Interciencia ISSN: 0378-1844 [email protected] Asociación Interciencia Venezuela

Hilgert, Norma I.; Pensiero, José F.; Marino, Gustavo; Lewis, Juan P.; DAngelo, Carlos Vegetation of the saladillo area (province of Santa Fe) in the South of the Chaco, Argentina Interciencia, vol. 28, núm. 9, septiembre, 2003, pp. 512-520 Asociación Interciencia Caracas, Venezuela

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Cómo citar el artículo Número completo Sistema de Información Científica Más información del artículo Red de Revistas Científicas de América Latina, el Caribe, España y Portugal Página de la revista en redalyc.org Proyecto académico sin fines de lucro, desarrollado bajo la iniciativa de acceso abierto VEGETATION OF THE SALADILLO AREA (PROVINCE OF SANTA FE) IN THE SOUTH OF THE CHACO, ARGENTINA

NORMA I. HILGERT, JOSÉ F. PENSIERO, GUSTAVO MARINO, JUAN P. LEWIS and CARLOS D’ANGELO

he area of the Saladillos there is a winter drought of variable town of Helvecia there are important rice lies at the eastern part length (Cáceres, 1980). cropping areas. of the of Santa Fe prov- The area can be divided In this paper the vegeta- ince center, comprising the western into two main physiographic sectors, the tion of the Saladillo Rivers area is ana- halves of the Garay and San Javier de- old Paraná River terrace and the coastal lyzed, using numerical methods. Plant partments and small parts of other admin- levee. In the first one, predominant soils communities are determined and de- istrative units. At its western limits are are natracualfs, silty loam with sodium scribed. the Toba and Saladillo Amargo rivers, carbonate and high pH. On the coastal while at the eastern limit the Paraná levee predominant soils are cuarzipsam- Material and Methods River valley is located (Figure 1). The re- ment, sandy or sandy loams with low nu- gion consists of plains with a consider- trient levels (Orellana and Priano, 1978). Physiognomic units of able but gentle slope from NW to SE, The area is covered by landscape were determined with and without any important orographic or woodlands, savannas, tall grasslands and 1:150000, 1:50000 and 1:20000 aerial topographic accidents. Most of it is on some prairies and hydrophilous meadows. photographs and mapped on 1:100000 what the Paraná River bed was, which Ragonese (1941) places the area in the charts from the Instituto Geográfico Mi- was modified by an upward movement of region of “espinillares” (prickly mimosa litar. Then, a general survey of the area the bedrock during the Quaternary (Gras- forests), Parodi (1945) considered the was performed in order to define commu- sino, 1986; Iriondo, 1991). Several rivers area as Chaquenian, and Cabrera (1953; nities of dominance type (Whittaker, that flow from N to S to the Paraná 1976) included the northern portion in 1980), dividing the vegetation into for- River drain the area; the main ones are the Chaco and the southern portion in the ests, savannas and grasslands. the Saladillo Amargo and the Saladillo Thorn forest and scrub. During November and Dulce, whose names mean “Bitter Brack- The region is relatively December 1994, 123 plots (4x4m) of her- ish” and “Sweet Brackish”, as an allusion well preserved, although there have been baceous communities were analyzed. This to their water taste and composition. lumbering, grazing and agricultural ac- plot size was chosen according to Lewis The climate (Table I) is tivities, as well as man-made fires. The et al. (1990) as the minimum sampling humid to sub humid and warm to temper- extreme south is used for vegetable area for this kind of communities. In ate; rainfall is mainly during summer and crops, tomatoes and carrots. Near the each plot general descriptions of the veg-

KEYWORDS / Argentina / Chaco / Forests / Grasslands / Savannas / Received: 04/23/2003. Modified: 08/25/2003. Accepted: 08/27/2003

Norma I. Hilgert. Dr., Universidad Nacional de Córdoba (UNC), Argentina. Professor and Researcher, Centro de Investigaciones Biológicas, Universidad Autónoma de Hidalgo, México. Researcher, CONICET, Ar- gentina. Address: Apartado Postal 69, Plaza Juárez, Pachuca, Hidalgo México C.P. 42001. e-mail: [email protected] José F. Pensiero. Dr., UNC. Professor, Facultad de Ciencias Agrarias, Universidad Nacional del Litoral (UNL), Argentina. Researcher, CONICET, Argentina. Gustavo Marino. Dr. in XX, Universidad Nacional de Buenos Aires, Argentina. Professor, Facultad de Ciencias Agrarias, UNL, Argentina. Juan P. Lewis. Ph.D., Cambridge University, England. Professor, Facultad de Ciencias Agrarias, Universidad Nacional de Rosario, Argentina. Researcher, CONICET Argentina. Carlos D’Angelo. M.Cs., Pontificia Universidad Católica de Chile. Professor, Facultad de Ciencias Agrarias, UNL, Argentina.

