Photosynthesis ( P n ), transpiration ( E ) and water use efficiency ( WUE ) of more than 66 arid sand species from different environmental habitats, shifting sand dune, fixed sand dune, lowland and wetland in ...Photosynthesis ( P n ), transpiration ( E ) and water use efficiency ( WUE ) of more than 66 arid sand species from different environmental habitats, shifting sand dune, fixed sand dune, lowland and wetland in the Maowusu Sand Area were analyzed and the relation among these characteristics and the resource utilization efficiency, taxonomic categories and growth forms of the species were assessed. The results showed that species from Chenopodiaceae, Gramineae, Leguminosae which possessed the C 4 photosynthesis pathway, or C 3 pathway and also with nitrogen_fixation capacities had higher or the highest P n values, i.e., 20～30 μmol CO 2·m -2 ·s -1 , while that of evergreen shrub of Pinaceae had the lowest P n values, i.e., 0～5 μmol CO 2·m -2 ·s -1 . Those species from Compositae, Scrophulariaceae, and Gramineae with C 3 pathway but no N_fixation capacity had the highest E rates, i.e., 20～30 mmol H 2O·m -2 ·s -1 and again the evergreen shrub together with some species from Salicaceae and Compositae had the lowest E rates, i.e., 0～5 mmol H 2O·m -2 ·s -1 . Species from Leguminosae, Gramineae and Chenopodiaceae with C 4 pathway or C 3 pathway with N_fixation capacity, both shrubs and grasses, generally had higher WUE . However, even the physiological traits of the same species were habitat_ and season_specific. The values of both P n and E in late summer were much higher than those in early summer, with average increases of 26%, 40% respectively in the four habitats. WUE in late summer was, however, 12% lower. Generally, when the environments became drier as a result of habitats changed, i.e., in the order of wetland, lowland, fixed sand dune and shifting sand dune, P n and E decreased but WUE increased.展开更多
Background:Habitat loss,fragmentation and decrease of habitat quality caused by urbanization have led to a dramatic decline in biodiversity worldwide.For highly urbanized areas,parks have become“islands”or habitat f...Background:Habitat loss,fragmentation and decrease of habitat quality caused by urbanization have led to a dramatic decline in biodiversity worldwide.For highly urbanized areas,parks have become“islands”or habitat fragments for wildlife.As an important indicator group of urban ecosystem health,the response of birds to urbanization has attracted the global attention of ecologists.Understanding the key factors affecting bird diversity in urbanized environment is crucial to the protection of biodiversity in urban ecosystems.Methods:We used the line-transect method to survey birds in 37 urban parks in Nanjing,China.We also measured a number of park characteristics(area,isolation,shape index,environmental noise,distance to city center,and habitat diversity)that are commonly assumed to influence bird diversity.We then used the information-theoretic multi-model inference approach to determine which park characteristics had significant impacts on bird species richness.Results:We found that park area,habitat diversity and the distance to city center were the best positive predictors of bird species richness in Nanjing urban parks.By contrast,park isolation,park shape and environmental noise had little or no influence on bird diversity.Conclusions:Our study highlights the importance of park area,habitat diversity and the distance to city center in determining bird diversity in Nanjing city parks.Therefore,from a conservation viewpoint,we recommend that large parks with complex and diverse habitats far away from the city center should be retained or constructed to increase bird diversity in urban design and planning.展开更多
Background:The Bar-headed Goose(Anser indicus)breeds across the high plains and plateau of Central Asia and winters in the Qinghai-Tibet Plateau(QTP),the Yunnan-Guizhou Plateau and the Indian sub-continent.Of the two ...Background:The Bar-headed Goose(Anser indicus)breeds across the high plains and plateau of Central Asia and winters in the Qinghai-Tibet Plateau(QTP),the Yunnan-Guizhou Plateau and the Indian sub-continent.Of the two recognized discrete flyways of the Bar-headed Goose,the Eastern Tibetan Flyway(ETF)is the larger,comprising at least six migration routes.However,we remain ignorant about their migratory connectivity,habitat use and effectiveness of site-safeguard mechanisms set in place for the species.Methods:We tracked 30 ETF Bar-headed Geese from Chinese and Mongolian breeding areas to their wintering grounds using GPS/GSM transmitters,to determine their migration routes and stopover staging patterns within the QTP,overlaying these upon GIS layers of protected area status and habitat type,to model their habitat selection.Results:In total,14 tagged Bar-headed Geese provided information on their entire autumn migration and 4 geese on their entire spring