كنشهاي متقابل بين گياه درمنه كوهي (Artemisia aucheri Boiss) و بروموس (Bromus tectorum L.) مطالعه موردي مراتع استپي نصرآباد استان يزد

Interactions between Artemisia aucheri Boiss and Bromus tectorum L: Case study, steppic rangeland of Nasr-Abad, Yazd,

Facilitation and competition were studied between perennial semi-shrub Artemisia aucheri Boiss and annual grass Bromus tectorum L. Near surface temperature and luminance, relative humidity of different soil depths and density of Bromus, were different under canopy of Artemisia as compared with those of the nearby open spaces. Soil humidity was the primary source for plant-plant interaction. Relative soil humidity weight was higher under Artemisia canopy, which was due to the lower air temperature and irradiance. Such conditions, enhanced establishment of Bromus under the canopy of Artemisia (facilitation effect). On the other hand, regression analysis indicated decreases in the Artemisia vigor by increasing the number of Bromus in its understory (competition effect). Accordingly, a cyclic dynamic is suggested, which starts by Artemisia establishment, continues with facilitation and competition, and terminates after Artemisa death. In conclusion, a high mortality rate of Artemisia shrubs in the Nasrabad rangelands, during dry years of 1999-2001, is partly because of the intense competition effects by Bromus tectorum