512 0378-1844/03/09/512-10 $ 3. 00/0 SEP 2003, VOL. 28 Nº 9 TABLE I METEOROLOGICAL DATA* OF FIVE STATIONS AROUND THE SURVEYED DATA (1941-1960)

Temperature (ºC) Rainfall Frost free period Meteorological Mean Av. min. Min. Av. max. Max. (mm) (days) stations

Vera 19.6 13.3 -5.6 27.15 43.4 1051 322 Reconquista 20.3 - - 26.5 - 1105 - Esperanza 18.4 12.6 -6.2 25.65 43.9 946 227 Goya 20.6 15.3 - - - 1213 - La Paz 19.5 13.9 - 25.9 - 1065 -

* Data from Servicio Meteorológico Nacional.

Figure 2. PCA scatter diagram of forest Figure 3. DECORANA scatter diagram of plots on the plane of axes I and II. : “es- forest plots on the plane of the first two axes. pinillares, +: “algarrobales”, *: “quebra- : “espinillares, +: “algarrobales”, *: “que- chales”. brachales”.

were ordered using a Detrend Correspon- (PCA), and classified according to Ward’s dence Analysis (DECORANA), and clas- method (McCune, 1993). In December sified with Ward’s Cluster analysis using 1995, the herbaceous layer was analyzed relative euclidean distance as a similarity in a similar way as the herbaceous com- measure (McCune, 1993). munities. According to their phy- Plant specimens were siognomic aspects and dominant species, determined and deposited in the her- 8 forest stands were selected during July barium of the Facultad de Agronomía y and August 1995. These stands were lo- Veterinaria, Universidad Nacional del cated in every low level disturbance area Litoral (Santa Fe). The nomenclature fol- found, without any recent anthropic activ- lows Zuloaga and Morrone (1994; 1996; ity, while areas that showed high frag- 1999). Figure 1. Map of the surveyed area. mentation or disturbance intensity were not considered as valid points for this Results etation and soil were recorded. All spe- study. The point-centered quarter method cies and their frequencies were recorded (Cottam and Curtis, 1956) was used to The PCA scatter dia- using the Braun-Blanquet (1979) cover- measure trees and shrubs. At each stand, gram of forest plots on the plane of axes abundance combined scale and then con- mean height and tree cover were as- I and II show three clusters arranged verted into the Westhoff and Van der sessed, together with total and layer flo- along a horseshoe gradient (Figure 2). Maarel (1980) scale. ristic richness and relative frequency of DECORANA analysis shows the same To avoid noise, 112 spe- each woody species. Vegetation profiles three clusters distributed according to a cies, which were found in less than 3 were made from 250m2 cartographic gradient along Axis I (Figure 3). The plots, were eliminated from the analysis quadrants (Davis and Richards, 1933; same three clusters can be recognized and an information matrix of 123 plots 1934). Data were analyzed using DECO- when the plots are classified with Ward’s and 165 species was constructed. Data RANA and Principal Component Analysis method (Figure 4).

SEP 2003, VOL. 28 Nº 9 513 TABLE II ASSOCIATION TABLE OF FORESTS WOODY LAYERS SHOWING ABSOLUTE FREQUENCY OF EACH SPECIES

ABC Tree species / Censuses 1 2 8 3 4 5 6 7 Acacia caven 73 72 38 1 9 Opuntia sp. 21 12 Geoffroea decorticans 13 29 21 7 19 3 2 Prosopis sp. 24625362516196 Celtis iguanaea 210311213 Schinus longifolia 1641782 Achatocarpus praecox 13 2 1 45 8 9 9 Sideroxylon obtusifolium 102147 Fagara rhoifolia 17 2 1 11 Aspidosperma quebracho-blanco 23 43 43 2 Prosopis affinis 1245 3 Acacia praecox 45621 Figure 4. Ward’s clustering technique den- Schinopsis balansae 16 13 5 drogram of woody plant communities. A: Scutia buxifolia 25 20 39 “espinillares”, B: “algarrobales”; C: “que- Stetsonia coryne 822 brachales”, the latter with variant C1: with Aspidosperma quebracho blanco and Proso- Capparis retusa 961 pis sp., and variant C2: with Eugenia uni- Eugenia uniflora 123 flora, Gleditsia amorphoides, Scutia buxi- Myrcianthes cisplatensis 31 folia and Hexachlamys edulis. Ruprechtia laxiflora 112 Phytolacca dioica 17 Acacia aroma 11 In most forests Geoffroea Carica quercifolia 10 decorticans, Prosopis sp., Achatocarpus Melia azederach 5 praecox, Celtis iguanaea and C. pallida are Ziziphus mistol 5 present and can be abundant. The first clus- Gleditsia amorphoides 4 ter (A) are “espinillares” where Acacia Hexachlamys edulis 8 caven predominates; the second (B) are Caesalpinia paraguariensis 2 “algarrobales” of Prosopis sp., which are floristically richer than the former cluster; Berberis ruscifolia 1 and the third (C) are “quebrachales” char- Erythrina crista-galli 5 acterized by the presence and abundance of Parkinsonia aculeate 3 Schinopsis balansae, Aspidosperma quebra- Specific Richness Trees 5 8 6 12 14 15 15 20 cho-blanco and Acacia praecox (Table II). Tree strata height (m) 6.75 7.75 6.5 14.35 16.65 17 17.8 16.2 The floristic richness of Shrub species the woody strata increases significantly Celtis pallida 819 229 4 3 3 northwards (Figure 5) and forests also Grabowskia duplicata 917210 become structurally more complex (Fig- Aloysia gratissima ar. chascoensis 5133 1 ures 6 and 7). Individuals of the tree Vassobia breviflora 16 15 3 Cestrum sp. 69 6 Allophyllus edulis 510 Tessaria dodoneifolia 1 Holmbergia tweedii 42 Lycium tenuispinosum 1 Jodina rhombifolia 2 Harrisia tortuosa 11 Lippia alba 12 Maytenus vitis-idaea 1 Sesbania virgata 63 Byttneria filipes 2 Trixis praestans 10 Senna pendula 1 Shrub strata height (m) 1.3 1.65 2.05 3.15 2.85 3.05 2.90 3.05 Specific Richness Trees 1 4 4 8 7 5 4 4 Total Specific Richness 6 12 10 20 21 20 19 24 Mean Distance 9.85 13.6 11 6.5 4.5 4.23 4.25 3.4 Figure 5. Floristic richness in relation to Woody Coverage (%) 20 70 30 60 80 90 80 95 latitude.

