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I. Silva et al. 2010. Lisbon’s public gardens, host place for world’s trees
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In this paper the authors have created a broad scope concept that covers all the garden
components which have been consciously designed to create a piece of Landscape art. This
“Landscape Value” concept is arrived at through the evaluation of various elements such as
artistic quality, aesthetic beauty, vegetation and landscape, and built elements.
The Landscape value
Landscape value is a broad scope concept that includes all the components under the influence
of the garden’s author in a process that leads to a piece of Landscape art, through the evaluation
of the aesthetic beauty, artistic quality and value of the built elements or vegetation. This value
includes also the garden’s external characteristics, such as the socioeconomic context of the
garden’s location which acts as a parameter restricting the garden’s public to a certain kind of
users, the aesthetic and artistic quality of the urban fabric, where we consider the state of
conservation, and, finally, the visual relation between the garden and the surroundings, through
a study of the series of views.
As regards Landscape Value, which is a broad item, features were assessed such as the aesthetic
and artistic quality of the built and botanical composition elements. As for botanical quality,
following a survey ‡ of the tree species in the garden, their diversity and singularity were
evaluated by means of specific scientific formulae. Since plants are a fragile element, easily lost,
altered or replaced over time, it was also important to value those trees which because of their
size, rarity or quality are deemed notable and classified as being of Public Interest § . In addition
to these criteria the garden’s scenic quality was assessed by studying its plant composition in
terms of trees, shrubs and flowers.
Botanical quality pertains to the vegetation’s richness, uniqueness and heritage interest. The
latter is based on each individual specimen’s size, rarity, age and health. The richness and
uniqueness of each specimen was obtained through accepted methods, as explained below.
The Botanical Diversity parameter for each Garden was quantified using a average of four
formulae: the Shannon index (1), the evenness index (2), the proportion of different species in
the garden relative to the total number of specimens, and the ratio of the number of species in
the garden compared to the total number of species in the set of gardens studied.
Botanical Diversity Method:
• Index 1: (Total of the tree species/ total of the garden’s tree specimens) (%)
• a) Class 1 Botanical Diversity Index: (1 if [0-33%]; 2 if [34-66%]; 3 if [67-
100%])
• b) Class 1 Botanical Diversity Index: (1 if [0-15%]; 2 if [16-31%]; 3 if [32-
50%])
• Index 2: (Total of the tree species/Total of tree specimens in the set of gardens) (%)
• a) Class 2 Botanical Diversity Index: (1 if [0-0,6%]; 2 if [0,7-1,2%]; 3 if [1,3-
2%])
• Index 3: Shannon index (1)
• Class 3 Shannon Index: (1 if [0-1,33]; 2 if [1,34-2,66]; 3 if [2,67-4])
• Index 4: Evenness (2)
‡ The tree survey was conducted during the academic year 2008/2009 with the assistance of third year Landscape Architecture
students at the Institute of Agronomy, Technical University of Lisbon.
§ The classification of trees or groups of trees of Public Interest is governed by Decree-Law nº 20 985 of 1932-03-07 and Decree-
Law nº 28 468 of 1938-02-15. The Ministry of Agriculture, Rural Development and Fisheries, through the AFN (National Forestry
Authority), is responsible for the classification pursuant to the terms of Regulatory Decree 10/2007 of 2007-02-27, published in the
Official Journal (Diário da República) nº 41.
Forest Landscapes and Global Change-New Frontiers in Management, Conservation and Restoration. Proceedings of the IUFRO Landscape Ecology
Working Group International Conference, September 21-27, 2010, Bragança, Portugal. J.C. Azevedo, M. Feliciano, J. Castro & M.A. Pinto (eds.)
2010, Instituto Politécnico de Bragança, Bragança, Portugal.