migration.Qinghai Lake marked birds overwintered in the QTP(n=2),geese tagged in Mongolia wintered either in the QTP(n=3)or in India/Bangladesh(n=9),representing three of the migration routes within the ETF.In total,tagged birds staged at 79 different stopover sites within QTP in autumn and 23 in spring,of which 65%(autumn)and 59%(spring)of all fixes fell within the boundaries of either National Nature Reserves(NNRs)or Important Birds Areas(IBAs)in the QTP.Bar-headed Geese predominantly occurred on four land-cover types:grassland(mostly by day),water bodies(at night),wetlands and bare substrates(salt flats,dry lake/river substrates and plough)with little change in proportion.Generalized linear mixed models comparing presence with pseudo-absence data suggested geese strongly selected for wetlands as staging habitat,avoiding bare substrates in spring.Conclusions:Based on our limited observations of these tagged geese,this study is the first to show that the current designated National Nature Reserves in place in the staging areas within the QTP appear adequate to prot展开更多
Nestedness is an important pattern frequently reported for species assemblages on islands or fragmented systems.However,to date,there are few studies that comprehensively investigated faunal nestedness and underlying ...Nestedness is an important pattern frequently reported for species assemblages on islands or fragmented systems.However,to date,there are few studies that comprehensively investigated faunal nestedness and underlying processes in urbanized landscapes.In this study,we examined the nestedness of bird assemblages and its underlying causal mechanisms in 37 urban parks in Nanjing,China.We used the line-transect method to survey birds from April 2019 to January 2020.We used the Weighted Nestedness metric based on Overlap and Decreasing Fill(WNODF)to estimate the nestedness of bird assemblages.We applied spearman partial correlation test to examine the relationships between nestedness ranks of sites and park characteristics(area,isolation,anthropogenic noise,number of habitat types,and building index),as well as between nestedness ranks of species and their ecological traits(body size,geographic range size,clutch size,minimum area requirement,dispersal ratio,and habitat specificity).We found that bird assemblages in urban parks were significantly nested.Park area,habitat diversity,building index,habitat specificity,and minimum area requirement of birds were significantly correlated with nestedness.Therefore,the nestedness of bird assemblages was caused by selective extinction,habitat nestedness,and urbanization.However,the nestedness of bird assemblages did not result from passive sampling,selective colonization,or human disturbance.Overall,to maximize the number of species preserved in our system,conservation priority should be given to parks with large area,rich habitat diversity,and less building index.From a species perspective,we should focus on species with large area requirement and high habitat specificity for their effective conservation.展开更多
文摘Photosynthesis ( P n ), transpiration ( E ) and water use efficiency ( WUE ) of more than 66 arid sand species from different environmental habitats, shifting sand dune, fixed sand dune, lowland and wetland in the Maowusu Sand Area were analyzed and the relation among these characteristics and the resource utilization efficiency, taxonomic categories and growth forms of the species were assessed. The results showed that species from Chenopodiaceae, Gramineae, Leguminosae which possessed the C 4 photosynthesis pathway, or C 3 pathway and also with nitrogen_fixation capacities had higher or the highest P n values, i.e., 20～30 μmol CO 2·m -2 ·s -1 , while that of evergreen shrub of Pinaceae had the lowest P n values, i.e., 0～5 μmol CO 2·m -2 ·s -1 . Those species from Compositae, Scrophulariaceae, and Gramineae with C 3 pathway but no N_fixation capacity had the highest E rates, i.e., 20～30 mmol H 2O·m -2 ·s -1 and again the evergreen shrub together with some species from Salicaceae and Compositae had the lowest E rates, i.e., 0～5 mmol H 2O·m -2 ·s -1 . Species from Leguminosae, Gramineae and Chenopodiaceae with C 4 pathway or C 3 pathway with N_fixation capacity, both shrubs and grasses, generally had higher WUE . However, even the physiological traits of the same species were habitat_ and season_specific. The values of both P n and E in late summer were much higher than those in early summer, with average increases of 26%, 40% respectively in the four habitats. WUE in late summer was, however, 12% lower. Generally, when the environments became drier as a result of habitats changed, i.e., in the order of wetland, lowland, fixed sand dune and shifting sand dune, P n and E decreased but WUE increased.
基金This work was supported by the National Natural Science Foundation of China(Grant No.31971545 and 31770462)Natural Science Foundation of Zhejiang Province(LZ18C030002).
