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Revista de la Facultad de Ciencias Agrarias. Universidad Nacional de Cuyo

versão impressa ISSN 1853-8665versão On-line ISSN 1853-8665

Rev. Fac. Cienc. Agrar., Univ. Nac. Cuyo vol.52 no.2 Mendoza dez. 2020

 

ORIGINAL ARTICLE

Diversity and conservational status of vascular plants of “Sierra de las Quijadas” National Park (San Luis, Argentina)

Diversidad y estado de conservación de la flora vascular del Parque Nacional “Sierra de las Quijadas” (San Luis, Argentina)

Elisa Margarita Petenatti 1, 2, 3; Marta Elena Petenatti 1, 2; María Virginia Príncipe 1; Paulina Cardoso-Schiavi 1, 2; Marcos Federico Pascuali 1; Luis Ángel Del Vitto1, 2, 3

1 Herbario y Jardín Botánico, y Área de Farmacognosia. Universidad Nacional de San Luis. Ejército de los Andes 950. D5700HHW San Luis. Argentina. empetenatti@gmail.com

2 Proyectos 2-1118 SECyT-UNSL y 22-Q816 SPU-ME.

3 IMIBIO-SL (CONICET/UNSL).

Originales: Recepción: 02/12/2019 - Aceptación: 01/10/2020


ABSTRACT

The “Sierra de las Quijadas” National Park, located in the NW of San Luis province, covers 150,252 hectares and preserves a sample of the Chaco-Monte ecotone, with communities of the “Dry Chaco”, and “Monte” ecoregions (partly “Monte of plains and plateaus” and partly “Monte of Sierras and bolsons”). It includes mixed forests, shrubby steppes, groves and galleries, rings of halophytes, “pajonales” and rushes. Our goals were to inventory and analyze the vascular flora as well as to identify the endemisms that require greater protection. We recorded 356 species distributed in 208 genera of 58 plant families. Eight taxa are new records for the native vascular flora of the province of San Luis. While 120 taxa are endemic to Argentina, four species turned out to be exclusive of the Park and surroundings: Atriplex quixadensis (Chenopodiaceae), Senecio hualtaranensis (Asteraceae), Sclerophylax difulvioi (Solanaceae) and Gomphrena colosacana var. andersonii (Amaranthaceae). These taxa suffer varying degrees of threat from population restriction, intense erosion and anthropic action: 3 are critically endangered (CR), other 3 are endangered (EN), 10 are vulnerable (VU), 25 near threatened (NT) and 79 cause minor concern (LC), requiring in many cases immediate and continued protection. Dicotyledons (74%) and Monocotyledons (25%) predominate, plus 2 Monilophyta species and 3 Gymnospermae. The six best represented families are Poaceae, Asteraceae, Fabaceae, Solanaceae, Verbenaceae and Bromeliaceae, which account for 56% of the species. Phanerophytes and Hemicryptophytes life-forms reach 24% each, followed by Chamaephytes (22%) and Therophytes (16%). This reveals a remarkable adaptation of the flora to the long dry season.

Keywords: Argentina; Life-forms; National parks; Plant conservation; San Luis; Sierra de las Quijadas; Vascular flora

RESUMEN

El Parque Nacional Sierra de las Quijadas está ubicado en el NW de la provincia de San Luis. Cubre 150.252 ha y preserva una muestra del ecotono Chaco-Monte, con comunidades de las ecorregiones “Chaco Seco” y “Monte” (en parte “Monte de llanuras y mesetas” y en parte “Monte de Sierras y bolsones”). Comprende bosques mixtos, estepas arbustivas, bosquecillos y galerías, “anillos” de halófitas y pajonales y juncales. El objetivo fue inventariar y analizar la flora vascular e identificar los endemismos que requieren mayor protección. Se registraron 356 especies distribuidas en 208 géneros de 58 familias. Ocho taxones específicos e infraespecíficos son nuevos registros para la flora vascular nativa de la provincia de San Luis. De los 120 taxones endémicos de Argentina presentes en el Parque, cuatro resultan endemismos exclusivos: Atriplex quixadensis (Chenopodiaceae), Senecio hualtaranensis (Asteraceae), Sclerophylax difulvioi (Solanaceae) y Gomphrena colosacana var. andersonii (Amaranthaceae). Estos taxones sufren diverso grado de amenaza por la restricción poblacional, la intensa erosión y la acción antrópica: 3 están en peligro crítico (CR), 3 en peligro (EN), 10 son vulnerables (VU), 25 casi amenazadas (NT) y 79 causan preocupación menor (LC), requiriendo en muchos casos protección inmediata y continuada. En la flora del PNSQ predominan las Dicotiledóneas (74%) y Monocotiledóneas (25%), más 2 especies de Monilófitas y 3 de Gimnospermas. Las seis familias mejor representadas son Poaceae, Asteraceae, Fabaceae, Solanaceae, Verbenaceae y Bromeliaceae, que reúnen el 56% de las especies. Las bioformas fanerófitos y hemicriptófitos incluyen 24% de las especies cada una, seguidas de caméfitos (22%) y terófitos (16%). Esto demuestra una notoria adaptación de la flora a la prolongada estación seca.

Palabras clave: Argentina; Bioformas; Conservación; Flora vascular; Parques nacionales; San Luis; Sierra de las Quijadas


INTRODUCTION

The “Sierra de las Quijadas” National Park (hereinafter, SQNP) is a natural and landscape reserve that protects the current flora and fauna, representative of the Biogeographical Provinces “Chaqueña” and “Monte” and their ecotones (in the sense of Cabrera, 1976). In addition, important paleontological and archaeological sites are also included in the framework of shocking geoforms for their scenic beauty and genetic complexity (figure 1).

Photo L. A. Del Vitto. / Foto L. A. Del Vitto.

Figure 1. The “Potrero de la Aguada” basin, seen from their eastern edge; in the background, the steep western edge.

Figura 1. La cuenca del “Potrero de la Aguada”, vista desde el borde oriental; al fondo, el escarpado borde occidental.

The goals of this work were to inventory and analyze the diversity of vascular flora as well as to identify the endemisms that require greater protection.

1. Location and extension

It is located at the NW end of the province of San Luis (Dpt. Ayacucho and Belgrano) and integrates the Federal System of Protected Areas (65). It extends between approx. 32° 21´ and 32° 55´ S and 66° 52´ and 67° 17´ W (figure 2) and covers 150,252 ha (approximately 2% of the total area of San Luis province and 35% of its protected areas).

