and habitat conservation.Both in situ and ex situ conservation of threatened plant species may improve their conservation status in future if address properly.展开更多
An approach is proposed for predicting turning and acceleration motion trend of the tropical cyclones over the South China Sea for 72 h in the extrapolated track coordinates.Cross-track (CT)and along-track(AT)componen...An approach is proposed for predicting turning and acceleration motion trend of the tropical cyclones over the South China Sea for 72 h in the extrapolated track coordinates.Cross-track (CT)and along-track(AT)components are defined according to the persistently extrapolated track coodinates based on observed positions at the initial and past 24 h times.A kind of straight- forward measure may be provided with CT and AT components for typhoon turning motion and ac- celeration motion.Canonical correlation analysis(CCA)is performed to reveal the correlaotions be- tween tropical cyclone tracks and environmental 500 hPa geopotential height fields.A stepwise dis- criminate analysis technique is adopted to derive the classification functions of the respective three categories for AT and CT components.Especially,categorical combinations of CT and AT compo- nents are divided into possible 9 regions corresponding with tropical cyclone behaviors.Not only can 9 motion trends of a tropical cyclone be predicted,but also the location and its maximum error at least in certain direction are available.The perfect prediction(PP)verifications indicate that the percent corrects for the CT and AT categories are 67% and 69% in the independent samples,73% and 53% in the dependent samples,respectively,higher than that of 33.3% for random chance; moreover,the rate for successfully forecasting that in which one of the nine regions the tropical cy- clones will fall at 72 h is about 40%,also higher than the stochastic probability of 11%.The method has been proved to be skillful and promising.展开更多
Introduction:Plant communities and soil factors might interact with each other in different temporal and spatial scales,which can influence the patterns and processes of the wetland ecosystem.To get a better understan...Introduction:Plant communities and soil factors might interact with each other in different temporal and spatial scales,which can influence the patterns and processes of the wetland ecosystem.To get a better understanding of the distribution of plants in wetlands and analyze their associations with environmental soil factors,the structure and types of plant communities in the eastern shore area of Lake Taihu were analyzed by two-way indicator species analysis and canonical correspondence analysis(CCA)ordination.The spatial distribution patterns of vegetation and the main factors affecting the distributions were investigated.Outcomes:Sixty-six sampling sites were selected to obtain vegetation species and soil environmental factor data.Results showed that 22 species from the 66 sites could be divided into seven communities:I:Arundo donax;II:A.donax+Phragmites australis;III:Zizania latifolia+Typha orientalis;IV:P.australis+Alternanthera philoxeroides+Polygonum hydropiper;V:P.australis;VI:P.australis+Humulus scandens;and VII:Erigeron acer+Ipomoea batatas+Rumex acetosa.Plant species and soil factors in the CCA analysis showed that I.batatas,E.acer,Chenopodium album,Polygonum lapathifolium,and Acalypha australis were mainly affected by pH,whereas Echinochloa crus-galli,Setaria viridis,and H.scandens were mainly affected by soil total phosphorus.Mentha canadensis and A.donax were mainly affected by soil conductivity,A.philoxeroides was mainly affected by soil organic matter and,Z.latifolia,Metaplexis japonica and P.hydropiper were mainly affected by available phosphorus.Conclusion:These results indicated that different plants adapted to different soil environmental factors and provided basic information on the diversity of Lake Taihu wetland vegetation.展开更多
[Objectives]To comprehensively and deeply explore the effects of different land cover types in the lower reaches of Niyang River on soil microbial biomass carbon and nitrogen,and to provide a scientific basis for the ...[Objectives]To comprehensively and deeply explore the effects of different land cover types in the lower reaches of Niyang River on soil microbial biomass carbon and nitrogen,and to provide a scientific basis for the rational use and sustainable management of land resources in this area.[Methods]Taking the 3 types of land cover(cultivated land,grass land and forest land)in the lower reaches of Niyang River in Tibet as the research object,the contents,distribution characteristics and relationships of soil organic carbon,organic nitrogen,microbial biomass carbon,microbial biomass nitrogen and readily oxidizable organic carbon,and their relationships were studied in 0-10,10-20,20-40,40-60,and 60-100 cm soil depth.