A number of isolated islands of Leymus chinensis ＋ herbosa community were investigated in fragmented habitat islands, by Braun-Blanquet field survey approach, in a degenerated meadow in the Songnen Plain, China in 20...A number of isolated islands of Leymus chinensis ＋ herbosa community were investigated in fragmented habitat islands, by Braun-Blanquet field survey approach, in a degenerated meadow in the Songnen Plain, China in 2007. These islands were classified as large, medium, and small scales on the basis of the island area （100-1000m2, large island; 50-100m2, middle island; 10-50m2, small island）. Each scale of the investigation involved eight islands. The responses ofβ-diversity patterns of plant taxon to the habitat fragmentation at local community and metacommunity levels were analyzed on different scales of 24 isolated islands. The results indicated that at the local community level, there were 57 species belonging to 20 families and 49 genera in large islands, 49 species belonging to 16 families and 40 genera in middle islands, and 27 species belonging to eight families and 23 genera in small islands, β-diversity indexes for species, genus and family in large, middle, and small islands varied greatly, and the highest value of the indexes was not noted in the largest island. However, the average of the data obtained at the three scales showed that across large islands, Whittaker indexes were low and Bray-Curtis similarity indexes were high, while across small islands, Whittaker indexes were high and Bray-Curtis similarity indexes were low. At the metacommunity level, Whittaker indexes for species and genus showed a great significantly negative double logarithmic correlation （p〈0.01） with the island area, whereas the Bray-Curtis indexes for species, genus and family showed a great significantly positive double logarithmic correlation （p〈0.01） with the island area. At both local community and metacommunity levels, tumovers of species and genus could respond more sensitively to spatial changes of plant diversity patterns than that of family. Hence, the species and the genus could be used for the analysis offl-diversity patterns of plant community.展开更多
Polychlorinated naphthalene （PCNs） have similar structure and toxicity with dioxin class （PCDD/Fs）, it can be detected in the global environmental and biological samples. This paper introduces the main sources of ...Polychlorinated naphthalene （PCNs） have similar structure and toxicity with dioxin class （PCDD/Fs）, it can be detected in the global environmental and biological samples. This paper introduces the main sources of PCNs in the environment and environmental fate, introduced emphasis with the emission characteristics of PCNs in burning and metal smelting process, this article summarized the current PCNs city environmental and biotic pollution level and distribution characteristics, summarized and discussed related research of PCNs pollution level and distribution characteristics near the various environmental media and organisms in the city. Finally, the paper put forward the research progress of PCNs in related research areas and challenges.展开更多
Aims Understanding the factors that control biodiversity distributions at different spatial scales has been a key challenge for conservation efforts.That biodiversity,reflected in differences in species compositions a...Aims Understanding the factors that control biodiversity distributions at different spatial scales has been a key challenge for conservation efforts.That biodiversity,reflected in differences in species compositions among sites(beta diversity),can be derived from species replacement(turnover)and is driven by multiple factors.Here,we sought to tackle this issue through two questions related to threatened Brazilian seasonally dry forests:(i)what is the contribution of species turnover to beta diversity?and(ii)which factors drive variations in species compositions among forest patches?Methods We sampled tree species and environmental variables(soils and climate)in 17 dry forest patches spaced almost 300 km apart.We used the beta diversity partitioning framework to determine the contribution of turnover.We used redundancy analysis,with properly controlled spatial structure,to assess the contributions of the environmental and spatial factors to the variations of the species composition.Important Findings Beta diversity among the patches was mainly represented by the turnover component(98.2%),with Simpson dissimilarity superior to other regions of the country(means of 0.89 and 0.71 in multiple site and pairwise measures,respectively).The environmental factors measured explained more than space,representing 30.3%of the variation of the species composition,of which 28.1%was nonspatially structured.We suggest that 300 km represents a threshold at which edaphic and climatic predictors have similar effects in determining community turnover(14.9%and 12.6%,respectively,without spatial structure).Thus,conservation strategies should be considered across landscapes to effectively protect tropical forest diversity,as even considering the different climatic aspects covered by the scale,landscaped edaphic varieties are important drivers of species turnover.展开更多