514 SEP 2003, VOL. 28 Nº 9 Figure 6. Cartographic diagrams of Forests a: “espinillares”, b: “algarrobales” and c: “quebrachales”. A: Prosopis alba, B: Geoffroea decorticans, C: Achatocarpus praecox, D: Acacia praecox, E: Acacia caven, F: Carica quercifolia, G: Schinus longifolia, H: Fagara rhoifolia, I: Phytolacca dioica, J: Prosopis affinis, L: Celtis pallida, M: Stetsonia coryne, N: Eugenia uniflora, O: Aspidosperma que- bracho-blanco, P: Scutia buxifolia, R: Schinopsis balansae, R: Ruprechtia laxiflora, T: Gleditsia amorphoides, U: Allophyllus edu- lis, V: Sideroxylon obtusifolium, X: Grabowskia duplicata, Z: Myr- Figure 7. Profiles of the same forests (a, b, c) as in Figure 6. Spe- cianthes cisplatensis. cies symbols (A-Z) as in Figure 6. layers are clumped on the three forest brevifolia that sometimes becomes dense where Aspidosperma quebracho-blanco types (Figure 6), so the canopy is not (Table II). There are some epiphytes, as and Prosopis sp. are abundant on saline continuous but shows gaps of different in “espinillares”, and some lianas such as soils with a very heterogeneous herba- sizes. Pithecoctenium cynanchoides, Dolichan- ceous layer formed by a mosaic of The “espinillares” are dra cynanchoides and Fosteronia glabre- “peladales”, with a low plant cover com- more frequent in the south of the region. scens. The herbaceous layer is heteroge- posed by Sporobolus pyramidatus, Era- They are relatively poor and have a 7m neous, with an important light penetration grostis lugens, Selaginella sellowii etc, a high tree layer that sometimes is very at in places, being abundant Cynodon depression cover with Luziola peruviana, disperse. The shrub layer is not conspicu- dactylon, Carex bonariensis, Paspalum Leersia hexandra, Panicum hians, and ous and Celtis pallida is the only relevant notatum, Setaria stolonifera, S. rhombifo- patches of spiny bromeliads Aechmea species. There are some epiphytes like lia, etc. In the shaded microsites Oplis- distichanta and Dyckia remotiflora var. Microgramma lycopodioides, Rhipsalis menus hirtellus subsp. setarius and montevidensis (Tables II and III; Figure 4 lumbricoides and Tillandsia sp. The her- Doryopteris pedata are frequent (Table C1); another variant with Eugenia baceous layer in this region is consider- III). uniflora, Gleditsia amorphoides, Scutia ably dense, covering close to 100% of The “quebrachales” are buxifolia, Hexachlamys edulis (Table II; the ground, and Stenotaphrum secunda- only present in the far north portion of Figure 4 C2). tum, Sida rhombifolia and Cynodon dac- the region. They are much richer than the When plots of herba- tylon are frequent (Table III). “algarrobales”, with a tree layer >15m ceous communities are classified accord- The “algarrobales” are high constituted by Schinopsis balansae ing to Ward’s method they appear similar, but floristically richer, than the and Aspidosperma quebracho-blanco, a grouped in two main clusters, one further “espinillares”. The tree layers are 10-15m lower tree stratum and a sometimes dense divided into four plant communities and high and there is a shrub layer of Celtis shrub layer (Figure 7). There are also the other with five very similar hygro- pallida, Grabowsquia duplicata, Vassobia variants of the “quebrachal”: one variant philous communities, a humid prairie, a