[Results]The soil organic carbon content of forest land was higher than that of grass land and cultivated land;the vertical change trend of soil organic carbon content decreased with the increase of depth(P<0.05),and it was mainly concentrated in the soil with a depth of 0-20 cm.The soil organic carbon content was significantly different among forest land,grass land and cultivated land(P<0.05),but there was no significant difference between cultivated land and grass land(P>0.05).The soil organic nitrogen content was significantly different among cultivated land,grass land,and forest land(P<0.05),but there was no significant difference between grass land and forest land(P>0.05).The readily oxidizable organic carbon,microbial biomass carbon and nitrogen in forest land were higher than that in cultivated land and grass land.The change trend of soil readily oxidizable organic carbon,microbial biomass carbon and microbial biomass nitrogen was similar to the change of soil organic carbon content,showing a significant positive correlation.In addition to being subject to land cover,soil microbial biomass carbon and nitrogen content were also subject to the interaction of factors such as soil temperature,humidity,pH and vegetation types.[Conclusions]Changes in land cover significantly affect soil organic carbon and 展开更多
The present study was carried out in Tungnath alpine meadows of Kedarnath Wild Life Sanctuary, Western Himalaya from subalpine to upper alpine zone. A total of four summits were selected along an altitudinal gradient ...The present study was carried out in Tungnath alpine meadows of Kedarnath Wild Life Sanctuary, Western Himalaya from subalpine to upper alpine zone. A total of four summits were selected along an altitudinal gradient and sampled for detailed vegetation analysis using multi summit approach as per Global observation research initiative in alpine environments(GLORIA). Species richness, diversity, and evenness among four summits as well as the interaction between environmental variables with plant communities were assessed. Monthly mean soil temperature was calculated using data retrieved from geo-precision temperature logger in order to identify the trend of soil temperature among different season and altitudinal gradient and its implications to plant communities. Soil samples were analyzed fromeach summit by collecting randomized composite soil samples. The indirect non-metric multidimensional scaling(NMDS) and direct canonical correspondence analysis(CCA) tools of ordination techniques to determine the linkage between plant species from various sample summits and biotic/abiotic environmental gradients were used in the present study. The results of the study demonstrated increase in species richness as soil temperature increases, the ecotone representing summits were found most warm summits followed by highest species richness. Annual soil temperature increased by 1.43°C at timberline ecotone. Whereas, at upper alpine zone the soil temperature increased by 0.810 C from year 2015 to 2016. S?rensen's similarity index was found to be increased between subalpine and upper alpine zone with increase in the presence of subalpine plant species at upper alpine zone. Both the ordination tools separate the subalpine summit and their respective vegetation from summits representingtimberline ecotone and upper alpine zone. Soil p H, altitude, soil cation exchange capacity were found as the key abiotic drivers for distribution of plant species.展开更多
基金Under the auspices of Chinese Academy Sciences Action Plan for the Development of Western China(No.KZCX2-XB3-10)Major State Basic Research Development Program of China(No.2011BAC09B02)+2 种基金Strategic Priority Research Program-Climate Change:Carbon Budget and Related Issues'of Chinese Academy of Sciences(No.XDA05070404,XDA05050205)National Natural Science Foundation of China(No.31070425,31000224,U1033004)Guangxi Provincial Program of Distinguished Expert in China
文摘In karst regions,the spatial heterogeneity of soil mineral oxides and environmental variables is still not clear.We investigated the spatial heterogeneity of SiO2,Al2O3,Fe2O3,CaO,MgO,P2O5,K2O,and MnO contents in the soils of slope land,plantation forest,secondary forest,and primary forest,as well as their relationships with environmental variables in a karst region of Southwest China.Geostatistics,principal component analysis(PCA),and canonical correlation analysis(CCA)were applied to analyze the field data.The results show that SiO2was the predominant mineral in the soils(45.02%–67.33%),followed by Al2O3and Fe2O3.Most soil mineral oxide components had a strong spatial dependence,except for CaO,MgO,and P2O5in the plantation forest,MgO and P2O5in the secondary forest,and CaO in the slope land.Dimensionality reduction in PCA was not appropriate due to the strong spatial heterogeneity in the ecosystems.Soil mineral oxide components,the main factors in all ecosystems,had greater influences on vegetation than those of conventional soil properties.There were close relationships between soil mineral oxide components and vegetation,topography,and conventional soil properties.Mineral oxide components affected species diversity,organic matter and nitrogen levels.
