Reconstruction of vegetation history in central Italy through a palynological approach. A case of study from Lago Lungo (Rieti basin)
Author(s)
Tunno, Irene
Date Issued
May 30, 2014
Type
Doctoral Thesis
Abstract
Lake sediments record climatic and ecological changes taking place at the time of their deposition. These changes are recorded as stratigraphic variations of physical and chemical properties and changes in species composition of plant and animal remains. Palynological studies provide consistent information of changes that occurred in a particular area especially where many historical documents are available. High-resolution reconstruction of vegetation history can be used to investigate the nature of the past environmental changes, disentangling the effects of climate and human activity on the landscape. A palynological study was carried out in the Rieti basin (Lazio, central Italy). This region has been colonized for millennia, from the pre-Roman period, and strong modifications, both of natural and anthropogenic origin, have occurred through time. Three sediment cores collected from Lake Lungo (371 m. a.s.l.) have been analyzed for a total length of 15 m.
Five zones, related to different phases in the evolution of the landscape, have been identified along the cores: an early period (zone 1; 2700-2040 yr BP; 680-30 BCE) characterized by woodlands, showing a natural system with a variety of natural tree species (e.g. Quercus, Fagus, Tilia, Acer) and few indicators of human activity; a second phase (zone 2; 2040-1150 yr BP; 30 BCE-870 CE) in which the human impact becomes more evident, as underlined by the increase of indicators of disturbance like herbs, Poaceae, ferns and charcoal; a third period (zone 3; 1150-600 yr BP; 870-1410 CE) showing the maximum rate of human impacts for the entire core: forest cover decreases abruptly while indicators of disturbance increase rapidly, indicating a high level of erosion linked to intensive deforestation; a forested phase (zone 4 600-210 yr BP; 1410-1800 CE) testifies the rapid forest recovery after a very intensive period of utilization (zone 3) facilitated by the decreased anthropogenic pressure and more favorable climatic conditions (cold and wet); a final phase (zone 5; 210-20 yr BP; 1800-2000 CE) representing the modern period, is characterized by a continuous but less dense forest cover together with high percentage of Poaceae, herbs and cultivated trees.
Climatic and anthropogenic signals have been identified throughout the responses of the vegetation under different pressures. Deforestation occurred during warm phases while woodland regeneration occurred during cold phases. At the same time the re-expansion of forest has been favored during wet periods when attempts to drain the Rieti basin have not been effective, reducing the human impact on the landscape. Historical documents have been used to support the palynological data indicating how particularly useful written records can be used in supporting paleoecologic research.
The results of this study, different from other research, have provided a high-resolution reconstruction of the vegetation history for the last 2700 years.
Additional information
Dottorato di ricerca in Scienze e tecnologie per la gestione forestale e ambientale
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