Impact of rainfall variability on yields of some plant species (Case Study: Mehriz rangeland of Yazad province)

Understanding the vegetation dynamics of arid rangelands is a prerequisite for their proper management. Water stress is the most crucial environmental stress for vegetation in this region and long-term monitoring experiments are an important tool to investigate rainfall variability impact. This study was conducted on Aliabad rangelands for nine years (1378- 1386). The aim was examining the effect of rainfall variability (year, season and period) on production of plant species. For this purpose four dominant species were selected and their canopy cover and production were monitored every year along permanent line transect in random plots. Precipitation data were collected from nearby stations. According to data of rainfall, amount of cumulative rain was determined at various periods. Relationships between variables of annual yield and amount of cumulative rain were analyzed by simple and multivariate (stepwise) regression methods. The Results indicated that many of plant species are affected by rainfall variability. However, various species reacted differently to the rainfall variability in terms of production. According to this result, annual yield of, Artemisia sieberi, Ephedra strobilaceae, Zygophyllum eurypterum can be estimated by rainfall data, but Salsola tomentosa production did not have significant relationship with rainfall variability. Result of curve fitting showed that yield response in Ephedra strobilaceae and Artemisia sieberi are in two forms of power and quadratic, respectively.