The slow rate of decomposition of fallen logs in nature is due to their

poor nitrogen content
low moisture content
low cellulose content
anaerobic environment around them

The correct answer is: D. anaerobic environment around them.

Decomposition is the process by which organic matter is broken down into simpler substances by microorganisms. The rate of decomposition is affected by a number of factors, including the availability of oxygen, moisture, and nutrients.

In an anaerobic environment, there is no oxygen present. This can occur in waterlogged soils or in the presence of dense organic matter. In an anaerobic environment, decomposition is slower because the microorganisms that break down organic matter require oxygen to do so.

The other options are incorrect because:

  • A. poor nitrogen content: Nitrogen is an essential nutrient for microorganisms, but it is not the only factor that affects the rate of decomposition.
  • B. low moisture content: Moisture is necessary for microorganisms to survive and reproduce, but it is not the only factor that affects the rate of decomposition.
  • C. low cellulose content: Cellulose is a type of carbohydrate that is found in plant material. It is a major component of wood, and it is one of the most difficult substances for microorganisms to decompose. However, the cellulose content of wood is not the only factor that affects the rate of decomposition.