HORTICULTURE IN ZOOS 39

Int. Zoo Yb. (1990) 2 9 3 9 4 1 Zoological Society of London

Designing the Montreal Biodome: tropical and boreal forest exhibits ROBERT DAVIDSON’ & JEAN-JACQUES LINCOURTZ ’Curator of Horticulture and Technical Agent, Jardin Botanique de Montreal, 4101 Sherbrooke-Est, Montreal, Canada H I X 2B2

The Montreal Biodome project will trans- form the Olympic Velodrome, one of the stadiums built for the 1976 Summer Olympic Games, into a living museum for the natural sciences to include aquarium and zoo functions in a natural environ- ment complemented with an educational content. For the past two years a team of professionals has been working on the project with the opening day set for 24 June 1992, Quebec’s National Holiday and the 350th anniversary of the founding of the City of Montreal.

The Velodrome is a vast enclosed concrete structure. The roof rises to a spectacular cupola, which is supported at four points without any interior column to take up space, and pierced with light wells covering 7060 mz, allowing an abun- dance of natural light inside. The main building, now housing a central exhibition area, a bicycle track and stands, measures 1.1 ha and the ceiling at the centre of the main structure reaches a maximum height of 34m. The peripheral area beneath the stands creates a large hall for exhibi- tion purposes while two lower levels of the Velodrome offer many service facilities.

The five essential components of the Biodome will be: (a) a tropical rain forest; (b) a boreal forest; (c) St Lawrence gulf and estuary; (d)a polar world; (e)a permanent discovery room called ‘Adap- tarium’. The four living ecosystems will be sited in the centre of the structure to encompass a main visitor circulation area. In this paper we discuss the plans for the tropical and boreal forest exhibits.

TROPICAL RAIN FOREST The tropical rain forest area will occupy a total surface area of 3143mZ and will represent one major geographic region: the Americas. Climate is the key factor in the ecology of tropical rain forests. Temperatures generally vary between 24 and 26°C but can range from 18-20°C to 33-36°C. The average annual rainfall is 1800mm although in some places it can be more than 2000 mm. Consequently, relative humidity is frequently near saturation point and never falls below 70%. There is no significant difference between seasons and there are about 12 hours sunlight daily all year round. These conditions enable plant life to grow without interruption to produce a rich and diverse flora.

For the comfort of visitors we have selected the minimum average tempera- ture of the natural environment. In summer temperatures will vary between 22°C at night and 28°C during the day, and in winter they will fall to between 21°C at night and 25°C during the day. To maintain these projected temperatures and keep a minimum relative humidity of 70%, essential conditions for the survival of the forests, the exhibit is to be covered with a transparent dome. This is necessary not only to avoid the effects of the cold climates of the neighbouring boreal forest and the St Lawrence marine habitat exhi- bits but also to avoid the dangers arising from condensation on the main dome of the building.

It is planned to maintain a minimum light intensity of 5500-6500 lux at a height

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of 0.5m and 15000-200001ux at 10m above the ground. To compensate for short winter days, a minimum daylength of eight hours and 42minutes in Montreal, artificial lighting will be provided. In summer the maximum daylength is 15 hours and 41 minutes and no additional lighting will be required. The light criteria to be used are based on a study of the seasonal variations in light in the Biodome, periods of sunshine and the inherent constraints of the building. The planned temperature conditions, rela- tive humidity and lighting should encour- age the growth and profusion of the plants in the tropical forests in the Biodome.

All of the plant life will be chosen from indigenous tropical rain-forest species. We have eliminated seasonal tropical and sub- tropical plants because the former require a dry-season dormant period and the latter require a brief cool spell.

Tn order to illustrate the diversity of the natural setting, plant life will be organized by forest types, primary, old secondary and initial secondary, then by habitat.

