News
Published online: 25 November 2004; | doi:10.1038/news041122-12
Cicada invasion feeds forests

Roxanne Khamsi
Insect broods kick-start forest ecosystems every 17 years.


A huge troop of cicadas known as Brood X emerges in the eastern United
States every 17 years, covering streets, cars and buildings with a crunchy
coating of insects. Although they aren't welcome in the cities, the
nutrients from the Magicicada carcasses provide a valuable boost to forest
ecosystems, says a California ecologist.

When the insects appear, the adults burrow up from the soil to mate, then
lay their eggs inside trees, allowing newborn larvae to travel back
underground. Once the mating season ends, these adults die and their bodies
litter the forest floor.

The most recent invasion took place last spring, in an area covering eastern
states such as Tennessee and Kentucky. Experts estimate that, in affected
areas, around 100 insects emerge from each square metre of ground, although
this number can vary from fewer than 10 to more than 300.

Scientists had already noticed that in the years following the cyclical
emergence of the cicadas, forest plants seem to have unusually high amounts
of nitrogen in their leaves. Nitrogen is normally a limiting factor in the
plants' growth.

So Louie Yang at the University of California, Davis, decided to investigate
further. He measured the levels of nutrients in experimental soil plots to
which he had added cicadas, and compared them with control plots that lacked
the extra insects.

Full text at Nature
http://www.nature.com/news/2004/041122/full/041122-12.html

Posted by
Robert Karl Stonjek
---
þ RIMEGate(tm)/RGXPost V1.14 at BBSWORLD * Info{at}bbsworld.com

---
 * RIMEGate(tm)V10.2áÿ* RelayNet(tm) NNTP Gateway * MoonDog BBS
 * RgateImp.MoonDog.BBS at 11/29/04 9:35:38 PM