Ref.: Parque Nacional: National Park.- Reserva Nacional: National Reserve.- Cauce temporario: Temporary stream.- Camino consolidado: unpaved road.- Camino asfaltado: paved road.- Ruta nacional: Major road.-Ruta provincial: State road.- Línea alta tensión: High voltaje line.- Límite interprovincial: interstate limit.- Zona inundable: Flood zone.- C°: Cerro / Hill.- Ea.: Estancia / Ranch.- Sa.: Sierra.- Dpto.: Departamento / Department.- Lag.: Laguna / Lagoon.- Sta.: Santa.- Va.: Villa / Village

Figure 2. Map of the “Sierra de las Quijadas” National Park and Reserve and surroundings.

Figure 2. Mapa del Parque Nacional y Reserva “Sierra de las Quijadas” y alrededores.

Of these, 73,785 ha correspond to the National Park (Category II, APN), surrounded in its limits N, S and E by a buffer zone of 76,467 ha, administered as a National Reserve (Category VI, APN; 10). The Park administration has been established in Hualtarán, a place located 116 km NNW from the city of San Luis.

2. Background

The preservation of the area was proposed by geologist and paleontologist José Román Guiñazú (1897-1991) (29, 48). Based on the project drawn up by the National Parks Administration (3, 38), Law N° 24015/1991 was approved, which gave it the status of National Park (6). Later the homologation of the management plan and zoning took place (4, 43, 44), based on numerous studies. Regarding the flora, the studies were developed from the creation of the Park itself (19, 20, 21, 22, 23, 49, 50), but did not reach the overall vision that is expected to be achieved through this work.

Ramsar Site N° 1012 “Lagoons of Guanacache, Desaguadero and El Bebedero” includes entirely the SQNP (17, 53, 66, 67, 68). This lacunar area and its sub-basins cover 962,370 ha. An environmental restoration program for the Lagoons of Guanacache was initiated in 2012 by the provinces of Nuevo Cuyo (Mendoza, San Juan, San Luis and La Rioja). Azudes (levee) were built to retain the water that the Desaguadero river drains permanently from the lagoons. Attempts are made to reinstate stable settlers (especially former inhabitants and descendants of “huarpes” people) who develop livelihoods in harmony with Nature at the Ramsar Site and in the Reserve that partially surrounds the Park, preserving the core area of the National Park.

3. Preserving objects

The SQNP protects the specific and ecosystem diversity of the ecotone among the biogeographical provinces “Monte” and “Chaqueña”, they keep the ecologic connectivity in the environment and preserve the drainage network at the Western slope in the Sierra de las Quijadas, which provides flows to the fluvial lacustrine system Desaguadero / Guanacache / Salinas del Bebedero.

In addition, the preservation of the environmental quality and scenic beauty of the public access sectors has been imposed on the Park, especially the area of “Potrero de la Aguada”, and the protection of their interesting geological formations, as well as the conservation of the archaeological and cultural heritage of the region.

Four plant species are so far exclusive endemisms of the SQNP and its immediate surroundings: Atriplex quixadensis Del Vitto, Múlgura & Petenatti (Chenopodiaceae), Gomphrena colosacana Hunz. & Subils var. andersonii Subils & Hunz. (Amaranthaceae), Sclerophylax difulvioi Del Vitto & Petenatti (Solanaceae) and Senecio hualtaranensis Petenatti, Ariza & Del Vitto (Asteraceae) (20, 22, 23, 49) (figure 3).

Photos by the Authors. / Fotos de los Autores.

Ref.: A, Sclerophylax difulvioi; B, Gomphrena colosacana var. andersonii; C, Atriplex quixadensis; D, Senecio hualtaranensis.

Figure 3. The four endemic plant species, exclusive to the SQNP and its surroundings.

Figure 3. Las cuatro especies vegetales endémicas exclusivas del PNSQ y alrededores.

Also several threatened taxa and regional and Argentine endemisms of flora and fauna are well represented: another 116 species of higher plants (in this work), 6 species of mammals, 13 of birds, 5 of reptiles, one of amphibians and one of fishes (28, 31, 32, 64), which find integral protection in the Park and the Reserve.

Finally, stand the spectacular beauty of a huge natural amphitheater called the “Potrero de la Aguada”, an immense depression that extends over 4,000 ha (figure 1, page 216).

4. Physical environment

The area that today occupies the Park and its surroundings constituted a continental Cretaceous sedimentary basin about 120 million years ago (Ma). The Andean orogeny (25 Ma), raised the Western edge forming the actual Sierra de las Quijadas (56). The fluvial and eolic sedimentation, gave rise to the plains and the bottom of the Lagunas de Guanacache.

Three geomorphological units have been recognized in the SQNP:

a) The bolson of the “Pampa de las Salinas” (in the E and NE) is and endorheic basin with “bajadas” from the edges of the mountains and central “playas” with extensive “salitrales”. The scarce vegetation is reduced to groves or bushes with some phreatophytes in the bajadas, and a steppe of halophytes in the playas, with the typical vegetation rings that obey the saline gradient (57).

b) The Las Quijadas-Gigante ranges constitute a massif block of crystalline basement, elevated during the Neogen Andean orogeny. The Sierra de las Quijadas is composed of igneous, sedimentary and metamorphic rocks of various ages (37) with some fossiliferous formations (56). A large erosive depression covers about 4,000 ha in the N of the Sierra: the “Potrero de la Aguada” (27). It constitutes the focal point of the SQNP and shows a spectacular succession of columns, cornices, steps and slopes, sculpted by the network of torrents that converge in the Potrero stream, sporadic tributary of the Desaguadero river (27, 37) (figure 1, page 216). Basin sediments are exposed in almost vertical walls on the western edge of depression; these sediments are formed by reddish-orange to deep red sandstones and fangolite, all of which form an impressive landscape (figure 1, page 216). The eastern edge, in turn, is extremely sinuous, dissected by strong erosion.

c) The alluvial girdle of the Desaguadero river comprises the lowlands to the W of the area (27, 45, 52). The river originates in the Guanacache system lakes and runs from N to S forming a flood plain and a rosary of temporary, shallow lagoons. The climate of the whole area shows hot summers and mild winters, compatible with an arid mountain climate (“árido serrano”). The records of various meteorological stations allow define it as BWh according the Köppen-Geiger climatic classification. Thermal amplitude is large, both daily and seasonal. Annual average maximum temperature is close to 24°C, and the average minimum temperature is ca. 10°C. In the warmest month (January) the average maximum is close to 31°C, while in the coldest month (July) the average minimum only reaches 3°C. The frost-free period (October to April) ranges between 150 and 210 days. The area is located below the 400 mm isohieta, and the rains decrease from the E (ca. 360 mm) to the W (no more than 80 mm), in a monsoon regime, since 80-95% of the precipitation takes place between October and April.

