عنوان مقاله [English]
The detection of changes in climate parameters indicates that climate change has begun in Iran and it is necessary to identify the habitats of potential species, present and future years, under climate warning models. In this regard, it should be examined whether the increase in temperature in the country will have a positive effect on the presence of species in rangeland habitats, or a negative effect?. For this purpose, the current and potential future range of Artemisia Aucheri for the next three decades (2050) were predicted under two climate warning models (Rcp4.5 and Rcp8.5).
In this connection; First, the event map (presence and absence) of A. Aucheri species was prepared at the level of rangeland habitats. Then, the values of predictive environmental variables were calculated at the species occurrence site. For this purpose, 19 bioclimatic variables and three physiographic variables (slope, direction, height) with a pixel size of 4.9× 4.9 km were used to model the distribution. The points of presence were marked with the number one and the absence with the number zero. Then, considering the values of each of the climatic and physiographic variables as independent variables and the amount of presence and absence of the species as a dependent variable; a regression relationship between species occurrence and environmental variables was calculated. In the next step; based on the resulting regression relationship, prediction maps of the current (present) range and the potential future range of A. Aucheri species for the next three decades (2050) were prepared. In this regard, data related to monthly temperature and precipitation for the base time period (current) and the future time period, with a resolution of 30 seconds, in small scale from the WorldClim.org database, under two climate warning models (milder scenario and The more severe scenario) (Rcp4.5 and Rcp8.5) was downloaded from the General Atmospheric Circulation Model (CCSM4) and the maps were modified using temperature and rainfall data from synoptic meteorological stations. Then, by modifying the temperature and rainfall layers, layers of 19 bioclimatic variables were generated in DIVA-GIS software. From the digital elevation model map in the GIS environment, slope percentage and slope direction maps were generated and used as physiographic variables. All peripheral layers were standardized in Arc-GIS software in terms of area, number of pixels and image system. Next, the calculated environmental variables were placed in the regression relationship presented in the previous step, which was obtained between species occurrence with climatic and physiographic variables. Then, in the context of the Biomod package in the R program; the statistical model was transformed into a species distribution map, and in accordance with the fitted values, in Arc GIS software, a map was generated with a value between zero and one, and values close to one indicate areas with high probability of occurrence of the species. To better map the current range and future potential range; output maps, with a probability of occurrence between zero and one, to four floors; Inadequate habitat (0-0.25), almost suitable habitat (0.25-0.5), highly suitable habitat (0.5-0.75) and very high fitness habitat (0.75-1), The grouping was intense and by referring to the coefficients of variables in regression relations, effective variables for the current range and potential future range were introduced. In this regard, the extent of conformity of the presence range of A. Aucheri species with the current range (present) and their potential range in the future was evaluated using kappa statistical coefficient.
Global warming due to increased greenhouse gas emissions; it has caused obvious changes in Iran's climate, including rising temperatures, increasing climatic hazards and decreasing rainfall, in the last two decades. In this regard, most scientific sources emphasize that the increase in temperature has reduced the coefficient of bioclimatic comfort, and some plant and animal species that are not able to adapt to climate change, they migrate from their permanent habitat or gradually disappear. In this study, this aspect of the issue, namely climate change and the distribution of plant species, was emphasized. Based on the results; among the climatic and topographic variables, only the temperature-related indicators, in order of importance, include; BIO9, BIO10, BIO5 and BIO1 were identified as effective on the distribution of A. Aucheri species. The values of the characteristics increase as the climatic conditions worsen and as a result, the suitable habitat level (more than 75% probability) of A. Aucheri species will decrease for the following decades. In other words, it is shrinking in response to climate change. In this regard, the suitable habitat area of this species (probability of occurrence more than 75%) according to the current forecast map is 274505 hectares, which is about 18% of the total rangeland habitats in the southern Alborz. Also, the suitable habitat area of this species according to the forecast maps for 2050, under two scenarios of Rcp4.5 and Rcp8.5, is 208175 and 131964 hectares, respectively, which has about 13 and 8% of the total rangeland habitats. Overall; the area belonging to the classes in which A. Aucheri is more likely to be present has decreased in 2050 than at present. This indicates that in the future, the presence of A. Aucheri species in the habitats of the region will decrease and the risk of its removal from the ecosystems is evident. In sum, climate change and the consequent increase in temperature characteristics will cause the vertical expansion of A. Aucheri species and its movement towards higher latitudes along the altitude gradient of the region. Hence, the lower (1100 m) and upper (2500 m) expected range of vegetation range and altitude range in which A. Aucheri was observed (3400-1800 m); it will change over the next three decades. In this regard, the expansion of plants to higher altitudes during recent periods, an example of species displacement under the influence of climate change, has been mentioned. Also, one of the most important effects of climate change is the displacement of the geographical area of plant species. Based on the results of the present study and similar studies, by determining the degree of overlap of the current range event with the potential future range (for the next decade) of plant species, according to two climate warning models (milder scenario and more severe scenario); The changes that will occur as a result of climate change over the next decade in the distribution of species can be examined. Also, the results will be applicable in conservation and vegetation restoration programs, and based on the results, it is possible to identify suitable climatically and topographically sites for species conservation and rangeland.