SEP 2003, VOL. 28 Nº 9 515 TABLE III ASSOCIATION TABLE OF FOREST UNDERSTORY

Communities A B C Forest understory censuses 10 1 12 3 2 11 5 7 6 13 4 8 14 9 Species / Forest censuses 81433456675676 Stenotaphrum secundatum 5 Chenopodium ambrosioides + Urtica urens 1 Anthemis cotula + Polygonum hydropiperoides + Phyla canescens + Alternanthera philoxeroides ++ Jaborosa integrifolia ++ 1 Bromus catharticus ++ ++ Sida rhombifolia 1+2232+ Cynodon dactylon 2333 3 +1 Carex bonariensis ++21 + +++ Cyperus esculentus +++++ Cyperus entrerianus 2+2+ Ludwigia bonariensis + Ludwigia peploides + Paspalum dilatatum + Aspilia pascalioides ++ Setaria parviflora ++ Verbena intermedia + Bidens pilosa + Baccharis salicifolia + Desmodium incanum 2+1 Paspalum notatum 35 Salpichroa origanifolia ++ 1 Leonurus sibiricus +++ Chaptalia nutans ++ Setaria stolonifera 241 Leptochloa virgata +1 + Trixis praestans +1 Dicliptera tweediana ++ Hypochaeris microcephala + Setaria fiebrigii +1 + Piptochaetium lasianthum ++ Oplismenus hirtellus subsp. Setarius 41 + Doryopteris pedata + Solanum sisymbriifolium + Eragrostis lugens 2 Poa lanigera 1 Gomphrena perennis 1 Ambrosia tenuifolia + Porophyllum obscurum 1 Petunia parviflora + Spergula ramosa + Figure 8. Ward’s clustering technique dendro- Dolichandra cynanchoides + gram of herbaceous plant communities. Substi- Ruellia coerulea ++ tution communities are 1: prairie of Paspalum Sporobolus pyramidatus 11 notatum, 2: tall grassland of Paspalum rufum, Selaginella sellowii 31 3: turf of Cynodon dactylon, 4: savanna of Dichondra microclayx 1 ++ + Spartina argentinensis. Hygrophilous commu- Commelina erecta + ++++ nities are 5: rushes of Schoenoplectus californi- Dyckia remotiflora var. 1 2 cus, 6: rushes of Thalia multiflora, 7: meadow Petunia linearis ++ of Ludwigia peploides, 8: hygrophilous turf of Sinningia tubiflora 2+ Echinochloa helodes, Leersia hexandra and Lepidium aletes ++ + Eleocharis parodii, 9: rushes of Typha domin- Herreria montevidensis ++ + gensis, 10: low turf of Luziola peruviana. Cystopteris diaphana +1++ Halophytes communities are 11: Panicum pri- Aechmea distichantha +33 onitis tall grasslands. 12: is a community of the halophytes Sarcocornia perennis, Sesuvium Harrisia tortuosa +++ portulacastrum and Spartina densiflora. Cucurbitella asperata ++

