Long-Term Changes in Plant Life Forms as a Consequence of Grazing Exclusion under Arid Climatic Conditions

El Ouara natural region (southern dry area of Tunisia) is characterized by harsh climatic conditions (high temperature, low rainfall). It is the preferred destination of many herds disturbing local ecosystems and loosing many palatable plant species. These climatic stresses and human disturbances affect the local natural vegetation communities. Conservation management has been imposed in order to preserve the national floristic heritage and biodiversity. Among the proposed techniques was the creation of Sidi Toui national park since 1991. This study aims to assess changes of flora life forms strategies (Raunkiaer, Noy-Meir and Grime types) inside and outside the park from 1990 to 2011. The Raunkiaer biologic spectrum is considered as a flora adaptation strategy to the climatic conditions. Noy-Meir classified plants on the basis of their photosynthetic activity during the dry season (arido-passive and arido-active species). The C-S-R Grime model gathered plants to three groups (Competitive (C), Stress-tolerant (S) and Ruderal (R)). The quadrat point method was used to evaluate the natural vegetation status. Main results are (i) Chameaphytes and Hemicryptophytes cover increased at the beginning and decreased after long period of protection, (ii) Therophytes dominate inside the park after 20years of protection, (iii) Arido-active species are sensible to human disturbance and long protection effects and (iv) the protection period decreased the cover of S, CS and CRS species and increased the RS ones. Copyright (c) 2015 John Wiley & Sons, Ltd.