基金Under the auspices of Major State Basic Research Development Program of China (973 Progrom) (No 2007CB106801)National Key Technology R&D Program of China (No 2006BAD16B06)National Natural Science Foundation of China (No 30470180,30770397)
文摘A number of isolated islands of Leymus chinensis ＋ herbosa community were investigated in fragmented habitat islands, by Braun-Blanquet field survey approach, in a degenerated meadow in the Songnen Plain, China in 2007. These islands were classified as large, medium, and small scales on the basis of the island area （100-1000m2, large island; 50-100m2, middle island; 10-50m2, small island）. Each scale of the investigation involved eight islands. The responses ofβ-diversity patterns of plant taxon to the habitat fragmentation at local community and metacommunity levels were analyzed on different scales of 24 isolated islands. The results indicated that at the local community level, there were 57 species belonging to 20 families and 49 genera in large islands, 49 species belonging to 16 families and 40 genera in middle islands, and 27 species belonging to eight families and 23 genera in small islands, β-diversity indexes for species, genus and family in large, middle, and small islands varied greatly, and the highest value of the indexes was not noted in the largest island. However, the average of the data obtained at the three scales showed that across large islands, Whittaker indexes were low and Bray-Curtis similarity indexes were high, while across small islands, Whittaker indexes were high and Bray-Curtis similarity indexes were low. At the metacommunity level, Whittaker indexes for species and genus showed a great significantly negative double logarithmic correlation （p〈0.01） with the island area, whereas the Bray-Curtis indexes for species, genus and family showed a great significantly positive double logarithmic correlation （p〈0.01） with the island area. At both local community and metacommunity levels, tumovers of species and genus could respond more sensitively to spatial changes of plant diversity patterns than that of family. Hence, the species and the genus could be used for the analysis offl-diversity patterns of plant community.
文摘Polychlorinated naphthalene （PCNs） have similar structure and toxicity with dioxin class （PCDD/Fs）, it can be detected in the global environmental and biological samples. This paper introduces the main sources of PCNs in the environment and environmental fate, introduced emphasis with the emission characteristics of PCNs in burning and metal smelting process, this article summarized the current PCNs city environmental and biotic pollution level and distribution characteristics, summarized and discussed related research of PCNs pollution level and distribution characteristics near the various environmental media and organisms in the city. Finally, the paper put forward the research progress of PCNs in related research areas and challenges.
基金This work was supported by the Fundação de Amparo à Pesquisa do Estado de Minas Gerais(FAPEMIG)[12.070/2009].
文摘Aims Understanding the factors that control biodiversity distributions at different spatial scales has been a key challenge for conservation efforts.That biodiversity,reflected in differences in species compositions among sites(beta diversity),can be derived from species replacement(turnover)and is driven by multiple factors.Here,we sought to tackle this issue through two questions related to threatened Brazilian seasonally dry forests:(i)what is the contribution of species turnover to beta diversity?and(ii)which factors drive variations in species compositions among forest patches?Methods We sampled tree species and environmental variables(soils and climate)in 17 dry forest patches spaced almost 300 km apart.We used the beta diversity partitioning framework to determine the contribution of turnover.We used redundancy analysis,with properly controlled spatial structure,to assess the contributions of the environmental and spatial factors to the variations of the species composition.Important Findings Beta diversity among the patches was mainly represented by the turnover component(98.2%),with Simpson dissimilarity superior to other regions of the country(means of 0.89 and 0.71 in multiple site and pairwise measures,respectively).The environmental factors measured explained more than space,representing 30.3%of the variation of the species composition,of which 28.1%was nonspatially structured.We suggest that 300 km represents a threshold at which edaphic and climatic predictors have similar effects in determining community turnover(14.9%and 12.6%,respectively,without spatial structure).Thus,conservation strategies should be considered across landscapes to effectively protect tropical forest diversity,as even considering the different climatic aspects covered by the scale,landscaped edaphic varieties are important drivers of species turnover.
