Invasive species get a bad ___1___—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 porcelain. When it creeps into forests, it forms dense carpets that can ___2___ native tree seedlings. And in the last 15 years, the grass has ___3___ rural roads throughout Pennsylvania's Rothrock State Forest—much faster than foresters expected.

Researchers thought the cause could be another human activity—___4___. They spray-painted 320,000 dead safflower seeds, and placed them along state forest roads. After routine road ___5___, they combed through the gravel 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 Ecological Society of America. [Emily Rauschert and David Mortensen, Human-mediated spread of invasive plants across a landscape]

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.
【視聽(tīng)版科學(xué)小組榮譽(yù)出品】
rap choke out infested road maintenance grading
入侵物種引來(lái)罵聲一片——而令它們迅速蔓延的卻是我們?nèi)祟悺Ｈ嶂窬褪侨肭治锓N之一，它是一種瓷器墊料，一百多年前從亞洲傳入。柔枝莠竹漸漸在森林里蔓延開(kāi)來(lái)，形成厚厚的一層“地毯”，阻礙當(dāng)?shù)貥?shù)木幼苗的生長(zhǎng)。過(guò)去15年里，柔枝莠竹遍布賓夕法尼亞州立原始森林公園的小路上，蔓延速度比林業(yè)學(xué)家預(yù)期得要快得多。 研究人員認(rèn)為造成這種后果可能是因?yàn)榱硪豁?xiàng)人類活動(dòng)——道路維修。他們噴涂了32萬(wàn)株干紅花種子，把它們鋪在公園道路旁。道路頻繁維護(hù)之后，它們從石礫縫中鉆出來(lái)重新覆蓋路面。研究人員還發(fā)現(xiàn)有些種子是從幾百英尺的地底下被帶出來(lái)的，要比它們自己上竄的距離大多了——這也許能解釋柔枝莠竹迅速蔓延的原因。 研究人員在美國(guó)生態(tài)學(xué)會(huì)的一次會(huì)議上公布了這項(xiàng)研究結(jié)果。 然而道路安全仍然相當(dāng)重要，于是研究人員提議每次少翻修一點(diǎn)路段，或者不要翻修得太頻繁。漂洋過(guò)海，跋山涉水，不管怎樣，人類走到哪里，入侵物種就跟到哪里。