Investigating the Role of Pistachio Orchards (Pistachio vera L.) on the Vegetation of Their Adjacent Rangelands

Background and Objectives: Microclimates are small areas in a general climate zone that have their own unique climatic conditions. Vegetation is one of the essential factors in the structure and function of terrestrial ecosystems and one of the basic links of the vital chain of water-soil-plants and atmosphere. One of the vegetations that has been cultivated in arid and semi-arid areas and is being developed in some of these areas, is pistachio orchards. This research, with the purpose of investigating the impact of pistachio (Pistachio vera L.) orchards on the vegetation of their adjacent rangelands, was performed in the Roshtkhar region of Razavi Khorasan.
Materials and Methods: First, three areas of pistachio orchards, as three replicates, that were similar in terms of climatic and physical conditions including topography (elevation and slope), soil characteristics (texture, structure, salinity, and depth of groundwater), and vegetation types, were selected. In each area, a pistachio garden was selected that was adjacent to a rangeland at least up to a distance of 100 meters, and after that was located a pistachio garden, abandoned agricultural land, rangeland, or irrigated agriculture. The percentage of canopy cover was measured along a 100-meter transect with 10 plots of 1 square meter by systematic random sampling method.  
Results: Results showed significant difference between the pistachio garden and abandoned agricultural land, rangeland, and irrigated agricultural land. Also, the average canopy cover of rangeland between two pistachio gardens was 58.4% greater than other land uses. The lowest canopy (37.4%) was related to the rangeland located between the pistachio garden and abandoned agricultural land. The highest changes in vegetation canopy were related to the pistachio garden- pistachio garden, with a standard deviation of 26.02. Also, the least changes in vegetation canopy were related to the pistachio garden- rangeland with a standard deviation of 18.14.
Conclusion: The results of this research showed the effect of pistachio orchards on the vegetation cover of the neighboring rangelands. The greatest effect is in the case where a rangeland area is located between two vast pistachio orchards. This effect can be caused by the creation of a microclimate resulting from the vegetation cover of pistachio gardens. The existence of these effects, which are caused by the creation of a microclimate due to the development of vegetation in a dry and desert area, can be considered for other areas under vegetation cover and in urban and industrial land uses.