Effect of precipitation and high temperature variability on forage production of some plant species in the Yazd steppe rangelands during the period of 2000-2008 (Case study: Ernan region)

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 and temperature variability impact. In this research، the reactions of the dominant plant species yield to meteorological variables such as rainfall and high temperature were studied at steppe rangeland in Ernan region during the period of 2000 to 2008. For this purpose، it was selected four dominant species and their forage production were measured every year with clipping and weighting method along four permanent lines transect in 60 random plots (2m × 2m). Meteorological data were collected from nearby climatological station. Relationship between main meteorological gradients and forage annual yield، analyzed by redundancy analysis. According to this result، total annual yield and annual yield of Artemisia sieberi and Salsola tomentosa had significant correlation with axis 1 (r = - 0. 93، r =- 0. 86 and r = - 0. 92 (and influenced by rainfall in December-March period and maximum temperature in July. In addition، forage yield of Salsola tomentosa is influenced by rainfall in the previaus year. Species yield of Ephedra strobilacea and Stipa barbata showed high correlation with axis 2 (r = 0. 64 and r = 0. 72 (and influenced by rainfall in December-March، April-June periods and maximum temperature in April. These meteorological gradients were related closely to the first two canonical axes، and accounted for 94. 9% of the species–environment relationship in the study sites.