Halophytic Flora of Argentina: A Checklist and an analysis of its diversity

Abstract

Saline terrestrial areas represent 3.32 % (92,600 km 2 ) of the Argentine continental territory. Halophytic vegetation is recognized in these regions likeedaphic or azonal depending on its association with saline or alkaline soils,not on the ecoregion's climates. The aims of this contribution are: (1) toprovide the first preliminary checklist of native vascular plants growing andcompleting their life cycle for saline continental areas of Argentina, and (2)to determine its endemism's, life forms and the ecoregions where these halophytes have been collected. A total of 673 halophytic taxa within 291 generaand 64 families of vascular plants were recorded in the various saline habitatsof Argentina, 23.17 % of them are endemics. The halophytic flora represents6.49 % of the total vascular flora of Argentina. Diversity shows a decreasing tendency from those geosystems that are less affected by hydrohalomorphicprocesses to those physically characterized by the maximum expression of the flooding-salinization processes. Historical factors along with occupational factors may have contributed in defining the current floristic pattern. Temporal fluctuations in depth, electrical conductivity and ionic composition of groundwater, are the main environmental factors determining the compositional variation of the saline vegetation of the country. Nearly all halophytes are flowering plants, only 0.30 % correspond to Ferns. Dicots comprised 67.31 % of the total (453 taxa in 48 families), while the remainder consisted of 216 taxa of Monocots (14 families), and only two Gymnosperm species. The family with the highest number of genera was: Asteraceae (53) followed by Poaceae (50), Fabaceae (21), Amaranthaceae (13), Solanaceae and Cactaceae (11), and Verbenaceae (10). The most represented genera are Atriplex (19), Lycium (18 taxa), Senecio (16), Chloris (12), Baccharis (12), Deyeuxia and Hordeum (11), Heliotropium (10), Gomphrena, Sporobolus, Solanum and Prosopis (9), Grindelia (8), Distichlis, Junellia, Glandularia (7) and Euphorbia , Aristida , Eragrostis and Festuca with 6 species. Regarding the life-form forms spectra, Hemicryptophytes are the predominant life-form and constitute 52.9 % of all recorded species, followedby Chamaephytes (21.84 %), Therophytes (10.10 %), Phanerophytes (7.13 %), Geophytes (5.79 %), Succulents (2.08 %), and Parasites (0.15 %). In the study area, the largest number of taxa was found in the Dry Chaco (26.95 %) followed by Espinal (18.31 %), Pampa (11.97 %), Patagonian Steppe (8.01 %), Puna (6.97 %), Monte of Plains and Plateaus (9.69 %), Humid Chaco (4.57 %), High Andes (4.06 %), Monte of Hills and Valleys (3.12 %), Iberá Marshes (2.81 %), Paraná Flooded Savanna (2.71 %), and Mesopotamian Savanna (0.83 %). When comparing the distribution of total endemics between the different ecoregions, Dry Chaco (33.65 %), appeared with the highest values followed Monte of Plains and Plateaus (18.27 %), Espinal (16.35 %); Patagonian Steppe (12.02 %), Puna (8 %) and Pampa (7.2 %). Surprisingly the number of halophytic taxa that grows in Argentina is very high, representing nearly 22 % of the total number cited for the world.