Rooms 41 and 42: results of the laboratory analyses on root systems

It is of real importance for all those who, like us, are concerned for the Domus Aurea and its vegetation, respectively a unique and irreplaceable archaeological heritage and a magnificent natural heritage, to discuss the difficult relationship between these two features in the park on the Oppian Hill.

View of the Oppian hill from above – Photo from Google Maps

View of the Oppian hill from above – Photo from Google Maps

As already mentioned in our earlier article of 14.12.2012, we have collected samples from parts of the root systems emerging from the wall surfaces inside Room 42; identical samples were later collected in Room 41.

Location of Rooms 41 and 42 – SSBAR Archive

Location of Rooms 41 and 42 – SSBAR Archive

These two rooms, from then onwards, were identified as Station 1 and Station 2.

The decision about where to collect the samples was dictated by the ability to effect the removal in a non-invasive way with respect to the structural and pictorial components of the monument.

After detailed inspection, four sampling areas were chosen, based both on their location and on the typological diversity of the root systems, visible even to the naked eye.

Collecting samples – SSBAR Archive

Collecting samples – SSBAR Archive


Room 42 Station 1 sampling area (no.1) – SSBAR Archive

Room 42 Station 1 sampling area (no.1) – SSBAR Archive


Station 2 – Room 41 roots emerging from a vertical stretch of wall – SSBAR Archive

Station 2 – Room 41 roots emerging from a vertical stretch of wall – SSBAR Archive

We selected samples on the basis of the potential to remove homogeneous pieces with a mean diameter of under a centimetre, between 5.00 and 8.00 mm. We collected a significant quantity of the roots emerging from the surface by cutting them and preserving them in an alcohol solution.

Example of a sample taken from Station 1 – Room 42 – SSBAR Archive

Example of a sample taken from Station 1 – Room 42 – SSBAR Archive


Example of a sample taken from Station 2 – Room 41 – SSBAR Archive

Example of a sample taken from Station 2 – Room 41 – SSBAR Archive

An initial visual examination immediately indicated morphological differences that allowed us to attribute the samples from Station 1 prevalently to conifers given their colour and the presence of resin, a characteristic of the division Pinophyta. The conifers present on the Trajanic Terrace are essentially the large pine trees along the avenue, which are therefore in a marginal position, and the large Himalayan pine in the centre of the upper garden, closer to the underground area where the sample was taken.

The Himalayan pine on the Oppian hill – SSBAR Archive

The Himalayan pine on the Oppian hill – SSBAR Archive

The samples from Station 2 belong exclusively to broad-leaved trees given their dark brown external colour, shape and woody consistency.

Transverse and longitudinal microscopic sections were then taken from the fresh samples collected using two technical procedures: immersion in alcohol and colouring with methylene blue.

The sections thus obtained were examined under a microscope to identify the species based on the distinctive features of the composition and arrangement of the root cells of each species sampled.

Sample no. 1: Root section immersed in alcohol – SSBAR Archive

Sample no. 1: Root section immersed in alcohol – SSBAR Archive


Sample no. 1: Root section coloured with methylene blue – SSBAR Archive

Sample no. 1: Root section coloured with methylene blue – SSBAR Archive

The analysis of the samples from Station 1 confirmed that they belonged to conifers of the genus Pinus.

In the microscope slides we saw the typical cellular organization of resin ducts specific to the genus Pinus: Pinus roxburghii Sarg. present on the Trajanic Terrace, the typical thickness of resin-secreting cells is immediately obvious in the fresh slide without colouration.

The samples from Station 2 were prepared in the same way for microscope analysis. Observation indicated the well-defined organization of the sap cells of broad-leaved trees, belonging to the genus Quercus, more evident in the slides with colouration.

Sample no. 2: Root section immersed in alcohol – SSBAR Archive

Sample no. 2: Root section immersed in alcohol – SSBAR Archive


Sample no. 2: Root section coloured with methylene blue – SSBAR Archive

Sample no. 2: Root section coloured with methylene blue – SSBAR Archive

In this first phase of recording and collecting representative portions of the root systems emerging from the monumental structures, we noted the complexity of their development in terms of both size and growth, constantly evolving and developing.

Room 41: Example of a newly forming root – SSBAR Archive

Room 41: Example of a newly forming root – SSBAR Archive

The extension of the root systems is notable given the current position of the trees on the Trajanic Terrace and their linear distance from the samples taken inside the rooms of the Domus Aurea. The linear distance between the Pinus roxburghii Sarg. trunk and the samples taken in Station 1 – Room 42 is over 25 metres. The samples taken in Station 2 – Room 41 are also an average linear distance of 25 metres from the trunks of the Quercus ilex L. trees.

