**4. Conclusion**

The study region receives an average annual rainfall of less than 300 mm, which explains it's belonging to the arid bioclimatic stage of climate. Precipitation has experienced a very marked interannual irregularity in recent years. The thermal amplitudes were lead to a much faster dieback of annual plants, subjected to intense evapotranspiration.

Climatic data from stations in the study region allowed us to observe the spatiotemporal evolution on a North–South gradient that depends on the irreversible phenomena such as aridity, evaporation (drying out of soils).

This work analyzes the variability of evapotranspiration for steppe vegetation. It is based on climate data measured at three meteorological stations in Naama region. The calculation of evapotranspiration by the water balance method, gave rather satisfactory results insofar as these results oscillate around the normal values of evapotranspiration for the three stations in the study region. Potential evapotranspiration (ETP) data estimated from Thornthwaite's method for the three stations (Mécheria, Naâma and Ain Sefra). The annual average value of potential evapotranspiration is of the order of 807 mm in Mécheria, 795 mm in Naâma de and Ain sefra at 847 mm. It is clearly 3 to 4 times higher than the value of the rainfall received. For this purpose, the PET generates a water deficit (drought) and/or favors a considerable influence on the soil and the growth of vegetation in the steppe ranges. In this steppe area of Naâma, the average annual precipitation is less than two thirds of the potential evapotranspiration (potential evaporation from the *Biophysical Effects of Evapotranspiration on Steppe Areas: A Case Study in Naâma… DOI: http://dx.doi.org/10.5772/intechopen.97614*

ground plus transpiration by plants). The high evapotranspiration confirm the climate aridity of the study area.

The vegetation can have an impact on the water balance by increasing evapotranspiration and reducing runoff, and the vegetation is characterized by various morphological, physiological adaptations such as xerophytes.

It is therefore easy to understand why most steppe species have low woody and herbaceous plants, and they have characteristics of xeropmorphism (*Stipa tenacissima, Lygeum spartum, Stipagrostis pungens*)) and sclerophyllia, especially in phanerophytes (*Quecus ilex, Pinus halepensis, Juniperus phoenicea, Juniperus oxycedrus, Pistacia atlantica*). They have as a result low size of plants and leaves, and low gross production. These plants reduce their exchange surfaces and close their stomata.

In perspective, it is necessary to assess this component of the water balance precisely from field measurements and to establish maps taking into account the particularities of the existing vegetation. This type of study makes it possible to formulate recommendations to better understand the species adapted to these climatic rigors.
