Tarbiat Modares University (TMU) ECOPERSIA 2322-2700 6 4 2018 11 01 Responses of Two Rangeland Noxious Plants Species to a Seasonal Drought 215 223 17241 EN E. Samari Biology Department, Sciences Faculty, Ferdowsi University of Mashhad, Mashhad, Iran M. Farzam Range & Watershed Management Department, Natural Recourses & Environment Faculty, Ferdowsi University of Mashhad, Mashhad, Iran P. Abrishamchi Biology Department, Sciences Faculty, Ferdowsi University of Mashhad, Mashhad, Iran Journal Article 1970 01 01 <strong>Aims</strong>: Drought and high temperatures are main environmental stresses for noxious plants in the arid environments. Responses of arid land plants to drought are complicated and include different adaptive mechanisms in terms of physiological, morphological, and phenological responses. This research aimed at investigating phenological and/or morphological responses of two globally important noxious plant species, <em>Centaurea virgata</em> Lam, and <em>Scariola orientalis</em> (Boiss.) Soják, during growth season of a dry year.<br> <strong>Materials & Methods:</strong> The present experimental research site was conducted in Noh-Dareh Mountains, Mashhad, Iran. Weekly field visits were done during the growth season (March to September) in 2011. Understory soil moisture and air temperature were recorded together with some morphological plant traits of both species. Daily air temperature and sporadic rainfalls were recorded and their possible effects on changes in plant phenology were investigated. The data were analyzed by SPSS 22 software, using t-test to examine differences in the selected parameters between the two species at each phenological stage.<br> <strong>Findings</strong>: Both species produced temporal rosette leaves that favored the high soil moisture in early growth season (March) and led to rapid shoot (stems and cauline leaves) production in the late April. However, they showed contrasting growth strategies in response to rain pulses and summer drought.<br> <strong>Conclusion</strong><strong>:</strong> <em>C. virgata</em> is a drought escaping and opportunistic plant that threats the native flora during spring of normal and wet years, whereas <em>S. orientalis</em> is a slow growing drought resistant species and can be a major treat both in dry and normal years. https://ecopersia.modares.ac.ir/article_17241_33f310507cba3f92ef26e1a311998f5d.pdf