Lourens Poorter talks with
ScienceWatch.com and answers a few questions about
this month's Fast Moving Front in the field of
Geosciences. The author has also sent along images of
Article: Wood mechanics, allometry, and
life-history variation in a tropical rain forest tree
Authors: van Gelder,
Journal: NEW PHYTOL, 171 (2): 367-378 2006
Addresses: Univ Wageningen & Res Ctr, Forest Ecol &
Forest Management Grp, POB 47, NL-6700 AA Wageningen,
Univ Wageningen & Res Ctr, Forest Ecol & Forest
Management Grp, NL-6700 AA Wageningen, Netherlands.
Inst Boliviano Invest Forestal, Santa Cruz, CA USA.
Why do you think your paper is highly
The paper addresses the importance of wood characteristics for the life
history variation of tropical trees. Wood density is emerging as a core
trait in functional plant ecology, because of its importance for the
biomechanics, architecture, water relations, and carbon gain of trees. The
unique contribution of the paper is that we evaluated wood properties for a
large number of coexisting tree species in a tropical rain forest
community, and we showed that they were closely associated with the shade
tolerance of tree species.
Does it describe a new discovery, methodology, or
synthesis of knowledge?
Arnold van Gelder
Wood density is often assumed to be an indicator of the shade tolerance of
tree species, but empirical evidence for this is sparse. The nice thing is
that we had a quantitative index of the shade tolerance of the species, and
we found that wood density was closely and positively associated with the
ability of species to persist in the shade.
The mechanisms that led to an increase in the survival of high-wood density
species in the shade were unclear, and it is thought that tree biomechanics
can play a role. What we did was to measure the biomechanical wood
properties of small trees in the field. This was a novel approach, because
normally this is only determined for dried adult wood of a few commercial
Would you summarize the significance of your paper
in layman's terms?
Species that are typically found in the shaded forest understory grow
slowly, and have to survive for a long time if they eventually want to make
it to the forest canopy. As much as 25% of all plants in the forest
understory are annually hit by falling branches, or broken off by mammals.
We found that species adapted to those conditions had dense and stiff wood,
which breaks less easily under falling debris, and enhances tree stability.
Species that are typically found in bright, open places in the forest have
to grow very fast in order to outcompete their neighbors and attain
maturity. These species have low density wood, which is very cheap to
construct, thus enabling fast stem height and diameter growth. These
different wood characteristics allow species therefore to occupy different
light "niches," which is thought to contribute to the high species richness
of the tropical rain forest.
How did you become involved in this research and
were there any particular problems encountered along the way?
The focus of my research is on the importance of functional trait variation
for species coexistence. I was especially interested in the importance of
traits for plant survival, a very much understudied component.
Arnold van Gelder, the lead author, is a civil engineer, who was interested
in doing his thesis on tree biomechanics. Frank Sterck, the other coauthor,
was interested in including these biomechanical traits in a tree model. In
combination, this was an ideal research team. We had the good luck to work
together with Jose Chuvina, an indigenous paratoxonomist who helped us with
the identification in the field, and with forest engineer Gregorio
Cerrogrande from the local Bolivian university, who helped us to determine
wood properties with a beautiful and well-working loading equipment machine
from the sixties.
Specific problems encountered: it rained for days, the river level was two
meters higher than the bridge, and in the end we had to cross the river
with a motorbike on a canoe to finally get to the field and finish the
Where do you see your research leading in the
We are now working on the importance of wood traits for drought tolerance;
how they facilitate water transport in the xylem in the wet season, and how
they prevent embolism and tree dysfunction in the dry season. Another
interesting aspect would be to model the implications of wood traits for
tree growth and survival.
Do you foresee any social or political implications
for your research?
Locally, the people are interested in these wood material properties,
because tropical rain forests harbor a tremendous amount of tree species,
whereas currently only a few species are commercially harvested for timber.
Many other species might be potentially interesting as well, as long as we
know their wood properties. In addition, tropical forests are an important
storehouse for carbon, and the potential for carbon storage is, amongst
others, determined by the wood density of the species. Insight into how
wood density varies across species, along with species composition, is
therefore needed if we want to make more accurate estimates about how much
carbon is stored within these forests.
Dr. Ir. Lourens Poorter
Forest Ecology and Forest Management Group and Resource Ecology Group
Center for Ecosystem Studies
Figure 1: Coauthor Arnold van Gelder doing the bending
Keywords: Lourens Poorter, functional plant ecology, wood
characteristics, wood traits, life history variation of tropical trees,
wood density, carbon gain of trees, high-wood density species, tree
biomechanics, tree stability, high species richness of the tropical rain
forest, drought tolerance.