Determination of state and transition and threshold model of semi-arid grasslands using rangeland health indicators (Case study: Tandoureh area, north Khorasan)

Vegetation dynamic concepts and models play an important role in the new paradigms of the rangeland science, but historically, their development have been remained abstracted and theoretical. Rangeland health concepts and methods provide a relatively suitable analytical and practical framework for applying these theories in the field. To make succession investigation feasible, we have used the chronosequence succession's concept to change time dimension into spatial dimension. Then, the Rangeland Health Assessment (RHA) protocol was applied to rank sites for their health as compared to those of the references area. After grouping sites based on their similarity in health rank and using ecological threshold, the catalogues of state, transition and threshold model of the study sites were provided. Then states, transitions and thresholds were interpreted. It was recognized that grazing intensity is the most important factor in health decline of sites and transition between states.