azadeh bazrmanesh; Mostafa Tarkesh; Hossein Bashari; Saeid Poormanafi
Abstract
In order to model the potential habitat of Bromus tomentellus Boiss and study the effect of climate change on the habitat of this species in Isfahan province method of modeling maximum entropy (MAXENT) were used. The species event data were determined by random categorization method using field visits ...
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In order to model the potential habitat of Bromus tomentellus Boiss and study the effect of climate change on the habitat of this species in Isfahan province method of modeling maximum entropy (MAXENT) were used. The species event data were determined by random categorization method using field visits and geographic information system including 60 rangeland locations as educational points. Also, 20 points of occurrence were surveyed using GPS in the western region of Isfahan as points of assessment. 22 environmental layers including 3 physiographic variables and 19 climate variables derived from temperature and rainfall were used in the modeling process. Using by Maxent, the relationship between species incidence and environmental factors was determined. Then, the effect of climate change using cluster variables of CCSM4 general circulation model was evaluated under two scenarios RCP2.6 (optimistic) and RCP8.5 (pessimistic) on geographic distribution of Br.tomentellus Boiss. Regarding the photo curves, the specie’s behavior relative to the environmental variables of Br.tomentellus Boiss in the range of 2500 to 3500 altitudes, slope 10 to 30 degrees, annual precipitation is 240 to 260 mm and the average temperature is 8 to 10 ° C are more likely to occur. The habitat of the species studied during the two periods of 2050 and 2070, it was observed that under the optimistic scenario, 46.1 square kilometers to the appropriate level of the habitat of the Br.tomentellus Boiss is increased and under a pessimistic scenario, about 35.74 km2 is reduced from the appropriate level of habitat of this species.
Mohsen Sarshad Ghahfarrokhi; Seyed Alireza Mousavi; Saeed Soltani; Saeed Pourmanafi
Abstract
Natural resources are valuable capitals for all nations. Rangelands as the most extensive natural ecosystems in Iran provide numerous services, including fodder production and red meat supply, soil conservation and water regulation. Although uncontrolled exploitation of these resources has imposed much ...
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Natural resources are valuable capitals for all nations. Rangelands as the most extensive natural ecosystems in Iran provide numerous services, including fodder production and red meat supply, soil conservation and water regulation. Although uncontrolled exploitation of these resources has imposed much pressure and caused many losses within the ecosystems. Impacts of overutilization of nomadic livestock on Semirom rangelands from runoff control perspective has been the core objective of this study. Considering the utilization conditions, vegetation cover was measured within the vegetation types before and after livestock grazing during 2013 grazing season. Curve Number method was selected to evaluate the runoffs originating from rainfalls with different return periods before and after livestock grazing and the difference was considered as the grazing impact. This externality was valuated using replacement cost method. Results showed that utilization pressure is extremely more than grazing capacity which has distorted water regulation function of the rangelands, e.g. it has increased the runoff volume from a rainfall with 2-year return period from 1660884 to 2600487 m3. In other words, it has diminished the potential of rangelands in controlling water runoffs. Economically speaking, the external damage to water regulation function of rangelands was calculated at the rate of 25391 million Rial/year. This information on the externalities of nomadic livestock will provide the useful basis for economic appraisal of the utilization process and adjustment or rectification of economic activities which entail social costs on their way towards private profits.
