NORTH CAROLINA—Across the globe, insects can decompose almost 30% of all fallen tree branches, trunk, and other deadwood. The findings have important implications for the global carbon cycle. USDA Forest Service scientists Michael Ulyshen and Grizelle Gonzalez were part of an international research team that investigated the role of insects in decomposing deadwood in ecosystems across the globe. The massive study took place across 55 sites on six continents and in three forest biomes: tropical, temperate and boreal.

Researchers placed pieces of wood native to each respective forest in mesh cages that excluded insects and in uncaged areas where insects had unlimited access. For example, at the Savannah River Site in South Carolina, Ulyshen placed small logs of water oak, sweetgum and pine. The researchers weighed the samples before and after to determine decomposition rates in each forest community.

The results confirmed that insects play a major role in cycling carbon. Globally, insects may decompose up to 29% of deadwood. The amount of wood that insects decomposed depended on forest biome. Insects accounted for 28.2% of the decomposition in tropical forests, 6.3% in temperate forests, and 3.3% in boreal forests.

Climate and temperature also affected decomposition rates. In warmer areas, rain and other precipitation increased decomposition. In cooler areas, more precipitation decreased decomposition. 

Understanding the forest carbon cycle is critical to accurate global climate change predictions. Read the article in Nature.