Climate Trivia: Decay and Rising Temperature

Living organic matter has its origins in the atmosphere: energy from the Sun enables plants and some microbes to build sugars out of water and atmospheric carbon dioxide. These sugars ultimately feed the rest of life on Earth. When an organism, or a part of an organism such as a leaf, dies, it decomposes and sends the carbon that made up its body back into the atmosphere as carbon dioxide. In a static climate, this carbon cycle is generally in balance, with about as much carbon dioxide being taken up each year as is released back into the atmosphere. When the climate changes, however, so does the carbon cycle. Of particular interest are the rates of decay of different types of dead plant matter (deciduous leaves, conifer needles, grasses, twigs, wheat stalks, etc.), and how these rates will respond to warmer temperatures.

Trivia Question: As temperatures warm, what happens to the rates at which different types of plant matter decompose?

a)    All types of plant matter decompose slower.
b)    Plant matter in colder climates, such as northern conifer forests and tundra, decompose faster. Plant matter in the tropics decomposes slower.

c)    It all depends on the type of plant! Rates of broadleaf decomposition increase, while decomposition rates of tougher materials like conifer needles and twigs don’t change much.
d)    Everything decomposes faster.

The correct answer is d. While the increases in the rate of decomposition of tough bits of organic matter like needles and twigs are not as dramatic compared to the increases in the rates for things like oak and maple leaves, everything decomposes faster as temperatures warm. A study of 27 North American ecosystems from the Alaskan tundra to Panamanian rainforests showed that while decomposition processes were highly diverse, being influenced by things like local differences in soil microbial communities and mineral composition, all ecosystems responded to increased temperatures with faster rates of organic matter decay.

Season: Fall

Source: Forney, DC and Rothman, DH. “Common structure in the heterogeneity of plant-matter decay.” Journal of the Royal Society Interface 9 (2012): 2255-2267.

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