Excerpt from the plan of the park: the extent of root systems – SSBAR Archive

Excerpt from the plan of the park: the extent of root systems – SSBAR Archive

One of the observations made in the various underground rooms is that the roots were found in a specific place: the roots become closer together and grow in a continuous way between the wall structures and the plaster.

The chemical composition of the mortars presents a complex mixture of mineral salts of varying nature and geolithological origin: this mixture seems to provide the fundamental nutrients for deep roots. Whenever these emerge from the mortars and become exposed, such as outside the plasterwork, the root ends generally protrude for a few tens of centimetres and then die.

Entrance to Room 42 with dead root ends emerging from the plaster – SSBAR Archive

Entrance to Room 42 with dead root ends emerging from the plaster – SSBAR Archive

By contrast, we find new side shoots from the roots in areas of wall that are still partially intact, where these continue to grow, preferably between the load-bearing structures and the plasterwork.

Additionally, the climate conditions (temperature, humidity, percolation of rainwater, etc.) constantly present in the Domus Aurea, which as we know is almost entirely underground, favour and guarantee a perfect environment for constant growth even during periods when dry conditions might cause problems outside.

The laboratory analyses thus confirmed that the roots emerging from the vaults and walls of rooms 41 and 42 are those of woody plants that, as already described in our earlier article, belong to the category of species presenting the highest risk in terms of their ability to cause damage not only to the decorations but also to the stability of the wall structures. This is evident in both of the rooms studied, where the surface affected by the roots is eroded to a greater depth than other walls in the same room.

In the foreground developing root systems  – SSBAR Archive

In the foreground developing root systems – SSBAR Archive

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Gli autori

Gabriella Strano

Gabriella Strano

Landscape architect. She has worked for the Soprintendenza Speciale per i Beni Archeologici di Roma since 1978 on the maintenance and enhancement of green areas on behalf of the Parks Authority. She was director of the works in the green areas in the Natural and Archaeological Park at Portus and participated in the planning of landscape projects. In 2011, she became a member of the Domus Aurea’s technical staff.
Irene Amici

Irene Amici

Awarded her degree in Biological Sciences and Landscape Architecture in 1999. She currently works as a freelance professional in the environmental sector, providing technical and scientific support for environmental planning and teaching in the public sector (protected areas, nature reserves, municipalities, provinces, regions, universities, research institutes). She has worked as a consultant to the Lazio region, the Parco Nazionale del Circeo and the Parco Nazionale Arcipelago di La Maddalena for conservation and monitoring as part of the Natura 2000 ecological network, on foreign and exotic species. She works with architectural, geological, agronomist and forestry companies for the integrated planning of multi-purpose interventions: environmental engineering and land protection; renaturalization of water courses; agricultural and forestry management planning; creation of thematic maps (land use maps, pedological maps, plant cover, ownership structure, ecosystems, habitats etc); development of local planning instruments; environmental impact assessments, environmental impact studies, impact assessments, environmental insertion studies and technical assistance on worksite management.
Pier Luigi Cambi

Pier Luigi Cambi

Holds a degree in Forestry with an M.A. in Parks, Gardens and Botanical Gardens Management. He has collaborated and worked with the Lazio Region, Abruzzo Region, AGEA, ARSIAL, schools, professional associations (CIA-ARPO), companies and professional studios. He works as an assistant and consultant to agricultural businesses. Other activities: forest use projects, natural engineering projects, HACCP plans, safety at work documents, plant health monitoring, evaluation of the stability of trees and plant endotherapy, assistance and consultancy to companies working in the disinfestation, disinfection and environmental hygiene sector, consultancy on entomology and parasites in anthropized environments. He organizes and teaches professional training courses. Has directed forestry and environmental worksites for Coop Eco Foreste (L’Aquila); tender management for cemetery services and urban parks projects for the L’Aquila municipality; tender management for the maintenance of green areas for Soc. Italtel; planning and implementation of works in “private and public green spaces”.

3 thoughts on “Rooms 41 and 42: results of the laboratory analyses on root systems

  1. Spero tanto che gli alberi non vengano abbattuti e che vengano trovate altre soluzioni. Perchè non mettere una specie di muro sotterraneo di lastre di metallo per proteggere la domus aurea?

  2. Spero che nessuno si opponga alla risistemazione del giardino sovrastante la domus. Bisogna pensare al male minore e alleggerirlo. Andrò a fotografare il pino, sono molto dispiaciuta per la sua sorte infausta. Ma, tant”è. Grazie per quello che fate per voi per noi e per tutti gli altri.

  3. Spero che la Domus sia salvagauardata. Se poi è necessario tagliare un paio di alberi pazienza. Cosa sono 70 anni confronto a 2.000?

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