Tree species-abundance in forests is a function of geographical area and climate, although it is not clear whether such relationships apply to mass islands. We examined the spatial pattern of tree species in mass isla...Tree species-abundance in forests is a function of geographical area and climate, although it is not clear whether such relationships apply to mass islands. We examined the spatial pattern of tree species in mass islands along the coast of Zhejiang, East China Sea using the Preston model, to identify the relationships between tree communities and climatic conditions. The results show that：（1） the biogeographical distribution of tree species-abundance conformes to Preston＇s log-normal pattern, and is in accordance with the findings in both tropical rainforests and estuarine forests;（2） the climatic factors related to tree communities in mass islands are similar to that of the subtropical zone, including the major species of evergreen needle-leaf, broad-leaf and deciduous broad-leaf forests. We conclude that the Preston model can be applied to the trees of mass islands and thus facilitate the systematic ecological researches of vegetation species＇ composition in subtropical zone.展开更多
Aims Fits of species-abundance distributions to empirical data are increasingly used to evaluate models of diversity maintenance and community structure and to infer properties of communities,such as species richness....Aims Fits of species-abundance distributions to empirical data are increasingly used to evaluate models of diversity maintenance and community structure and to infer properties of communities,such as species richness.Two distributions predicted by several models are the Poisson lognormal(PLN)and the negative binomial(NB)distribution;however,at least three different ways to parameterize the PLN have been proposed,which differ in whether unobserved species contribute to the likelihood and in whether the likelihood is conditional upon the total number of individuals in the sample.Each of these has an analogue for the NB.Here,we propose a new formulation of the PLN and NB that includes the number of unobserved species as one of the estimated parameters.We investigate the performance of parameter estimates obtained from this reformulation,as well as the existing alternatives,for drawing inferences about the shape of species abundance distributions and estimation of species richness.Methods We simulate the random sampling of a fixed number of individuals from lognormal and gamma community relative abundance distributions,using a previously developed‘individual-based’bootstrap algorithm.We use a range of sample sizes,community species richness levels and shape parameters for the species abundance distributions that span much of the realistic range for empirical data,generating 1000 simulated data sets for each parameter combination.We then fit each of the alternative likelihoods to each of the simulated data sets,and we assess the bias,sampling variance and estimation error for each method.Important Findings Parameter estimates behave reasonably well for most parameter values,exhibiting modest levels of median error.However,for the NB,median error becomes extremely large as the NB approaches either of two limiting cases.For both the NB and PLN,>90%of the variation in the error in model parameters across parameter sets is explained by three quantities that corresponded to the proportion of species not observed in the展开更多
基金The Investigation and Assessment of Tree Species Resources and Its Relation to Controlling Factors in Mass Islands Program of SOA
文摘Tree species-abundance in forests is a function of geographical area and climate, although it is not clear whether such relationships apply to mass islands. We examined the spatial pattern of tree species in mass islands along the coast of Zhejiang, East China Sea using the Preston model, to identify the relationships between tree communities and climatic conditions. The results show that：（1） the biogeographical distribution of tree species-abundance conformes to Preston＇s log-normal pattern, and is in accordance with the findings in both tropical rainforests and estuarine forests;（2） the climatic factors related to tree communities in mass islands are similar to that of the subtropical zone, including the major species of evergreen needle-leaf, broad-leaf and deciduous broad-leaf forests. We conclude that the Preston model can be applied to the trees of mass islands and thus facilitate the systematic ecological researches of vegetation species＇ composition in subtropical zone.
基金Australian Research Council(grants CE0561435 and DP0880544)James Cook University.
文摘Aims Fits of species-abundance distributions to empirical data are increasingly used to evaluate models of diversity maintenance and community structure and to infer properties of communities,such as species richness.Two distributions predicted by several models are the Poisson lognormal(PLN)and the negative binomial(NB)distribution;however,at least three different ways to parameterize the PLN have been proposed,which differ in whether unobserved species contribute to the likelihood and in whether the likelihood is conditional upon the total number of individuals in the sample.Each of these has an analogue for the NB.Here,we propose a new formulation of the PLN and NB that includes the number of unobserved species as one of the estimated parameters.We investigate the performance of parameter estimates obtained from this reformulation,as well as the existing alternatives,for drawing inferences about the shape of species abundance distributions and estimation of species richness.Methods We simulate the random sampling of a fixed number of individuals from lognormal and gamma community relative abundance distributions,using a previously developed‘individual-based’bootstrap algorithm.We use a range of sample sizes,community species richness levels and shape parameters for the species abundance distributions that span much of the realistic range for empirical data,generating 1000 simulated data sets for each parameter combination.We then fit each of the alternative likelihoods to each of the simulated data sets,and we assess the bias,sampling variance and estimation error for each method.Important Findings Parameter estimates behave reasonably well for most parameter values,exhibiting modest levels of median error.However,for the NB,median error becomes extremely large as the NB approaches either of two limiting cases.For both the NB and PLN,>90%of the variation in the error in model parameters across parameter sets is explained by three quantities that corresponded to the proportion of species not observed in the
