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When we think about food webs, we usually imagine predators and prey in a never-ending cycle. But there’s another, less visible chain, made up of soil organisms that decompose leaf litter (dead leaves, twigs, plant fragments). A network of worms, insects, springtails that break down, mix, and transform organic matter, releasing vital nutrients back into the soil. These nutrients feed plants, which feed herbivores, which feed carnivores, and so on.

To speed up decomposition, adding manure is a well-known practice, especially in agriculture. But not all poop is created equal. That’s why a team of researchers set out to discover how yak dung affects litter decomposition. The study was conducted on a Tibetan plateau in China, at 3500 meters above sea level. Scientists observed yaks for six days, recording the amount and distribution of dung and urine. They collected fresh dung and urine (stored separately in freezers to preserve nutrients) and also gathered plant litter, which was sterilized, dried, and cut into 2 cm pieces.

They used this material to create 15x15 cm decomposition bags (litterbags), each containing 10 g of litter. Some had coarse mesh (allowing soil invertebrates to enter – “with fauna”), others had fine mesh (excluding fauna – “without fauna”). Each bag received one of four treatments: no addition (control), dung only, urine only, or dung + urine. The bags were placed in a yak-free plot and left to decompose. The study lasted a total of 660 days.

Results? In the absence of soil fauna, there were no major differences between treatments. But in their presence, bags with dung (alone or with urine) decomposed much faster – decomposition rates increased by up to 116%!

Animal feces provide sugars, proteins, and amino acids – nutrients for microbes and decomposers. Soil fauna mix, break down, and stimulate microbial biomass. In short: yak poop works, but only if the soil is alive.

See You Soon, and Good Science!