Schinopsis balansae forests: a population study in the southern area of the Cuna Boscosa in Santa Fe (Argentina)

The Schinopsis balansae forests in the southernmost area of the Cuna Boscosa in Santa Fe, develop in two different geomorphologic and edaphic zones: the Vera Plain Area and the Belt with Reconquista Relief. Due to soil differences, land use differs between zones with different consequences for survival of Schinopsis populations. A polygon including equal surface areas of both zones was established, where landscape pattern attributes and Schinopsis populations variables were quantified. Trees with diameter at breast heigth larger than 10 cm and their sexual expression were recorded. The surface area with natural forest cover, patch size, percentage of occupation, and total and mean patch perimeters were much larger in the Vera Plain Area. The number of patches and their perimeter: area ratio were higher in the Belt with Reconquista Relief, where the cultivated area is almost seven times larger than in the Vera Plain Area. In both areas, there were fewer trees in the lower diameter class than in the successional class, suggesting population decrease. During the 3-year research period, 30,4% of females and 7,6% of males flowered, while no flowering occurred in 62% of the individuals. In the Belt with Reconquista Relief there are few individuals of low diametric class but many individuals of higher diametric classes, indicating population ageing. Since S. balansae is a heliophyte species, regeneration within the forests is limited. While in the Vera Plain Area it might have the role of pioneer in undisturbed areas, in the Belt with Reconquista Relief, without available areas for colonization processes, the populations fate is uncertain.