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
Topographic and edaphic variables are the main ecological factor determining species spatial variability on mountainous forests. A field study was performed in central Alborz to investigate how the edaphic and topogra...Topographic and edaphic variables are the main ecological factor determining species spatial variability on mountainous forests. A field study was performed in central Alborz to investigate how the edaphic and topographic parameters can affect the tree and shrub communities. Initially, 27 forest stands were identified and the homogeneous units were separated regarding physiognomy. In each single homogeneous unit, one random sample plot （1000 m^2） and totally 43 plots were established. In each plot, the presence and abundance of all trees and shrubs were recorded and four soil samples were taken from depths of 0-5 and 5-20 cm. Concerning classification results, eight different forest communities were identified. The lowest and highest soil pH values were observed in Malus orientalis and pistacia-Amygdalus communities, respectively. The water saturation percent of pure- and mixed Juniperus excelsa and Rhus coriaria was the highest amongst communities. The clay content was the highest in pure J.excelsa. The 0-5 organic matter and Nitrogen content in mixed J. excelsa were significantly higher than pure J. excelsa and other communities. The CCA （Canonical Correspondence Analysis） altitude, precipitation, pH, results indicated that the EC, SP, clay and CaCO3 are the most important factors determine the distribution of trees and shrub in central Alborz.展开更多
Invasive plant species are exerting a serious threat to biological diversity in many regions of the world. To understand plant invasions this study aims to test which of the two plant invasiveness hypotheses; ‘low na...Invasive plant species are exerting a serious threat to biological diversity in many regions of the world. To understand plant invasions this study aims to test which of the two plant invasiveness hypotheses; ‘low native diversity' vs. ‘high native diversity', is supported by the regional distribution patterns of invasive plant species in the Himalayas,Nepal. This study is based on data retrieved from published literatures and herbarium specimens. The relationship between invasive plant species distribution patterns and that of native plant species is elucidated by scatter plots, as well as by generalized linear models. The native plant species and invasive plant species have similar distribution patterns and the maximum number of invasive plant species is found in the same altitudinal range where the highest richness for native tree species is found. There is a clear trend of higher invasive plant richness in regions where native tree species richness is relatively high.Consequently, the native plant richness is highest in the central phytogeographic region, followed by the eastern and the western regions, respectively. The invasive plant species also follows a similar trend.Additionally, the invasive plant species richness was positively correlated with anthropogenic factors such as human population density and the number of visiting tourists. This study supports the hypothesis that ‘high native diversity' supports or facilitates invasive plant species. Further, it indicates that nativeand invasive plant species may require similar natural conditions, but that the invasive plant species seem more dependent and influenced by anthropogenic disturbance factors.展开更多
Issues of scale and aggregation become important when large range of space and time scales is considered in landscape models.However,identifying appropriate levels of aggregation to accurately represent the processes ...Issues of scale and aggregation become important when large range of space and time scales is considered in landscape models.However,identifying appropriate levels of aggregation to accurately represent the processes and components of ecological systems is challenging.A raster-based spatially explicit forest landscape model,LANDIS,was used to study the effects of spatial aggregation on simulated spatial pattern and ecological process in Youhao Forest Bureau of the Small Khingan Mountain in Northeastern China.The model was tested over 500 simulation years with systematically increased levels of spatial aggregation.The results show that spatial aggregation significantly influences the simulation of fire disturbance,species abundance,and spatial pattern.Simulated fire regime was relatively insensitive to grain size between 30.m and 270.m in the region.Spatial aggregation from 300.m to 480.m dramatically decreased fire return interval(FRI) and increased mean fire size.Generally,species abundance and its aggregation index(AI) remained higher level over simulation years at the fine-grained level of spatial aggregation than at coarser grains.In addition,the simulated forest dynamics was more realistic at finer grains.These results suggest that appropriate levels of spatial aggregation for the model should not be larger than 270m.展开更多
The spatial and temporal distribution patterns of the zooplankton of Chabahar Bay, Gulf of Oman were investigated. Zooplankton sampling was collected twice a season at five stations in Chabahar Bay. Sampling was done ...The spatial and temporal distribution patterns of the zooplankton of Chabahar Bay, Gulf of Oman were investigated. Zooplankton sampling was collected twice a season at five stations in Chabahar Bay. Sampling was done during July-August 2007 （SW-monsoon）, October-November 2007 （post-monsoon）, January-February 2008 （NE-monsoon）, and March-May 2008 （pre-monsoon）. Five stations were investigated throughout Chabahar Bay. Four species of Oncaeidae （Oncaea media, Oncaea minuta, Oncaea venusta and Oncaea clevei） were identified. The abundance of Oncaea media was maximum in the post-monsoon （〉 700 ind..m3） and disappeared in pre-monsoon while Oncaea minuta was maximum in post-monsoon （〉 130 ind..m3） and disappeared in NE-monsoon and pre-monsoon. Oncaea venusta showed the highest abundance in post-monsoon （〉 370 ind..m3） and the lowest in pre-monsoon （〈 55 ind..m-3）. The highest abundance of Oncaea clevei was in post-monsoon （〈 240 ind..m-3） and lowest in NE-monsoon. Overall, the highest abundance of Oncaeidae was observed in post-monsoon. The results showed that depth was the most important factor controlling abundance of the Oncaeidae. Spatially, the highest abundance of Oncaeidae species was found in off shore stations. Four species of this family showed positive correlation with depth. Also, O. venusta showed negative correlation with salinity that showed this species prefers low saline water.展开更多
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.