The water deficit is continuous throughout the year (El Retamo), although some sites have a short, relatively wet season in summer (La Tranca, La Calera), as shown by the climate diagrams of figure 4 (page 220) (Walter & Lieth’s model, 1967), which summarize the climatic conditions of these three localities that circumscribe the SQNP.

Drawn by L. A. Del Vitto. / Dibujado por L. A. Del Vitto.

Figure 4. Climate diagrams of three locations near SQNP.

Figura 4. Climogramas de tres localidades cercanas al PNSQ (according / según Walter & Lieth, 1967).

The annual average relative humidity is 55%. The prevailing winds correspond to the SW (dry) and NE (with low humidity) quadrants. The only semi-permanent watercourse in the area is the Desaguadero river, whose salinity is increased during the rainy season due to the leaching of adjacent lands. It has been reported that groundwater is not suitable for human or animal consumption (31).

All soils that present in this area are genetically young, sedimentary (47), developed under an aridic and thermal regime (low rainfall and relative high soil temperatures), whereby the orders Entisols and Aridisols predominate (47, 70, 71). Among the first, with little differentiation of horizons, the calcareous torriortents in the mountain range, and the typic torriortents in the piedmont plain are presented. The aridisols have little organic matter and they are bit leached, characteristic of semideserts and deserts, here they are represented by the paleorthids from the arid piedmont plain, and the calciorthids and salorthids corresponding to the salt depressions (47). In addition to shallow lithosols on the slopes or mountain peaks, in the profile explored by the roots (0-3 m deep) loessic sediments are found (to the E of the line of sierras), as well as alluvial (between the Western slope of the mountains and the Desaguadero plain) and fluvio-lacustrine ones (on the plain of the Desaguadero). Finally, around the lagoons along the river, lacustrine sediments are found. Its physicochemical characteristics are decisive for the vegetation (46).

5. Paleontology

A large number of fossils have been exhumed in the SQNP area and its surroundings (a lot of them novel), mainly in sediments of the Lower Cretaceous (5). In relation to the macroflora highlights leaves, flowers, pollen and seeds of Angiosperms and impressions of primitive vascular plants and of Bryophytes, as well as palynomorphs (spores and some pollen). Other important fossils are bony fish (Semionotides), the pterosaur Pterodaustro guinazui Bonaparte (up to 3 m large wingspan, unique for its peculiar cranial and dental shape that suggests a lacustrine diet), and numerous arthropods, particularly insects and crustaceans; also bivalve, worms, and traces like dinosaur ichnites (5, 8, 36, 37, 55).

6. Archaeology

Some archeological sites document the establishment of ancient settlers in the SQNP area. Notable are the clay, semi-buried oven, almost 1 m in diameter, with an age close to 1,000 years, of which its functionality is still discussed; it is speculated that they were used to cook food or small pieces of pottery (39, 43). A few rock art friezes have been found, too (37).

7. Fauna

The fauna also shows ecotonal characteristics, with typical species of Chacoan, Andean and Patagonian biogeographic regions. The “collared peccary”, Pecari tajacu (Linnaeus) and the “Chacoan mara”, Dolichotis salinicola Burmeister represent the former; meanwhile, the “Andean condor”, Vultur gryphus Linnaeus, denote the presence of Andean region; finally, the Patagonian region is represented above all by the “South American gray fox”, Lycalopex gymnocercus (Fischer) and the “Patagonian mara”, Dolichotis patagonum (Zimmermann), as well as other representatives of various zoological groups (22). Indeed, other conspicuous inhabitants are the “guanaco”, Lama guanicoe (Müller); the “pink fairy armadillo” or “pichiciego”, Chlamyphorus truncatus Harlan; the “Argentine boa”, Boa constrictor occidentalis Philippi; and the “Chaco tortoise”, Chelonoidis chilensis Gray. As for the birdlife, the SQNP represents a key place for the protection of the “crowned solitary eagle” or “águila coronada”, Buteogallus coronatus (Vieillot), as well as another species with relictual populations (30). In relation with the herpetofauna, 25 species have been recorded (28, 35), including the “Chaco sand lizard” or “chelco”, Liolaemus chacoensis Shreve, and the “Mendoza four-eyed frog” or “desert frog”, Pleurodema nebulosum (Burmeister). Many of these species constitute small populations, thus requiring a high level of protection. On the other hand, two species of exotic invaders mammals are an additional pressure factor for the environment: the “wild ass” (feral donkeys, Equus asinus Linnaeus), and the “European wild boar”, Sus scrofa scrofa Linnaeus (26).

MATERIALS AND METHODS

The plant materials studied for this work reach 739 exsiccata, mostly preserved in the Herbarium, National University of San Luis (acronym: UNSL). They were collected by classical botanical methods (prospecting, samples selection, pressing, drying, mounting and preservation) during 1989-2018 in the area of the SQNP and surroundings (figure 2, page 217), in the course of 28 collection trips from spring to autumn. In a few cases the presence of a plant was recorded by a live collection (mainly cacti) or field observation properly documented. Other specimens preserved in Argentine herbaria (CORD, CTES, MERL, SI, VMSL) were also studied, while the data bank “Documenta Florae Australis”© (Instituto de Botánica Darwinion, Buenos Aires) was checked, too.

In general, the nomeclature was updated following the criteria supported by Flora Argentina (2), Angiosperm Phylogeny Group IV (15, 69) as well as recent taxonomic reviews.

The taxa were sorted by supra-specific groups, and within each family, in alphabetical order of genera. Habit and life-form were evaluated for each case (9, 42, 54), as well as the origin and status in the country, mentioning a voucher specimen from the area under study for each taxon.

For the exclusive or regional endemisms present in the Park, the degree of threat or conservation status is indicated, according to the criteria formulated in PlanEAr (51) and in IUCN Guidelines (7, 33); when the species has not been previously included in those assessments, a regional rating is proposed (24).

