Charlotte Michaels

Geography 26, Spring 2003

Native Habitat of Orchids in Australasia

ABSTRACT: Orchids are a hobby of mine, therefore I am going to show the distribution of orchids native to Australasia. I started with public databases I could access, but am having trouble finding good information that the spatial distribution can be shown from.

INTRODUCTION: It is my hope the information collected will be of interest to non-orchid growers and perhaps pique their curiosity about them. Growing them personally I have found each plant unique in its growing and blooming patterns, and am interested in where they have originated from and the environment of their parentage .

'Australasia' means the Commonwealth of Australia and all its Territories, together with New Zealand, New Caledonia, Vanuatu, Fiji, Papua New Guinea including the Bismark Archipelago, Solomon Islands, West Irian, all islands south-east of a line joining 0 degrees latitude, 130 degrees east longitude and 20 degrees south latitude and 120 degrees east longitude and all islands east of Australia to the International Date Line and south of the Equator.

Starting with natural propagation smoke appears to be the missing link in understanding the horticulture of some Australian plant species. It has been known for many years that fire has played a significant role in the evolution of Australian plants and habitat burning triggers germination in many plants.

Recent experiments in Western Australia have shown that smoke from the burning of plant material enhances seed germination in a wide range of native species. We are all aware that fires help forests to burn off undergrowth to let new seedling take hold and grow, but until I undertook this project I was unaware of how smoke could and does affect seeds. Smoke can either be applied directly or as smoked water; however, smoked water is more practical for people propagating on a small scale.

Smoked water and details on its use are available from:

Friends of Kings Park
Kings Park and Botanic Garden
West Perth WA 6005

One genus, the Vanda is widely distributed throughout Australasia from China through the Philippines, Indonesia, Malaysia, New Guinea and Australia, Myanmar, Thailand, India and Sri Lanka. Many Vanda hybrids are composites of several genera whose species were once considered as members of the genus Vanda including V. sanderiana (Euanthe sanderiana which is the only species in this genus), V. cristata (Trudelia cristata), and V. teres (Papilionanthe teres).

In nature, moth orchids grow high up on the branches of trees in humid tropical forests in Asia and Australasia. They are epiphytes, meaning they grow on the surface of the tree's bark in association with ferns, mosses and other epiphytic plants. Frequent rainfall and warm temperatures result in a very thick lush canopy of treetops, which blocks most of the sunlight and prevents it from reaching the forest below. Phaleanopsis orchids thrive in these warm, moist, low-light conditions. But rainfall in the tropics can be erratic, sometimes not occurring for weeks at a time, and these plants have adapted to survive these short droughts.

Understanding how moth orchids grow in nature makes it easier to grow them in cultivation. In nature, they grow on the surface of the bark of a tree. When it rains the water drains off quickly. In cultivation, these plants also require fast drainage.

Another important requirement is temperature. In nature, orchids grow in warm tropical forests.

In their treetop homes, most of the light is blocked by the top of the forest canopy and they have adapted to growth in low-light conditions.

Orchids of one type or another are found near the limits of vegetation. They are found from northern Sweden and Alaska, and south to Tierra del Fuego and Macquarrie Island. Very few vascular plants are found further north or south. The terrestrials have the widest distribution, being mainly limited to the tropical and subtropical environments. The only median area where they are absent is the extreme desert environments, although even here some can be found in sheltered desert canyons and oases, and in cactus thorn scrub habitats.

Like some other plant groups, orchids are more diverse in the tropical belt than at the higher latitudes. Studies have shown that orchids are most abundant and diverse in habitats receiving over 1 00 inches of rainfall per annum, where no month receives less than 2 - 3 inches. Extremely wet or dry habitats contain few species. Dew or cloud condensation is important in some otherwise 'dry' habitats.

AREA	GENERA	SPECIES
North America	26	153
Tropical America	. 306	8266
Tropical Africa	134	3131
Eurasia	49	664
Tropical Asia	250	6800
Australasia	68	602

If you wish to see different species of orchids, there are obvious areas where you should go to see the greatest number!

TROPICAL AND SUBTROPICAL (mean temperature of coldest month about 15.5°C for forest vegetation, and mean temperature of coldest month above 10°C for all other physiognomic types).

1. Tropical rainforest (evergreen or semi-evergreen forest of humid tropics, usually tall)

(corresponds to Olson seasonal tropical forest and broad-leaved humid forest. Also includes swamp forest).

Leaf cover above a level 8m off ground, >50% . No more that 50% loss of canopy leaf cover at any one time during average year.

(1a= Rainforest of well-drained soils <25% loss of canopy leaf cover, 1b=semi-evergreen forest 25-50% loss of canopy leaf cover,

2. Monsoon or dry forest (medium height, deciduous or mainly deciduous forest of warm climates)

(not corresponding to an Olson category; approximately a sub-division of seasonal tropical forest)

Leaf /branch cover above a level 8m off the ground, >50% during peak month of leafiness. >50% loss of canopy leaf cover at some stage in average year, except for Australian Eucalyptus dry forests, where limit of rainforest is defined by where Eucalyptus becomes >50% of canopy.

3. Tropical woodland (relatively low, open tree canopy, usually deciduous)

(Corresponds to subdivision of Olson tropical savanna and woodland;).

Leaf /branch cover above 8m off ground, 50%-20%.

4. Tropical thorn scrub and scrub woodland (low, woody, usually deciduous)

(Incorporates Olson succulent and thorn woods, and also overlaps with warm or hot shrub and grassland)

Leaf /crown cover above 8m off ground less than 20%, but total leaf cover between 0.8-8m off ground greater than 20%.

5. Tropical semi-desert (sparse scrub or sparse grassland)

(Corresponds to subdivision of Olson desert and semi-desert)

Less than 2% vegetation cover above 80cm off the ground. 25-4% vegetation cover between 0 and 80cm off the ground, during an average year.

6. Tropical grassland (fairly closed grassland without many trees or shrubs)

(Corresponds to subdivision of Olson tropical savanna and woodland, and overlaps with warm or hot shrub and grassland)

10. Broadleaved temperate evergreen forest (fairly tall, many broadleaved evergreen/semi-deciduous angiosperm trees but conifers also tend to be abundant, in moist climate).

24. Temperate and montane steppe (grasslands and other herb-lands, closed or fairly dense sward)

(Corresponds to subdivision of Olson cool grassland/scrub)

(24b=sparser, short-grass steppe, 21a=dense tall-grass steppe)

Leaf/branch cover above 80cm less than 2%. Vegetation cover above ground, greater than 25%.

http://www.soton.ac.uk/~tjms/austral.html

http://www.soton.ac.uk/~tjms/austral.html

http://www.anos.org.au/

http://florawww.eeb.uconn.edu/pdf/Orchid%20Classification.pdf

http://www.anos.org.au/information/acnos/acnos.htm

http://www.calm.wa.gov.au/science/florabase.html

http://www.rbgkew.org.uk/friends/madagascar/

http://www.lib.berkeley.edu/EART/vegmaps4.html#pacific