Plant communities phytolith assemblages relationship with the native flora from El Palmar National Park (Entre Ríos Province, Argentina).

PATTERER, NOELIA AND ALEJANDRO ZUCOL

Colorado

Encuentro; 8th International Meeting on Phytolith Research; 2011

PaleoResearch Institute, Golden, Colorado

Palms are common plant components in the tropical vegetation of America, distributed to warm temperate climate regions. El Palmar National Park is a nature reserve comprising a palm tree savannah and shrubs, and is one of the southernmost distributions of this plant group, in this particular case Butia yatay. Located in the east of Entre Ríos province is a relic of 8500 ha, distributed in patches between components of the semiarid forest, gallery forest and pampean grassland (namely mesopotamic prairie). In the present contribution the phytolith analysis of the principal vegetal species of the El Palmar National Park natural communities, selected by their coverage percentage were made. Phytolith extraction was performed by carbonation/calcination technique from leaf samples of selected species. Firstly, the population census carried out showed that grasses (Poaceae) has the highest percentage of coverage in the grassland, with significant values in the forest palm area, being fairly constant in the native forest. Sedges (Cyperaceae) are sparse; there were only low values in the semi-dense forest palm and grassland areas. Shrubs are abundant in the native forest and very scarce in grasslands. While tree species were absent, with the exception of the palms climax community. The principal selected species, in addition to the aforementioned palm (Butia yatay) are Axonopus argentinus,A. compressus, Setaria parviflora, Digitaria sacchariflora, Paspalum notatum and Schizachyrium microstachyum (panicoid grasses); Eragrostis lugens and Esporolobus indicus (chloridoid grasses); Bromus aulecticus (pooid grasses); Cyperus reflexus and C. aggregates (Cyperaceae); Baccharis trimera (Asteraceae) and other dicotyledons as Wahlenbergia linarioides and Glandularia peruviana. In regard to their phytolith assemblages, Butia yatay palm was characterized by abundance of the globular echinate type (mostly ranging 5-12 μm in diameter), vascular elements, and small irregular elements. The panicoid grasses were characterized by bilobates with straight lobes, concave and/or convex edges, and crosses; articulated or isolated, associated an elongated elements of sinuous edge very frequent, stomata; polyhedral and vascular elements less frequents. In the chloridoid grasses, the association present, isolated and articulated elements, as bilobates of lobes straight and/or convex, truncated cones, associated with elongated, fan-shaped and polyhedral, with stomata and point shaped, less frequents. For the only species within pooid grasses, the association was characterized by frequent oblong and crenate types, as well as less frequent point-shaped, square, crescent-shaped, and truncated-cone types. Cyperaceae species are characterized by the presence of hat-shaped or conical elements isolated and/or articulated, with rounded or hexagonal bases, associated with phytolith originated in vascular elements. Asteraceae species show the presence of prismatic rectangular phytoliths jointly with irregular phytoliths, silicified vascular elements, and articulated stomata complex. While the remaining dicots show scarce phytolith material, was presented fundamentally as silicified hairs associated with irregular cells, small elongated and papillated elements. This is the first contribution to the knowledge of the phytoliths in El Palmar National Park flora. It tested whether the various existing communities can be differentiated through phytolith assemblages. This study represents an initial step for further analysis of soils and sediments to reconstruct the recent evolutionary history of warm temperate savannahs.