基金supported by the National Natural Science Foundation of China (Grant No. 91025002)
文摘Understanding the factors that drive variation in species distribution is a central theme of ecological research. Although several studies focused on alpine vegetation, few efforts have been made to identify the environmental factors that are responsible for the variations in species composition and richness of alpine shrublands using numerical methods. In the present study, we investigated vegetation and associated environmental variables from 45 sample plots in the middle Qilian Mountains of the northwestern China to classify different community types and to elucidate the species- environment relationships. We also estimated the relative contributions of topography and site conditions to spatial distribution patterns of the shrub communities using the variation partitioning. The results showed that four shrub community types were identified and striking differences in fioristic composition were found among them. Species composition greatly depended on elevation, slope, shrub cover, soil pH and organic carbon. The important determinants of species richness were soil bulk density and slope. No significant differences in species richness were detected among the community types. Topography and site conditions had almost equal effects on compositional variation. Nonetheless,a large amount of the variation in species composition remained unexplained.
基金supported by the National Natural Science Foundation of China(No.51279033).
文摘Underwater direction of arrival(DOA)estimation has always been a very challenging theoretical and practical problem.Due to the serious non-stationary,non-linear,and non-Gaussian characteristics,machine learning based DOA estimation methods trained on simulated Gaussian noised array data cannot be directly applied to actual underwater DOA estimation tasks.In order to deal with this problem,environmental data with no target echoes can be employed to analyze the non-Gaussian components.Then,the obtained information about non-Gaussian components can be used to whiten the array data.Based on these considerations,a novel practical sonar array whitening method was proposed.Specifically,based on a weak assumption that the non-Gaussian components in adjacent patches with and without target echoes are almost the same,canonical cor-relation analysis(CCA)and non-negative matrix factorization(NMF)techniques are employed for whitening the array data.With the whitened array data,machine learning based DOA estimation models trained on simulated Gaussian noised datasets can be used to perform underwater DOA estimation tasks.Experimental results illustrated that,using actual underwater datasets for testing with known machine learning based DOA estimation models,accurate and robust DOA estimation performance can be achieved by using the proposed whitening method in different underwater con-ditions.
基金This work was financially supported by the National Key Technology R&D Program of China(No.2006BAJ04A06)the National High-Tech Research and Development Program(863 Program)of China(No.2003AA644020).
文摘To understand the influence patterns and interactions of three important environmental factors,i.e.soil water content,oxygen concentration,and ammonium addition,on methane oxidation,the soils from landfill cover layers were incubated under full factorial parameter settings.In addition to the methane oxidation rate,the quantities and community structures of methanotrophs were analyzed to determine the methane oxidation capacity of the soils.Canonical correspondence analysis was utilized to distinguish the important impact factors.Water content was found to be the most important factor influencing the methane oxidation rate and Type II methanotrophs,and the optimum value was 15%(w/w),which induced methane oxidation rates 10-and 6-times greater than those observed at 5%(w/w)and 20%(w/w),respectively.Ambient oxygen conditions were more suitable for methane oxidation than 3%oxygen.The addition of 100 mg-N·kg^(-1) drysoil of ammonium induced different effects on methane oxidation capacity when conducted at low or high water content.With regard to the methanotrophs,Type II was sensitive to the changes of water content,while Type I was influenced by oxygen content.Furthermore,the methanotrophic acidophile,Verrucomicrobia,was detected in soils with a pH of 4.9,which extended their known living environments.
基金Project supported by the National Basic Research Program (973) of China (No. 2011CB409901-01)the National Natural Science Foundation of China (No. 4081011)
文摘The impacts of rainfall direction on the degree of hydrological response to rainfall properties were investigated using comparative rainfall-runoff experiments on a small-scale slope(4 m×1 m),as well as canonical correlation analysis(CCA).The results of the CCA,based on the observed data showed that,under conditions of both upstream and downstream rainfall movements,the hydrological process can be divided into instantaneous and cumulative responses,for which the driving forces are rainfall intensity and total rainfall,and coupling with splash erosion and wash erosion,respectively.The response of peak runoff(Pr)to intensity-dominated rainfall action appeared to be the most significant,and also runoff(R)to rainfall-dominated action,both for upstream-and downstream-moving conditions.Furthermore,the responses of sediment erosion in downstream-moving condition were more significant than those in upstream-moving condition.This study indicated that a CCA between rainfall and hydrological characteristics is effective for further exploring the rainfall-runoff-erosion mechanism under conditions of moving rainfall,especially for the downstream movement condition.