RESULTS AND DISCUSSION

1. Observations on the flora and vegetation

The area is a meeting point for the floristic streams of “Chaco” and “Monte”, which form here an ecotone with facies in which elements of one or the other predominate. The biogeographical province of the “Monte” is represented by its sparse xerophytic low forests and the shrub formations dominated by resinous and / or spinescent plants, while the “Chaqueño Serrano District” of the Chacoan biogeographical province shows its typical mountain and pedemontane forests, although low and impoverished in species at this latitude (13, 14, 40, 58, 61).

The plant communities in general correspond to the “Dry Chaco” and “Monte” ecoregions (11). It is estimated that in the core area, the first extends over 59,680 ha, while the latter does so over 14,110 ha, adding the 73,785 ha referred to above (64). The predominant vegetation units can be defined following Oyarzábal et al. (2018) as xerophyte forests with “quebracho blanco” (Aspidosperma quebracho-blanco Schltdl.), in transition towards steppe formations of Zygophyllaceae and halophytes. From a territorial approach, there are differences in the distribution of the ecoregions of the “Monte” in the Park itself, in relation of the published cartography (41); indeed, the presence of the mountains and endorheic basins stretches towards the S the limit of the “Monte of sierras and bolsons”, while the district called “Monte of plains and plateaus” extends by the W and SE of the Park.

Considering the specific composition, in some sectors it can be affirmed that these are communities of the “Monte” enriched with “Chaco” elements (1, 13). Regarding ecosystem complexes, it identifies the plains and interserran valleys, the endorheic bolsons and the saline areas, in addition to the strictly mountain environment, which broadly matches with the descriptions of Morello et al. (2012) and Oyarzábal et al. (2018).

Woodlands

The predominant formation is an open, tri-stratified, mixed forest, dominated by “quebracho blanco” (Aspidosperma quebracho-blanco) and “algarrobos” (Prosopis spp.), whose tops rarely touch. This association is typical of the “Chaco” / “Monte” ecotone (1, 12). The “quebracho blanco”, a Chacoan species, reaches here 6-8 m high and stands out on the canopy of the “algarrobos” (especially P. flexuosa DC. f. flexuosa, typical of Monte), which is more continuous but lower. The environment is notoriously xeric, and therefore species of the “Monte” dominate in the shrub stratum next to numerous Cacti (Cereus aethiops Haw., Opuntia sulphurea Gillies ex Salm-Dyck and some species of Tephrocactus) and a “cháguar”, the bromeliad Deinacanthon urbanianum (Mez) Mez, whose fruits are a precious resource for wild fauna. They are joined by various grasses with a spring-summer cycle, but which have little coverage. Trees and shrubs support a large amount of non-parasitic, epiphytic bromeliads, the “claveles del aire” (Tillandsia spp.), which is the genus with the highest specific richness in the SQNP.

Galleries

In some hills, the gorges show riparian vegetation of shrubs or armed little trees, especially “espinillos” (Vachellia spp., Parasenegalia spp.) and “algarrobos” (Prosopis spp.), which often constitute galleries over the course of temporary streams. In the drier interfluves, the same species appear but shrubby, dominated by low sized specimens of “quebracho blanco”.

“Jarillales” and “retamales”

In the Eastern foothills of the Sierra de las Quijadas there are sectors with gentle slopes and clay-matrix soil, in which resinous evergreen bushes dominate, the “jarillas” (especially Larrea cuneifolia Cav.), while in flat and salinized sectors there is a “retamal” almost pure constituted by plants of Bulnesia retama (Gillies ex Hook. & Arn.) Griseb., that here do not exceed one meter of height.

Swamps (“cenagales”)

In the contact area between the foothills and the plain there are swamps dominated by “chilcas” and “chilquillas”, Baccharis salicifolia (Ruiz & Pav.) Pers. and B. glutinosa Pers., accompanied by “pájaro bobo”, Tessaria absinthioides (Hook. & Arn.) DC., and the bush-like “bejuco”, Austrobrickellia patens (D. Don ex Hook. & Arn.) R.M. King & H. Rob., along with a few other swamp species.

“Huayquerías” or bad-lands

The intense erosive processes that take place on the slopes of the Sierras have created a typical landscape of “huayquerías” (bad-lands). There the plant cover is very poor and stands out for its resistance to drought, soil salinization and erosive dynamics. It consists mostly of isolated specimens of “zampas” (especially Atriplex lithophila A. Soriano, accompanied by A. argentina Speg., A. spegazzinii A. Soriano ex Múlgura, A. quixadensis), cushions of “rosetilla” (Gomphrena colosacana var. andersonii, an exclusive endemic to this Sierra and the neighboring Sierra del Gigante), as well as “verdolagas”, Halophytum ameghinoi (Speg.) Speg. and Sclerophylax spp., and a low, spinescent shrub, the “cuerno de cabra”, Adesmia trijuga Gillies ex Hook. & Arn. A lot of species of “claveles del aire” (Tillandsia spp.) take advantage of the few phorophytes that offer them the “huayquerías”. A curious Fabaceous bush with vigorous spinescent branches, called “chica”, Ramorinoa girolae Speg., inhabits natural “balcony” levels on the edges of the “Potrero de la Aguada”, reaching up to 3 m high; these are robust specimens about to fall due to the collapse of the substrate, which show their partially denuded roots. Three species, hitherto unique to the Sierra de las Quijadas, have been described from this environment in the course of previous studies: “zampilla” (Atriplex quixadensis), “romerillo blanco” (Senecio hualtaranensis) and a perennial “verdolaga” (Sclerophylax difulvioi) (20, 23, 49).

Scarps and balconies of the “Potrero de la Aguada”

The steep edges of this immense depression, and especially the surface of the slopes and landings or bleachers that follow each other with almost no continuity solution in the walls rising on both sides of the depression (figure 1, page 216), show a steppe constituted by shrubs and subshrubs that resist the constant soil erosion. There are notorious two species of “cháguar” arranged in semilunar structures, the bromeliads Dyckia velascana Mez and Deuterocohnia longipetala (Baker) Mez, which form strong bushes provided with fleshy and spinescent leaves. Close to them, grow some Cacti, grasses and other small plants.

