SPATIOTEMPORAL EVOLUTION OF PLANT DIVERSITY AND EDAPHIC CHARACTERISTICS IN THE STEPPES OF ALFA......

During three years of monitoring (2013-2014-2015), we followed the spatial and temporal fluctuations of floristic and soil characteristics in three sampling stations in the Alfa (Stipa tenacissima) steppes in the municipality of Maâmora (region of Saida, western Algeria). Annually, 21 phytosociological statements were conducted on the three sampling stations for this purpose. Station 1 is a well-developed alfa exclosure, Station 2 is a somewhat degraded alfa exclosure, and Station 3 is a degraded alfa exclosure. The floristic study has revealed annual variation in the number of species as a result of annual rainfall variations. Indeed, the three stations recorded a maximum rate of 29 species in 2013, the year of high rainfall (517 mm), in contrast to 2014, when drought was severe (295, 9 mm), resulting in a decrease in the number of species to 22. Overall, therophyts predominate in the biological spectrum of these species, which is dominated by Poaceae, Asteraceae, and Caryophylaceae during the observation period. The soil investigation reveals that the three stations' soils have a silty-sandy texture, are shallowly depleted in organic matter, have low humidity, are salt-free, have an alkaline pH, and contain a significant amount of total limestone. To the spatial and temporal scales studied in this study, changes in these edaphic factors are extremely obvious. The factorial analysis of correspondences (AFC) approach highlights the existence of two distinct groups of stations. Stipa tenacissima (TR) = -0,493, hemicryptophytes (He) = -0,424, geophytes (Geo) = -0,114, a soil surface horizon with improved thickness (PR) = -0,316, better moisture (HUM) = -0,102, organic metter (MO) = -0,278) are all linked to Station 1. Stations 2 and 3 are associated with Group 2 (therophyts (TH) = -0,103, chamaephyts (CHA) = 0,516, and sand (SB) = 0,106). Reflecting the degree of middle of opening that is associated to a gradient of aridity evolving on a substrate dominated by sand and silt (AR = 0,092, CaT = 0,197), reflecting the degree of middle of opening that is related to a gradient of aridity.

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