文摘Kalam Kohistan is a dry,temperate hilly region in the Hindu Raj Series of the Greater Hindu Kush Mountains with diverse forests.As plant distribution and composition is expression of a range of various environmental variables,ecological and floristic attributes of vegetation in the Laikot Forests were therefore evaluated via consecutive explorative trips.These forests have not been evaluated ecologically before due to harsh climatic conditions and issues of accessibility and the study in hand is one of the first in its nature.Quantitative ecological techniques were used to sample forest vegetation and identify species in quadrats of 2 m×2 m for herbs,5 m×5 m for shrubs and 10 m×10 m for trees.All the data of 195 plant species and environmental factors were analyzed via Two-way Cluster Analysis and Canonical Correspondence Analysis using PCORD and CANOCO software.Among 195 plant species from 63 families were 27 species of Asteraceae,the most-speciose family,followed by Poaceae(20 spp.).The dominant life form was therophyte(86 spp.;44%share),followed by phanerophyte(41 spp.;21%share).For the leaf size spectrum,most prevalent was nanophyll(73 spp.;44%)followed by microphyll(66 spp.,34%)and mesophyll(44 spp.;23%).Calcium carbonate,pH,potassium,sand,silt,organic matter,slope aspect and grazing significantly influenced species composition,distribution and habitat.The floristic variation in the region was diverse due to elevational and aspect gradients and thus devided into three zones.This vegetation zonation can be utilized for forest management,species and habitat conservation.Both in situ and ex situ conservation of threatened plant species may improve their conservation status in future if address properly.
文摘An approach is proposed for predicting turning and acceleration motion trend of the tropical cyclones over the South China Sea for 72 h in the extrapolated track coordinates.Cross-track (CT)and along-track(AT)components are defined according to the persistently extrapolated track coodinates based on observed positions at the initial and past 24 h times.A kind of straight- forward measure may be provided with CT and AT components for typhoon turning motion and ac- celeration motion.Canonical correlation analysis(CCA)is performed to reveal the correlaotions be- tween tropical cyclone tracks and environmental 500 hPa geopotential height fields.A stepwise dis- criminate analysis technique is adopted to derive the classification functions of the respective three categories for AT and CT components.Especially,categorical combinations of CT and AT compo- nents are divided into possible 9 regions corresponding with tropical cyclone behaviors.Not only can 9 motion trends of a tropical cyclone be predicted,but also the location and its maximum error at least in certain direction are available.The perfect prediction(PP)verifications indicate that the percent corrects for the CT and AT categories are 67% and 69% in the independent samples,73% and 53% in the dependent samples,respectively,higher than that of 33.3% for random chance; moreover,the rate for successfully forecasting that in which one of the nine regions the tropical cy- clones will fall at 72 h is about 40%,also higher than the stochastic probability of 11%.The method has been proved to be skillful and promising.
基金The research in this article was funded by the Special Forestry Project of Public Interests[201404305,200904001].
文摘Introduction:Plant communities and soil factors might interact with each other in different temporal and spatial scales,which can influence the patterns and processes of the wetland ecosystem.To get a better understanding of the distribution of plants in wetlands and analyze their associations with environmental soil factors,the structure and types of plant communities in the eastern shore area of Lake Taihu were analyzed by two-way indicator species analysis and canonical correspondence analysis(CCA)ordination.The spatial distribution patterns of vegetation and the main factors affecting the distributions were investigated.Outcomes:Sixty-six sampling sites were selected to obtain vegetation species and soil environmental factor data.Results showed that 22 species from the 66 sites could be divided into seven communities:I:Arundo donax;II:A.donax+Phragmites australis;III:Zizania latifolia+Typha orientalis;IV:P.australis+Alternanthera philoxeroides+Polygonum hydropiper;V:P.australis;VI:P.australis+Humulus scandens;and VII:Erigeron acer+Ipomoea batatas+Rumex acetosa.Plant species and soil factors in the CCA analysis showed that I.batatas,E.acer,Chenopodium album,Polygonum lapathifolium,and Acalypha australis were mainly affected by pH,whereas Echinochloa crus-galli,Setaria viridis,and H.scandens were mainly affected by soil total phosphorus.Mentha canadensis and A.donax were mainly affected by soil conductivity,A.philoxeroides was mainly affected by soil organic matter and,Z.latifolia,Metaplexis japonica and P.hydropiper were mainly affected by available phosphorus.Conclusion:These results indicated that different plants adapted to different soil environmental factors and provided basic information on the diversity of Lake Taihu wetland vegetation.