Bottom of the Valley of “Potrero de la Aguada”

The interfluves of the bottom of this depression are occupied by brushwoods in which spinescent species such as “garabato”, Senegalia gilliesii (Steud.) Seigler & Ebinger; “mancapotrillo”, Plectrocarpa tetracantha Gillies ex Hook. & Arn., and the Chacoan element called “prendedor”, Mimosa ephedroides (Gillies ex Hook. & Arn.) Benth., prevail. The streams are bordered by a gallery of bushes, especially Tessaria dodoneifolia (Hook. & Arn.) Cabrera, called “chilca dulce”.

Eastern plain towards the Desaguadero river

A steppe of halophilic shrubs on soils with a visible salt crust appears between the course of the Desaguadero river and the mountain range. In some areas dominate “zampas” (Atriplex spp.) accompanied by “palo azul”, Cyclolepis genistoides Gillies ex D. Don; “piquillín de la víbora”, Lycium tenuispinosum Miers; “retortuño”, Prosopis strombulifera (Lam.) Benth., and several grasses, which mostly with a spring-summer cycle. Occasionally in this community appear “chañares” (Geoffroea decorticans) of small size, and intricate shrubs such as “matorro”, Prosopis sericantha Gill. ex. Hook. & Arn. To the edges (less saline) “jarillas”, Larrea cuneifolia Cav., L. divaricata Cav., and “ala de loro”, Monttea aphylla (Miers) Benth. & Hook., predominate.

Salinized depressions and bolsons

In places with higher salinity, the dominant shrubs are exclusively Chenopodiaceae, such as “vidriera”, Suaeda divaricata Moq.; “jumes”, Allenrolfea vaginata (Griseb.) Kuntze and A. patagonica (Moq.) Kuntze; “vinagrillo”, Sarcocornia ambigua (Michx.) M.A. Alonso & M.B. Crespo; and “apén”, Heterostachys ritteriana (Moq.) Ung.-Sternb., often in concentric rings in the order indicated, that obey the increasing saline gradient.

Dunes

Towards the interior of the Western plain, there are dunes covered totally or partially with plants resistant to burial, either by means of strong rhizomes or by emitting adventitious roots. Outstanding are the “junquillares” of Sporobolus rigens (Trin.) E. Desv., often accompanied by “tupe”, Panicum urvilleanum Kunth, and the almost pure “blanquillales” which cover large extensions, formed by Hyalis argentea D. Don ex Hook. & Arn., called “olivillo” or “blanquilla” because its white-silvered stems and leaves. They are pioneer plants that fix the dunes, allowing the subsequent ecesis of annual and perennial herbs, and then facilitate the settlement of shrubs like the “algarrobo de guanaco”, Prosopis argentina Burkart.

Desaguadero flood plain

This plain, which at certain points is extensive and of very little slope, occupies the Western part of the Park. It is prodigal in annual and perennial herbs, particularly halophytes, while on the edges (called “albardones”, which downstream form true ravines up to several meters high) there are copses of “algarrobos” (especially Prosopis flexuosa f. flexuosa); these trees demarcate current watercourses and also paleochannels for their phreatophytic behavior (59, 72). Sometimes, they are accompanied by the “quebracho blanco”. The shrubs and trees mentioned also border the small streams that lead to the river, sometimes becoming a gallery.

Salix humboldtiana Willd., the “sauce criollo” or “red willow”, must have dominated the riparian environment of the Desaguadero basin in past times; today, due to its water high requirements in summer, it is only found forming isolated copses on the banks of the San Juan river.

Extensive hydrophilic associations occur in the fluvian-lacustrine plain of Desaguadero and in the temporary lagoons of the Guanacache complex. They are especially “juncales” y “totorales” dominated by Schoenoplectus californicus (C.A. Meyer) Soják, called “hunco” or “totora”, a tall Cyperaceae that constituted the essential raw material to manufacture rafts by the aborigines (60, 74) and Typha domingensis Pers. and T. subulata Crespo & R.L. Pérez- Moreau, which develop whith free water and even at depths of 1.5 m. Can also see here “carrizales” of Phragmites australis (Cav.) Trin. ex Steud., sometimes in areas with saturated soil and at times with free water. Other “juncales”, this time from Juncus balticus Willd. and J. acutus L. (Juncaceae) prefer waterlogged soils. In the shallow and still waters of the shores the “berrillo”, Bacopa monnieri (L.) Wettst., and other herbaceous dicots and grasses are frequent. The margins of the watercourses and some reservoirs inside the bed, subject to periodic flows, are frequently marked by Cortaderia selloana (Schult. & Schult. f.) Asch. & Graebn. (“Pampa grass” or “cortadera”), a vigorous grass that reaches up to 2 m high.

In flat and flooded places, with highly saline soil, there are “patches” dominated by grasses of very short lawn, such as “pasto salado”, Distichlis spicata (L.) Greene; “pasto tul”, Muhlenbergia asperifolia (Nees & Meyen ex Trin.) Parodi; and “chépica”, Cynodon dactylon (L.) Pers. In other places there are colonies of “chilca”, Baccharis salicifolia, and “chilquilla”, B. glutinosa, and other marsh plants that at least support periodic water stagnations, such as the “pájaro bobo”, Tessaria absinthioides (Hook. & Arn.) DC. An adventitious shrub or little tree, the “tamarisk”, Tamarix ramosissima Ledeb. is very well adapted to this environment with variable humidity and high salinity; it reaches here up to 4 m high and often occurs in almost pure populations, especially in the banks of the riverbed.

Peridomestic plants

Several species appear at the edge of routes, and others constitute the peridomestic vegetation, including native ones that are tolerated near dwellings, as “algarrobos”, “quebracho blanco”, “molles morados” (Schinus spp.) and “chañar”, as well as a few cultivated plants, especially “visco”, Parasenegalia visco (Lorentz ex Griseb.) Seigler & Ebinger, and “Siberian elm”, Ulmus pumila L. In relation to “aguaribay” or “Peruvian peppertree”, Schinus areira L., it is found here near the Southern limit of its wild populations. In the case of the “tamarisk” or “salty cedar” already mentioned, it was surely naturalized in the SQNP since colonial times, after invading the watersheds of the main tributaries of the Desaguadero river. Other plants are also weeds, mainly Eurasiatic, such as “wild lettuces”, Lactuca saligna L., L. serriola L.; “sow thistles”, Sonchus asper (L.) Hill, S. oleraceus L.; “thistles”, Cirsium vulgare (Savi) Ten., Carduus spp.; “dandelion”, Taraxacum officinale F.H. Wigg.; “wild radish”, Raphanus sativus L.; “Russian thistle”, Salsola kali L.; “corregüela” or “bindweed”, Convolvulus arvensis L.; and so on.

