جستجوی مقالات مرتبط با کلیدواژه "ecological niche modeling" در نشریات گروه "آبخیزداری، بیابان، محیط زیست، مرتع"

The aim of this study was to predict the habitat expansion of Festuca ovina by maximum entropy method and to determine the effective factors on its spread in the elevation gradient of Moghan-Sabalan rangelands of Ardabil province. The 28 study sites were selected and in each study site 3 transects and along each 100-meter transect 10 plots of 1 1m2 with a distance of 10 meters from each other were selected for sampling. Soil sampling in each study site was sampled from two depths of 0-15 and 15-30 cm. Soil properties using spatial statistics, topographic characteristics using digital elevation model, climatic information using meteorological data of the region, and land use measurements prepared with the help of a user map. Prediction maps related to the distribution of F.ovina were prepared using the maximum entropy modeling method. The role of environmental factors affecting the distribution of the species was investigated using the Jackknife method and response curves. Height variables, slope, patch size (coefficient of variation), potassium (15-30 cm depth), and lime (0-15cm depth) had the highest share in the model. The area under the curve index (AUC) was 0.86, which indicates the accuracy and average efficiency of the model in identifying the most desirable distribution areas. The kappa coefficient obtained from the comparison of forecast and actual maps was 0.72, which is at a very good level.

Understanding the effect of climate change on distribution of plant species is essential for sustainable management and conservation of rangelands, especially in arid and semi-arid ecosystems which are vulnerable to desertification, because of their sensitivity and frangibility to climate change. Due to the complexity of natural systems and phenomenon of climate change, species distribution models are used to understand the impact of climate change on potential niche of species. In this study, five modeling algorithms including artificial neural network, generalized boosting method, classification tree analysis, multivariate adaptive regression splines and maximum entropy were used to predict current and future distribution of Artemisia sieberi Besser in Central Iran. First, the ensemble model as the average predicted probability of single models’ occurrence was created. Next, pessimistic (RCP 8.5) and optimistic (RCP 2.6) scenarios of CCSM4 and NorESM1-ME climate models for the years of 2050 and 2070 were evaluated to assess the trend in spatio-temporal variations of distribution. For this purpose, layers of environmental factors including six bioclimatic and two physiographic variables were used as inputs of species distribution models. Among the environmental variables, altitude, annual precipitation, isothermality, and slope had the most impact on the habitat suitability. Modeling evaluation indicated that the generalized boosting model had better predictions of climatic habitats than other models, and ensemble model than single models. Maximum probability of species presence was determined in plains and low slope areas at altitude of 1000-2000 m and annual precipitation of 100-200 mm. Analysis of the climate change scenarios showed that, the species habitat would be decreased in 2070 more than 2050, leading to the expansion of desert areas. The results can be used for planning to combat desertification in the habitat of Artemisia sieberi, as well as its restoration and rehabilitation in the vast regions of Iran.

Two opposing questions concerning differences among ecological niches of closely-related taxa in similar or adjacent habitats have long been a subject of debate. Did different populations of a species inhabit different ecological niches and undergo speciation due to the interruption of gene flow, or did speciation occur earlier, which later on caused closely-related taxa to inhabit similar habitats? In this study, we investigated the differences between the ecological niche climate of two subspecies of the Eurasian nuthatch (rubiginosa and persica), and the impact such differences had on speciation of these subspecies over different time scales, from the past to the present. To do so, we performed tests of niche equivalency and modeled niche similarities in geographical and environmental spaces of the Alborz and Zagros Mountains. Results revealed that the ecological niche climate overlap between clades of the Alborz and Zagros is insignificant, and tests of niche similarity and niche equivalency between the two subspecies of these mountain ranges were significant. Thus, niche conservatism could be inferred for these subspecies, highlighting the speciation of each subspecies in geographically allopatric regions, prior to their migration to the Alborz and Zagros Mountains. Our results suggest that each population of the Eurasian nuthatch in these ranges could be regarded as an evolutionary significant unit, and each subspecies requires proper conservation management.