基金Natural Science Foundation of Tibet Autonomous Region(XZ2019ZRG-60).
文摘[Objectives]To comprehensively and deeply explore the effects of different land cover types in the lower reaches of Niyang River on soil microbial biomass carbon and nitrogen,and to provide a scientific basis for the rational use and sustainable management of land resources in this area.[Methods]Taking the 3 types of land cover(cultivated land,grass land and forest land)in the lower reaches of Niyang River in Tibet as the research object,the contents,distribution characteristics and relationships of soil organic carbon,organic nitrogen,microbial biomass carbon,microbial biomass nitrogen and readily oxidizable organic carbon,and their relationships were studied in 0-10,10-20,20-40,40-60,and 60-100 cm soil depth.[Results]The soil organic carbon content of forest land was higher than that of grass land and cultivated land;the vertical change trend of soil organic carbon content decreased with the increase of depth(P<0.05),and it was mainly concentrated in the soil with a depth of 0-20 cm.The soil organic carbon content was significantly different among forest land,grass land and cultivated land(P<0.05),but there was no significant difference between cultivated land and grass land(P>0.05).The soil organic nitrogen content was significantly different among cultivated land,grass land,and forest land(P<0.05),but there was no significant difference between grass land and forest land(P>0.05).The readily oxidizable organic carbon,microbial biomass carbon and nitrogen in forest land were higher than that in cultivated land and grass land.The change trend of soil readily oxidizable organic carbon,microbial biomass carbon and microbial biomass nitrogen was similar to the change of soil organic carbon content,showing a significant positive correlation.In addition to being subject to land cover,soil microbial biomass carbon and nitrogen content were also subject to the interaction of factors such as soil temperature,humidity,pH and vegetation types.[Conclusions]Changes in land cover significantly affect soil organic carbon and
基金conducted as a part of the project Alpine Ecosystem Dynamicssupported by SAC,ISRO,Ahmedabad,India(EPSA/ABHG/ALPINE/PRACRITI-II 01/13)
文摘The present study was carried out in Tungnath alpine meadows of Kedarnath Wild Life Sanctuary, Western Himalaya from subalpine to upper alpine zone. A total of four summits were selected along an altitudinal gradient and sampled for detailed vegetation analysis using multi summit approach as per Global observation research initiative in alpine environments(GLORIA). Species richness, diversity, and evenness among four summits as well as the interaction between environmental variables with plant communities were assessed. Monthly mean soil temperature was calculated using data retrieved from geo-precision temperature logger in order to identify the trend of soil temperature among different season and altitudinal gradient and its implications to plant communities. Soil samples were analyzed fromeach summit by collecting randomized composite soil samples. The indirect non-metric multidimensional scaling(NMDS) and direct canonical correspondence analysis(CCA) tools of ordination techniques to determine the linkage between plant species from various sample summits and biotic/abiotic environmental gradients were used in the present study. The results of the study demonstrated increase in species richness as soil temperature increases, the ecotone representing summits were found most warm summits followed by highest species richness. Annual soil temperature increased by 1.43°C at timberline ecotone. Whereas, at upper alpine zone the soil temperature increased by 0.810 C from year 2015 to 2016. S?rensen's similarity index was found to be increased between subalpine and upper alpine zone with increase in the presence of subalpine plant species at upper alpine zone. Both the ordination tools separate the subalpine summit and their respective vegetation from summits representingtimberline ecotone and upper alpine zone. Soil p H, altitude, soil cation exchange capacity were found as the key abiotic drivers for distribution of plant species.