Some exotic, anemochorous forage plants, such as “buffel grass”, Cenchrus ciliaris L., have reached the SQNP, but until now they only appear at the edges of routes in the limits of the Park.

2. On the land use and livestock activity

The NW of San Luis, that is to say almost all of the Departments of Belgrano and Ayacucho, has severe water and soil limitations for the development of agricultural and livestock activities (especially scarce and irregularly distributed rainfall, and high susceptibility to soil erosion) (47, 62), which have accelerated desertification processes (18). In contrast, the Western highlands (particularly the Sierra del Gigante, located south of the SQNP) have been and are nowadays exploited with some intensity by their mining resources.

Until the recent past, logging was intense, reducing forests to their current expression, generally restricted to galleries on watercourses, mountain slopes or deep ravines. Almost the entire region has been classified as a “native forest” (categories I and II, within the meaning of Provincial Law IX-0697-2009), that providing for some degree of protection to the plant and animal diversity and establishing restrictive conditions for the land use (63).

It is probable that cattle farming has been practiced here since the Spanish colonization. The very name “Sierra de las Quijadas” would refer to bones derived from cattle slaughter practiced in the area, and the toponym “Potrero de la Aguada” perhaps it refers to the fact that the area was used by the herders to keep the cattle safe during transit through the old path (“rastrillada”) to the NW, which is now national route 147. The area has capacity for cattle breeding and rearing (25) and to a lesser extent for other subsistence activities. Outside the core area of the SQNP, some cattle farms remain, although the APN’s agreed management policy tends to reduce the number of heads and therefore the effects on vegetation and soil.

3. The vascular flora

The vascular flora of the SQNP is represented so far by 356 species (plus 99 infraspecific taxa), corresponding to 208 genera of 58 families (table 1).

Table 1. Number of genera, species and infraspecific taxa per family.

Tabla 1. Número de géneros, especies y taxones infraespecíficos por familia.

Ref.: (1): alternative name / nombre alternativo.

It comprises 2 species of Monilophyta, 3 of Gymnosperms and the remaining of Angiosperms (88 of Monocotyledoneae and 263 of Dicotyledoneae).

The 58 families of vascular plants of the SQNP represent approximately 24% of the families present in the Argentinian flora. Likewise, the 208 genera found here comprise 10.6% of the genera of the whole country, while the 356 species of the SQNP represent 3.6% of the total species of Argentina. These percentages have been calculated based on the estimates of Zuloaga et al. (1999) and Del Vitto et al. (2011).

Ten families are represented by more than 10 species each, adding 253 species, which constitutes just over two thirds of the local flora (71%). Of these, Poaceae represent 16.3% of the total, Asteraceae constitute ca. 13.8%, Fabaceae 8.7%, Solanaceae 6.7%, Verbenaceae 5.9%, Bromeliaceae 5%, Chenopodiaceae 4.5%, and Cactaceae, Malvaceae and Amaranthaceae reach 3.6 to 3.1% each. On his part, Zygophyllaceae, Euphorbiaceae and Boraginaceae contribute 2 to 1.7% each, while Convolvulaceae, Apocynaceae, Nyctaginaceae and Portulacaceae reach only 1.4% each of the species of the Park. The 18 families that include 2 to 4 species make up 11.2%, and the 23 families represented by a single species reach 6.5% of the total species.

The diversity within each genus is not high, something to be expected in a warm and dry area at these latitudes (table 2, page 226).

Table 2. Number of specific and infraspecific taxa per Genus.

Tabla 2. Número de taxones específicos e infraespecíficos por género.

Only four of them reach or exceeds ten species and infraspecific taxa (Tillandsia with 19, Gomphrena and Prosopis 13 each, and Solanum with 10). The following 15 genera count between 9 and 5 species and infraspecific taxa each, while the rest of the genera comprise 4 taxa or less. It is notable that most genera (141, i.e. 68% of them) are represented by only one species.

The four endemic species (table 3), hitherto exclusive to these mountains are as follows: Atriplex quixadensis, Sclerophylax difulvioi, Senecio hualtaranensis and Gomphrena colosacana var. andersonii.

Table 3. Endemic taxa, exclusive to the SQNP and surroundings.

Tabla 3. Taxones endémicos, exclusivos del PNSQ y alrededores.

Their habitat is restricted to the “huayquerías” of the Sierra de las Quijadas, and the slopes and landings of the edges of the “Potrero de la Aguada”, where they support both intense erosion and drought, as well as the compaction and high salinity of the soil. On the other hand, G. colosacana var. andersonii is a small cushion that also appears, although to a lesser extent, in the neighboring Sierra del Gigante.

These 4 species represent 40% of the endemic plants exclusive of the territory of San Luis province (7). In turn, the total number of Argentine endemic plants that find protection in the limits of the Park add up 116 species (one third of the total vascular flora of the Park, tables 3, page 226 and 4, page 228-230), which represent approx. 6% of the endemic plants throughout Argentina, according to records provided by Zuloaga et al. (1999).

Table 4. Conservational status of Argentinian endemic taxa recorded in the SQNP.

Tabla 4. Estado de conservación de los taxones endémicos de Argentina registrados en el PNSQ.

Table 4 (cont.). Conservational status of Argentinian endemic taxa recorded in the SQNP.

Tabla 4 (cont.). Estado de conservación de los taxones endémicos de Argentina registrados en el PNSQ.

Table 4 (cont.). Conservational status of Argentinian endemic taxa recorded in the SQNP.

Tabla 4 (cont.). Estado de conservación de los taxones endémicos de Argentina registrados en el PNSQ.

This latter proportion can be considered high in relation to the Argentine flora as a whole, and is related to the comparatively high number of endemic genera and species typical of the “Chaco” and “Monte” biogeographical provinces. These include Halophytum ameghinoi Speg., a species restricted to the driest sites of the “Argentinian arid diagonal” and the unique species of the country’s only endemic botanical family, Halophytaceae.

