Scientists studying trees ranging from saplings to 130 years old in Canada's northern forests have discovered that the period since a fire last swept through an area determines how much carbon the forest can store. Twenty to forty year old stands absorb more carbon than those 70 years old and older, despite being smaller and having less biomass or plant material.

Boreal or northern forests account for close to 25 percent of total carbon stored in vegetation and soils in the Earth's biosphere. Wildfires burn down individual areas every 40 to 250 years and are an important part of this ecosystem. Whether or not these forests are likely to lower or raise levels of carbon dioxide in the atmosphere depends on how these carbon reserves respond to, and recover from, both climate change and disturbances such as wildfires.

NASA funded part of this study under its Earth Science Enterprise (ESE), whose mission is to understand and protect our home planet. Earth Science in NASA seeks to understand trends in land cover and land use, such as forest fires, that drive global climate. Another Earth Science program objective is to understand the Earth system's response to natural and human-induced changes, and effects on global carbon cycle.

Marcy Litvak, plant ecologist at The University of Texas at Austin and lead author of the study that appeared in a recent issue of the Journal of Geophysical Research - Atmospheres, said that the ability of tree stands to store carbon changes as they regenerate from fire. Forests will store more or less carbon depending on the dominant tree species, the amount of moss cover, and changes in forest structure due to fire. Those factors determine how much total carbon is exchanged with the atmosphere.

Carbon is transferred from the atmosphere to the forest through the process of photosynthesis. Carbon is returned to the atmosphere through the process of respiration as soil microorganisms decompose dead organic m
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Contact: Rob Gutro
rgutro@pop900.gsfc.nasa.gov
301-286-4044
NASA/Goddard Space Flight Center
21-Mar-2003

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