Biodeterioration of stone in relation to microclimate in the Ta Nei Temple – Angkor (Cambodia)

In the favourable tropical climatic conditions of Angkor, Khmer temples, which have been abandoned for many centuries, have been suffered from a wide range of biodeterioration processes. Ta Nei temple, which is still surrounded by a luxuriant forest, was selected as an appropriate site for testing the influence of microclimate on stone conservation. Not only big trees are growing on and all around the monument, but also different patinas of algae and cyanobacteria, lichens, mosses and higher plants are colonizing the temple stones. Field observations and laboratory analyses were carried out to establish the different phenomenologies of biodeterioration, their frequency and distribution in relation to water percolation, shadowing, ventilation and typology of stone. Data on the variations of these communities were collected in the field and evaluated on the basis of the ecology of the species. These data were related to temperature, light, ventilation and relative humidity measured in the site and gave rise to the identification of a clear ecological trend of different biological communities. The first colonizing community, which start to grow with minimum level of water in the substrate, is the Trentepohlietum, a pioneer coenosis widely spread in relatively xeric and shady conditions. It is followed by the Scytonemo-Gloeocapsetum in conditions of increasing water and light and then by various lichen communities (with dominance of Lepraria and Pyxine). With progressive higher water content of the substrate, communities of mosses and ferns colonize and grow on the stone. As noticed for other monuments, when the dynamism is blocked or limited by edaphic factors, these deterioration patterns change according to the environmental factors and not as successional stages. The knowledge of these relationships is very useful for evaluating the feasible use of indirect control methods against the various biological colonizers, and therefore for establishing the best microclimatic conditions for stone conservation.