Evaluating the change process of vegetation patches of semi-steppe rangelands using landscape metrics

The pattern of the landscape and its corresponding changes is a comprehensive reflection of the ecology of the environment. The existing ecological processes in different scales cause the fragmentation and disintegration of the landscape structures and cause changes in the spatial distribution and fate of the patches in it. Plant patches are a relatively homogeneous part of the landscape, which have different responses to natural disturbances and management actions, and indicate the history of the management governing the region. It seems necessary to use detection methods to determine the process of changes in the distribution pattern with the passage of time in an ecosystem. Landscape metrics are one of the most important detection methods that provide the basis for quantification of the structure and spatial pattern of the landscape and make the nature of dispersion and distribution of its structural components comparable. The present study was conducted with the aim of investigating the process of changes in the pattern of plant patches in Broujen city, which is located in a heterogeneous landscape in central Zagros. For this purpose, Landsat satellite images from 1990 and 2019 were used and then classified in Idrisi TerrSet software. This has led to the production of classification maps with various patches and placing them in seven different classes in terms of the plant community. In order to quantify landscape pattern at the class level, CA, PLAND, ED, TE, ENN-MN, and SHAPE-MN metrics were calculated using Fragstats software. The results indicate a decrease in degradation and an increase in patch stability in the Astragalus verus, Astragalus verus-Bromus tomentellus, and Astragalus verus-Stipa hohenackeriana classes. On the other hand, the landscape covered by Bromus tomentellus, Bromus tomentellus-Stipa hohenackeriana, and Stipa hohenackeriana classes has been increasing, which shows the expansion of the classes and the reduction of their disintegration. The results also show that except for the Bromus tomentellus class, which shows the increase in complexity and the irregular shape of its patches, the trend of changes in other classes is downward, and it shows that during the period under investigation, the shape of the patches of each class becomes simpler and more regular.