Climate change is altering the timing and magnitude of biogeochemical fluxes in many high- elevation ecosystems. The consequent changes in alpine nitrification rates have the potential to influence ecosystem scale res...Climate change is altering the timing and magnitude of biogeochemical fluxes in many high- elevation ecosystems. The consequent changes in alpine nitrification rates have the potential to influence ecosystem scale responses. In order to better understand how changing temperature and moisture conditions may influence ammonia oxidizers and nitrification activity, we conducted laboratory incubations on soils collected in a Colorado watershed from three alpine habitats （glacial outwash, talus, and meadow）. We found that bacteria, not archaea, dominated all ammonia oxidizer communities. Nitrification increased with moisture in all soils and under all temperature treatments. However, temperature was not correlated with nitrification rates in all soils. Site-specific temperature trends suggest the development of generalist ammonia oxidzer communities in soils with greater in situ temperature fluctuations and specialists in soils with more steady temperature regimes. Rapidly increasing tempera- tures and changing soil moisture conditions could explain recent observations of increased nitrate production in some alpine soils.展开更多
Distributions of invasive species are commonly predicted with species distribution models that build upon the statistical relationships between observed species presence data and climate data. We used field observatio...Distributions of invasive species are commonly predicted with species distribution models that build upon the statistical relationships between observed species presence data and climate data. We used field observations, climate station data, and Maximum Entropy species distribution models for 13 invasive plant species in the United States, and then compared the models with inputs from a General Circulation Model （hereafter GCM-based models） and a downscaled Regional Climate Model （hereafter, RCM-based models）. We also compared species distributions based on either GCM-based or RCM-based models for the present （1990-1999） to the future （2046- 2055）. RCM-based species distribution models replicated observed distributions remarkably better than GCM- based models for all invasive species under the current climate. This was shown for the presence locations of the species, and by using four common statistical metrics to compare modeled distributions. For two widespread invasive taxa （Bromus tectorum or cheatgrass, and Tamarix spp. or tamarisk）, GCM-based models failed miserably to reproduce observed species distributions. In contrast, RCM-based species distribution models closely matched observations. Future species distributions may be significantly affected by using GCM-based inputs. Because invasive plants species often show high resilience and low rates of local extinction, RCM-based species distribution models may perform better than GCM-based species distribution models for planning containment programs for invasive species.展开更多
Species distribution models are increasing in popularity for mapping suitable habitat for species of management con- cern. Many investigators now recognize that extrapolations of these models with geographic informati...Species distribution models are increasing in popularity for mapping suitable habitat for species of management con- cern. Many investigators now recognize that extrapolations of these models with geographic information systems （GIS） might be sensitive to the environmental bounds of the data used in their development, yet there is no recommended best practice for ＂clamping＂ model extrapolations. We relied on two commonly used modeling approaches： classification and regression tree （CART） and maximum entropy （Maxent） models, and we tested a simple alteration of the model extrapolations, bounding ex- trapolations to the maximum and minimum values of primary environmental predictors, to provide a more realistic map of suit-able habitat of hybridized Africanized honey bees in the southwestern United States. Findings suggest that multiple models of bounding, and the most conservative bounding of species distribution models, like those presented here, should probably replace the unbounded or loosely bounded techniques currently used [Current Zoology 57 （5）： 642-647,2011].展开更多
An invasive population of Burmese pythons(Python molurus bivittatus)is established across several thousand square kilometers of southern Florida and appears to have caused precipitous population declines among several...An invasive population of Burmese pythons(Python molurus bivittatus)is established across several thousand square kilometers of southern Florida and appears to have caused precipitous population declines among several species of native mammals.Why has this giant snake had such great success as an invasive species when many established reptiles have failed to spread?We scored the Burmese python for each of 15 literature-based attributes relative to predefined comparison groups from a diverse range of taxa and provide a review of the natural history and ecology of Burmese pythons relevant to each attribute.We focused on attributes linked to spread and magnitude of impacts rather than establishment success.Our results suggest that attributes related to body size and generalism appeared to be particularly applicable to the Burmese python’s success in Florida.The attributes with the highest scores were:high reproductive potential,low vulnerability to predation,large adult body size,large offspring size and high dietary breadth.However,attributes of ectotherms in general and pythons in particular(including predatory mode,energetic efficiency and social interactions)might have also contributed to invasion success.Although establishment risk assessments are an important initial step in prevention of new establishments,evaluating species in terms of their potential for spreading widely and negatively impacting ecosystems might become part of the means by which resource managers prioritize control efforts in environments with large numbers of introduced species.展开更多
Habitat suitability models have been used to predict the present and future potential distribution of a variety of spe- cies. Eurasian tree sparrows Passer montanus, native to Eurasia, have established populations in ...Habitat suitability models have been used to predict the present and future potential distribution of a variety of spe- cies. Eurasian tree sparrows Passer montanus, native to Eurasia, have established populations in other parts of the world. In North America, their current distribution is limited to a relatively small region around its original introduction to St. Louis, Missouri. We combined data from the Global Biodiversity Information Facility with current and future climate data to create habitat suitability models using Maxent for this species. Under projected climate change scenarios, our models show that the distribution and range of the Eurasian tree sparrow could increase as far as the Pacific Northwest and Newfoundland. This is potentially important in-formation for prioritizing the management and control of this non-native species [Current Zoology 57 （5）： 648--654, 2011].展开更多
文摘Climate change is altering the timing and magnitude of biogeochemical fluxes in many high- elevation ecosystems. The consequent changes in alpine nitrification rates have the potential to influence ecosystem scale responses. In order to better understand how changing temperature and moisture conditions may influence ammonia oxidizers and nitrification activity, we conducted laboratory incubations on soils collected in a Colorado watershed from three alpine habitats （glacial outwash, talus, and meadow）. We found that bacteria, not archaea, dominated all ammonia oxidizer communities. Nitrification increased with moisture in all soils and under all temperature treatments. However, temperature was not correlated with nitrification rates in all soils. Site-specific temperature trends suggest the development of generalist ammonia oxidzer communities in soils with greater in situ temperature fluctuations and specialists in soils with more steady temperature regimes. Rapidly increasing tempera- tures and changing soil moisture conditions could explain recent observations of increased nitrate production in some alpine soils.
