- Back to Brazilian Amazon region, it seems that nowadays the number of genera
exceeds 100 and the number of species exceeds 600, it means than 25% of the total
of Brazilian orchids. In your works you have said that if there is as genus that
can represent the Orchidaceae flora in Amazon region, this genus is Catasetum.
After that which one is predominated, I mean what genus presents more species
and what genus is spread out although with less species?
KL - The Brazilian Amazon region has always been considered comparatively poor in number of orchids species and it is in fact if we consider our continental dimensions and compare to what is referred to other countries such as Ecuador, Colombia, Peru and Venezuela. Nevertheless, we should say that regarding to Orchidaceae flora, Brazil is the country less researched - may be in the same situation as Bolivia. However, in the last two decades, we have many discoveries and citations about species that we thought just occur in neighbor countries. In this point of view, we should point out the work done by João Batista F. Silva who, with Professor Manuela F. F. DA Silva, has been published a lot things. With this, we can reach those numbers.
However, comparing to southeast region, specially the states of Espirito Santo and Minas Gerais (deducting, of course, the destroyed places...), the diversity in Amazon Orchidaceae is smaller. The density is also much much smaller, we can walk for years in certain types of vegetation in North region to find just a few plants. Besides, just few Brazilian Amazon species (unlikely different from Colombia and Ecuador) have horticultural values, it means, ornamental interest.
believe that Maxillaria,
among the genera, is the most
abundant and is found in every type
Cattleya, just in restrict areas.
Pleurothallis and Octomeria,
among the "micro-orchids", are also
found in almost every place.
The Catasetinae, however, have in fact,
in Amazon region, their center of dispersion,
mainly Catasetum and Cycnoches. Clowesia
and Dressleria predominate in Colombia and
Central America and Mormodes seems to
be shared between Brazil and Mexico.
Some of Mexican species have so much differences that some people think about
to separate them and create a new genus.
ON - It is true there is not just an "only one Amazon region" but many. That would be the difficulty found to cultivate (out of the habitat) the species coming from this region.
We talk about dryland forests, woodlands, altitudes, daily rains, high heat, cool at night.
How is this? It means that the species do not need the same climate conditions?
There are species that need shadow, some others high luminosity, some humid conditions, some less? Which species need less light? Which are more demanding in this specific point? Which species are more difficult to be cultivated?
KL - Here we should mention the phytogeographical subdivision for Brazilian Amazon proposed by Duke and Black, later modified by Prance and correlated with Orchidaceae by Pedro Ivo S. Braga in his thesis. Braga did an extensive study about the Mid Amazon woodlands and showed the differences in the Orchidaceae family there.
I have to make remarks about the temperature, pluviometry and air humidity. The thermal regimen in Amazon region is practically unchangeable, with oscillation which amplitude is not enough to paralyze the biological activities. In great part of the Amazon region, the nocturnal temperatures, though lower than the diurnal, does not drop under 19º C, exception to the areas in the hillsides. The steam of water comes from the ocean and the forest. Although a hot and humid climate predominates in this region, the variation of the distribution of the rains, that could present differences even of six months from one region to another, provides many kinds of climate.
In the forest, the average temperatures are high all year round, at about between 26 to 29ºC, the absolute maximum reaching 38,8º C and the absolute minimum 22º C, which justifies the climate so hot all over the year. The higher temperature in Amazon region occurs in the east cerrado (woodland Savannah) areas, next to Maranhão, where, during the drought season, can reach 41º C.
There are regions where it rains every day of the year, such in the mountainous woods of upper Negro River. The plants inside an ecosystem produce organized groups with distinct and stratified form, getting in this way, suitable luminosity and ventilation; some genera of orchids thrive in an exuberant way in those conditions. The lack of dry season is the rule, not the exception. In many places, however, just little or none precipitation occurs during some months of the year, which is emphasized in the north (Roraima's fields, for example) and in the south (such in the state of Rondônia). With so many agents to influence, the annual pluviometric regimen varies considerably from one place to other, provoking differences, as for example, in the blooming season of the same species according to the region of occurrence - inverting completely the phenological spectrum when in latitude more distant from north and south hemisphere. Where there is no seasonal variations of temperature and luminosity, the agent that seems to induce more the phases of development of orchids - blooming, rooting, vegetative grown - is the regime of rains. It should be copied in artificial conditions of cultivation.
It is also suitable to use the occasion to inform about the kinds of vegetation. The Amazon landscape is presented by a dense forest with big floral diversity and big biomass, generically named tropical rainforest or tropical pluvial forest. The quantity of epiphyte varies according to the type of vegetation. The main kinds of vegetation are the dryland forests; the flooded forests (várzeas, igapós, etc.); the fields of dryland; the woodlands, the mountainous thicket and sandbank vegetation. There are transition areas which distribution is not uniform, presenting isolated "islands" or "blotches" of a type or another. The great part of orchids fits well in just one or some of those types and is never found in adverse vegetational types.
dryland forests cover 90% of the Brazilian Amazon (3,3 millions of km2).
In general, the height of the crown of the trees is at about 30 to 40 m with relativity thin trunks that branched near the top struggling for light.