Tables 3 (page 226) and 4 (page 228-230) also indicate the degree of threat facing each of the endemic species, according to the risk scale developed by PlanEAr (2015-2019) and the criteria of the IUCN (2012), or the assessment of Ayarragaray et al. (2015). When the species has not been previously included in these assessments, the authors propose a qualification at regional level.

Many of these endemisms require immediate and continuous protection, since in general they are grouped into small populations of very restricted distribution, located in sites that are currently undergoing severe processes of environmental disturbance, both natural and anthropic.

We consider that all species included in tables 3 (page 226) and 4 (page 228-230) are in some way threatened, in most cases according to the regional application of the IUCN criteria (2012) and to a lesser extent due to their inclusion in the Red Lists of IUCN (2019). Thus, three of them are critically endangered (CR, 2.6% of threatened species preserved in the SQNP), three others are endangered (EN, 2.6%), 10 are vulnerable (VU, 8.6%), 25 are almost threatened (NT, 21.5%) and 79 can be considered of minor concern (LC, with 64.7%).

As for the specific and infraspecific taxa of the Cactaceae Family (17 at all in the SQNP) are listed in Appendix II of the IUCN Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), which establishes the aim “to ensure that international trade in specimens of wild animals and plants does not threaten their survival” (16).

About twenty species (approximately 6% of the total flora) are exotic plants, and mostly of them take part of the peridomestic vegetation in the SQNP and surroundings; these values are close to those indicated for the province of San Luis (75). They include 12 adventitious and 5 naturalized species, while the “buffel grass” (Cenchrus ciliaris cv.) is considered escaped from cultivation.

As for two tree species (Parasenegalia visco and Schinus areira), they are grown on farms and villages; when they are abandoned to their fate, they can last for a few years. The relative proximity of the native populations of both species raises doubts about their status as indigenous or cultivated, and explains their adaptation to Park environmental conditions.

4. Life-forms in the SQNP flora

The analysis of the position of the surviving buds of the studied taxa allowed establishing the biological types and subtypes of each one (tables 5-9, page 230-248).

Table 5. Raunkiaer´s life-forms in the SQNP vascular flora.

Tabla 5. Bioformas de Raunkiaer en la flora vascular del PNSQ.

*When more than one biological type or subtype could be diagnosed in a taxon, the most exposed form was chosen for computation purposes.

Cuando más de un tipo biológico pudo ser diagnosticado para un taxón, a los fines del cómputo se eligió la forma más expuesta.

Table 5 (cont.). Raunkiaer´s life-forms in the SQNP vascular flora.

Tabla 5 (cont.). Bioformas de Raunkiaer en la flora vascular del PNSQ.

Table 6 / Tabla 6. Monilophyta.

Table 7 / Tabla 7. Gymnospermae.

Table 8 / Tabla 8. Angiospermae - Monocotyledoneae.

Table 8 (cont.) / Tabla 8 (cont.). Angiospermae - Monocotyledoneae.

Table 8 (cont.) / Tabla 8 (cont.). Angiospermae - Monocotyledoneae.

Table 8 (cont.) / Tabla 8 (cont.). Angiospermae - Monocotyledoneae.

Table 9 / Tabla 9. Angiospermae - Dicotyledoneae.

Table 9 (cont.) / Tabla 9 (cont.). Angiospermae - Dicotyledoneae.

Table 9 (cont.) / Tabla 9 (cont.). Angiospermae - Dicotyledoneae.

Table 9 (cont.) / Tabla 9 (cont.). Angiospermae - Dicotyledoneae.

Table 9 (cont.) / Tabla 9 (cont.). Angiospermae - Dicotyledoneae.

Table 9 (cont.) / Tabla 9 (cont.). Angiospermae - Dicotyledoneae.

Table 9 (cont.) / Tabla 9 (cont.). Angiospermae - Dicotyledoneae.

Table 9 (cont.) / Tabla 9 (cont.). Angiospermae - Dicotyledoneae.

Table 9 (cont.) / Tabla 9 (cont.). Angiospermae - Dicotyledoneae.

Table 9 (cont.) / Tabla 9 (cont.). Angiospermae - Dicotyledoneae.

Table 9 (cont.) / Tabla 9 (cont.). Angiospermae - Dicotyledoneae.

Table 9 (cont.) / Tabla 9 (cont.). Angiospermae - Dicotyledoneae.

Ref.: Ph: phanerophytes / fanerófitos; Ch: chamaephytes / caméfitos; Hc: hemicryptophytes / hemicriptófitos; Cr: cryptophytes / criptófitos; Th: therophytes / terófitos; Ep: epiphytes / epífitos; Par: parasites / parásitos.

According to the relative % corresponding to each one, the spectrum of the vascular flora of the Park was elaborated, which was compared with the Raunkiaer´s “normal” spectrum (54) (figure 5, page 231).

Figure 5. Life-forms spectrum of the SQNP vascular flora in comparison with the Raunkiaer’s “normal” spectrum (1934). Percentage values.

Figure 5. Espectro biológico de la flora vascular del PNSQ comparado con el espectro “normal” de Raunkiaer (1934). Valores porcentuales.

The flora of the SQNP presents almost all biological types and most of the subtypes defined by Raunkiaer (1934) and later authors (9, 42). Phanerophytes, Hemicryptophytes, and Chamaephytes dominate (24.7; 24.6; and 22.3%, respectively). This is directly related to the environmental conditions and the structure of the communities, in which mixed, open and tri-stratified forests prevail on the one hand, dominated by a sclerophyll species (Aspidosperma quebracho-blanco) accompanied by deciduous trees (Prosopis spp.), shrubs, and both perennial and annual herbaceous plants, with low coverage. On the other hand, there are large areas with shrub steppes, composed mainly of evergreen, resinous nanophanerophytes (Larrea spp., Zuccagnia punctata Cav.), and halophilic chamaephytes. The therophytes (16%) show the highest degree of adaptation of many species to the severity of the dry season, as well as to the periodicity of flooding in the Desaguadero river basin.

Within each type, one or at most two subtypes predominate. Thus, nanophanerophytes comprise 18.7% of the taxa, while microphanerophytes (the unique trees in the region, always low) reach only 5.4%. The suffruticose chamaephytes, with 15.8%, represent the majority of the chamaephyte type, complemented by the succulent ones (3.8%), which are mostly pulviniform Cacti. Caespitose hemicryptophytes include, by themselves, 13.3% of the taxa, mostly perennial grasses. Among the cryptophytes, the rhizomatous geophytes (4.1%) stand out, with a minor participation of helophytes and hydrophytes, which of course show greater representativeness and coverage in flooded areas. Scapose therophytes represent the majority of annual plants, reaching 7% of the taxa; although with about 2% each, cespitose, reptant, subrosulated and succulent therophytes are also well represented. Holoepiphytes comprise 4.1%, while holoparasites only reach ca. 0.3%.

