Autecology of Zygophyllum atriplicoides in the rangelands of Northern Khorasan province

Ecological studies on range plants enhance our knowledge on the rangeland ecosystems which are useful for their planning and management. By doing field and laboratory experiments during 2008-2009، ecological conditions were studied in the main habitats of Z. atriplicoides in the rural and winter rangelands of Northern Khorasan province (NKP). Forage quality was also studied at different phonological stages. According to the results، Z. atriplicoides grows in the habitats with mean annual rainfall ranging from 260-380 mm، temperature 8-16 ºC، and altitude 680-1200 meter a. s. l. Topography was as plains and rolling lands، with geologic formations being conglomerate، marl، shale and sandstone. Soil texture was silty loam، weak alkaline، and poor in phosphorus and nitrogen. Vegetative growth and flowering stages were simultaneously occurred at early April till early June، but seed ripening and shedding happened at late June-mid August. Toward the end of growing season، ADF and NDF increased while crude protein decreased، which led to a gradual decrease in forage quality. Ability for growing in different habitats – from cold dry to warm humid- and having protein content and metabolic energy higher than the critical level for rangeland livestock are the relative advantages، whereas significant leaf reduction in response to drought and heat stresses، inability for growing in saline lands and low palatability and preference values are the major disadvantage for Z. atriplicoides in the rangeland of Iran. The most suitable time for livestock grazing and seed collection of Z. atriplicoides in the NKP are May-June and July، respectively.