Usually the trunks have no more than 1m diameter at the
|base, except sumaúma, the chestnut tree and the piquiá, that can reach more than 3,5m diameter and exceed 50m high. Those forests are completely closed on the top, forming a canopy however they are clean at the underneath and it is easy to walk over a dense layer of organic material in decomposition (litter). Rare species can be endemic to a restrict area or have an ample distribution; it means that, for example, Coryanthes speciosa Hook. can be found in an extensive area but just a few specimens each time, and that Pleurothallis kerrii Braga can just be found, and even so in rare prevalence, in a limited area. Those forests are dark at the floor, with species adapted to little light. Near to the ground, micro-orchids and genera such as Batemania, Lycomormium, Paphinia, Peristeria, Polycycnis, Stanhopea, Xylobium and others proliferate among liquens and briofitas, while lianas, bromeliads and orchids that love more light spread out on the upper branches. At about 80% of the dryland forest are not exposed to be flood, the most meaningful is the high wood with homogenous appearance, but the woods of lianas next to Tocantins River, the drought woods with caducous (or deciduous) tree in the transition with the Brazilian Central cerrado (Savannah), the bamboo woods in the state of Acre, the campinaranas and mountainous woods are important.|
campinaranas or Amazon caatingas that form blotches in all Hiléia, most
expressive on upper Negro River, are source of water rich in humic and fulvic
acids that form the rivers with dark water.
Its trees are, in general, 20m height in the highest parts and from 7 to 8m in the lower parts; the trunks are thinner and can have epiphytes from the bottom to the top.
With more palm trees, more humidity and allowing bigger penetration of light, they are rich in orchids.
the flowering, the mountainous or fog thickets, in highland areas, with more ventilation,
high humidity and lower temperatures are also very interesting.
The flood forests correspond to 5 to 10% of the Amazon region. The flood of the rivers periodically inundates them. The flower composition is distinguished by the presence of palm trees (buriti, açaí, paxiuba, buçu). Those trees shelter many species of orchids, mainly of the genera Catasetum and Galeandra and Bifrenaria longicornis Lindl. The flood forests can be arranged into:
|Várzea forests (flood plains): cover the lowland plains that stay under water for months due to the flooding of the white water rivers. Median biomass, very clean underneath, inconstant luminosity. They are exuberant in the high part of Amazonas River (Solimões) and in the region between Trombetas and Tapajós Rivers.|
forests: they are permanently or during months flood by black or white water rivers.
The biomass is poor, the light is diffused, the vegetation is specialized, the trees have exposed roots to give support or with breathing functions. The epiphytes are abundant.
The water is transparent or dark, acid, stagnated or almost stagnated.
There we find Cattleya violacea, Oncidium lanceanum, Brassia
and many other Orchidaceae species. The humidity is high mainly at night,
all year long, even when there is no rain. The ventilation and higher luminosity
in the riverbank make easy the proliferation of orchids and other associated epiphytes.
Forests of flood terraces and swamps or tide várzeas are very poor in orchids.
and flood forests, there are
in Brazilian Amazon, the
open vegetal formations:
the fields and cerrados (woodland Savannah), gramineae, in Roraima (Brazil) and "Gran Sabana" in Venezuela;
the fields of dryland in
Marajó Island, in Humaitá (Madeira river), Prainha (Little Beach) and Monte Alegre (lower Amazonas River),
flood and sunny, with few shrubs and palms, woodlands and small mountainous vegetation.
From these, just the last two are remarkable concerning orchids.
The open woodlands cover 34.000 km2 in Central Amazon, in small-discontinued areas surrounded by the dryland forests. The soil is extremely poor, sandy, the biomass is mediocre, the vegetation is rachitic with accentuated scleromorphism. The shrubs and small trees appear in groups, under what the orchids are assembled, such as Epidendrum, Encyclia, Sobralia, Catasetum, Eulophia, etc. There is an enormous quantity of epiphytes and particular endemism. In the woodlands of the state of Amazonas, in Brazil, Cattleya eldorado Linden stands out; in the woodlands of the state of Pará, Cattleya violacea Rolfe can be found, although in smaller density. With those conditions, we can found in just one tree, macucu (Aldina heterophylla Spr. ex Benth) nothing less than 45 species of orchids, of the follow genera: Maxillaria (9), Epidendrum (5), Pleurothallis (5), Encyclia (5), Sobralia (3), Catasetum (3), Cattleya (2), Orleanesia (2), Brassavola (1), Brassocattleya (1), Caularthron (1), Rudolfiella (1), Bulbophyllum (1), Rodriguezia (1), Aganisia (1), Bifrenaria (1), Scuticaria (1), Jacquiniella (1), Nanodes (1) - this in just one open woodland in the state of Amazonas.
Finally, inside the open vegetal formations, we have lower mountainous vegetation, with changeable appearance, high luminosity, winds, frequent dense fogs, and lower nocturnal temperature, found in the borders of the prairie of the Amazon. The epiphytes are abundant in that formation, improper researched.
Obviously, the temperature, respecting the referred limits, and the relative humidity of the air adjusted according to region of origin are the great challenge of the growers of the orchids coming from Amazon region, in subtropical and temperate regions and in big latitudes. Keep the relative humidity of the air constantly near to the saturation could be necessary to make some species resist more than two or three years in cultivation.
Even inside the same genera, such as Catasetum, cultural requirements are very different according to the species.