Trends in fragmentation and connectivity of Paspalum quadrifarium grasslands in the Buenos Aires province, Argentina

Abstract

Background Despite its wide distribution worldwide, only 4.6% of temperate grasslands are included within systems of protected areas. In Argentina, this situation is even more alarming: only 1.05% is protected. The study area (central area of the southern Salado River basin) has a large extent of grasslands of Paspalum quadrifarium (Pq) which has been target since the middle of the last century of a variety of agricultural management practices including fire burning for cattle grazing. Methods Five binary images of presence-absence data of Pq from a 42-year range (1974–2016) derived from a land cover change study were used as base data. Morphological Spatial Pattern Analysis (MSPA), Morphological Change Detection (MCD) and Network Connectivity Analysis (NCA) were performed to the data using Guidos Toolbox (GTB) for the estimation of habitat and connectivity dynamics of the Pq patches (fragments). Results A loss of the coverage area and habitat nuclei of this grassland was observed during the study period, with some temporal oscillation but no recovery to initial states. Additional drastic reduction in connectivity was also evident in resulting maps. The number of large Pq grassland fragments (>50 ha) decreased at beginning of the study period. Also, fragmentation measured as number of components (patches) was higher at the end of the study period. The Pq pajonal nuclei had their minimum representativeness in 2000, and recovered slightly in area in 2011, but with a significant percentage increase of smaller patches (=islets) and linear elements as bridges and branches. Large corridors (mainly edge of roads) could be observed at the end of the study period, while the total connectivity of the landscape pattern drops continuously. Statistics of links shows mean values decreasing from 1974 to 2016. On the other hand, maximum values of links decreased up to 19% in 2011, and recovered to a 54% of their original value in 2016. Discussion Pq fragmentation and habitat reduction could have an impact on the ecosystem functioning and the mobility of some species of native fauna. The connecting elements of the landscape were maintained and/or recovered in percentage in 2011 and 2016. This fact, although favoring the dispersion of the present diversity in the habitat nuclei could cause degradation by an edge effect. Part of the area has the potential to be taken as an area of research and as an example of livestock management, since it is the one that would most preserve the biodiversity of the Pq environment. On the methodological side, the use of a proved tool as GTB is useful for monitoring dynamics of a grassland-habitat fragmentation.

Trends and land surface phenological responses to climate variability in the Argentina Pampas

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Novedades sobre la distribución de Colletia spinosissima, Pterocaulon balansae y Saccharum villosum en Tandilia (Buenos Aires) y sus posibles causas

“…Asimismo es probable que la distribución haya sido afectada por el factor antrópico. Sus poblaciones pueden haber disminuido al fragmentarse los pajonales de Paspalum quadrifarium (Gandini et al, 2019) con los que se encontraba asociada (Vervoorst, 1967), o por el contrario, su avance puede haberse facilitado por las rutas, caminos y vías de la red de ferrocarriles que actuarían como corredores biológicos, dado que se la ha encontrado en terraplenes (Vervoorst, 1967) y bordes de rutas.…”

Ecosystem stability of temperate grasslands in response to variability of hydrological conditions

“…These edaphic characteristics represent the main limiting factor for the development of agricultural activity. Therefore, areas of natural and semi‐natural grasslands predominate, constituting a floristic reservoir of the vegetation that dominated this landscape typically used as a source of forage for cattle (Gandini et al, 2019).…”