文摘Topographic and edaphic variables are the main ecological factor determining species spatial variability on mountainous forests. A field study was performed in central Alborz to investigate how the edaphic and topographic parameters can affect the tree and shrub communities. Initially, 27 forest stands were identified and the homogeneous units were separated regarding physiognomy. In each single homogeneous unit, one random sample plot （1000 m^2） and totally 43 plots were established. In each plot, the presence and abundance of all trees and shrubs were recorded and four soil samples were taken from depths of 0-5 and 5-20 cm. Concerning classification results, eight different forest communities were identified. The lowest and highest soil pH values were observed in Malus orientalis and pistacia-Amygdalus communities, respectively. The water saturation percent of pure- and mixed Juniperus excelsa and Rhus coriaria was the highest amongst communities. The clay content was the highest in pure J.excelsa. The 0-5 organic matter and Nitrogen content in mixed J. excelsa were significantly higher than pure J. excelsa and other communities. The CCA （Canonical Correspondence Analysis） altitude, precipitation, pH, results indicated that the EC, SP, clay and CaCO3 are the most important factors determine the distribution of trees and shrub in central Alborz.
基金part of the research project ‘Legal frameworks for Conservation of Biodiversity and Ecosystem Services in the Himalayas (HIMALINES)’ funded by the Norwegian Research Council (190153/V10) Olaf Grolles Legat
文摘Invasive plant species are exerting a serious threat to biological diversity in many regions of the world. To understand plant invasions this study aims to test which of the two plant invasiveness hypotheses; ‘low native diversity' vs. ‘high native diversity', is supported by the regional distribution patterns of invasive plant species in the Himalayas,Nepal. This study is based on data retrieved from published literatures and herbarium specimens. The relationship between invasive plant species distribution patterns and that of native plant species is elucidated by scatter plots, as well as by generalized linear models. The native plant species and invasive plant species have similar distribution patterns and the maximum number of invasive plant species is found in the same altitudinal range where the highest richness for native tree species is found. There is a clear trend of higher invasive plant richness in regions where native tree species richness is relatively high.Consequently, the native plant richness is highest in the central phytogeographic region, followed by the eastern and the western regions, respectively. The invasive plant species also follows a similar trend.Additionally, the invasive plant species richness was positively correlated with anthropogenic factors such as human population density and the number of visiting tourists. This study supports the hypothesis that ‘high native diversity' supports or facilitates invasive plant species. Further, it indicates that nativeand invasive plant species may require similar natural conditions, but that the invasive plant species seem more dependent and influenced by anthropogenic disturbance factors.
基金Supported by National Natural Science Foundation of China (No.30870441,40331008)the Project of Chinese Academy of Sciences (No.KSCX2-SW-133)
文摘Issues of scale and aggregation become important when large range of space and time scales is considered in landscape models.However,identifying appropriate levels of aggregation to accurately represent the processes and components of ecological systems is challenging.A raster-based spatially explicit forest landscape model,LANDIS,was used to study the effects of spatial aggregation on simulated spatial pattern and ecological process in Youhao Forest Bureau of the Small Khingan Mountain in Northeastern China.The model was tested over 500 simulation years with systematically increased levels of spatial aggregation.The results show that spatial aggregation significantly influences the simulation of fire disturbance,species abundance,and spatial pattern.Simulated fire regime was relatively insensitive to grain size between 30.m and 270.m in the region.Spatial aggregation from 300.m to 480.m dramatically decreased fire return interval(FRI) and increased mean fire size.Generally,species abundance and its aggregation index(AI) remained higher level over simulation years at the fine-grained level of spatial aggregation than at coarser grains.In addition,the simulated forest dynamics was more realistic at finer grains.These results suggest that appropriate levels of spatial aggregation for the model should not be larger than 270m.
文摘The spatial and temporal distribution patterns of the zooplankton of Chabahar Bay, Gulf of Oman were investigated. Zooplankton sampling was collected twice a season at five stations in Chabahar Bay. Sampling was done during July-August 2007 （SW-monsoon）, October-November 2007 （post-monsoon）, January-February 2008 （NE-monsoon）, and March-May 2008 （pre-monsoon）. Five stations were investigated throughout Chabahar Bay. Four species of Oncaeidae （Oncaea media, Oncaea minuta, Oncaea venusta and Oncaea clevei） were identified. The abundance of Oncaea media was maximum in the post-monsoon （〉 700 ind..m3） and disappeared in pre-monsoon while Oncaea minuta was maximum in post-monsoon （〉 130 ind..m3） and disappeared in NE-monsoon and pre-monsoon. Oncaea venusta showed the highest abundance in post-monsoon （〉 370 ind..m3） and the lowest in pre-monsoon （〈 55 ind..m-3）. The highest abundance of Oncaea clevei was in post-monsoon （〈 240 ind..m-3） and lowest in NE-monsoon. Overall, the highest abundance of Oncaeidae was observed in post-monsoon. The results showed that depth was the most important factor controlling abundance of the Oncaeidae. Spatially, the highest abundance of Oncaeidae species was found in off shore stations. Four species of this family showed positive correlation with depth. Also, O. venusta showed negative correlation with salinity that showed this species prefers low saline water.