文摘Background:Habitat loss,fragmentation and decrease of habitat quality caused by urbanization have led to a dramatic decline in biodiversity worldwide.For highly urbanized areas,parks have become“islands”or habitat fragments for wildlife.As an important indicator group of urban ecosystem health,the response of birds to urbanization has attracted the global attention of ecologists.Understanding the key factors affecting bird diversity in urbanized environment is crucial to the protection of biodiversity in urban ecosystems.Methods:We used the line-transect method to survey birds in 37 urban parks in Nanjing,China.We also measured a number of park characteristics(area,isolation,shape index,environmental noise,distance to city center,and habitat diversity)that are commonly assumed to influence bird diversity.We then used the information-theoretic multi-model inference approach to determine which park characteristics had significant impacts on bird species richness.Results:We found that park area,habitat diversity and the distance to city center were the best positive predictors of bird species richness in Nanjing urban parks.By contrast,park isolation,park shape and environmental noise had little or no influence on bird diversity.Conclusions:Our study highlights the importance of park area,habitat diversity and the distance to city center in determining bird diversity in Nanjing city parks.Therefore,from a conservation viewpoint,we recommend that large parks with complex and diverse habitats far away from the city center should be retained or constructed to increase bird diversity in urban design and planning.
基金Our study was supported by the National Natural Science Foundation of China(Grant No.31870369&No.31970433&No.31670424)China Biodiversity Observation Networks(Sino BON)The funders had no role in study design,data collection and analysis,decision to publish,or preparation of the manuscript.
文摘Background:The Bar-headed Goose(Anser indicus)breeds across the high plains and plateau of Central Asia and winters in the Qinghai-Tibet Plateau(QTP),the Yunnan-Guizhou Plateau and the Indian sub-continent.Of the two recognized discrete flyways of the Bar-headed Goose,the Eastern Tibetan Flyway(ETF)is the larger,comprising at least six migration routes.However,we remain ignorant about their migratory connectivity,habitat use and effectiveness of site-safeguard mechanisms set in place for the species.Methods:We tracked 30 ETF Bar-headed Geese from Chinese and Mongolian breeding areas to their wintering grounds using GPS/GSM transmitters,to determine their migration routes and stopover staging patterns within the QTP,overlaying these upon GIS layers of protected area status and habitat type,to model their habitat selection.Results:In total,14 tagged Bar-headed Geese provided information on their entire autumn migration and 4 geese on their entire spring migration.Qinghai Lake marked birds overwintered in the QTP(n=2),geese tagged in Mongolia wintered either in the QTP(n=3)or in India/Bangladesh(n=9),representing three of the migration routes within the ETF.In total,tagged birds staged at 79 different stopover sites within QTP in autumn and 23 in spring,of which 65%(autumn)and 59%(spring)of all fixes fell within the boundaries of either National Nature Reserves(NNRs)or Important Birds Areas(IBAs)in the QTP.Bar-headed Geese predominantly occurred on four land-cover types:grassland(mostly by day),water bodies(at night),wetlands and bare substrates(salt flats,dry lake/river substrates and plough)with little change in proportion.Generalized linear mixed models comparing presence with pseudo-absence data suggested geese strongly selected for wetlands as staging habitat,avoiding bare substrates in spring.Conclusions:Based on our limited observations of these tagged geese,this study is the first to show that the current designated National Nature Reserves in place in the staging areas within the QTP appear adequate to prot
基金Supported by the National Natural Science Foundation of China(31770462 and 31971545)Natural Science Foundation of Zhejiang Province(LZ18C030002).
文摘Nestedness is an important pattern frequently reported for species assemblages on islands or fragmented systems.However,to date,there are few studies that comprehensively investigated faunal nestedness and underlying processes in urbanized landscapes.In this study,we examined the nestedness of bird assemblages and its underlying causal mechanisms in 37 urban parks in Nanjing,China.We used the line-transect method to survey birds from April 2019 to January 2020.We used the Weighted Nestedness metric based on Overlap and Decreasing Fill(WNODF)to estimate the nestedness of bird assemblages.We applied spearman partial correlation test to examine the relationships between nestedness ranks of sites and park characteristics(area,isolation,anthropogenic noise,number of habitat types,and building index),as well as between nestedness ranks of species and their ecological traits(body size,geographic range size,clutch size,minimum area requirement,dispersal ratio,and habitat specificity).We found that bird assemblages in urban parks were significantly nested.Park area,habitat diversity,building index,habitat specificity,and minimum area requirement of birds were significantly correlated with nestedness.Therefore,the nestedness of bird assemblages was caused by selective extinction,habitat nestedness,and urbanization.However,the nestedness of bird assemblages did not result from passive sampling,selective colonization,or human disturbance.Overall,to maximize the number of species preserved in our system,conservation priority should be given to parks with large area,rich habitat diversity,and less building index.From a species perspective,we should focus on species with large area requirement and high habitat specificity for their effective conservation.
