Initial observations from invasive Asian crazy worm experiment show signs of possible effects

Post by Jiangxiao Qiu

After four months of incubation in the UW-Arboretum, the first year of our Asian crazy worm experiment came to an end in October. We have been investigating what effects this newly arrived invasive species, formally called Amynthas agrestis, could have on the Yahara Watershed’s soils and ecosystems.

It seemed like all the soil cores had just been sitting there quietly for several months, without major changes. However, a close-up view shows something interesting.

The experiment's site in the UW Arboretum. Photo by Jiangxiao Qiu

The experiment’s site in the UW Arboretum. Photo by Jiangxiao Qiu

The photos below show the differences in plant litter on the surfaces of two forest soil cores, one with worms (right) and one without worms (left). The soil core without worms has an almost equal amount of litter as when we started the experiment, which suggests that the Asian crazy worm, which eats forest litter, could substantially reduce the amount of foliage on the forest floor. Reduced litter could alter the decomposition and nutrient cycles in forest ecosystems.

The soil core on the left contained Asian crazy worms; the one on the right was worm-free. Photo by Jiangxiao Qiu

The soil core on the right contained Asian crazy worms; the one on the left was worm-free. Photo by Jiangxiao Qiu

Besides consuming litter, these invaders also alter the soils. One of the worms’ main signatures is their casts, or poop, which have a unique crumb-like appearance. Rich in nutrients and microbial activity, the casts can influence soil’s chemical properties, as well as physical properties, such as how much water it can hold. We don’t know yet what these worms’ casts can do to local soils, however.

The crumb-like clumps on this soil are worm casts. Photo by Jiangxiao Qiu

The crumb-like clumps on this soil are worm casts. Photo by Jiangxiao Qiu

While there were not many visible differences between the prairie soil cores with and without worms, the worms did survive in these soils and also left casts. This suggests they may alter prairie soils too.

Can you spot the worm casts on this prairie soil core? Photo by Jiangxiao Qiu

Can you spot the worm casts on this prairie soil core? Photo by Jiangxiao Qiu

Some worms even grew to an astonishing size during the course of the experiment. The worm pictured here grew to a length of roughly 14 cm!

Photo by Jiangxiao Qiu

Photo by Jiangxiao Qiu

As a next step in our experiment, we will be analyzing the soil and litter samples. We are interested in the extent to which the changes in litter quantity and quality could alter important physical and chemical soil properties, such as soil texture and pH, and nutrient content, as well as how these effects may differ among forest and prairie soils. This analysis will take us one step closer to understanding how the Asian crazy worm could impact the Yahara Watershed’s ecosystems.

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