516 SEP 2003, VOL. 28 Nº 9 TABLE III (Continues) tall grassland and a halophyte community ASSOCIATION TABLE OF FOREST UNDERSTORY (Figure 8). Most of these communi- Communities A B C ties have an upper layer often >1m high of Forest understory censuses 10 1 12 3 2 11 5 7 6 13 4 8 14 9 the dominant species and a lower stratum with most other species. The general cover Opuntia chacoensis 2 is usually very high, ranging from 70 to Petiveria alliacea 1 90% of the ground, although plots of the Berberis ruscifolia + halophyte community may have a high pro- Eleusine tristachya ++ portion of bare soil (Table IV). Floristically Stipa neesiana ++2they are very poor and in some plots there Sisyrinchium pachyrhizum ++is an almost pure population of the domi- Hordeum stenostachys ++11+nant species. They contain very few con- Panicum stoloniferum 2+stant species and usually very few species Panicum sabulorum 1+or even none at all in the highest constancy Juncus bufonius ++++1 class, while most species are at the lowest Eryngium coronatum +++constancy class (Table V). Marsilea ancylopoda +1 Some of these communi- Pluchea sagittalis 11ties are floristically poorly defined (Table Eriochloa punctata 11VI) and often the most abundant species Panicum hians 2 are of low constancy. Luziola peruviana 2 The four communities of Leersia hexandra + the first cluster are three substitution com- Cyperus corymbosus + munities and Spartina argentinensis tall Acmella decumbens +++grasslands. In these communities Cynodon Eleocharis parodii + +++ dactylon, Setaria parviflora, Aster squama- Paspalum intermedium 1 tus, Cyperus entrerianus, Eryngium echi- Axonopus suffultus + natum and Chaetotropis elongata are fairly Asclepias flava + constant. Of the substitution communities, 1 Gomphrena pulchella ++and 2 are the richest floristic communities Briza subaristata +2of the region with 133 and 115 species re- Pfaffia glomerata +++corded in each of them and the highest av- Heimia salicifolia ++erage number of species per plot, while Juncus capillaceus +2+ community 3 is rather poor, with Cynodon Stenandrium dulce ++ dactylon as the dominant species. Sporobo- Bromelia serra +3 lus indicus, Conyza bonariensis, Dichondra Rivina humilis +3microcalyx and Sisyrinchium platense are Piptochaetium stipoides 2 common in the three communities. The first Stipa hyaline 1++ + ++ 2 two substitution communities are very close Oxalis sp. + + + to each other (Figure 8), Paspalum no- Specific Richness 15 20 11 16 12 14 26 10 15 17 12 16 17 13 tatum, Eragrostis lugens, Deyeuxia viridifla- C Richness 2311222-12-224 3 vescens and Verbena gracilescens are fairly Coverage (%) 100100 95 80 80 70 40 60 30 60 60 95 70 90 constant and faithful to the first one, and Height (cm) 25 15 15 10 40 30 20 5 10 60 50 50 10 40 the second community appears to be a hu- mid variant of the first one with Eryngium TABLE IV paniculatum, Cyperus corymbosus, Paspa- STRUCTURAL DATA OF HERBACEOUS COMMUNITIES lum rufum, Paspalum intermedium, etc. The first is a rather low and comparatively rich Community 123456789101112prairie or turf, while the second community Census number 14 9 14 10 14 5 14 7 4 12 11 5 is a tall grassland. % coverage 90 90 77 76 85 75 80 95 95 89 90 65 Community 3 is a turf of Height (cm) EHS 60 170 60 80 180 160 180 - 200 - 160 110 Cynodon dactylon with few other species, Height (cm) EHI 5 15 10 5 20 30 7 30 10 10 5 20 which may be the result of plowing and Total number of species 133 115 91 94 44 28 63 57 27 38 86 10 overgrazing the Spartina argentinensis tall Average species/census 29 24 6-19 25 9 9 17 10 2-11 3-10 18 6 grasslands and savannas. Community 4 is a tall TABLE V grassland or savanna of Spartina argentin- CONSTANCY DATA OF HERBACEOUS PLANT COMMUNITIES ensis. The dominant species cover is vari- able, and at high places the floristic rich- Number of species 123456789101112 ness is low, and vice versa. Other species of the community are Sarcocornia perennis, Class I 85 77 67 72 27 17 43 42 24 31 62 13 Sesuvium portulacastrum, Eryngium coro- Class II 27 29 19 14 11 7 12 8 - 4 15 2 natum and Cynodon dactylon. Class III 16 64632644 -5 - In the other main cluster Class IV 4 2 - 12123 -223 Class V 1 - 1111 - -1121 are gathered hygrophilous communities to- gether with Panicum prionitis tall grasslands

