Application of Landscape Ecology Indices in Monitoring and Assessing Desertification (Case Study: Omrani Area of Gonabad)

Desertification is one of the most important degenerative phenomena in many arid and semi-arid regions. Climate change and human activities have led to the increase of desertification and desert development in these areas. The application of ecological indices of the landscape is a simple and practical method to monitor and evaluate desert development. This research was carried out with the aim of investigating the ability of the indices to monitor and evaluate the desertification in one of the main focal points of the wind erosion crisis in the Omrani area of Gonabad. In the next stage, land use and land cover maps were prepared using Landsat 5 and 8 satellite images for the years 1987 and 2017. Each type of land use and land cover was considered as a landscape element preparing the map of the landscape elements of the study area. Then, the amount of the diversity, dominance and the evenness indices of each landscape element were calculated. Then, the changes of landscape elements were studied between 1987 and 2017 through the Marcov matrix model in the ecology. The results showed that the amount of diversity and evenness indices have increased by 0.315 and 0.135, respectively, while the amount of the dominance index has decreased by 0.315 in 2017. Besides, the area of rangeland has decreased by 10.4%, while the area of the desert element has increased by 1.7%. The results showed that the average desertification rate has been 20 hectares per year from 1987 to 2017 years. Accordingly, in the event of the abandonment of the arable lands, the desertification development process in the region will be intensified due to lack of water resources which will show a strong and increasing effect of the desert element on the entire landscape.
Extended Abstract
1- The application of ecological indicators has increasingly been used to determine landscape features. The analysis of these indicators is based on the land use map and user-generated maps that are derived from satellite images and aerial photographs. For this purpose, each land use can be considered as a landscape element, and its changes over the time, are monitored and evaluated. The present study aims at monitoring and evaluating desertification in the Omrani area of Gonabad by using the ecological landscape indicators. The Omrani area of Gonabad is one of the main critical areas of wind erosion in the Gonabad County. Therefore, the ecological indicators of diversity, dominance and the evenness of the landscape have been investigated in 1987 and 2017.
2- At first, the ecological indices of diversity, dominance and the evenness of the landscape and Marcov matrix model in ecology were defined. Then, land use and land cover maps were prepared using Landsat 5 and 8 satellite images in the 1987 and 2017 years. Each type of land use and land cover was considered as a landscape element preparing the map of the landscape elements of the study area. Then, the amount of the diversity, dominance and the evenness indices for each the landscape elements was calculated. In the next stage, the changes of the landscape elements were studied between 1987 and 2017 through the Marcov matrix model in ecology.
3- The amount of the diversity index in the entire landscape of the studied area has increased from 1.291 in 1987 to 1.606 in 2017. The amount of the diversity index for desert elements of the landscape has increased from 0.501 in 1987 to 0.552 in 2017. Diversity index shows the degree of homogeneity and heterogeneity of the elements of the landscape. An increase in the diversity index indicates an increase in heterogeneity across the landscape. The non-desert landscape is covering 72.6 percent of the entire landscape. Therefore, increasing the amount of the diversity index indicated that the area of desert landscape elements has increased and the development trend of desertification has been positive. Besides, the amount increase of the diversity index of the desert landscape elements proves the development of the desert landscape elements in the study area. The results of the diversity index showed the desertification development trend in the entire landscape.
The amount of the dominance index in the entire landscape of the studied area has decreased from 1.294 in 1987 to 0.979 in 2017. The amount of the diversity index for desert elements of the landscape has decreased from 0.5 in 1987 to 0.45 in 2017. The reduction of the dominance index represents that the dominance of the main element of the landscape decreased relative to the total landscape. The dominant element has been rangeland in the landscape. Therefore, reducing the amount of the dominance index indicates a decrease in the dominance of the rangeland element in the landscape and the transformation of it to the desert elements. Therefore, the decrease in the amount of the dominance index is a good index to show the development of the desertification.
The amount of the evenness index in the entire landscape of the studied area has increased from 0.361 in 1987 to 0.496 in 2017. The amount of the evenness index for desert elements of the landscape has increased from 0.316 in 1987 to 0.365 in 2017. Considering the extent of desert elements in the study area, which cover less than 50 percent of the total landscape, an increase in the evenness index indicates the development of the desertification. From 1987 to 2017, the area, covered by the rangeland, has been diminished and added to the area of other elements. In the case of the desert elements of the landscape, the increase of the evenness index indicates the trend of desertification development in the entire landscape. The results showed that the average desertification rate has been 20 hectares per year from the 1987 to 2017 years. Accordingly, in the event of the abandonment of the arable lands due to lack of water resources, the desertification development process in the region will be intensified showing a strong and increasing effect of the desert element on the entire landscape.
4- The results of the study showed that the elements of the landscape and types of land use can serve as inputs for monitoring and assessment of desertification. Therefore, indicators for monitoring and evaluating the landscape elements, including diversity, dominance and evenness indices, along with the Marcov matrix model, can be used to study the variations of the spatial patterns of the landscape and their dynamic variations over the time. In addition, the ecological indicators of the landscape used in this study can be used to study other changes caused by natural or human factors, including the long-term effects of climate change and droughts, land use change and urban development