Studio preliminare su tassocenosi a chilopodi in ambienti forestali lungo un gradiente di urbanizzazione: il caso di Roma
Author(s)
Baini, Francesco
Date Issued
April 10, 2017
Type
Doctoral Thesis
Abstract
Arthropods of urban area have been studied for years. Recently, the effects of urbanization
have been studied on numerous taxa of soil macroarthropods in different urban areas of Central and
northern Europe. While not recognizing a similar pattern of distribution of biodiversity in the
investigated cities, these studies have shown that urbanization has significant effects on the
structural parameters of the community, like abundance, diversity and richness. In particular, it was
noted that the highly specialized faunal elements are those most susceptible to the effects of
urbanization and tend to decrease from the peripheral areas to the central ones.
With the aims to obtain more information on spatial distribution of soil macroarthropods
communities and on their degree of conservation in Rome, in the “Capitolina” area a
macroecological study has been carried out. This study may provide useful information on the
conservation status of the the green areas of Rome, employing Arthropods as indicators of
environmental quality, which play a key role in the function of many ecosystem processes.
The purpose of comparing data obtained on Rome with data from other European cities, like
in the research program GLOBENET, is another reason for starting this research project.
Using spatial analysis with GIS and field direct survyes, three forest fragments, arranged
along a gradient of urbanization and located within protected areas and historical villas in the
northwest quadrant of the city of Rome and the adjacent suburban areas, were identified (Villa
Pamphili PAM, Riserva Regionale Natural di Monte Mario MAR, Oasi WWF di Macchiagrande di
Fregene FRE).
The fragments are different for: i) distance from the center of the town, ii) surrounding
matrix, iii) type of management. Based on these characteristics, each fragment was attributed to one
of the following three categories: urban, suburban, rural.
The study aims to examine the relative importance of the urban landscape structure of Rome
and the quality of forest habitats for abundance, species richness and diversity of forest Centipede
communities.
Specifically, we will proceed (i) a description of the structural parameters of communities
in forest fragment selected along the urban, (ii) a determination of the degree of conservation of the
communities, (iii) an assessment of the effects of some environmental variables and degree of
urbanization on individual species.
Based on the obtained data, the present study aims to explore the biodiversity hypothesis of
distribution in urban environments, theorized in previous works:
Intermediate Disturbance Hypothesis;
Increasing Disturbance Hypothesis;
Habitat Specialist Hypothesis;
Opportunistic Species Hypothesis.
Within each of the three study areas (Villa Pamphili, Monte Mario, Oasi di Macchiagrande)
three forest fragments were selected as sampling stations, within phytosociological class Querceta
ilicis Br.-Bl., whose dominant tree species holm oak (Q. ilex).
Spatial analysis with GIS and field work have allowed to characterize the surrounding
spatial structure and the internal one of the three forest fragments.
Also within the three selected fragments, every two sampling sessions were recorded values
of four environmental structural variables, calculated within a radius circumference of 2 m, taking
as a center of the circle each trap .
It was determined a sampling protocol that involves the use of two traps stations, each
formed by 4 traps for each of the forest fragments.
Each sampling session took place in the time of 21-31 days, starting from the month of June
2015 until June 2016.
For the statistical analysis, the following indices were used:
Jaccard index;
Bruy Curtis index;
Dominance classes;
Morisita index;
Shannon Wiener diversity index;
Pielou index (evenness).
In addition, in order to study the effects of environmental variables and the degree of
urbanization on the number of captured individuals of each species in each trap it was made a
multivariate analysis of ordinal type (CCA, Canonical Correspondence Analyses).
The following comparison tests were applied to test the statistical significance of differences
or similarities between the various data sets:
Nested ANOVA;
Tukey Test;
Spearman correlation coefficient.
The study found that:
The three taxocoenoses investigated differ from each other as regards the structural aspects
of the biotic community. Monte Mario is characterized by a greater complexity as regard the
specific composition of the centipede community investigated, counting the greatest number of
species, an endogean component of community particularly diversified and a substantial percentage
of forest species; these community characteristics are probably related to moderately complex
structural conditions of the fragment of Monte Mario (MAR) and its proximity to other probable
"source" areas, given the high percentage of forest matrix surrounding the fragment. For the
analysis of the abundances, the data obtained indicate greater activity of centipedes in MAR,
probably for the presence of a significant population of Lithobius tylopus, endemic Apennine and
tied to stable forest habitats. In addition, tests carried out for abundance values of the species
indicate that communities present in Villa Pamphili (PAM) and Fregene (FRE) are currently in a
state of less stability and complexity than in Monte Mario, typical of successional stages or subject
to disturbance.
The data obtained in relation of the specific complexity and the diversity indices, further
into the intermediate habitat (MAR) along the urbanization gradient could partially confirm the
Intermediate Disturbance Hypothesis, and the Increasing Disturbance Hypothesis. On the contrary,
the Habitat Specialist Hypothesis and Opportunistic Species Hypothesis are not confirmed.
Therefore, the distribution of centipede communities of the sampled areas seems to deviate
from the models found in other urban areas, with a prevalence of species and greater biodiversity in
the intermediate area of Monte Mario. Similar results for the area of Rome were obtained on other
taxa, both of Arthropods that of Vertebrates.
For determining the distribution of biodiversity, is also clear the role of the structural
heterogeneity inside the fragment, not only its position in the urban matrix, and this aspect was
statistically quantified in this project. Monte Mario, characterized by a higher degree of
stratification and structural complexity than the other two, is the station with the largest number of
species including, in particular, some species of Geophilomorpha and Crytopidae particularly
affected by such structural diversity and completely and missing in the communities found in Villa
Pamphili and Fregene.
Additional information
Dottorato di ricerca in Ecologia forestale
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