SEP 2003, VOL. 28 Nº 9 517 TABLE VI ASSOCIATION TABLE OF HERBACEOUS PLANT COMMUNITIES

Species / Community 123456789101112 Verbena gracilescens III Deyeuxia viridiflavescens III Scoparia montevidensis II Aeschynomene denticulata II Paspalum urvillei II Funastrum clausum II Hypochaeris chillensis II Verbena intermedia II Wahlenbergia linarioides II Conyza monorchis II Figure 9. DECORANA scatter diagram of Hydrocotyle bonariensis II herbaceous communities on the plane of the Eragrostis lugens III first two axes. *: substitution communities, Galium richardianum II : hygrophilous communities, 0: halophytic Juncus capillaceus II communities. Kyllinga odorata II Paspalum notatum III or savannas, and halophytes communities. Agalinis communis II Five of the hygrophilous communities are Borreria verticillata II very close to each other (5 to 9); they are Cyclospermum leptophyllum II II the rushes of Schoenoplectus californicus (5) Cyperus rigens II II which appear in rather deep depressions, Conyza bonariensis II II flooded almost the whole year, with an up- Lepidium spicatum III II per layer of variable density of Schoenoplec- Juncus bufonius III II tus californicus and sometimes a lower layer Acicarpha tribuloides II II very similar to the other hygrophilous com- Scutellaria racemosa III II munities or a Pistia stratiotes pleuston. Eleocharis montana II III III Community 9 is similar to this community, Paspalum intermedium II but the upper layer is a very dense popula- Paspalum rufum II tion of Typha domingensis and hardly any Parietaria debilis II other species. Communities 6, 7 and 8 are Ambrosia tenuifolia II very similar to each other with the differ- Eryngium paniculatum IV ence between 6 and 7 being the presence of Phalaris angusta II a tall layer of Thalia multiflora and Juncus microcephalus II Sagittaria montevidensis, community 7 is a Cyperus corymbosus III II meadow of Ludwigia peploide and commu- Plantago myosuros II III II nity 8 is a hygrophilus turf where Echi- Sporobolus indicus IV II III nochloa helodes, Leersia hexandra and Dichondra microcalyx II II II Eleocharis parodii are very frequent. Com- Carex bonariensis IV II II munity 10 is also a low turf of hydrophilous Sisyrinchium platense III II II gramineae dominated by Luziola peruviana. Setaria parviflora V III II III II The most different communities of this Eryngium echinatum III II III III group are successively chained to the hygro- Cynodon dactylon IV III V III philous communities. Panicum prionitis tall Chaetotropis elongata III II II III grasslands in the first place and then the Cyperus entrerianus III IV II II II II II community of halophytes (12). The first one Aster squamatus II III III IV II III has an upper layer of the dominant species Paspalum plicatulum II II II and a low one composed mainly by more Pluchea sagittalis III II II hygrophilous species. The most common Panicum hians IV II III II species of the halophytes communities are Rhynchospora scutellata II II II II fleshy Chenopodiaceae (Sarcocornia Heimia salicifolia II II perennis) and Sesuvium portulacastrum, and Briza subaristata III II in some places it has an upper layer of Phyla canescens II II Spartina densiflora that can be very dense. Malvella leprosa III II When data are analyzed Cyperus reflexus II II with DECORANA, the hygrophilous com- Desmodium incanum III II munities are pulled to one side by the first Gamochaeta coarctata III II axis and all others to the right, while the Sporobolus pyramidatus II second axis pulls the halophyte commu- Heliotropium curassavicum II II nity to the upper part of the dispersion Spergula platensis II diagram and most other plots to the bot- Gomphrena celosioides II tom (Figure 9). Hymenoxys anthemoides II

