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The epiphytes' unique
photosynthetic pathway
lot of water – something that could be avoided, of course, if the
pores remained closed. But that would mean the plants were
unable to feed themselves. So they are leftwith theunappealing
options of dying either of “hunger” or “thirst”.
CAM plants, however, have found an elegant solution to the
dilemma of plants in areas of lowprecipitation. They open their
pores at night when humidity levels are higher, meaning that
substantially less water is lost; they store CO2 in the form of an
organic acid, and use this reservoir in the daytime so that they
cancontinuephotosynthesingevenwith their pores closed. This
reduceswater loss by a factor of between 10 and 100 compared
with normal plants – one of many adaptations to aridity, which
in itself justifies the designation “desert in the rainforest”.
In aworld increasingly dominatedby humanbeings, what does
the future hold for these plants that have adapted to regular
dry periods? In spite of the ongoing destruction of the tropical
forests we can hope that large stretches of forest areas will
remain intact. But will these provide a suitable habitat? Sadly,
this is by nomeans certain because climate changemeans that
the weather is becoming more extreme even in the furthest
corners of the Earth.
For species less well-adapted to dry periods, an extraordinary
drought like the one observed in the Amazon region in 2010
can mean extinction. To what extent this has already happe-
ned no one knows because of the lack of applicable long-term
studies. In view of the large-scale shift from primary forest to
agricultural land use, science is also increasingly looking at
what is happening to flora and fauna in secondary vegetation,
the termused for the spontaneously emergingwoods and tree
plantations as well as isolated
trees that are (still) common in
grazing areas across Latin Ame-
rica. The growing conditions
for epiphytes in these loosely-formed secondary forests and,
more particularly, in isolated trees, are much more arid than
in natural forests.
A series of studies carried out by my working group and
colleagues around the world has now shown that epiphyte
communities in such places are clearly distinguishable from
those in undisturbed forests. The results of research for a
dissertation carried out a few years ago in the lowlands of
Panama show that species normally found in the damp areas
of a forest are largely absent, whereas species which normally
grow exposed to the light in some cases develop better there
than in their normal habitat. This applies inparticular to species
with CAM. Generally speaking, however, biodiversity is red-
uced – sometimes drastically – and it is not improbable that
this negative trend will become more pronounced over time.
ADAAD-fundeddissertation currently underway inOldenburg
is examining whether this is actually the case. In view of the
fact that a significant amount of the fauna living in the forest
canopy is dependent on these epiphytes, even losses at the
current rate are likely to have a cascade effect on the animal
world. So this is not good news for the inhabitants of the
“desert in the rainforest”.
Der Autor The author
Prof. Dr. Gerhard Zotz ist seit 2006 Hochschullehrer für „Funktionelle
Ökologie“ in Oldenburg. Er studierte Biologie in Würzburg, wo er
1993 promovierte. Nach Forschungsaufenthalten am Smithsonian
Tropical Research Institute in Panama und an der State University
of Vermont, Burlington, USA, habilitierte er sich 1998 in Würzburg.
Derzeit fasst Zotz die Ergebnisse seiner über 20-jährigen Forschun-
gen zu Epiphyten in einer großen Monographie zusammen.
Prof. Dr. Gerhard Zotz has taught “Functional Ecology” in Oldenburg
since 2006. He studied biology in Würzburg, where he obtained
his PhD in 1993. After research periods at the Smithsonian Tropical
Research Institute in Panama and at the State University of Vermont,
Burlington, USA, he earned his habilitation in Würzburg. Zotz is cur-
rently compiling the results of more than two decades of research
on epiphytes into an extensive monograph.
Urwaldriese: Auf einem einzigen Baum können
sich mehr als 100 Epiphytenarten tummeln.
Jungle giant: a single tree can accommodate
more than 100 epiphyte species.