توصيفگر ها :
ظرفيت چرايي , مراتع نيمهاستپي , استان كهگيلويه و بويراحمد , موديس , سنتينل-2 , مدلسازي , خشكسالي , مدل CASA
چكيده انگليسي :
Rangeland and forests are among the biggest national assets in the world. The role of these ecosystems is vital in providing fodder for domestic and wild animals, soil conservation, preventing floods, increasing water infiltration and underground water, production of medicinal-industrial plants, and preservation of plant and animal genetic resources. Researchers have reported increase in the number of livestock, severe grazing, and early grazing to be the most important factors in the destruction of vegetation in Iran and other countries. The lack of balance between the available forage supplies with livestock demand is one of the most important causes of rangeland’s destruction. The main goal of this research was to determine the grazing capacity using field measurements and remote sensing data in the rangelands of Kohgiluyeh and Boyer Ahmad province. In this research, the Net Primary Production (NPP) and grazing capacity of rangelands were determined using field sampling, satellite images, and modeling techniques. Factors affecting the grazing capacity of rangelands, such as animal daily requirement, the length of the grazing period, allowable utilization of rangeland plant species, fodder production, animal grazing area, the nutritional requirements of each livestock unit, and the length of the grazing period, were used to calculate grazing capacity in the study area. In addition, grazing capacity was determined using rainfall conditions and average production from 2009 to 2018 (average of 10 years) along with the rangeland production in the sampling year. First, to estimate the NPP, climate elements such as average monthly temperature, total monthly precipitation, and monthly sunny hours from meteorological stations were collected, and the amount of effective solar radiation was calculated and zoned according to the number of sunny hours and the location of the region, and mapped in the GIS environment. NPP of rangeland types was estimated using the CASA model, NDVI vegetation index extracted from MODIS and Sentinel-2 images, and climatic data including average monthly temperature, sunshine hours, and rainfall. The accuracy assessment of the NPP map was performed using field measurements and range management plans of the Natural Resources and Watershed Management Administration of Kohgiluyeh and Boyer-Ahmad Province. The NPP potential of the region was also determined using the Miami model, and the impact of human activities on the NPP was investigated by comparing the Miami and CASA model outputs. Finally, the grazing capacity map was obtained using monthly NPP maps, forage production, rangeland condition, plant allowable utilization, animal grazing area, and slope map. The Standard Index of Annual Precipitation (SIAP) was calculated using rainfall data to investigate the effects of drought on grazing capacity in the study area. The production obtained from satellite images varied between 2.4 and 393.2 kg ha−1 in 2018. Also, the results showed that the difference between actual and potential production in the province was more than 56 gC/m2/month, which could indicate the negative effects of human intervention in the pasture ecosystems of the region. The high correlation of 80% between production maps and field measurements, as well as the significance of these relationships in all vegetation types (p<0.05), made it possible to use satellite data in the estimation of grazing capacity. The minimum and maximum grazing capacities in a 100-day period were 1809 and 297146 animal units (AU) respectively, in 258387 ha.
