Plant secondary succession age-related changes in landfills

Sanitary landfills are widely used for large-scale final disposal of municipal wastes. The material covering the wastes is diverse in nature and bears propagules of different plant species, which develops spontaneously on the sites after waste disposal stops. The aim of this study was to detect the main patterns of vegetation secondary succession over the landfill cells, despite the differences in area and surface work intensity at the landfills. Over the span of two years, eight samplings were carried out on each of the 13 cells from the three active landfills in Buenos Aires. The relative cover for each plant species and the soil’s mechanic resistance were registered. The vegetation cover reached 80 % after five years and a decrease in soil´s mechanic resistance was observed 5 years after closure. Regarding the floristic composition of the assemblages, most of the herbaceous species found were native (42 %) and perennials (62 %). The dominant species in all the cells was Cynodon dactylon. The heterogeneity of the assemblages between the three places prevented the configuration of an age linked pattern. However, some regularities arise: exotics are dominant along the whole succession; meanwhile, natives gain in proportionality consistently with the age of the cells. Most of the dominant species are characteristic of perturbed environments, but in the oldest cells some species belong to the climax pampean steppe; so, an orientated human intervention would be necessary to achieve a dominance of natives.