518 SEP 2003, VOL. 28 Nº 9 TABLE VI (Continues) ests of Schinopsis balansae appear in the ASSOCIATION TABLE OF HERBACEOUS PLANT COMMUNITIES north of the region and are strictly cha- quenian forests (Ragonese, 1941; Cabrera, Species / Community 123456789101112 1976; Lewis and Pire, 1981). The “algarro- bales” and “espinillares” are more wide- Hypochaeris microcephala II spread towards the south, but as in the Portulaca cryptopetala II Chaco, on low saline soils there are “alga- Eryngium coronatum II II rrobales” of Prosopis sp. (Lewis and Pire, Spartina argentinensis V 1981; Lewis, 1991). Cienfuegosia drummondii II The most widespread her- Euphorbia serpens II baceous communities of the region are tall Neptunia pubescens II grasslands. Hygrophilous communities, on Eriochloa punctata III the other side, cover relatively little space Salvinia biloba II and are confined to small internal depres- Utricularia gibba II sions. Azolla caroliniana II The two most important Pistia stratiotes VII tall grasslands are the Spartina argentinensis Enhydra anagallis II III III and Panicum prionitis. The former is a halo- Luziola peruviana III IV III III V IV philous community very widespread further Limnoboium spongia IV II II II north which covers a considerably large area Schoenoplectus californicus IV II in the submeridional lowlands of the Chaco Lemna sp. III II (Lewis et al., 1990) and in most depressed Thalia multiflora V saline areas of the eastern Chaco (Morello Hydrochleys nymphoides II and Adámoli, 1974; Lewis and Pire, 1981). Oplismenopsis najada III II II Also there are Spartina argentinensis tall Myriophyllum aquaticum III grasslands surrounding lake Mar Chiquita in Echinochloa crusgalli II Cordoba (Sayago, 1969), and there are sev- Solanum glaucophyllum IV eral smaller stands further south, down to Hydrocotyle ranunculoides II IV o Cissus palmata II parallel 33 S (Lewis and Collantes, 1973; Eichhornia crassipes II D’Angelo et al., 1987). The latter is the Nymphoides indica II most important grassland of the Paraná Paspalum distichum II River valley (Franceschi and Lewis, 1979) Eclipta prostrata II II but is very common in depressed areas of Mikania cordifolia II III II the eastern Chaco (Lewis and Pire, 1981) Isolepis cernua II II II II and the Paranense phytogeographical prov- Polygonum hydropiperoides II II III III III II ince (Cabrera and Willink, 1980). There are Sagittaria montevidensis II II II III also other tall grasslands, such as the Echinochloa helodes II IV Paspalum rufum ones, but they are the result Eleocharis elegans III of the destruction of one of these communi- Paspalidium paludivagum II ties. These communities are hyper-seasonal Alternanthera philoxeroides III III III savannas (Sarmiento, 1984), and are flooded Typha domingensis V during some periods followed by rather long Ludwigia bonariensis II II II II II III II II droughts, with some scattered trees. Often, Pontederia cordata II II tall grasslands are burnt in order to improve Leersia hexandra II II II IV II III their forage quality, as the re-sprouts of the Eleocharis parodii II IV IV dominant species are more palatable than the Ludwigia peploides II II III IV IV old sclerophyllous leaves. However, periodi- Vernonia sp. II V cal fires reduce the floristic richness of these Cyperus virens III II III communities and promote the strong domi- Panicum prionitis III V nance of the tall bunch grasses Panicum pri- Juncus densiflorus II onitis and Spartina argentinensis. Carex riparia II Among the hygrophilous Cyperus esculentus II communities, both the Schoenoplectus cali- Sesuvium portulacastrum II IV fornicus rushes and the Typha domingensis Cressa truxillensis II ones are very widespread on the American Sarcocornia perennis II V continent. The former species is found in the Spartina densiflora IV Pampa region (Vervoorst, 1967; Lewis et al., Polygonum aviculare IV 1985), in the Chaco (Morello and Adámoli, 1974; Lewis and Pire, 1981; Franceschi and Lewis, 2000), on the valley of the Paraná Discussion latitudinal one, as floristic richness, stratifica- River (Burkart, 1957; Franceschi and Lewis, tion and complexity increase northwards. 1979), and even on the high Andes (Heiser, There are three kinds of But there may be an elevation gradient as 1979). The latter species is also found in the forests that are not very different from each well. Further north from this region, floristic Pampa region (Vervoorst, 1967), in the other in the region. They are ordered along richness of tree layers increases even more Chaco region (Franceschi and Lewis, 2000), gradients. The most important gradient is a (Lewis, 1991; Lewis et al., 1994). The for- the Brasilian Pantanal (Prance and Schaller,

