In these earthworm-free forests, when leaves fall onto the forest floor and plants and animals die, they build up into what’s called the duff（腐殖质）layer. In this area, it was just bacteria that broke down the organic material for plants to consume and take up. Earthworms come in, they do their job and do it extremely well — they take that forest floor and turn it into the rich black soil you find in your garden.

　　That sounds great-but the local plants and animals in the Great Lakes region are used to living with the duff layer, not in the rich soil associated with earthworms. In addition, the rich top soil left by earthworms can wash out in a heavy rain. The differently produced soil is a problem as well. There’s a mat of fine roots in that duff layer-that’s where a lot of our native plants put their root system. When that duff is gone, it’s a lot harder for them to put their roots into the mineral（矿物质的）soil.

　　1. What is the author’s attitude towards the work of invasive earthworms ?

　　A. Supportive.

　　B. Worried.

　　C. Doubtful.

　　D. Respectful.

　　2. How does the Asian species affect the ecosystem of the Great Lakes Region?

　　A. By changing the soil.

　　B. By Killing the native species.

　　C. By eating the native plants.

　　D. By serving as fishing bait.

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