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

Photosynthetically fixed carbon is eventually degraded by micro-organisms and two major forms of carbon result methane $\left(\mathrm{CH}_4\right)$ and carbon dioxide \left(\mathrm{CO}_2\right)$. The micro-organisms breakdown the complex compounds of dead protoplasm of producers and consumers absorb some of the decomposition products and release simple substances. The slow rate of decomposition of fallen logs in nature is due to their low moisture content. The cellulose is in high amount in fallen logs. The environment arround the fallen logs is aerobic,$i e, \mathrm{O}_2 is present.