Moisture and temperature controls on nitrification differ among ammonia oxidizer communities from three alpine soil habitats

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.

Regional climate model downscaling may improve the prediction of alien plant species distributions

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.

Ecological correlates of invasion impact for Burmese pythons in Florida

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.