During the summer of 1976,using the basal area criterión and the ring method, botanical composition and coverage percentage were recorded at 18 sampling stations in the Patagonic Steppe (A), 9 in the Natural Pastures of Ultima Esperanza (B), 4 in the Mesophitic Bush Biotic Province (C), 4 in the Natural Pastures of the Forest Area (D), and 9 in the FIat Humid Lowlands, located in the above mentioned zones.
Three, 30 m lineal, transects were stablished in each sampling station, each one with 100 observation rings. Results are given in tables containing the species detected and their respective area coverage percentages.
In A, the dominant grass is Festuca gracillima (Coirán), that gives its name tothearea (Coironal); in B, the most abundant species is Stipa neesiana: in C, 75% of the area is covered by ChiIliotrichium diffusum, F. gracillima and “mantillo” (decomposed or under advanced decomposition vegetable material); in D, Holcus lanatus, Poa pratensis, and Trifolium repens are characteristic species; and in E, the more frequent forage species are P. pratensís, Carex acaulis, Agrostis canina and Hordeum comosum. Cyperaceous species are also frequent.
In A and B, a high percentage of the soil is “uncovered” (with no vegetation), due mainly to excessive grazing and low rainfall; this problem was not detected under the C, D, and E conditions.