But steven strauss , a forest biologist at oregon state university , says that because of the great genetic variation in willows and poplars , genetic modification may not be necessary .

但是俄勒冈州立大学（oregonstateuniversity）的史提芬斯特劳斯（stevenstrauss）指出，鉴于柳树和杨树的种类繁多，它们不一定需要进行基因改造。