As global change accelerates, quantifying the role of forests in the carbon cycle becomes ever more urgent. Modelers seek simple predictors of forest biomass and carbon flux. Over the last decade, the theory of metabolic ecology generated testable explanations, derived from physical and biochemical principles, for a wide range of ecological patterns. However, in two Ecology Letters articles, Helene Muller-Landau and colleagues show that tree growth, mortality and abundance in fourteen tropical forests deviate substantially from metabolic ecology predictions, especially for large trees. Instead, observed variation within and among forests supports alternative models presented by the CTFS team.
Are tropical forest structure and dynamics too complex for universal explanations?
"When you walk through different tropical forests, or graph data from different forests, there are certain features that, at first glance, look similar everywhere '" the presence of some very large trees, or the general shape of the tree size distribution curve," explains first author, Helene Muller-Landau from the University of Minnesota. "So you start to think that there might be some general explanations. But the closer you look, the more differences you find '" differences that can'TMt be captured or even decently approximated by any single picture or formula."
Tropical forests give modelers a run for their money. Trees range from spindly understory shrubs to enormous buttress-rooted rainforest giants festooned with vines and peppered with orchids, ferns and bromeliads. Tropical trees depend on animals for pollination and seed dispersal and are constantly assaulted by insects, fungi, maelstrom and machete. Furthermore, soils, rainfall, the frequencies of hurricanes and fires, and assemblages of animals and plants in tropical forests all vary widely from one forest to another.
Prospecting in a gold mine of data
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Contact: Helene Muller-Landau
Smithsonian Tropical Research Institute
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