The lowland seasonally dry subtropical forests in central Argentina: vegetation types and a call for conservation
Prepared by Sebastián R. Zeballos, Melisa A. Giorgis, Marcelo R. Cabido, Alicia T.R. Acosta, María del Rosario Iglesias & Juan J. Cantero
The introductory photo illustrates the actual conservation status of the lowland seasonally dry subtropical forest in central Argentina and perhaps in many other places in the Neotropics. Forests have been reduced to small and isolated remnant patches surrounded by nearby agricultural matrices. The conversion of forests started at the beginning of the 20th century driven mainly by timber and firewood extraction, jointly with the expansion of agriculture and grazing fields. Nowadays, the last forest remnants are further threatened by the establishment of several invasive exotic species. Notwithstanding the dramatic condition of these forests, there was almost no floristic and phytosociological knowledge of the remnant patches at the time we started our survey.
In South America, the southernmost seasonally dry subtropical forests are included in the Espinal phytogeographic province. As a consequence of the lack of floristic and phytosociological knowledge, a comprehensive classification of these forests is not available, which has generated a serious disagreement among different authors concerning their extent and status. At the same time, this complicates the development of conservation and restoration practices.
With this framework in mind, we planned the study of the floristic heterogeneity, diversity and the spatial patterns of native forest types of the Espinal phytogeographic province in central Argentina. The survey was concentrated in Córdoba province, where, according to previous research, most of the forest types reported so far were likely to be present. Our working group at the National University of Córdoba and the National Research Council (CONICET) has been involved in vegetation survey studies in central Argentina for a long time contributing with the local and national administrations in the conservation and management of natural areas.
In this article, we report four native woody vegetation types (Aspidosperma quebracho-blanco forest; Zanthoxylum coco forest; Geoffroea decorticans forest; and Prosopis caldenia forest) segregated along gradients associated mainly to precipitation and temperature seasonality, jointly with a soil water availability gradient probably determined by soil texture (i.e. sand, lime and clay content) and sodium content. Also, we provide both a map depicting the extent of the Espinal phytogeographic province within the study area and an updated map of the current distribution of Espinal forest patches and the surface devoted to protected natural areas. We should emphasize that the cover of these woody patches represents less than 4% of the extension that Espinal had in Córdoba at the beginning of the 20th century, and only 1.05% of it is under protection.
Another issue that deserved our attention is the presence of alien woody species throughout the four forest types described, even though we have not included patches dominated by exotic tree species into our sampling design. The establishment of these invasive species might trigger several habitat modifications (e.g., the physical structure) transforming the native forest into “novel ecosystems” with a strong potential to change ecosystem functioning. This topic claims for urgent policy measures by the local authorities.
Despite the dramatic changes that have taken place in the Espinal forests, we consider that the four vegetation types identified in our study are still representative, in terms of floristic composition, of the seasonally dry subtropical forests that covered the study area a few centuries ago. An essential further step for their conservation is to establish new protected areas that include as many as possible of these last forest relicts. Nowadays, the conservation status of the Espinal forests is uncertain and, at this time, its survival depends almost entirely on the goodwill of private owners.
This is a plain language summary for the paper of Zeballos et al. published in the Vegetation Classification and Survey (https://doi.org/10.3897/VCS/2020/38013).