SEP 2003, VOL. 28 Nº 9 519 1982), and similar communities with Typha ACKNOWLEDGEMENTS León RJC, Anderson DL (1983) El límite occidental angustifolia and Typha latifolia exist up to del pastizal pampeano. Tuexenia 3: 67-83. León RJC, Marangon N (1980) Delimitación de co- North America (Grace and Wetzel, 1981). The authors thank Ruben munidades en el pastizal puntano. Sus relacio- The other hygrophilous communities are Favot, Marcial Bugnon, Jorge Carbone and nes con el pastoreo. Bol. Soc. Arg. Bot. 19: very similar to each other and are very com- Pablo Carletti for their collaboration in field- 277-288. mon on the whole Chaco region, and similar work, Susana Stofella for her orientation and Lewis JP (1991) Three levels of floristical variation as well to some of the communities in the training with the Multivariate Analysis, in the forest of Chaco, Argentina. J. Veget. Sci. 2: 125-130. Paraná River valley. Guillermo Gil for Figure drawings, and Lewis JP, Collantes MB (1973) El Espinal On very saline soils of the Alejandro Córdoba for improving the En- Periestépico. Ciencia e Investigación 29: 345- Chaco-pampean plain there are communities glish text. Finantial aid was provided by 408. characterized by the presence of succulent CAID, Universidad Nacional del Litoral and Lewis JP, Pire EF (1981) Reseña sobre la vegetación plants, fundamentally Sarcocornia perennis. CONICET. del Chaco santafesino. La vegetación de la Re- pública Argentina. INTA, Serie Fitogeográfica We have not enough data, but some of the 18: 1-48. stands have an upper layer of Spartina REFERENCES Lewis JP, Collantes MB, Pire EF, Carnevalle NJ, densiflora and in other regions tall grass- Bocanelli SJ, Stofella SL, Prado DE (1985) lands of this species have been described Braun-Blanquet J (1979) Fitosociología. Blume. Ma- Floristic groups and Plant communities of (Lewis et al., 1985; 1990; D’Angelo et al., drid, Spain. 820 pp. southeastern Santa Fe, Argentina. Vegetatio 60: Burkart A (1957) Ojeada sinóptica sobre la vegeta- 67-90. 1987). Communities with fleshy chenopods, ción del delta del río Paraná. Darwiniana 11: Lewis JP, Pire EF, Prado DE, Stofella SL, different Sarcocornia species, together with 457-561. Franceschi EA, Carnevale NJ (1990) Plant com- Spartina, are common in marshes located at Cabrera AL (1953) Esquema fitogeográfico de la munities and phytogeographical position of a both sides of the Atlantic Ocean (Rieley and República Argentina. Rev. Mus. La Plata (N.S.) large depression in the Great Chaco, Argentina. 8, Sec. Bot. 33: 87-168. Vegetatio 86: 25-38. Page, 1990). Lewis JP, Pire EF, Vesprini JL (1994) The mixed If Tables III and VI are Cabrera AL (1976) Regiones fitogeográficas argenti- nas. ACME. Buenos Aires, Argentina. 85 pp. dense forest of the Southern Chaco. Contribu- tion to the study of the flora and vegetation of compared, the forest understory has a high Cabrera AL, Willink A (1980) Biogeografía de Amé- the Chaco VIII. Candollea 49: 159-168. proportion (31%) of Winter graminea that rica Latina. OEA. Serie Biológica Nº13. Wash- are scarce in the grassland and savanna re- ington DC, USA. 122 pp. McCune B (1991) Multivariate analysis on the PC- ORD system. Oregon State University. Corvallis, gions, where most grasses are Summer Cáceres LM (1980) Caracterización climática de la USA. 139 pp. graminea. provincia de Santa Fe. Ministerio de Agricultura y Ganadería. Santa Fe. Departamento Aguas. Morello J, Adámoli J (1974) Las grandes unidades Lumbering, fire, grazing Santa Fe, Argentina. 35 pp. de vegetación y ambiente del Chaco argentino. and agriculture constitute the main distur- Vegetación y ambiente de la Provincia del Cha- Carnevale NJ, Torres PS, Lewis JP (1999) Análisis co. INTA. Ser. Fitogeográfica 13: 1-130. numérico y estacionalidad de las comunidades bance sources in the region. Fires shape the Orellana JA, Priano LJJ (1978) Origen y distribución higrófilas de los bajos submeridionales tall grasslands, but plowing promotes their de los suelos santafesinos. Revista FAVE 1: 117- santafesinos (Argentina). Bol. Soc. Arg. Bot. 34: substitution by other grassland types. Forests 198. 39-46. Parodi LR (1945) Las regiones fitogeográficas ar- are completely destroyed to give way to ag- Cottam G, Curtis JT (1956) The use of distance riculture or forage crops, which are later gentinas y sus relaciones con la industria fo- measures in phytosociological sampling. Eco- restal. Plant Sci. Lat. Amer. 16: 127-132. logy 37: 451-460. abandoned and replaced by one of the sub- Prance GT, Schaller GB (1982) Preliminary studies stitution communities. On the best drier and D’Angelo CD, Prado DE, Stofella SL, Lewis JP of some vegetation types of the Pantanal, Mato less saline soils appear the Paspalum no- (1987) The Subchaquenian vegetation of the Grosso, Brazil. Brittonia 34: 228-251. province of Santa Fe (Argentina). Phyto- Ragonese AE (1941) La vegetación de la provincia tatum prairie, which is rather similar to the coenologia. 15: 329-352. “flechillar de abra” found in a neighboring de Santa Fe. Darwiniana 5: 369-416. Davis TAW, Richards PW (1933) The vegetation of Rieley JO, Page S (1990) Ecology of Plant area (Hilgert and D’Angelo, 1996) and the Moraballi, British Guiana: an ecological study Communities. Logman. Harlow, England. 178 Pampean “flechillares” (Vervoorst, 1967; of a limited area of tropical rainforest. Part I. J. pp. Ecol. 1: 350-384. León and Marangon, 1980; León and Ander- Sarmiento G (1984) The ecology of Neotropical Davis TAW, Richards PW (1934) The vegetation of Savannas. 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The hygrophilous commu- Scirpus californicus (Cyperaceae) y Totorales de Classification of Plant Communities. W. Junk. nities are strongly chained together as occurs Typha domingensis (Typhaceae) en los bajos The Hague, Netherlands. pp. 287-339. submeridionales (Argentina). Bol. Soc. Arg. Bot. Whittaker RH (1980) Dominance Types in in other regions (Carnevale et al., 1999). 34: 171-178. This fact and the scatter diagram of data Classification of Plant Communities. In Grassino SB (1986) Análisis integral de la provincia Whittaker RH (Ed.) Classification of Plant analyzed with DECORANA strongly suggest de Santa Fe. Imprenta Oficial de la Provincia Communities. W. Junk. The Hague, that all communities are distributed along de Santa Fe. Argentina. 383 pp. Netherlands. pp. 65-81. two main gradients, possibly a soil moisture Grace JB, Wetzel RG (1981) Habitat partitioning Zuloaga FO, Morrone O (ed.) (1994) Catálogo de la one and a salinity one, although this has to and competitive displacement in cattails familia Poaceae en la República Argentina. (Typha): Experimental field studies. American be proved in other studies. Monographs in Systematic Botany. Vol. 47. Naturalist 118: 463-474. Missouri Botanical Garden 178 p. The region is an impover- Heiser CB (1979) The Totora (Scirpus californicus) Zuloaga FO, Morrone O (eds.) (1996) Catálogo de ished Chaco, lying also in the far south, is in Ecuador and Perú. Econ. Bot. 32: 222-236. las plantas vasculares de la República Argentina less tropical and winter is colder. Also, it ap- Hilgert NI, D’Angelo CH (1996) Las Comunidades I. Monographs in Systematic Botany. Vol. 60. pears to have a strong influence of the Vegetales de los Dptos. Castellanos y Las Colo- Missouri Botanical Garden. USA. 323 pp. nias (Santa Fe). Bol. Soc. Arg. Bot. 32: 3-16. Paraná River, so the vegetation has strong Zuloaga FO, Morrone O (ed.) 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