Compared to the “normal” spectrum in the Raunkiaer concept (54), that of the SQNP flora presents almost half of phanerophytes, more than double chamaephytes and a similar number of hemicryptophytes, cryptophytes and therophytes (figure 5, page 231). It also includes near 5% of epiphytes (particularly “claveles del aire”, non-parasitic bromeliads of the genus Tillandsia), two species of hemiparasites, Ligaria cuneifolia (Ruiz & Pav.) Tiegh. and Tripodanthus flagellaris (Cham. & Schltdl.) Tiegh., and one species of an absolute parasite, Prosopanche americana L.

5. New records for the flora of San Luis province

In the course of this study, specimens of 8 taxa not previously reported for the native flora of the Province of San Luis were identified. They are, in alphabetic order: Adesmia cordobensis Burkart var. cordobensis (Fabaceae); Aloysia polystachya (Griseb.) Moldenke and Glandularia aristigera (S. Moore) Tronc. (Verbenaceae); Gomphrena boliviana Moq. f. boliviana (Amaranthaceae); Salsola kali L. var. hirsuta Hornem. and S. kali L. var. tragus (L.) Moq. (Chenopodiaceae); and finally Tillandsia andicola Gillies ex Baker and T. angulosa Mez (Bromeliaceae). Tables 8 and 9 (pages 233-248) enclose the corresponding voucher specimens.

CONCLUSIONS

The “Sierra de las Quijadas” National Park and the surrounding National Reserve comprise 150,252 ha. They are located at the NW end of the province of San Luis (Argentina). Arid mountain climate predominates, usually dry and warm. It preserves a sample of the Chaco- Monte ecotone, with the typical communities of the ecoregions called “Dry Chaco” and “Monte” (both “Monte of plains and plateaus” and “Monte of Sierras and bolsons”). In the diverse environments (low mountains, foothills, bad-lands, depressions and endorheic basins, temporary lagoons and the flood plain of the Desaguadero river) there are mixed forests, shrub steppes of orophilic and halophilic plant communities, copses of phreatophyte, galleries of tall shrubs, brushwoods, “rings” of halophytes, “pajonales”, rushes and reed beds in flood areas.

Nowadays, the vascular flora of the SQNP includes 356 species (plus 99 infraspecific taxa), that is, 3.6% of the total from Argentina. These species are distributed in 208 genera belonging to 58 plant families. The vast majority are Dicots (74%) and Monocots (25%), to which 2 species of ferns and 3 species of Ephedra are added. The best represented families are Poaceae (16.3% of the total species), Asteraceae (13.8%), Fabaceae (8.7%), Solanaceae (6.7%) and Verbenaceae (5.9%), while Bromeliaceae, Chenopodiaceae, Cactaceae, Malvaceae and Amaranthaceae contribute with around 3-5% each. Meanwhile, Zygophyllaceae, Euphorbiaceae, Boraginaceae Convolvulaceae, Apocynaceae, Nyctaginaceae and Portulacaceae only reach 1.4-2% each of the species of the Park. Another 18 families include 2 to 4 species each (11.2%), and the other 23 families have only one species each (6.5% of the total species).

The specific/infraspecific diversity of each genus is low. Four of them (Tillandsia, Prosopis, Gomphrena and Solanum) add 55 taxa (12% of the Park flora), while the following 15 genera are represented by 9 to 5 taxa each (21%). Finally, most genera (i.e. 161) are represented only by 1 or 2 taxa each, totaling 40% of the studied flora.

Four species are endemic unique to the Park and its surroundings: Atriplex quixadensis, Senecio hualtaranensis, Sclerophylax difulvioi and Gomphrena colosacana var. andersonii. Another 116 endemic Argentine species are present in the Park. As far as we know, and including the previous four, some live in very restricted areas. In total they represent ca. 33% of the vascular flora of the Park, and 6% of the endemic plants of the whole country, including Halophytum ameghinoi, a noteworthy species restricted to western Argentina; it is the unique representative of the only endemic family in this country, Halophytaceae.

These endemic taxa suffer a different degree of threat: 3 are included in the category of critically endangered (CR), 3 other are endangered (EN), 10 vulnerable (VU), 25 near threatened (NT) and 75 as least concern (LC). Many of the endemisms require immediate and continuous protection, because they are grouped in small populations, in places with both natural and anthropic environmental disturbance.

The diversity of habitats and microhabitats allows the existence of the majority of life-forms types and subtypes, especially phanerophytes and hemicryptophytes, with ca. 25% of the taxa each, mostly shrubs and low trees for the former and caespitose and scapose perennial herbs for the last. They are followed by chamaephytes (22%, mostly subshrubs) and therophytes (16%). Together they reveal a remarkable adaptation to the prolonged dry season.

Additionally, the presence of 8 taxa not yet reported for the native vascular flora of the province of San Luis is documented: Adesmia cordobensis Burkart var. cordobensis (Fabaceae); Aloysia polystachya (Griseb.) Moldenke and Glandularia aristigera (S. Moore) Tronc. (Verbenaceae); Gomphrena boliviana Moq. f. boliviana (Amaranthaceae); Salsola kali L. var. hirsuta Hornem. and S. kali L. var. tragus (L.) Moq. (Chenopodiaceae); Tillandsia andicola Gillies ex Baker and T. angulosa Mez (Bromeliaceae).

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ACKNOWLEDGEMENTS

The authors are extremely grateful to the Directors and Curators of the Argentinian herbaria SI, CORD, CTES and MERL. Our thanks to Dr. D.S. Pagano (UNSL) for a fruitful exchange of ideas; to Mag. L. Zuppa (UNSL) for her valuable corrections in the English version of the manuscript; and the APN Regional Centro that allowed us to work in the SQNP. The financial support of the Projects 2-1118 (SECyT-UNSL) and 22-Q816 (SPU-ME) is also appreciated, as well as the invaluable contribution of the Staff of the Journal, its Academic Committee and anonymous reviewers.

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