Effect of habitat protection on plant vegetation characteristics and rangeland condition of Zayandehrud watershed management research site

The study of vegetation changes under habitat protection conditions has a significant role in rangeland management. The studies confirm that permanent changes in rangelands in terms of plant composition, canopy cover, and forage production are influenced by ecological and management factors. This research was conducted to investigate and monitor the plant vegetation indices of semi-steppe rangelands of central Zagros for five years (2016-2020) at the Zayandehrud watershed management research site (Isfahan province). 

 Vegetation sampling was performed by a systematic random method in each exclosure and grazed site during 2016-2020. Vegetation characteristics, including the percentage of canopy cover of species, the percentage of gravel, bare soil, and litter were determined in each plot. For this purpose, four 100-meter segments were used. Then, ten plots (with 1 x 1-meter dimensions) were established with the same distance. In total, vegetation cover was measured in 80 plots of one square meter in exclosure and grazed sites. To calculate rangeland production, ten samples of each plant species were collected, and their canopy cover percentage was measured. After drying and weighing the samples, by establishing regression equations between the canopy cover percentage and the weight of the dried samples, the amount of production of plant species was determined separately for growth form and palatability class. Rangeland's condition was also evaluated according to the four-factor method and by scoring the factors of soil, vegetation, plant composition and age classes, and plant vigor. After collecting the data in Microsoft Excel, the variance analysis for the vegetation traits was done as a completely random design in a factorial format. This was done through the GLM (General Linear Model) method. Tukey's test investigated vegetation traits mean comparison in MINITAB 16 software. 

The analysis of variance showed a significant difference between vegetation indices, including total canopy cover and production, separately for growth form and palatability class. This was in the exclosure and grazed sites during the assessment period. The average percentage of canopy cover in exclosure sites during different years was 26.7%, 13.7%, 25.84%, 33.74%, and 13.33%. In grazed sites, it was 22.33%, 12.65%, 27.09%, 30.9%, and 11.59%, respectively. Total production at the exclosure site during different years was 624.26, 349.86, 556.79, 894.54, 664.53 kg/ha. Production at the grazed site was 456.45, 243.85, 455.6, 605.47, and 323.44 kg/ha, respectively. The highest values of canopy cover and production belonged to 2019, which was a wet year based on meteorological indices. The lowest canopy cover and production were assigned to 2017 (a drought year). The highest amount of litter was found at the exclosure site. The highest percentage of bare soil and annual plant canopy cover was obtained from the grazed site. The highest percentage of canopy cover and production in the exclosure site belonged to Stipa hohenackeriana. At the grazed site, Hedysarum criniferum and Stipa hohenackeriana accounted for the highest canopy cover and production, respectively. According to the four-factor method, the rangeland condition at the disclosure site was fair in 2016, 2018, and 2019 and poor in 2017 and 2020. At the grazed site, the rangeland condition was fair in 2018 and 2019 and poor in the rest of the years. 

 The comparison of vegetation parameters inside and outside the exclosure shows the good condition of vegetation inside the exclosure. It also shows the effectiveness of the exclosure in rangeland rehabilitation. Balanced livestock grazing on the vegetation caused no significant difference between vegetation characteristics, such as canopy cover in the exclosure and grazed sites. Continuous evaluation and monitoring of rangelands through creating a regular database of vegetation indicators and investigating their changes under different managements. This investigation of their relationship with climatic factors can provide the necessary background for fundamental rangeland planning and management.