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Hadrien

Lalagüe


Amazonian rainforest stretches over 5.5 millions square kilometers. It is a huge territory holding the highest diversity of living beings although paradoxically one of the least studied and understood what?.

Trees are keystone living organism in this ecosystem. They protect the soil from heavy rains and from the equatorial sun radiations. Under the canopy, in the shadow, with a high humidity and a mean temperature of 26°C, a unique and lush life emerged. A recent study* reveals that the Amazonian forest is composed of 16.000 tree species, but most of the area is occupied by only 227 of these. Although we now have a better idea of the diversity and the distribution of tropical tree species, we still have a poor understanding of how trees adapt, both during their lifetime to rapid variations (plasticity), and slower changes across generations (evolution).

On of the main characteristics of the trees are their remarkable longevity. They appear to us as immortal because they survive to many human generations and their environment seems as our, which is stable. Nevertheless mankind recently became aware of the unstable property of our world, and consequently worries about the future. How trees adapted to the past environment changes and how they will adapt to the future changes?

In order to provide some elements of response to this fundamental question, scientists study the physiologic and genetic features of tree populations living in contrasted environments.
Following this method, a sampling campaign was achieved in French Guyana on the wapa (Eperua falcata). Physiologic traits were measured on trees genetically close but living in flooded area or on the contrary in well drained area. This study came as a complement to previous studies on the same trees.
I succinctly present here one part of the study which consisted to sample leaves situated at the top of the trees.
To climb tree in security, we first have to launch a small weight attached to a thin cord over a solid branch situated at 20-25m high. Once this first step done, the climbing rope is attached to one extremity of the thin cord and the latter is pulled until to dispose the climbing rope over the branch. One extremity of the rope is anchored to a trunk and the climber can start the ascents from the other rope extremity. Once arrived at the first branch, the climber starts a difficult ascend from one branch to another in order to arrive to the top of the canopy were he collects samples. The numerous ascending rope exercises are exhausting in a hot and humid environment, but the main limiting factor come from the dense vegetation that makes everything more complicated. In addition, the numerous ants living in the epiphyte plants and dead wood do not hesitate to attack and inject a great diversity of toxins when disturbed by the climber. During the day, the quantity of chlorophyll and the thickness of the sampled leaves are measured and the evening the leaves are scanned. During the day, the quantity of chlorophyll and the thickness of the sampled leaves are measured and the evening the leaves are scanned. The two base camps. One of these camp is situated close to a creek, ideal place where to cool off among the piranhas. But toes are not good baits, heads and legs of chickens are much more efficient.
To finish, two short videos.




* ter Steege et al. 2013 Hyperdominance in the Amazonian Tree Flora. Science, 342 (6156)