Monica Giannini

Different ability of three Mediterranean oak species to tolerate progressive water stress

Inter-comparisons in the gas exchange patterns and root characteristics under both well-watered and drought conditions were done in three-years-old seedlings of three oak species (Quercus cerris L., Q. frainetto Ten., and Q. ilex L.) growing in controlled environment. Well-watered Q. cerris had greater physiological performances than other oaks, but under drought it was not able to face the water stress showing also structural modifications such as reduction of root length and average diameter. On the other hand, Q. ilex maintained root growth both in drought or well-watered soils. Moreover, it was able to keep open stomata also under water stress, although stomatal conductance (gs) was low. Q. frainetto had an intermediate position in regard to its physiological and root structural characteristics between Q. cerris and Q. ilex under drought stress. For all oaks the relationship between gs and the ratio of sub-stomatal and ambient CO2 concentration (Ci/Ca) highlighted the dynamic adaptation of gs to the increase of hydraulic resistances of leaf, stem, and roots portions, more evident during the air humidity change and progressive soil dehydration. This suggests a well-triggered above-and under-ground mechanism to endure the drought stress.

Remote sensing and field analysis of urban green in Rome

Remote sensing is an important tool for the spatial description of urban green, it is often used in landscape ecology to detect habitat fragmentation and the alterations caused by man on the territory; furthermore the use of remote sensing is important for the detection of vegetation functional conditions. In this study some vegetation indices have been analysed and a land use map has been created using Landsat TM images of the city of Rome and of some of its outskirts. Remote sensing data have been integrated with field data (leaf area index and leaf fluorescence measurements) carried out on holm oak and coniferous woods. The values of the functional vegetation indices indicate a physiological alteration for the communities inside the city; the fluorescence data have confirmed this result. From a structural point of view, the NDVI map highlights the presence of some green corridors. The good correlation between the values of NDVI and LAI has allowed us to estimate LAI for the entire area analysed. This research has furnished quantitative data on structural and functional characteristics of the study area. The upscaling approach has shown a good performance of analysing and monitoring vegetation subjected to a different anthropogenic impact.

Relationships between leaf area index (LAI) and vegetation indices to analyze and monitor Mediterranean ecosystems

The analysis of LAI is of great importance to evaluate the structural characteristics of a plant community. Vegetation types remote sensed analysis is a useful tool for the investigation of structural and functional characteristics of ecosystems. The integration of data acquired at these two different spatial scales contributes to the management of the land use and in particular of protected areas for the conservation of biodiversity. Field measuraments (LAI) and remote sensed data (Landsat 5 TM) were performed in the Circeo National Park and in the Presidential Estate of Castelporziano (located along the coast of Lazio, Italy, and characterised by Mediterranean climate). In this study the relationships between LAI and vegetation indices (NDVI, PVI, SAVI, GVI) were analysed; the NDVI showed the best correlation with the LAI. Using NDVT/LAI low power we estimated the LAI for the entire study areas on a multitemporal basis and plotted different LAI maps. The results obtained permitted to define a useful approach to analyse the canopy conditions of Mediterranean ecosystems on a multitemporal scale and also to highlight the effects of biotic and abiotic causes on vegetative growth as phytophagous attac and climatic stress due to local annual variability and to potential climatic change.

Remote sensing analysis of Mediterranean ecosystem canopies and upscaling studies

This study analyzed a natural site located in Central Italy which is a part of the Circeo National Park. An integrated approach was developed to correlate remote sensing TM data with field measurements of Leaf Area Index (LAI). Six vegetation types were discriminated by a supervised classification of the Circeo forest. Approximately 80% of the surface of the territory analyzed is dominated by natural mixed oak woody communities. Pine reforested areas are also present. LAI field measurements were correlated with normalized difference vegetation index (NDVI) obtaining a high correlation (y equals 15.587X2.2967; r2 equals 0.88). An estimation of LAI for the entire forest was performed and an LAI map created. The correlation between the measured and the estimated LAI was also high (r2 equals 0.91). The study shows the potential of spatial scale integration to analyze and to monitor plant coenosis in Mediterranean areas.

Metropolitan area of Rome: an integrated vegetation study by remote sensing and field data

The objective of this work is to assess the impact of environmental stresses, both natural (water stress, due to summer dryness typical of the Mediterranean climate) and anthropogenic (atmospheric pollution), on the vegetation in sites of great naturalistic value and under strong anthropic pressure in the Rome metropolitan area. The species Quercus ilex L. (holm oak), an evergreen oak, has been studied through ecophysiological measurements performed in the field and Landsat TM images relating to the Rome metropolitan area. The results obtained show a greater degree of structural and functional alteration in individual holm oaks within the urban area compared with those in the protected areas outside of the central zone. In particular, in 1993 the main stress factor for vegetation is attributable to climatic conditions, whereas in 1998 ozone atmospheric concentration caused an evident alteration of the parameters studied.