Friday, May 14, 2004

The Davis' TRF challenge - source or sink for carbon?

The Clarks contributions at La Selva is indeed fascinating, Adrian. They shared the directors salary and set up an environment that facilitated reasearch, including a grid system that has outlived GPS since the forest canopy is too dense.

But are tropical forests are a sink or source for carbon? Their La Selva hypothesis is based on slowed tree growth during warmer (El Nino) years in the 80's and 90's - the trees were not growing, i.e. not fixing carbon but are instead respiring constantly, generating carbon dioxide. With their comprehensive dataset, they found this to be true even of warmer night temperatures.

When they combined forces with Keeling, essentially suggesting a positive feedback mechanism (rainforests are a source of carbon when warmer, making it warmer), they might have stretched it a little. Because what happens at La Selva may not happpen elsewhere, right?

But I guess that's how scientists have always approached tropical rainforest (TRF) biology - hypotheses built on site specific data (for practical reasons). When we cornered Ian Turner before our final exams, we had discovered most of the exciting TRF theories were based on a house of cards. He greeted our excitement with some amusement. That's why I, at least, found exams useful - so many of us had clarity then.

But tropical forests may not be a sink either - just that some ideas are more popular than others, and we love to believe, so theory eventually degenerate into false dogma.

The Smithsonian worldwide plots will attempt to pin some things down but remember to stay incredulous. After all, everything you know is wrong.

Good catch, dei.

1 comment:

chengpuay said...

Hi Siva,
Another point oof interest to note is that rainforests, or plants of any sort, act as carbon sinks only when the trees are growing, i.e. the carbon assimilated is converted to plant material for growth. After the trees reached maturity, they become carbon sources; and contribute carbon dioxide into the atmosphere via respiration. So reforestation may not be the sure way of alleviating the green house effect.
Which in turn opens up another can of worms, is the greenhouse effect really happening? Personally I love this concept of the Greenhouse effect, for this is one thing that politicians understand and notice. Efforts to curb Greenhouse effect benefits ecosystems.