The visual appearance of the forest will also be adapted to the building's architec- tural features and northern location. Many large trunked artificial trees will rise up through the plant cover to create the illusion of a canopy some 30m over the visitors' heads. Big natural trees will be placed in such a way so as to take advantage of a maximum penetration of light. Ground cover, shrubbery and tree- like vegetation will be used to recreate the natural terracing of plant life, the density of plants being representative of each forest type. Vines and numerous epiphytal plants will cling to the trees.

In order to cohabit with animals in the forest the selected plants must: ( I ) be adaptable, hardy, and capable of with- standing handling and possibly some damage from herbivores; ( 2 ) tolerate parasites and diseases; (3) be non-toxic to the animal species present. Plants will be selected that are of botanical, aesthetic or economic interest. Commercial nurseries

offer a limited choice of rain-forest species but contributions from the Montreal Botanical Garden's collection, which includes an abundance of tropical plants. will help to provide diversity.

BOREAL FOREST The boreal forest habitat will occupy a n area of 2780 m2. The main exhibit will be a 110 m2 beaver pond linked with what will look like a water network along which river otters, racoons, lynx, aquatic birds and other animals will be exhibited. Artificial mountains surrounding the habitat will support a retention net to allow birds to fly freely.

Inside and around the animal exhibits plants will create an appropriate represen- tation of a boreal forest which consists of conifers, such as spruce Piceu and pine Pinus, with a few birch Betulu, Aspen Populu.~ tremulu and Red maple Arc,,. ruhrum. Certain objectives were set after ;I study of the natural environment to deter- mine patterns or guidelines to help land- scape architects and designers regarding: ( I ) the choice of plants, (2) the association of species within the forest. (3) the local- ization of plants and their associations. particularly in relation t o topography. water and nature of soil. and (4) conservation of these plants inside the building all year round.

Light requirements will be supplied naturally through the skylights and if necessary from artificial sources at critical points. An important factor will be the range of temperatures required to allow the period of dormancy essential for hardy plants to complete their annual cycle. Specific to the needs of the plants during dormancy it will be necessary to stop watering and feeding. and to decrease the ambient air temperature. We determined that an eight-to-ten-week cold period will be enough to break true dormancy and resume growth. According to plant physiologists the most effective temperatures are those slightly above freezing and if the temperature rises above

HORTICULTURE IN ZOOS 41

13°C the effectiveness of the cold period could be inhibited. The range of tempera- tures during the eight-to-ten-week cold period are planned to fluctuate from 3°C at night to 12°C during the day which will be necessary to provide a minimum degree of comfort for visitors.

The length of the period of cold necessary before a plant resumes growth depends on the species and origin: for example, birches and poplars Populus need a shorter cold period than other species, such as walnuts Juglans and oaks Quercus spp., and Red maples grown in Florida may be dormant for four to five weeks while for those grown in Montreal this period lasts for seven months from October to May. Since the true dormancy period is shorter for species of southern regions, trees and shrubs will be purchased from nurseries where winter is shorter. It is hoped to use specimens which will resemble northern spruce and pine but will actually be other species. For example, Norway spruce Picea abies grown in Oregon is very similar to our Black spruce Picea mariana; River birch Betula nigra is not hardy enough to with- stand the climate in Montreal but inside the Biodome it will be a good substitute

for Paper birch Betula papyrifera with its similar white bark. Oregon nurseries also grow Red maples which are similar to those in Montreal except that they require a shorter cold period.

Engineers were needed to design a means of creating the temperature condi- tions required. The ventilation system will provide cool air from outside and since winter temperatures prevail during natural dormancy periods, as much cold air as is needed will be available. Owing to the depression created by the surrounding mountains the cold air should remain in the habitat. The ventilation system will also effect neighbouring habitat exhibits and decrease their temperatures but this should not create problems; the polar world will be under glass, the St Lawrence estuary is also a northern habitat, and the tropical forest is enclosed and separated from the other ecosystems.

There are potential problems that have to be considered and we might have to select other species of plants or modify temperatures to allow for plant adap- tations. A mechanical transportation system and high clearance greenhouses have also been planned, to replace plants during the first months of acclimatization.