| Abstrakt: |
Continuous degradation of vegetation and rangeland soil is mainly due to natural or human factors such as overgrazing; thus, it is necessary to know the extent of changes in rangeland ecosystems and their causes for rangeland management. Based on this, the trend of vegetation changes and soil indices in two exclosure and grazing sites in the Meyghan desert rangelands of Arak were studied from 2017 to 2021. At each location, to measure plant parameters such as cover percent, density, and yield, the random-systematic sampling method was used along six transects at distances of 100 m from each other, and soil sampling was also done during vegetation survey transects. The results showed that the percent of canopy cover of vegetation in the grazed site during the census period ranged from 23.43 to 28.67% and in the exclosure site from 32.8 to 40% in different years. The average total forage yield during the census period ranged in the exclosure site from 174.6 to 203.5 kg/ha and in the grazed one from 117.2 to 139.1 kg/ha in different years. The highest values of canopy cover and annual forage yield were observed in the rainiest of the year 2019, with 490 mm of rainfall, and the lowest values of the mentioned parameters in the least rainy year, 2021, with 223 mm of annual rainfall. Rangeland's condition by the four factors method has varied from weak to good in the exclosure site and from poor to moderate in the grazing one in different years. Rangeland trend in different years in the exclosure site has been positive or fixed, and in the grazing one has been negative. Examination of soil indices showed that during the evaluation period in the exclosure and the grazed site, changes in organic carbon, potassium, and nitrogen indices were significant (p<0.05), and changes in other indices were not significant. The regression test results showed that the amount of annual rainfall and rainfall of the growing season had the highest positive correlation with changes in canopy cover and forage yield of plants. After that, organic carbon, nitrogen, phosphorus, and potassium factors showed a high correlation with fluctuations in canopy and plant yield. In general, livestock grazing and climatic fluctuations, especially changes in annual rainfall had the highest impact on changes in vegetation characteristics of the studied rangelands. [ABSTRACT FROM AUTHOR] |
