Investigating the effect of fluctuations of climatic elements on the environmental changes of the pastures of Kohgiluyeh and Boyer Ahmad provinces, a case study of the Abrizkobgian watershed area

Master's thesis in natural geography, climatological trend in environmental planning

Abstract

Plenty of altitudes and extreme altitude changes and of course wide fluctuations in temperature, humidity, annual precipitation and so on. It has caused the province of Kohgiluyeh and Boyar Ahmad, located in the southwestern half of the country, to be a bridge between the habitats of the four growing regions of the world (Iran and Turan, Sahara and Arabian, Sindh and Sudan, and Mediterranean). And it includes the longitude ?6°51° to ?38°51° east located in the cities of Boyer Ahmad and Dana, which is considered to be one of the cold and humid regions in terms of climate and is a part of the sub-basins of the Great Karun. Among the climatic elements, humidity and temperature fluctuations are the most effective variables that determine the vegetation cover and its changes, and it is effective on most of the vegetation indicators, including density, production and their condition (suitable, average and unsuitable). Considering that the main goal of this research is to investigate the relationship between the fluctuations of the climatic elements (rainfall and temperature) and changes in the vegetation cover (the amount of pasture production), therefore, the effects of intermittent and consecutive droughts and droughts on the amount of pasture production, in the range Kabgian basin has been investigated. In determining wet and dry periods, 3 and 5 year moving averages were used. Standard Rainfall Index (SPI) method has been used to investigate the drought and drought conditions of the study area. In order to determine the relationship between the fluctuations of climatic elements and the amount of pasture production, in addition to investigating and analyzing this relationship using statistical methods of relationships and regression models and correlation coefficients, using multivariable regression equations and analyzing with the entry method (Step wise), the most effective rainfall and temperature timings on changes in the amount of pasture production in the study area were determined. In general, the results confirm the existence of a significant relationship between production and annual precipitation and reject the existence of a significant relationship between production and average annual temperature. Nevertheless, there is a significant relationship between some other timings of temperature and precipitation, such as the maximum temperature in April and the total rainfall from January to June, with the amount of fodder production in the region's pastures. Based on the proof of the significant relationship between some timings of climatic elements and the amount of pasture production in the region, to determine critical areas in terms of pasture production and grazing and determine its status in three levels (suitable, average and unsuitable) in representative years of drought and drought, from soft Arc Gis software was used. The resulting maps for the state of pasture production according to climatic fluctuations show the environmental effects in the form of an increase in critical areas in terms of pasture production in dry years and a decrease in critical areas in terms of production in droughts, in the study area.

Key words: Kohgiluyeh and Boyer Ahmad, Kabegian, climatic elements, quantitative changes in pastures, Standard Precipitation Index (SPI), Geographical Information System (GIS)

Chapter First

General Research Framework

1- Statement of the problem

Although climate refers to the general and stable state of the air in a region and has relative stability, this stability is true in short-term processes and may not have much validity in the long-term. As the study of the earth's past shows, weather conditions along with other internal and external developments of the earth have undergone changes and cold and hot or dry and wet periods have replaced each other repeatedly (Marianji et al., 2012: 3). Among the climatic elements, temperature and precipitation have large fluctuations. In low latitudes that are exposed to intense radiation, temperature fluctuations are low, and in moderate and higher latitudes, annual temperature fluctuations are higher. Also, precipitation has many fluctuations in different regions of the world (Alijani and Kaviani, 2014: 26).

Since climate affects the distribution of vegetation and climatic fluctuations also include short-term fluctuations of climatic elements (temperature and precipitation) in a short period of time, therefore these fluctuations can affect nature, especially vegetation (Pourkhbaz et al., 2016: 15). So that the growth and development level of vegetation is related to these elements.Due to the sensitive ecological situation, pastures are affected by climatic fluctuations, especially precipitation and temperature (Noori et al., 2010: 2).