文摘Distributions of invasive species are commonly predicted with species distribution models that build upon the statistical relationships between observed species presence data and climate data. We used field observations, climate station data, and Maximum Entropy species distribution models for 13 invasive plant species in the United States, and then compared the models with inputs from a General Circulation Model （hereafter GCM-based models） and a downscaled Regional Climate Model （hereafter, RCM-based models）. We also compared species distributions based on either GCM-based or RCM-based models for the present （1990-1999） to the future （2046- 2055）. RCM-based species distribution models replicated observed distributions remarkably better than GCM- based models for all invasive species under the current climate. This was shown for the presence locations of the species, and by using four common statistical metrics to compare modeled distributions. For two widespread invasive taxa （Bromus tectorum or cheatgrass, and Tamarix spp. or tamarisk）, GCM-based models failed miserably to reproduce observed species distributions. In contrast, RCM-based species distribution models closely matched observations. Future species distributions may be significantly affected by using GCM-based inputs. Because invasive plants species often show high resilience and low rates of local extinction, RCM-based species distribution models may perform better than GCM-based species distribution models for planning containment programs for invasive species.
文摘Species distribution models are increasing in popularity for mapping suitable habitat for species of management con- cern. Many investigators now recognize that extrapolations of these models with geographic information systems （GIS） might be sensitive to the environmental bounds of the data used in their development, yet there is no recommended best practice for ＂clamping＂ model extrapolations. We relied on two commonly used modeling approaches： classification and regression tree （CART） and maximum entropy （Maxent） models, and we tested a simple alteration of the model extrapolations, bounding ex- trapolations to the maximum and minimum values of primary environmental predictors, to provide a more realistic map of suit-able habitat of hybridized Africanized honey bees in the southwestern United States. Findings suggest that multiple models of bounding, and the most conservative bounding of species distribution models, like those presented here, should probably replace the unbounded or loosely bounded techniques currently used [Current Zoology 57 （5）： 642-647,2011].
基金supported by the Department of the Interior’s Office of Insular Affairsthe Vero Beach office of the US Fish and Wildlife Service+4 种基金the US Geological Survey’s Greater Everglades Priority Ecosystem Science and Invasive Species programsEverglades National Parksupported by Davidson Collegethe Associated Colleges of the Souththe J.E.and Majorie B.Pittman Foundation.
文摘An invasive population of Burmese pythons(Python molurus bivittatus)is established across several thousand square kilometers of southern Florida and appears to have caused precipitous population declines among several species of native mammals.Why has this giant snake had such great success as an invasive species when many established reptiles have failed to spread?We scored the Burmese python for each of 15 literature-based attributes relative to predefined comparison groups from a diverse range of taxa and provide a review of the natural history and ecology of Burmese pythons relevant to each attribute.We focused on attributes linked to spread and magnitude of impacts rather than establishment success.Our results suggest that attributes related to body size and generalism appeared to be particularly applicable to the Burmese python’s success in Florida.The attributes with the highest scores were:high reproductive potential,low vulnerability to predation,large adult body size,large offspring size and high dietary breadth.However,attributes of ectotherms in general and pythons in particular(including predatory mode,energetic efficiency and social interactions)might have also contributed to invasion success.Although establishment risk assessments are an important initial step in prevention of new establishments,evaluating species in terms of their potential for spreading widely and negatively impacting ecosystems might become part of the means by which resource managers prioritize control efforts in environments with large numbers of introduced species.
文摘Habitat suitability models have been used to predict the present and future potential distribution of a variety of spe- cies. Eurasian tree sparrows Passer montanus, native to Eurasia, have established populations in other parts of the world. In North America, their current distribution is limited to a relatively small region around its original introduction to St. Louis, Missouri. We combined data from the Global Biodiversity Information Facility with current and future climate data to create habitat suitability models using Maxent for this species. Under projected climate change scenarios, our models show that the distribution and range of the Eurasian tree sparrow could increase as far as the Pacific Northwest and Newfoundland. This is potentially important in-formation for prioritizing the management and control of this non-native species [Current Zoology 57 （5）： 648--654, 2011].
