SSS 2011-08-10
时间：2011-09-05 05:35:53
搜索关注在线英语听力室公众号：tingroom，领取免费英语资料大礼包。
（单词翻译）
Invasive species get a bad rap—but we humans are usually to blame for their spread. Take Japanese stiltgrass, an invasive that arrived from Asia nearly 100 years ago as a packing material for porcelain1. When it creeps into forests, it forms dense2 carpets that can choke out native tree seedlings3. And in the last 15 years, the grass has infested4 rural roads throughout Pennsylvania's Rothrock State Forest—much faster than foresters expected.
Researchers thought the cause could be another human activity—road maintenance. They spray-painted 320,000 dead safflower seeds, and placed them along state forest roads. After routine road grading, they combed through the
gravel5 to recover them. And they found that some seeds had been carried hundreds of feet down the road. Much farther than the few feet seeds can travel on their own—perhaps explaining the grass' rapid spread.
They presented those results at a meeting of the
Ecological6 Society of America.
Still, roads need to be safe for drivers. So the researchers propose smoothing shorter segments at a time, or doing it less frequently. Because where humans go, invasives often follow—whether by sea or on land.
Thanks for the minute. For Scientific American's 60-Second Science, I'm Christopher Intagliata.
分享到：
Error Warning!
出错了
Error page: /?aid=155326&mid=3
Error infos: Got error 28 from storage engine
Error sql: select `l`.`tag`,`l`.`index`,`l`.`level_id`,`b`.`id`,`b`.`word`,`b`.`spell`,`b`.`explain`,`b`.`sentence`,`b`.`src` from `new_wordtaglist` `l` left join `new_word_base` `b` on `l`.`tag`=`b`.`word` where `l`.`arc_id`='155326' and `l`.`level_id`>='' group by `b`.`word` order by `l`.`index` asc