Basically, natural vegetation reflects all the effects of weather factors. Therefore, it is not surprising if it is observed that there is a complete correspondence between the vegetation zones and the climatic zones. So there is a clear harmony between the types of climate and the types of plants. There is a deep relationship between the climate and the type of vegetation, and the climate factor is one of the factors that determine the type of vegetation of each geographical region (Naresh, 1380: 6). Undoubtedly, nature (vegetation communities) in the world is widely affected by climate fluctuations. In other words, the maps related to the distribution of vegetation communities are compatible with the main climatic lines of the region (Jafarpour, 1381: 15). In Iran, changes in vegetation cover are under the influence of climate and climatic fluctuations. But it should be noted that Iran is a very diverse land in terms of climate. According to the studies conducted in Iran, for example, in the southern regions of the country, a high fluctuation of rainfall is observed, and such fluctuations are effective in the vegetation of different regions (Alijani, 1379: 4-1).

     Kohgiluyeh and Boyer Ahmad provinces are at the forefront of the Mediterranean rain-producing currents that enter the country from the southwest and west and receive a significant amount of moisture from the currents in the form of atmospheric precipitation. Also, this province is affected by the currents of the North Atlantic Ocean and the Persian Gulf, the former entering the country from the northwest and the latter from the southwest after crossing the Caucasus. The rainfall regime of the region is Mediterranean, like other parts of Iran, and as a result, it has a dry period of 5 to 8 months, which lasts from the beginning of May to the end of November and sometimes until December (Yousefi, 1378: 17). In addition, on the other hand, it is under the influence of the high pressure of the tropical zone in the summer season. Relatively high temperatures when this high pressure rule leads to an increase in evaporation and transpiration of plants in this region, which in turn affects the changes in the surface and growth of plants in the region.

The topographical conditions governing the province (the highest altitude, Dana with 4430 meters and the lowest altitude, Charazan with 197 meters above sea level) caused it to be divided into two regions from the point of view of climate (iceland with cold climate) and humid and tropical with hot and dry climate). Due to being located in the arid belt, this province has faced the phenomenon of drought intermittently (Hedayati Dezfuli, 1384: 1). This phenomenon has also affected the fields, natural resources, forests and pastures of this province.

Management of any resource is not possible without its accurate and scientific knowledge. Considering the dynamic nature of pastures and the occurrence of short-term and long-term changes in it, the knowledge of this resource should be deepened to include information about the process and how the changes are. Recognizing the trend and amount of changes, which is necessary for long-term management of pastures, requires long-term information to provide the desired basic data and to enable the analysis of the changes and the role of external factors. Therefore, it is necessary to design a system for the continuous investigation of pasture habitats in the country in order to provide the necessary information according to the extent of pastures in different climatic regions and different management conditions (Arzani et al., 1382: 5-10).

The watershed of the Kabegian River is located 20 km from the city of Yasuj, the capital of Kohgiluyeh and Boyar Ahmad provinces, with an area of ??845.8 square kilometers, a part of Boyar Ahmad counties. And it is Dana, that nearly 72.5% of its area is forest and pasture and the other 27.5% is agricultural, residential, rocky and non-exploitable land from the point of view of pasture.

In this research, the statistical data related to the temperature and precipitation elements of the rain gauge and evapotranspiration stations of the study area, as well as the data and findings related to the amount of pasture production, and the relationship between the fluctuations of climatic elements (temperature and precipitation) and vegetation changes The amount of fodder production in the region is analyzed in detail, the results of which can be used by planners in various fields, including agriculture, crisis management, meteorology, natural resources, environment, etc. be used.

1-2- Importance of the problem

Since changes in quantitative parameters such as the abundance, composition and structure of vegetation and production in pastures are affected by non-living factors [1] (such as rainfall) and living factors [2] (such as livestock grazing), therefore it is important to recognize the factors and separate them in the way of decision-making in pasture matters (Anderson & et al, 1981).