The tree species of the Argentine woods reach the figure of 400 and many of them are actively exploited. They have been especially studied by the botanists Lillo and Spegazzini.
We will remember for Misiones the following species of economic importance: Ilex paraguariensis St. Hil. of the Aquifoliaceae, a tall tree with large foliage, common in certain areas called yerbales. Quite exploited and semi-destroyed in its spontaneous state, it is now cultivated for the value of its leaves whose infusion, mate, is the substitute for tea and coffee; Cordia aliodora (R. et Pav.) Cham., Of the Borraginaceae, called their negro ; Brazilian auracaria Argentina Rich, of the Pinaceae, which is the pine of Brazil; Piptadenia rigida Benth., Of the Leguminosae, whose hard wood is highly valued, is called curupayrá ; Pterogyne nitens Tul., Also of the Leguminosae, known by the name of ybyraró also lives in Salta, where they call it tipa colorada or pole mortero ; Cabralea oblongifoliolata C. DC., Of the Meliacee, is the cancherana ; Cedrela fissilis Vell. var. macrocarpa C. DC. from the same family as the previous one, the most precious tree of Misiones, the well-known cedar, whose wood is the most exported; Balfourodendron Riedelianum Engl., Of the Rutaceae, called guatambú – morotí which provides a very elastic wood; Aspidosperma olivaceum Müll., Of the Apocinaceae, known by the name of guatambú amarillo ; Tecoma ipe Mart., Of the Bignoniacee, the lapacho negro, the most valuable wood after the cedar, etc. In the woods of Tucumán, Salta and Jujuy, the following important essences are found with many others: Iuglans australis Gris., The well-known nogal of Tucumán, a wood much appreciated for the manufacture of furniture; Piptadenia macrocarpa Benth., Of the Leguminosae, commonly called cebil colorado, used for carpentry work and whose bark is an excellent tanning agent; Miroxylon toluiferum L. f., Of Leguminosae, commonly known as quinaquina, much appreciated for its cabinet-making works, as well as as a medicinal plant for the balm it produces; Astronium urundeuva Fr., of the Anacardiaceae, commonly known as urunde ; Cedrela Lilloi C. DC., A species very similar to the cedar of Misiones, acquires great development and its wood is a little softer and more stringy.
Where it rains less, the woods are sparse and vigorous herbaceous vegetation develops, grasslands or savannahs with islands of trees and it is not uncommon to find tunnel woods arranged along the course of rivers and streams. This is the characteristic vegetation of immense expanses north of Santa Fe, Chaco, Formosa, north of Corrientes, and south of Misiones. In these woods, less in these last two political divisions, we find the quebracho colorado, Schinopsis Lorentzii Enhl. and Ref. Balansae Engl. (Anacardiaceae); the latter, of great industrial importance, is actively exploited for the tannin extracted from it. They also live there ‘s urunday (Astronium), the rosewood (Bulnesia), etc., mixed with elements of the forests of Brazil, Bolivia and Paraguay and with elements of fruit trees: chañar, varî algarrobos, etc.
Herbaceous vegetation depends on the frequency or scarcity of rains; in the rainy areas the grasses, for example, acquire an enormous development. These plants reach heights relevant to the family and, at times, have lignified bases and the leaves are quite hard. The genera Andropogon, Triodia, Panicum, Chloris, Paspalum, Pappophorum etc. are represented, which often mix with Composite and with numerous other species of different families.
To take advantage of the zootechnical performance of natural grasses, the estancieros practice the burning of the fields, an always dangerous procedure, by which the plants return to develop giving a more tender pasture.
The picture that we have summarized is completed in many districts with the presence of palm trees in large quantities: the yatay (Cocos yatay Mart.) In Corrientes, south of Misiones etc. and the caranday (Copernicia ailstralis Becc.) in the Chaco and Formosa.
To give an approximate idea of the floristic richness of this sub-tropical formation, we will add that no less than 500 new species of seagrasses have been recognized within six years and as many are being studied that will be gradually illustrated.
According to nexticle.net, the phytogeographic formation of the Pampean prairie, which should not be confused with the national territory of the Pampas, includes the most fertile and richest part of the country, in an area of approximately 500,000 square kilometers. It is limited to the east by Paraná and includes the province of Buenos Aires, in its almost totality, the south of the province of Santa Fe and Córdoba and the extreme NE. of the territory of the Pampa. The banks of the Paraná and Plata rivers have a special flora consisting of elements of Mesopotamia and sub-tropical woodlands and savannas, and the great delta of Paraná offers lush sub-tropical vegetation which, according to the environment, is markedly hygrophilous.
The soil of the Pampeana prairie is of uniform composition, formed by the so-called pampean loess, a clayey-sandy earth of fine grain, without pebbles, and of considerable fertility, almost perfectly horizontal; this fact facilitates the danger of floods. Natural streams or deposits of water are scarce or of minor importance, but the aquifers are practically inexhaustible.
The rainfalls are immense in this formation, and oscillate numerically between 50 and 100 per year, reaching mm. 1000 of annual average. If these rains were better distributed, and were more regular, this region could be prodigiously rich from an agricultural-zootechnical point of view.
The climate is temperate or warm temperate, and sometimes there are no real winters. The following figures give an idea of the Pampean climatology:
The irregularity of the rain regime means that, despite the fact that it is a continuous vegetation, which completely covers the soil, it is clearly xerophilous due to the hot summers with many times prolonged drought.